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Posted: 4/13/2011 5:09:21 PM EDT
[#1]
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I've been a boiler Engineer since 1975. I've worked on and operated all kinds of boilers, from high pressure to low pressure. I've seen safety valves that would not lift when they were suppose to. I've seen low water safety valves stuck, boiler still running, and no water inside. I've had high pressure tubes in a water tube boiler firebox blow and rip apart. I've had the end of a waterwall drum blow. ( We let it gush water for 2 days while trying to cool the boiler down.) But by far, what is the most dangerous, and still happens way too much, is somebody bypassing the purge cycle for the firebox. Most all of your explosions today are caused by this. There is a reason most boilerrooms are built away from the main buildings. If the boiler blows up, only the engineers will be killed. ...why would anyone do that? I mean, its so obviously dumb, and I see no upside at all. 
A purge cycle? Must be a high-efficiency boiler as all others are natural draft and thus always pruging while between heat calls. Please elaborate? I am curious. I think he means when lighting. The burner side goes through a purge before the pilot is lit. I could see maybe a damper not opening when it's supposed to during purge (and an obvious bypass of the open feedback switch) and combustibles still inside, but other than that how does can any modern BMS purge be bypassed? |
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Posted: 4/13/2011 5:10:46 PM EDT
[#2]
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Prepurge and postpurge are utilized regardless of wether it's induced draft, forced draft, etc. Thats apples and oranges. I have no experience with natural draft boilers but he said that they don't require steam purges, so I was replying to that. I hear ya |
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Posted: 4/13/2011 5:10:57 PM EDT
[#3]
Its amazing the variety of people here on Arfcom.
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Posted: 4/13/2011 5:13:12 PM EDT
[#4]
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Our firm recently settled a very important death case. In April 2006, Steve Thrasher was employed at the Rock Tenn paper mill in Demopolis, Ala. He was sent to check the operation of one of the mill steam boilers. The subject boiler, roughly 30 feet square and 60 feet tall, was built and installed in the mid-1950s and had been in continuous operation for over 50 years. Although the ASME boiler code specifies that tubing of steam power boilers should be inspected regularly, portions of the subject boiler tubing were encased in a concrete-like material known as a refractory and were never inspected during the life of the boiler. The boiler inspection company hired to perform the annual inspections is recognized as a leader in boiler technology but it never utilized its own ultrasound or x-ray inspection technology on the boiler. Rather, the company simply relied on visual inspections of the portions of the boiler that were readily accessible. As a result, dangerously thin sections of steam tubing encased within the refractory were never discovered.
Unfortunately, as Steve Thrasher walked by the boiler one of the internal tubes failed and violently ruptured. The force of the tube failure blew a hole in the steel outer casing of the boiler and spewed superheated steam directly onto Steve. Somehow Steve managed to walk to the mill control room and was first transported to the local emergency room and then to the burn trauma unit at South Alabama in Mobile. Despite world class burn care, Steve Thrasher died from his burns. After extensive case preparation which included multiple depositions of experts in metallurgy, boiler operation, inspection techniques and burn care, this case settled a week before we were set to select a jury. The amount and terms of the settlement agreement are confidential. Mike Andrews handled this case for the family. He and his staff did a tremendous job in working this case up. This was a friend of mine, there was another explosion back in the 50's that killed several and injured a few others. You may not want to watch this but I believe this is your friend right before his passing... This is the boiler explosion I was referring to in my above post. http://m.youtube.com/index?desktop_uri=%2F&gl=US#/watch?xl=xl_blazer&v=kxu6VMt9n8E Your link doesn't take me to a video but I don't think there are cameras where it happened. |
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Posted: 4/13/2011 5:17:38 PM EDT
[#5]
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A purge cycle? Must be a high-efficiency boiler as all others are natural draft and thus always pruging while between heat calls. Please elaborate? I am curious. In the petrochemical and refining industries they're almost always induced draft, as far as I know. Prepurge and postpurge are utilized regardless of wether it's induced draft, forced draft, etc. Thats apples and oranges. When a steamer fires up, it's a immediate pilot light off, them the mains after the pilot proves. Shut down happens when pressure is reached. No pre or post purge. In hot water, there is always a pre purge and post purge on high efficiency sealed combustion boilers. As for power burners, yes, it does pre-purge. One pic I posted is a power burner type boiler. |
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Posted: 4/13/2011 5:18:20 PM EDT
[#6]
Quoted: Quoted: Quoted: Our firm recently settled a very important death case. In April 2006, Steve Thrasher was employed at the Rock Tenn paper mill in Demopolis, Ala. He was sent to check the operation of one of the mill steam boilers. The subject boiler, roughly 30 feet square and 60 feet tall, was built and installed in the mid-1950s and had been in continuous operation for over 50 years. Although the ASME boiler code specifies that tubing of steam power boilers should be inspected regularly, portions of the subject boiler tubing were encased in a concrete-like material known as a refractory and were never inspected during the life of the boiler. The boiler inspection company hired to perform the annual inspections is recognized as a leader in boiler technology but it never utilized its own ultrasound or x-ray inspection technology on the boiler. Rather, the company simply relied on visual inspections of the portions of the boiler that were readily accessible. As a result, dangerously thin sections of steam tubing encased within the refractory were never discovered. Unfortunately, as Steve Thrasher walked by the boiler one of the internal tubes failed and violently ruptured. The force of the tube failure blew a hole in the steel outer casing of the boiler and spewed superheated steam directly onto Steve. Somehow Steve managed to walk to the mill control room and was first transported to the local emergency room and then to the burn trauma unit at South Alabama in Mobile. Despite world class burn care, Steve Thrasher died from his burns. After extensive case preparation which included multiple depositions of experts in metallurgy, boiler operation, inspection techniques and burn care, this case settled a week before we were set to select a jury. The amount and terms of the settlement agreement are confidential. Mike Andrews handled this case for the family. He and his staff did a tremendous job in working this case up. This was a friend of mine, there was another explosion back in the 50's that killed several and injured a few others. You may not want to watch this but I believe this is your friend right before his passing... This is the boiler explosion I was referring to in my above post. http://m.youtube.com/index?desktop_uri=%2F&gl=US#/watch?xl=xl_blazer&v=kxu6VMt9n8E Your link doesn't take me to a video but I don't think there are cameras where it happened.  |
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Posted: 4/13/2011 5:20:23 PM EDT
[#7]
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I've been a boiler Engineer since 1975. I've worked on and operated all kinds of boilers, from high pressure to low pressure. I've seen safety valves that would not lift when they were suppose to. I've seen low water safety valves stuck, boiler still running, and no water inside. I've had high pressure tubes in a water tube boiler firebox blow and rip apart. I've had the end of a waterwall drum blow. ( We let it gush water for 2 days while trying to cool the boiler down.) But by far, what is the most dangerous, and still happens way too much, is somebody bypassing the purge cycle for the firebox. Most all of your explosions today are caused by this. There is a reason most boilerrooms are built away from the main buildings. If the boiler blows up, only the engineers will be killed. ...why would anyone do that? I mean, its so obviously dumb, and I see no upside at all.
A purge cycle? Must be a high-efficiency boiler as all others are natural draft and thus always pruging while between heat calls. Please elaborate? I am curious. I think he means when lighting. The burner side goes through a purge before the pilot is lit. I could see maybe a damper not opening when it's supposed to during purge (and an obvious bypass of the open feedback switch) and combustibles still inside, but other than that how does can any modern BMS purge be bypassed? A vent damper has micro switches that will not allow a light off if the damper is not fully opened. All this is controlled by the ignition control module or the boiler's circuit board if equipped. Power burner? yes. natural draft, no. |
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Posted: 4/13/2011 5:23:31 PM EDT
[#8]
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Our firm recently settled a very important death case. In April 2006, Steve Thrasher was employed at the Rock Tenn paper mill in Demopolis, Ala. He was sent to check the operation of one of the mill steam boilers. The subject boiler, roughly 30 feet square and 60 feet tall, was built and installed in the mid-1950s and had been in continuous operation for over 50 years. Although the ASME boiler code specifies that tubing of steam power boilers should be inspected regularly, portions of the subject boiler tubing were encased in a concrete-like material known as a refractory and were never inspected during the life of the boiler. The boiler inspection company hired to perform the annual inspections is recognized as a leader in boiler technology but it never utilized its own ultrasound or x-ray inspection technology on the boiler. Rather, the company simply relied on visual inspections of the portions of the boiler that were readily accessible. As a result, dangerously thin sections of steam tubing encased within the refractory were never discovered.
Unfortunately, as Steve Thrasher walked by the boiler one of the internal tubes failed and violently ruptured. The force of the tube failure blew a hole in the steel outer casing of the boiler and spewed superheated steam directly onto Steve. Somehow Steve managed to walk to the mill control room and was first transported to the local emergency room and then to the burn trauma unit at South Alabama in Mobile. Despite world class burn care, Steve Thrasher died from his burns. After extensive case preparation which included multiple depositions of experts in metallurgy, boiler operation, inspection techniques and burn care, this case settled a week before we were set to select a jury. The amount and terms of the settlement agreement are confidential. Mike Andrews handled this case for the family. He and his staff did a tremendous job in working this case up. This was a friend of mine, there was another explosion back in the 50's that killed several and injured a few others. You may not want to watch this but I believe this is your friend right before his passing... This is the boiler explosion I was referring to in my above post. http://m.youtube.com/index?desktop_uri=%2F&gl=US#/watch?xl=xl_blazer&v=kxu6VMt9n8E Your link doesn't take me to a video but I don't think there are cameras where it happened.  http://www.youtube.com/watch?v=kxu6VMt9n8E
That's not him, I think that is from a plant in Paris Tennessee. |
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Posted: 4/13/2011 5:26:23 PM EDT
[#9]
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Posted: 4/13/2011 5:28:03 PM EDT
[#10]
When I first started my job, I worked nights. We had an old Kewanee Type "C" at the time. It had an old atmospheric damper that was probably at least 14-16" in diameter. On windy nights that sumbitch would bang around like crazy. I kept looking for vandals throwing shit at the building until I realized what it was!
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Posted: 4/13/2011 5:31:41 PM EDT
[#11]
BUMP with fixed pics, page 1
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Posted: 4/13/2011 5:58:34 PM EDT
[#12]
Quoted: Quoted: Don;t think some of you are getting this right, this is how it was explaned to me: Boiler runs low on water and boiler plate is exposed and proceeds to glow red hot. At that point water is introduced to red hot boiler plate and violently flashes off producing a large volume of superheated steam at extremely high pressures. The sudden sharp rise in pressure overwhelms the safeties and blows the boiler. We had a steam tractor explode a few years back, killed a couple of people. They said it was low on water and when the tractor went down a small grade,the water ran to one end of the boiler and exposed the boiler plate thus allowing it to get red hot. When the tractor returned to level ground it blew up, because the water ran back over the glowing boiler plate. Do steam locomotives or tractors have strong mechanical water pumps that replenish water as it runs low? I ask because it couldn't be a simple system since as much pressure would be imparted on the 'feed' as is going to the pistons. What he described is the common low water explosion of a modern boiler. Steam locomotives and tractors are a different beast in terms of feedwater, pistons, injectors, or pumps can be used. Just some background, I'm an engineer who works as a boiler controls technician. Lets go over the causes of catastrophic boiler occurrences. They can be broken to three basic categories: combustion, pressure vessel failure, low water. Combustion: You are firing hydrocarbons in an enclosed area with minimal air (typically 3-4% O2 left over from the 20.9 you start with, once you remove the water vapor from the flue gas). If, as a previous poster mentioned, you have a buildup of combustibles in the furnace and it is not purged from the furnace before firing (purge time, there must be pre-firing and post-firing purges in the cycle), you can ignite these with catastrophic results. Lets look at a common boiler, the firetube:  These are some hot water Cleaver-Brooks boilers, they appear to be 60" models (I found the image randomly on google) which covers 125-200 bhp sizes, firing from 5.4 million btu/hr to 8.4 million btu/hr. This is still considered a small boiler, and commonly used in heating applications in smaller apartment communities. If one were to flood this with gas and bypass purge, the baffles will be destroyed, doors potentially blown off, one of this size I know of had its inner door pressed almost perfectly into the outer door (on the front door there is a flat inner door that holds refractory and separates the flue gasses from the incoming combustion air which is in the area between the outer shell of the front door and the inner door)...and this is one of the most resilient designs to that kind of failure. Now...look at the industrial watertube, common to find in medium to large industrial plants, operating between 100 and 500 psi steam pressure (some up to 4200, depending on application).  It is hard to judge size from this picture, but it appears to be on the small end, perhaps 30-60 thousand pounds of steam evaporated per hour. IF you are unlucky enough to have a small combustion occurrence on this, 100k+ will be the damage done instantly. The flat walls will be bowed out, the water wall tubes which are butted up and welded together can be split, refractory walls on the front and rear will have to be replaced, and the boiler will be out of service for several months. Pressure: What causes pressure failures is generally a degradation of the steel due to thermal stress, oxygen pitting, or chemical corrosion. Thermal stress is from a variety of things from firing in high fire without giving sufficient time for the vessel to expand and water to circulate naturally through it, to cold water into a hot boiler, hot water into a cold boiler, etc. All of these lead to cracking. Combined with high pressures it can cause a rupture. Oxygen pitting, is pitting due to oxygen that can no longer be present in the water (once at boiling, oxygen solubility goes to 0), so it latches onto the steel walls. Chemical corrosion can be from excess chemicals used to treat the water being used, so it eats the steel, or carbon dioxide presence in the feedwater causing acidic corrosion. While a small area of any of these will cost a nice bit of money to fix, significant extents of any of these will force the vessel to be condemned. Running it past when it is condemned is a sure way to have a catastrophic failure. Low water: As previously mentioned, if the low water controls fail and the heat cannot be sinked into the water, it is absorbed into the steel which holds a lot less btu/pound/degree, and as the metal heats up, it loses its structural strength. If it is glowing and sinking down, the introduction of water will hit that steel, water will absorb that heat and flash, causing a pressure spike due to the volumetric expansion (1lb of steam takes up 1600 times as much volume as 1 lb of water), this change also causes a brittle condition of the steel due to freezing martensite in the grain of the metal. The firetube mentioned earlier will turn into a rocket in this state, sending itself through block walls, precast, across a few hundred feet of parking lot, throwing its rear door the other way. Poor water can cause similar issues as low water as scale buildup will cause insulation of the fireside from the waterside, leading to increasing fireside heating surface temperatures, causing the following (I love how it's a frowny face):  At the end of the day though, with modern controls, steel, and codes, you have to do something stupid for these things to blow up. Getting rid of the purge cycle for instance isn't possible on new controls, that went out when the cam drive flame safeguards went out, a few still there, but not too common anymore. Low water controls, people are using transmitters and floats that monitor water level, know when the boiler is running and if the water doesn't move, it assumes that the float is scaled up and shuts the boiler down. Modern parallel positioning sets FGR to 0 during purge to complete the cycle more effectively. Continuous blowdown and monitoring of it by conductivity prevents scaling. Annual fireside and waterside inspections monitor for dangerous conditions developing. Combustion tuneups lessen the chance of combustion explosions. Hope that was informative and interesting lesson on boilers everyone. |
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Posted: 4/13/2011 6:03:18 PM EDT
[#13]
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BUMP with fixed pics, page 1 Cool! I run 5 PSI on my steam plant also. |
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Posted: 4/13/2011 6:16:25 PM EDT
[#14]
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Don;t think some of you are getting this right, this is how it was explaned to me: Boiler runs low on water and boiler plate is exposed and proceeds to glow red hot. At that point water is introduced to red hot boiler plate and violently flashes off producing a large volume of superheated steam at extremely high pressures. The sudden sharp rise in pressure overwhelms the safeties and blows the boiler. We had a steam tractor explode a few years back, killed a couple of people. They said it was low on water and when the tractor went down a small grade,the water ran to one end of the boiler and exposed the boiler plate thus allowing it to get red hot. When the tractor returned to level ground it blew up, because the water ran back over the glowing boiler plate. Do steam locomotives or tractors have strong mechanical water pumps that replenish water as it runs low? I ask because it couldn't be a simple system since as much pressure would be imparted on the 'feed' as is going to the pistons. What he described is the common low water explosion of a modern boiler. Steam locomotives and tractors are a different beast in terms of feedwater, pistons, injectors, or pumps can be used. Just some background, I'm an engineer who works as a boiler controls technician. Lets go over the causes of catastrophic boiler occurrences. They can be broken to three basic categories: combustion, pressure vessel failure, low water. Combustion: You are firing hydrocarbons in an enclosed area with minimal air (typically 3-4% O2 left over from the 20.9 you start with, once you remove the water vapor from the flue gas). If, as a previous poster mentioned, you have a buildup of combustibles in the furnace and it is not purged from the furnace before firing (purge time, there must be pre-firing and post-firing purges in the cycle), you can ignite these with catastrophic results. Lets look at a common boiler, the firetube: http://i5.photobucket.com/albums/y192/TAKnight/rental2.jpg These are some hot water Cleaver-Brooks boilers, they appear to be 60" models (I found the image randomly on google) which covers 125-200 bhp sizes, firing from 5.4 million btu/hr to 8.4 million btu/hr. This is still considered a small boiler, and commonly used in heating applications in smaller apartment communities. If one were to flood this with gas and bypass purge, the baffles will be destroyed, doors potentially blown off, one of this size I know of had its inner door pressed almost perfectly into the outer door (on the front door there is a flat inner door that holds refractory and separates the flue gasses from the incoming combustion air which is in the area between the outer shell of the front door and the inner door)...and this is one of the most resilient designs to that kind of failure. Now...look at the industrial watertube, common to find in medium to large industrial plants, operating between 100 and 500 psi steam pressure (some up to 4200, depending on application). http://i5.photobucket.com/albums/y192/TAKnight/4-boil-7-17-08-mg-d.jpg It is hard to judge size from this picture, but it appears to be on the small end, perhaps 30-60 thousand pounds of steam evaporated per hour. IF you are unlucky enough to have a small combustion occurrence on this, 100k+ will be the damage done instantly. The flat walls will be bowed out, the water wall tubes which are butted up and welded together can be split, refractory walls on the front and rear will have to be replaced, and the boiler will be out of service for several months. Pressure: What causes pressure failures is generally a degradation of the steel due to thermal stress, oxygen pitting, or chemical corrosion. Thermal stress is from a variety of things from firing in high fire without giving sufficient time for the vessel to expand and water to circulate naturally through it, to cold water into a hot boiler, hot water into a cold boiler, etc. All of these lead to cracking. Combined with high pressures it can cause a rupture. Oxygen pitting, is pitting due to oxygen that can no longer be present in the water (once at boiling, oxygen solubility goes to 0), so it latches onto the steel walls. Chemical corrosion can be from excess chemicals used to treat the water being used, so it eats the steel, or carbon dioxide presence in the feedwater causing acidic corrosion. While a small area of any of these will cost a nice bit of money to fix, significant extents of any of these will force the vessel to be condemned. Running it past when it is condemned is a sure way to have a catastrophic failure. Low water: As previously mentioned, if the low water controls fail and the heat cannot be sinked into the water, it is absorbed into the steel which holds a lot less btu/pound/degree, and as the metal heats up, it loses its structural strength. If it is glowing and sinking down, the introduction of water will hit that steel, water will absorb that heat and flash, causing a pressure spike due to the volumetric expansion (1lb of steam takes up 1600 times as much volume as 1 lb of water), this change also causes a brittle condition of the steel due to freezing martensite in the grain of the metal. The firetube mentioned earlier will turn into a rocket in this state, sending itself through block walls, precast, across a few hundred feet of parking lot, throwing its rear door the other way. Poor water can cause similar issues as low water as scale buildup will cause insulation of the fireside from the waterside, leading to increasing fireside heating surface temperatures, causing the following (I love how it's a frowny face): http://i5.photobucket.com/albums/y192/TAKnight/Picture153.jpg At the end of the day though, with modern controls, steel, and codes, you have to do something stupid for these things to blow up. Getting rid of the purge cycle for instance isn't possible on new controls, that went out when the cam drive flame safeguards went out, a few still there, but not too common anymore. Low water controls, people are using transmitters and floats that monitor water level, know when the boiler is running and if the water doesn't move, it assumes that the float is scaled up and shuts the boiler down. Modern parallel positioning sets FGR to 0 during purge to complete the cycle more effectively. Continuous blowdown and monitoring of it by conductivity prevents scaling. Annual fireside and waterside inspections monitor for dangerous conditions developing. Combustion tuneups lessen the chance of combustion explosions. Hope that was informative and interesting lesson on boilers everyone. Great post! I blown down once a week. My chemical salesman checks my pH once/year. I don't think they've ever done a conductivity analysis. I usually do a wet close too. |
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Posted: 4/13/2011 6:20:22 PM EDT
[#15]
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Don;t think some of you are getting this right, this is how it was explaned to me: Boiler runs low on water and boiler plate is exposed and proceeds to glow red hot. At that point water is introduced to red hot boiler plate and violently flashes off producing a large volume of superheated steam at extremely high pressures. The sudden sharp rise in pressure overwhelms the safeties and blows the boiler. We had a steam tractor explode a few years back, killed a couple of people. They said it was low on water and when the tractor went down a small grade,the water ran to one end of the boiler and exposed the boiler plate thus allowing it to get red hot. When the tractor returned to level ground it blew up, because the water ran back over the glowing boiler plate. Do steam locomotives or tractors have strong mechanical water pumps that replenish water as it runs low? I ask because it couldn't be a simple system since as much pressure would be imparted on the 'feed' as is going to the pistons. What he described is the common low water explosion of a modern boiler. Steam locomotives and tractors are a different beast in terms of feedwater, pistons, injectors, or pumps can be used. Just some background, I'm an engineer who works as a boiler controls technician. Lets go over the causes of catastrophic boiler occurrences. They can be broken to three basic categories: combustion, pressure vessel failure, low water. Combustion: You are firing hydrocarbons in an enclosed area with minimal air (typically 3-4% O2 left over from the 20.9 you start with, once you remove the water vapor from the flue gas). If, as a previous poster mentioned, you have a buildup of combustibles in the furnace and it is not purged from the furnace before firing (purge time, there must be pre-firing and post-firing purges in the cycle), you can ignite these with catastrophic results. Lets look at a common boiler, the firetube: http://i5.photobucket.com/albums/y192/TAKnight/rental2.jpg These are some hot water Cleaver-Brooks boilers, they appear to be 60" models (I found the image randomly on google) which covers 125-200 bhp sizes, firing from 5.4 million btu/hr to 8.4 million btu/hr. This is still considered a small boiler, and commonly used in heating applications in smaller apartment communities. If one were to flood this with gas and bypass purge, the baffles will be destroyed, doors potentially blown off, one of this size I know of had its inner door pressed almost perfectly into the outer door (on the front door there is a flat inner door that holds refractory and separates the flue gasses from the incoming combustion air which is in the area between the outer shell of the front door and the inner door)...and this is one of the most resilient designs to that kind of failure. Now...look at the industrial watertube, common to find in medium to large industrial plants, operating between 100 and 500 psi steam pressure (some up to 4200, depending on application). http://i5.photobucket.com/albums/y192/TAKnight/4-boil-7-17-08-mg-d.jpg It is hard to judge size from this picture, but it appears to be on the small end, perhaps 30-60 thousand pounds of steam evaporated per hour. IF you are unlucky enough to have a small combustion occurrence on this, 100k+ will be the damage done instantly. The flat walls will be bowed out, the water wall tubes which are butted up and welded together can be split, refractory walls on the front and rear will have to be replaced, and the boiler will be out of service for several months. Pressure: What causes pressure failures is generally a degradation of the steel due to thermal stress, oxygen pitting, or chemical corrosion. Thermal stress is from a variety of things from firing in high fire without giving sufficient time for the vessel to expand and water to circulate naturally through it, to cold water into a hot boiler, hot water into a cold boiler, etc. All of these lead to cracking. Combined with high pressures it can cause a rupture. Oxygen pitting, is pitting due to oxygen that can no longer be present in the water (once at boiling, oxygen solubility goes to 0), so it latches onto the steel walls. Chemical corrosion can be from excess chemicals used to treat the water being used, so it eats the steel, or carbon dioxide presence in the feedwater causing acidic corrosion. While a small area of any of these will cost a nice bit of money to fix, significant extents of any of these will force the vessel to be condemned. Running it past when it is condemned is a sure way to have a catastrophic failure. Low water: As previously mentioned, if the low water controls fail and the heat cannot be sinked into the water, it is absorbed into the steel which holds a lot less btu/pound/degree, and as the metal heats up, it loses its structural strength. If it is glowing and sinking down, the introduction of water will hit that steel, water will absorb that heat and flash, causing a pressure spike due to the volumetric expansion (1lb of steam takes up 1600 times as much volume as 1 lb of water), this change also causes a brittle condition of the steel due to freezing martensite in the grain of the metal. The firetube mentioned earlier will turn into a rocket in this state, sending itself through block walls, precast, across a few hundred feet of parking lot, throwing its rear door the other way. Poor water can cause similar issues as low water as scale buildup will cause insulation of the fireside from the waterside, leading to increasing fireside heating surface temperatures, causing the following (I love how it's a frowny face): http://i5.photobucket.com/albums/y192/TAKnight/Picture153.jpg At the end of the day though, with modern controls, steel, and codes, you have to do something stupid for these things to blow up. Getting rid of the purge cycle for instance isn't possible on new controls, that went out when the cam drive flame safeguards went out, a few still there, but not too common anymore. Low water controls, people are using transmitters and floats that monitor water level, know when the boiler is running and if the water doesn't move, it assumes that the float is scaled up and shuts the boiler down. Modern parallel positioning sets FGR to 0 during purge to complete the cycle more effectively. Continuous blowdown and monitoring of it by conductivity prevents scaling. Annual fireside and waterside inspections monitor for dangerous conditions developing. Combustion tuneups lessen the chance of combustion explosions. Hope that was informative and interesting lesson on boilers everyone. Great pics. I would love to get in on the real big stuff. Mine are all 1.5mil BTI or less, but that is still really big. 
I absolutely LOVE what I do.... |
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Posted: 4/13/2011 6:23:39 PM EDT
[#16]
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Don;t think some of you are getting this right, this is how it was explaned to me: Boiler runs low on water and boiler plate is exposed and proceeds to glow red hot. At that point water is introduced to red hot boiler plate and violently flashes off producing a large volume of superheated steam at extremely high pressures. The sudden sharp rise in pressure overwhelms the safeties and blows the boiler. We had a steam tractor explode a few years back, killed a couple of people. They said it was low on water and when the tractor went down a small grade,the water ran to one end of the boiler and exposed the boiler plate thus allowing it to get red hot. When the tractor returned to level ground it blew up, because the water ran back over the glowing boiler plate. Do steam locomotives or tractors have strong mechanical water pumps that replenish water as it runs low? I ask because it couldn't be a simple system since as much pressure would be imparted on the 'feed' as is going to the pistons. What he described is the common low water explosion of a modern boiler. Steam locomotives and tractors are a different beast in terms of feedwater, pistons, injectors, or pumps can be used. Just some background, I'm an engineer who works as a boiler controls technician. Lets go over the causes of catastrophic boiler occurrences. They can be broken to three basic categories: combustion, pressure vessel failure, low water. Combustion: You are firing hydrocarbons in an enclosed area with minimal air (typically 3-4% O2 left over from the 20.9 you start with, once you remove the water vapor from the flue gas). If, as a previous poster mentioned, you have a buildup of combustibles in the furnace and it is not purged from the furnace before firing (purge time, there must be pre-firing and post-firing purges in the cycle), you can ignite these with catastrophic results. Lets look at a common boiler, the firetube: http://i5.photobucket.com/albums/y192/TAKnight/rental2.jpg These are some hot water Cleaver-Brooks boilers, they appear to be 60" models (I found the image randomly on google) which covers 125-200 bhp sizes, firing from 5.4 million btu/hr to 8.4 million btu/hr. This is still considered a small boiler, and commonly used in heating applications in smaller apartment communities. If one were to flood this with gas and bypass purge, the baffles will be destroyed, doors potentially blown off, one of this size I know of had its inner door pressed almost perfectly into the outer door (on the front door there is a flat inner door that holds refractory and separates the flue gasses from the incoming combustion air which is in the area between the outer shell of the front door and the inner door)...and this is one of the most resilient designs to that kind of failure. Now...look at the industrial watertube, common to find in medium to large industrial plants, operating between 100 and 500 psi steam pressure (some up to 4200, depending on application). http://i5.photobucket.com/albums/y192/TAKnight/4-boil-7-17-08-mg-d.jpg It is hard to judge size from this picture, but it appears to be on the small end, perhaps 30-60 thousand pounds of steam evaporated per hour. IF you are unlucky enough to have a small combustion occurrence on this, 100k+ will be the damage done instantly. The flat walls will be bowed out, the water wall tubes which are butted up and welded together can be split, refractory walls on the front and rear will have to be replaced, and the boiler will be out of service for several months. Pressure: What causes pressure failures is generally a degradation of the steel due to thermal stress, oxygen pitting, or chemical corrosion. Thermal stress is from a variety of things from firing in high fire without giving sufficient time for the vessel to expand and water to circulate naturally through it, to cold water into a hot boiler, hot water into a cold boiler, etc. All of these lead to cracking. Combined with high pressures it can cause a rupture. Oxygen pitting, is pitting due to oxygen that can no longer be present in the water (once at boiling, oxygen solubility goes to 0), so it latches onto the steel walls. Chemical corrosion can be from excess chemicals used to treat the water being used, so it eats the steel, or carbon dioxide presence in the feedwater causing acidic corrosion. While a small area of any of these will cost a nice bit of money to fix, significant extents of any of these will force the vessel to be condemned. Running it past when it is condemned is a sure way to have a catastrophic failure. Low water: As previously mentioned, if the low water controls fail and the heat cannot be sinked into the water, it is absorbed into the steel which holds a lot less btu/pound/degree, and as the metal heats up, it loses its structural strength. If it is glowing and sinking down, the introduction of water will hit that steel, water will absorb that heat and flash, causing a pressure spike due to the volumetric expansion (1lb of steam takes up 1600 times as much volume as 1 lb of water), this change also causes a brittle condition of the steel due to freezing martensite in the grain of the metal. The firetube mentioned earlier will turn into a rocket in this state, sending itself through block walls, precast, across a few hundred feet of parking lot, throwing its rear door the other way. Poor water can cause similar issues as low water as scale buildup will cause insulation of the fireside from the waterside, leading to increasing fireside heating surface temperatures, causing the following (I love how it's a frowny face): http://i5.photobucket.com/albums/y192/TAKnight/Picture153.jpg At the end of the day though, with modern controls, steel, and codes, you have to do something stupid for these things to blow up. Getting rid of the purge cycle for instance isn't possible on new controls, that went out when the cam drive flame safeguards went out, a few still there, but not too common anymore. Low water controls, people are using transmitters and floats that monitor water level, know when the boiler is running and if the water doesn't move, it assumes that the float is scaled up and shuts the boiler down. Modern parallel positioning sets FGR to 0 during purge to complete the cycle more effectively. Continuous blowdown and monitoring of it by conductivity prevents scaling. Annual fireside and waterside inspections monitor for dangerous conditions developing. Combustion tuneups lessen the chance of combustion explosions. Hope that was informative and interesting lesson on boilers everyone. Great pics. I would love to get in on the real big stuff. Mine are all 1.5mil BTI or less, but that is still really big. http://i868.photobucket.com/albums/ab250/Timcohydronics/DSC00551.jpg http://i868.photobucket.com/albums/ab250/Timcohydronics/DSC00973.jpg http://i868.photobucket.com/albums/ab250/Timcohydronics/DSC00877.jpg http://i868.photobucket.com/albums/ab250/Timcohydronics/P2120319.jpg http://i868.photobucket.com/albums/ab250/Timcohydronics/P1310278.jpg http://i868.photobucket.com/albums/ab250/Timcohydronics/PA120091.jpg I absolutely LOVE what I do.... Is that a Tekmar 9 stage boiler control on the wall? |
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Posted: 4/13/2011 6:28:35 PM EDT
[#17]
Quoted:
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Don;t think some of you are getting this right, this is how it was explaned to me: Boiler runs low on water and boiler plate is exposed and proceeds to glow red hot. At that point water is introduced to red hot boiler plate and violently flashes off producing a large volume of superheated steam at extremely high pressures. The sudden sharp rise in pressure overwhelms the safeties and blows the boiler. We had a steam tractor explode a few years back, killed a couple of people. They said it was low on water and when the tractor went down a small grade,the water ran to one end of the boiler and exposed the boiler plate thus allowing it to get red hot. When the tractor returned to level ground it blew up, because the water ran back over the glowing boiler plate. Do steam locomotives or tractors have strong mechanical water pumps that replenish water as it runs low? I ask because it couldn't be a simple system since as much pressure would be imparted on the 'feed' as is going to the pistons. What he described is the common low water explosion of a modern boiler. Steam locomotives and tractors are a different beast in terms of feedwater, pistons, injectors, or pumps can be used. Just some background, I'm an engineer who works as a boiler controls technician. Lets go over the causes of catastrophic boiler occurrences. They can be broken to three basic categories: combustion, pressure vessel failure, low water. Combustion: You are firing hydrocarbons in an enclosed area with minimal air (typically 3-4% O2 left over from the 20.9 you start with, once you remove the water vapor from the flue gas). If, as a previous poster mentioned, you have a buildup of combustibles in the furnace and it is not purged from the furnace before firing (purge time, there must be pre-firing and post-firing purges in the cycle), you can ignite these with catastrophic results. Lets look at a common boiler, the firetube: http://i5.photobucket.com/albums/y192/TAKnight/rental2.jpg These are some hot water Cleaver-Brooks boilers, they appear to be 60" models (I found the image randomly on google) which covers 125-200 bhp sizes, firing from 5.4 million btu/hr to 8.4 million btu/hr. This is still considered a small boiler, and commonly used in heating applications in smaller apartment communities. If one were to flood this with gas and bypass purge, the baffles will be destroyed, doors potentially blown off, one of this size I know of had its inner door pressed almost perfectly into the outer door (on the front door there is a flat inner door that holds refractory and separates the flue gasses from the incoming combustion air which is in the area between the outer shell of the front door and the inner door)...and this is one of the most resilient designs to that kind of failure. Now...look at the industrial watertube, common to find in medium to large industrial plants, operating between 100 and 500 psi steam pressure (some up to 4200, depending on application). http://i5.photobucket.com/albums/y192/TAKnight/4-boil-7-17-08-mg-d.jpg It is hard to judge size from this picture, but it appears to be on the small end, perhaps 30-60 thousand pounds of steam evaporated per hour. IF you are unlucky enough to have a small combustion occurrence on this, 100k+ will be the damage done instantly. The flat walls will be bowed out, the water wall tubes which are butted up and welded together can be split, refractory walls on the front and rear will have to be replaced, and the boiler will be out of service for several months. Pressure: What causes pressure failures is generally a degradation of the steel due to thermal stress, oxygen pitting, or chemical corrosion. Thermal stress is from a variety of things from firing in high fire without giving sufficient time for the vessel to expand and water to circulate naturally through it, to cold water into a hot boiler, hot water into a cold boiler, etc. All of these lead to cracking. Combined with high pressures it can cause a rupture. Oxygen pitting, is pitting due to oxygen that can no longer be present in the water (once at boiling, oxygen solubility goes to 0), so it latches onto the steel walls. Chemical corrosion can be from excess chemicals used to treat the water being used, so it eats the steel, or carbon dioxide presence in the feedwater causing acidic corrosion. While a small area of any of these will cost a nice bit of money to fix, significant extents of any of these will force the vessel to be condemned. Running it past when it is condemned is a sure way to have a catastrophic failure. Low water: As previously mentioned, if the low water controls fail and the heat cannot be sinked into the water, it is absorbed into the steel which holds a lot less btu/pound/degree, and as the metal heats up, it loses its structural strength. If it is glowing and sinking down, the introduction of water will hit that steel, water will absorb that heat and flash, causing a pressure spike due to the volumetric expansion (1lb of steam takes up 1600 times as much volume as 1 lb of water), this change also causes a brittle condition of the steel due to freezing martensite in the grain of the metal. The firetube mentioned earlier will turn into a rocket in this state, sending itself through block walls, precast, across a few hundred feet of parking lot, throwing its rear door the other way. Poor water can cause similar issues as low water as scale buildup will cause insulation of the fireside from the waterside, leading to increasing fireside heating surface temperatures, causing the following (I love how it's a frowny face): http://i5.photobucket.com/albums/y192/TAKnight/Picture153.jpg At the end of the day though, with modern controls, steel, and codes, you have to do something stupid for these things to blow up. Getting rid of the purge cycle for instance isn't possible on new controls, that went out when the cam drive flame safeguards went out, a few still there, but not too common anymore. Low water controls, people are using transmitters and floats that monitor water level, know when the boiler is running and if the water doesn't move, it assumes that the float is scaled up and shuts the boiler down. Modern parallel positioning sets FGR to 0 during purge to complete the cycle more effectively. Continuous blowdown and monitoring of it by conductivity prevents scaling. Annual fireside and waterside inspections monitor for dangerous conditions developing. Combustion tuneups lessen the chance of combustion explosions. Hope that was informative and interesting lesson on boilers everyone. Great pics. I would love to get in on the real big stuff. Mine are all 1.5mil BTI or less, but that is still really big. http://i868.photobucket.com/albums/ab250/Timcohydronics/DSC00551.jpg http://i868.photobucket.com/albums/ab250/Timcohydronics/DSC00973.jpg http://i868.photobucket.com/albums/ab250/Timcohydronics/DSC00877.jpg http://i868.photobucket.com/albums/ab250/Timcohydronics/P2120319.jpg http://i868.photobucket.com/albums/ab250/Timcohydronics/P1310278.jpg http://i868.photobucket.com/albums/ab250/Timcohydronics/PA120091.jpg I absolutely LOVE what I do.... Is that a Tekmar 9 stage boiler control on the wall? Tekmar, but I forget the model number. Just 2-stage IIRC, but has idle, and WWSD and many cool features. |
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Posted: 4/13/2011 6:31:20 PM EDT
[#18]
I have never seen one blow up in person, but my dad has dealt with the aftermath. This was back in the '80s - same thing that's been described before, water flow got messed up, boiler got red hot, water hit it & flashed to steam instantly. Blew a steel end cap through the reinforced concrete wall, thoroughly destroying everything in its way.
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Posted: 4/13/2011 6:35:12 PM EDT
[#19]
Quoted: Quoted: Quoted: Quoted: Quoted: I've been a boiler Engineer since 1975. I've worked on and operated all kinds of boilers, from high pressure to low pressure. I've seen safety valves that would not lift when they were suppose to. I've seen low water safety valves stuck, boiler still running, and no water inside. I've had high pressure tubes in a water tube boiler firebox blow and rip apart. I've had the end of a waterwall drum blow. ( We let it gush water for 2 days while trying to cool the boiler down.) But by far, what is the most dangerous, and still happens way too much, is somebody bypassing the purge cycle for the firebox. Most all of your explosions today are caused by this. There is a reason most boilerrooms are built away from the main buildings. If the boiler blows up, only the engineers will be killed. ...why would anyone do that? I mean, its so obviously dumb, and I see no upside at all. A purge cycle? Must be a high-efficiency boiler as all others are natural draft and thus always pruging while between heat calls. Please elaborate? I am curious. I think he means when lighting. The burner side goes through a purge before the pilot is lit. I could see maybe a damper not opening when it's supposed to during purge (and an obvious bypass of the open feedback switch) and combustibles still inside, but other than that how does can any modern BMS purge be bypassed? A vent damper has micro switches that will not allow a light off if the damper is not fully opened. All this is controlled by the ignition control module or the boiler's circuit board if equipped. Power burner? yes. natural draft, no. timco, It is clear that the boilers you primarily deal with are atmospheric burners, these don't require any purge, like you said as your natural draft through your draft hood is sufficient. On anything requiring a fan a purge cycle must be used to push out any combustibles. These power burners are used for any of the higher inputs and are pretty much all you'll find after a couple million btu/hr input. Two I saw today for instance utilize 63 million btu/hr in high fire, you can't burn that much gas or oil without the appropriate fan. As the size goes up, the damages from explosions go up. electricsheep, As for why someone would do that...a picture is worth a thousand words...  "Oh shit, I don't have steam, I need to get this relit right now!" "...shit didn't light" *spins cam, bypassing cycle* "...shit didn't light" *spins cam, bypassing cycle* "...shit didn't light" *spins cam, bypassing cycle* "...shit didn't light" *spins cam, bypassing cycle* "...shit didn't light" *spins cam, bypassing cycle* BOOM That's an old control from the 60s that is no longer supported by Honeywell, but you know what they say about old technology, it lasts, and there are a few left. |
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Posted: 4/13/2011 6:35:42 PM EDT
[#20]
Quoted:
I have never seen one blow up in person, but my dad has dealt with the aftermath. This was back in the '80s - same thing that's been described before, water flow got messed up, boiler got red hot, water hit it & flashed to steam instantly. Blew a steel end cap through the reinforced concrete wall, thoroughly destroying everything in its way. Most likely, boiler ran "dry", condensate or make up was pumped in, flashed and boom! 
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Posted: 4/13/2011 6:38:16 PM EDT
[#21]
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I've been a boiler Engineer since 1975. I've worked on and operated all kinds of boilers, from high pressure to low pressure. I've seen safety valves that would not lift when they were suppose to. I've seen low water safety valves stuck, boiler still running, and no water inside. I've had high pressure tubes in a water tube boiler firebox blow and rip apart. I've had the end of a waterwall drum blow. ( We let it gush water for 2 days while trying to cool the boiler down.) But by far, what is the most dangerous, and still happens way too much, is somebody bypassing the purge cycle for the firebox. Most all of your explosions today are caused by this. There is a reason most boilerrooms are built away from the main buildings. If the boiler blows up, only the engineers will be killed. ...why would anyone do that? I mean, its so obviously dumb, and I see no upside at all.
A purge cycle? Must be a high-efficiency boiler as all others are natural draft and thus always pruging while between heat calls. Please elaborate? I am curious. I think he means when lighting. The burner side goes through a purge before the pilot is lit. I could see maybe a damper not opening when it's supposed to during purge (and an obvious bypass of the open feedback switch) and combustibles still inside, but other than that how does can any modern BMS purge be bypassed? A vent damper has micro switches that will not allow a light off if the damper is not fully opened. All this is controlled by the ignition control module or the boiler's circuit board if equipped. Power burner? yes. natural draft, no. timco, It is clear that the boilers you primarily deal with are atmospheric burners, these don't require any purge, like you said as your natural draft through your draft hood is sufficient. On anything requiring a fan a purge cycle must be used to push out any combustibles. These power burners are used for any of the higher inputs and are pretty much all you'll find after a couple million btu/hr input. Two I saw today for instance utilize 63 million btu/hr in high fire, you can't burn that much gas or oil without the appropriate fan. As the size goes up, the damages from explosions go up. electricsheep, As for why someone would do that...a picture is worth a thousand words... http://i5.photobucket.com/albums/y192/TAKnight/r4140.jpg "Oh shit, I don't have steam, I need to get this relit right now!" "...shit didn't light" *spins cam, bypassing cycle* "...shit didn't light" *spins cam, bypassing cycle* "...shit didn't light" *spins cam, bypassing cycle* "...shit didn't light" *spins cam, bypassing cycle* "...shit didn't light" *spins cam, bypassing cycle* BOOM That's an old control from the 60s that is no longer supported by Honeywell, but you know what they say about old technology, it lasts, and there are a few left. My Cleaver Brooks ran one of those, up until 3 years ago. It was replaced by a couple of Lochinvars. I went through a couple of those old hamster tread mills as well as a couple of infared amplifiers before we shit canned her. I made a Jacob's Ladder out of her old 12KV ignition transformer!
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Posted: 4/13/2011 6:42:27 PM EDT
[#22]
We sell and service hot water pressure washers/ steam cleaners.
Over the last 19 years I have seen a half dozen steam explosions. The majority involve people who bypass safety features. The most unusual one was a guy who told me is unit was sitting behind his house for a few weeks and just blew up. I thought "yeah, right dude". Well come to find out that is probably exactly what happened due to ice. It had 3 safety features and one of them was a flow switch that is designed to cut the burner off when the water isn't flowing through it. He took that off to drain the coil to prevent freezing and left it hanging upside down, effectively turning the switch on due to gravity. The switch was also evidently in the on position. The the pressure switch, we surmised activated because of the extreme cold caused a little water in it to freeze and push the plunger up activating it. This all happenrd and the burner kicks on and "boom" the coil explodes. I've seen then knock the burner off the unit and send it flying 50 ft across a shop. I've had them rattle the windows so bad I thought it was going to break them. |
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Posted: 4/13/2011 6:46:25 PM EDT
[#23]
Quoted: Great post! I blown down once a week. My chemical salesman checks my pH once/year. I don't think they've ever done a conductivity analysis. I usually do a wet close too. Bottom blowing once a week (open knife valve, then open slow, close slow, close knife valve, open and close slow, most open the "fast" valve and dump it hard, not the right way, I apologize if you already know this procedure), is what is recommended by ASME for lower pressure steam like at your plant. The same is true of your water columns, however, I would do those daily. As for chemicals, the plants I see with good water quality and no scale at the end of the year have their maintenance check the water quality on a weekly or semi-weekly basis and constantly tweak on the pumps until it's just right. Every month or every couple of months is not enough of a sample size for accurate water control. I would recommend you get with the chemical man about getting a test kit and some test procedures as well as an explanation of which test tells you what. Since you have low pressure and cannot run a deaerator, you will be using a chemical to remove oxygen, it has to be 24ppm or higher to function, so you check it a few times a week and if it's getting low, turn the pump up just a little, if it's getting high, turn it down a little. The difference in results that this gets is just night and day. Conductivity is based on your total dissolved solids and if it gets out of balance (high) you will see foaming/surging and probably trip ALWCO. This is controlled by blowdowns, if it starts getting above 3000, increase frequency/duration of blowdowns, if below 2000 back off on it a little. Watching your makeup water softeners is also important as this is what can cause scaling of the boiler quick, it's a very easy test and if pink instead of blue, there's a problem with your softener. |
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Posted: 4/13/2011 6:57:20 PM EDT
[#24]
Quoted:
Quoted:
Great post! I blown down once a week. My chemical salesman checks my pH once/year. I don't think they've ever done a conductivity analysis. I usually do a wet close too. Bottom blowing once a week (open knife valve, then open slow, close slow, close knife valve, open and close slow, most open the "fast" valve and dump it hard, not the right way, I apologize if you already know this procedure), is what is recommended by ASME for lower pressure steam like at your plant. The same is true of your water columns, however, I would do those daily. As for chemicals, the plants I see with good water quality and no scale at the end of the year have their maintenance check the water quality on a weekly or semi-weekly basis and constantly tweak on the pumps until it's just right. Every month or every couple of months is not enough of a sample size for accurate water control. I would recommend you get with the chemical man about getting a test kit and some test procedures as well as an explanation of which test tells you what. Since you have low pressure and cannot run a deaerator, you will be using a chemical to remove oxygen, it has to be 24ppm or higher to function, so you check it a few times a week and if it's getting low, turn the pump up just a little, if it's getting high, turn it down a little. The difference in results that this gets is just night and day. Conductivity is based on your total dissolved solids and if it gets out of balance (high) you will see foaming/surging and probably trip ALWCO. This is controlled by blowdowns, if it starts getting above 3000, increase frequency/duration of blowdowns, if below 2000 back off on it a little. Watching your makeup water softeners is also important as this is what can cause scaling of the boiler quick, it's a very easy test and if pink instead of blue, there's a problem with your softener. Thanks dude. I dump mine fast and hard. Boiler shuts down and re-fires. I thought that was sufficient? I will do it the way you suggest from now on! 
Believe it or not, we don't soften our water, we used to. I have ran anti-corrosive and anti-sludge chem. My chemical is injected whenever I take on city water. I know we are cutting corners and not doing things "by the book", but the state fire marshall and insurance inspectors pass us, so the administrators give us minimal budget to maintain. |
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Posted: 4/13/2011 6:59:00 PM EDT
[#25]
Quoted: I'm not really sure what a boiler is. But from what i know it seems ineffiecient way to power something. It is a surprisingly efficient way to heat something that needs to be hotter than refrigerant (heat moving) will allow. 99% on a condensing gas heating boiler for instance. High pressure steam is usually low 80s due to the higher temperatures involved, but higher temps are always going to mean lower efficiency. You can still get it up to 95% on high pressure steam if you have all the right requirements and have a system of economizers to recover the heat. 100psi steam is 327 F, your normal feedwater is 227 F, your normal makeup is 60 F, if you coil your feedwater in the stack and use that 327-450 F flue gas to heat that feedwater from 227 to say 240 and bring your stack temp to 275 you get around 85-86% efficiency, put the make up water and get it down so that your water vapor from burning hydrocarbons condenses and you can get to 90%, heat your combustion air with an air to air preheater, and humidify that and you can get to 95. That's a lot of shit on there that costs a lot of money and the last one generally isn't worth the investment, the 2nd one is only worth it if 30% or more of your feedwater is from makeup, the first is almost always worth it. As for POWER, if you're using steam to spin a turbine, your efficiency of your engine increases as your steam temperature increases, but it can only get to 1050 degrees due to limitations of steel. they put it up at sometimes as high as 4200 psi and run it through multiple turbines down to 100 degree F steam in a vacuum to get that last little bit out of it. They heat the feedwater at different stages, sometimes as many as 5-6 times. It's still around 40% efficient at that point, nuclear only 33% or so, but it really can't get much higher. The best performing diesel engines for instance run at 55% or so, and that would not be effective for mass production of power due to wear on the components. Heat engines have a lot of limitations, but electricity wouldn't exist otherwise. |
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Posted: 4/13/2011 7:03:07 PM EDT
[#26]
Quoted:
Quoted:
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Great post! I blown down once a week. My chemical salesman checks my pH once/year. I don't think they've ever done a conductivity analysis. I usually do a wet close too. Bottom blowing once a week (open knife valve, then open slow, close slow, close knife valve, open and close slow, most open the "fast" valve and dump it hard, not the right way, I apologize if you already know this procedure), is what is recommended by ASME for lower pressure steam like at your plant. The same is true of your water columns, however, I would do those daily. As for chemicals, the plants I see with good water quality and no scale at the end of the year have their maintenance check the water quality on a weekly or semi-weekly basis and constantly tweak on the pumps until it's just right. Every month or every couple of months is not enough of a sample size for accurate water control. I would recommend you get with the chemical man about getting a test kit and some test procedures as well as an explanation of which test tells you what. Since you have low pressure and cannot run a deaerator, you will be using a chemical to remove oxygen, it has to be 24ppm or higher to function, so you check it a few times a week and if it's getting low, turn the pump up just a little, if it's getting high, turn it down a little. The difference in results that this gets is just night and day. Conductivity is based on your total dissolved solids and if it gets out of balance (high) you will see foaming/surging and probably trip ALWCO. This is controlled by blowdowns, if it starts getting above 3000, increase frequency/duration of blowdowns, if below 2000 back off on it a little. Watching your makeup water softeners is also important as this is what can cause scaling of the boiler quick, it's a very easy test and if pink instead of blue, there's a problem with your softener. Thanks dude. I dump mine fast and hard. Boiler shuts down and re-fires. I thought that was sufficient? I will do it the way you suggest from now on!
Believe it or not, we don't soften our water, we used to. I have ran anti-corrosive and anti-sludge chem. My chemical is injected whenever I take on city water. I know we are cutting corners and not doing things "by the book", but the state fire marshall and insurance inspectors pass us, so the administrators give us minimal budget to maintain. He is talking about blowing down the boiler itself. You are describing blowing down the low water cut off. That can be opened fast no problem. Fresh water with oxygen is the enemy. My boiler reps say not to soften as the cast iron wants the minerals. |
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Posted: 4/13/2011 7:06:47 PM EDT
[#27]
Quoted:
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Great post! I blown down once a week. My chemical salesman checks my pH once/year. I don't think they've ever done a conductivity analysis. I usually do a wet close too. Bottom blowing once a week (open knife valve, then open slow, close slow, close knife valve, open and close slow, most open the "fast" valve and dump it hard, not the right way, I apologize if you already know this procedure), is what is recommended by ASME for lower pressure steam like at your plant. The same is true of your water columns, however, I would do those daily. As for chemicals, the plants I see with good water quality and no scale at the end of the year have their maintenance check the water quality on a weekly or semi-weekly basis and constantly tweak on the pumps until it's just right. Every month or every couple of months is not enough of a sample size for accurate water control. I would recommend you get with the chemical man about getting a test kit and some test procedures as well as an explanation of which test tells you what. Since you have low pressure and cannot run a deaerator, you will be using a chemical to remove oxygen, it has to be 24ppm or higher to function, so you check it a few times a week and if it's getting low, turn the pump up just a little, if it's getting high, turn it down a little. The difference in results that this gets is just night and day. Conductivity is based on your total dissolved solids and if it gets out of balance (high) you will see foaming/surging and probably trip ALWCO. This is controlled by blowdowns, if it starts getting above 3000, increase frequency/duration of blowdowns, if below 2000 back off on it a little. Watching your makeup water softeners is also important as this is what can cause scaling of the boiler quick, it's a very easy test and if pink instead of blue, there's a problem with your softener. Thanks dude. I dump mine fast and hard. Boiler shuts down and re-fires. I thought that was sufficient? I will do it the way you suggest from now on!
Believe it or not, we don't soften our water, we used to. I have ran anti-corrosive and anti-sludge chem. My chemical is injected whenever I take on city water. I know we are cutting corners and not doing things "by the book", but the state fire marshall and insurance inspectors pass us, so the administrators give us minimal budget to maintain. He is talking about blowing down the boiler itself. You are describing blowing down the low water cut off. That can be opened fast no problem. Fresh water with oxygen is the enemy. My boiler reps say not to soften as the cast iron wants the minerals. Ah, my bad. When dumping the lower valves, I have always done that fast too. When the water runs clear, I close it. Thanks for clarifying! |
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Posted: 4/13/2011 7:12:42 PM EDT
[#28]
Quoted: Quoted: Quoted: Quoted: Great post! I blown down once a week. My chemical salesman checks my pH once/year. I don't think they've ever done a conductivity analysis. I usually do a wet close too. Bottom blowing once a week (open knife valve, then open slow, close slow, close knife valve, open and close slow, most open the "fast" valve and dump it hard, not the right way, I apologize if you already know this procedure), is what is recommended by ASME for lower pressure steam like at your plant. The same is true of your water columns, however, I would do those daily. As for chemicals, the plants I see with good water quality and no scale at the end of the year have their maintenance check the water quality on a weekly or semi-weekly basis and constantly tweak on the pumps until it's just right. Every month or every couple of months is not enough of a sample size for accurate water control. I would recommend you get with the chemical man about getting a test kit and some test procedures as well as an explanation of which test tells you what. Since you have low pressure and cannot run a deaerator, you will be using a chemical to remove oxygen, it has to be 24ppm or higher to function, so you check it a few times a week and if it's getting low, turn the pump up just a little, if it's getting high, turn it down a little. The difference in results that this gets is just night and day. Conductivity is based on your total dissolved solids and if it gets out of balance (high) you will see foaming/surging and probably trip ALWCO. This is controlled by blowdowns, if it starts getting above 3000, increase frequency/duration of blowdowns, if below 2000 back off on it a little. Watching your makeup water softeners is also important as this is what can cause scaling of the boiler quick, it's a very easy test and if pink instead of blue, there's a problem with your softener. Thanks dude. I dump mine fast and hard. Boiler shuts down and re-fires. I thought that was sufficient? I will do it the way you suggest from now on! Believe it or not, we don't soften our water, we used to. I have ran anti-corrosive and anti-sludge chem. My chemical is injected whenever I take on city water. I know we are cutting corners and not doing things "by the book", but the state fire marshall and insurance inspectors pass us, so the administrators give us minimal budget to maintain. He is talking about blowing down the boiler itself. You are describing blowing down the low water cut off. That can be opened fast no problem. Fresh water with oxygen is the enemy. My boiler reps say not to soften as the cast iron wants the minerals. On blow downs, yes. There are generally two valves at the bottom, one that's a knife type valve and one that's a slow wheel opening valve. This is not necessarily how yours is piped in as low pressure follows different requirements, but the principle of allowing the bottom blowdown to start and end slowly still applies, this allows the pipes to heat up and won't kick sludge back into the middle of the boiler as water rushes toward the drain opening. On LWCO, yes, just cranking it open is generally fine, but I still do it a little slow. Not common for a float to flatten, but I've seen it happen. As for soft water on cast iron... I haven't heard that, but I don't generally work on cast iron units, I generally don't work on low pressure steam either, I'm primarily involved with high pressure steam in plants running 100-125 psi. Soft water will increase your ph which is a barrier against corrosion from carbonic acid though, and any scale on the heating surface will decrease efficiency and increase thermal stress on the heating surface. |
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Posted: 4/13/2011 7:17:03 PM EDT
[#29]
In for the stories. I just fired up a boiler at work that has been idle for a few months so the controls guy could so his thing, changing over to a new control system. I made sure to get it up to pressure before opening it up to the steam header. That water hammer shit scared the shit out of me the first time I heard it. It's a nice reminder that you are messing with shit that could really fuck you up.
Glad to see the water chemistry discussion. We take it pretty seriously now. I've had to replace a bunch of stuff due to previous chemistry problems. I couldn't believe that a bronze actuator could could get so pitted in a few years.
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Posted: 4/13/2011 7:25:08 PM EDT
[#30]
Quoted:
Quoted:
Quoted:
Quoted:
Quoted:
Great post! I blown down once a week. My chemical salesman checks my pH once/year. I don't think they've ever done a conductivity analysis. I usually do a wet close too. Bottom blowing once a week (open knife valve, then open slow, close slow, close knife valve, open and close slow, most open the "fast" valve and dump it hard, not the right way, I apologize if you already know this procedure), is what is recommended by ASME for lower pressure steam like at your plant. The same is true of your water columns, however, I would do those daily. As for chemicals, the plants I see with good water quality and no scale at the end of the year have their maintenance check the water quality on a weekly or semi-weekly basis and constantly tweak on the pumps until it's just right. Every month or every couple of months is not enough of a sample size for accurate water control. I would recommend you get with the chemical man about getting a test kit and some test procedures as well as an explanation of which test tells you what. Since you have low pressure and cannot run a deaerator, you will be using a chemical to remove oxygen, it has to be 24ppm or higher to function, so you check it a few times a week and if it's getting low, turn the pump up just a little, if it's getting high, turn it down a little. The difference in results that this gets is just night and day. Conductivity is based on your total dissolved solids and if it gets out of balance (high) you will see foaming/surging and probably trip ALWCO. This is controlled by blowdowns, if it starts getting above 3000, increase frequency/duration of blowdowns, if below 2000 back off on it a little. Watching your makeup water softeners is also important as this is what can cause scaling of the boiler quick, it's a very easy test and if pink instead of blue, there's a problem with your softener. Thanks dude. I dump mine fast and hard. Boiler shuts down and re-fires. I thought that was sufficient? I will do it the way you suggest from now on!
Believe it or not, we don't soften our water, we used to. I have ran anti-corrosive and anti-sludge chem. My chemical is injected whenever I take on city water. I know we are cutting corners and not doing things "by the book", but the state fire marshall and insurance inspectors pass us, so the administrators give us minimal budget to maintain. He is talking about blowing down the boiler itself. You are describing blowing down the low water cut off. That can be opened fast no problem. Fresh water with oxygen is the enemy. My boiler reps say not to soften as the cast iron wants the minerals. On blow downs, yes. There are generally two valves at the bottom, one that's a knife type valve and one that's a slow wheel opening valve. This is not necessarily how yours is piped in as low pressure follows different requirements, but the principle of allowing the bottom blowdown to start and end slowly still applies, this allows the pipes to heat up and won't kick sludge back into the middle of the boiler as water rushes toward the drain opening. On LWCO, yes, just cranking it open is generally fine, but I still do it a little slow. Not common for a float to flatten, but I've seen it happen. As for soft water on cast iron... I haven't heard that, but I don't generally work on cast iron units, I generally don't work on low pressure steam either, I'm primarily involved with high pressure steam in plants running 100-125 psi. Soft water will increase your ph which is a barrier against corrosion from carbonic acid though, and any scale on the heating surface will decrease efficiency and increase thermal stress on the heating surface. I'm going from memory right now (and a couple of drinks  ) but I think all I have on the bottom of mine are ball valves. I also run my steam boilers in tandem, by that, I mean that they are not isolated. The head and pressure are the same in both no matter which one is running. What is your opinion of that? It is acceptable practice, right? What situation (if any, besides major problems) would call for isolating them? My hydronics are set up on an automatic lead-lag configuration.
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Posted: 4/13/2011 7:26:10 PM EDT
[#31]
We had a water heater at an elementary school explode about 30 years ago. Killed a bunch of kids and a teacher.
http://www.esmagazine.com/Articles/Feature_Article/8b110b674dda8010VgnVCM100000f932a8c0____ "It was shortly after noon in the busy cafeteria. Children were seated at tables, enjoying lunch when a concrete wall, which separated the lunchroom from the kitchen, blew in. An 80-gallon water heater had exploded and launched itself skyward. The children seated nearest the wall were crushed and killed as concrete and steel were propelled from the epicenter of the blast. It was a horrific scene. In all, seven were killed and 36 lay injured." |
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Posted: 4/13/2011 7:30:17 PM EDT
[#32]
Quoted: In for the stories. I just fired up a boiler at work that has been idle for a few months so the controls guy could so his thing, changing over to a new control system. I made sure to get it up to pressure before opening it up to the steam header. That water hammer shit scared the shit out of me the first time I heard it. It's a nice reminder that you are messing with shit that could really fuck you up. Glad to see the water chemistry discussion. We take it pretty seriously now. I've had to replace a bunch of stuff due to previous chemistry problems. I couldn't believe that a bronze actuator could could get so pitted in a few years. At a major food producer, has a 60kpph watertube that went down due to controls being 20 years old and completely fried. They had been told for years to upgrade them and if they did not, it would go down at the least opportune time. While attempting to fix the problem the controls LCD displays flashed all on, then all off as the boiler rumbled violently down to low fire. went from 125 psi to 15 psi quickly and without the continued evaporation of water, the condensate came back and didn't get called to go into the boiler and flooded the surge tank and eventually the boiler as the feedwater valve control was one that went out. Shut down unit as production is screaming, operator comes over and fires unit with it flooded into the header. 24" steam header goes 1 foot each way side to side shaking insulation everywhere. Started up a surge tank with a sparge-tube injected steam heater (pipe with holes in it at the bottom of the tank to warm the water). Vented tank we just open the steam strait to it, BANG BANG BANG as the construction foreman backs away.. Another plant I asked them to start their back up, they hadn't run it in 2 months, flooded header, steam drum, they start opening the valve before even turning the boiler on, that condensed water in the line starts hammering and I point out it's hammering badly and walk outside. He gets the point and asks what I would do as the change over only happens when one boiler has failed and the other needs to be started. Fired unit up warmed it up and slowly opened up to the system once near header pressure. |
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Posted: 4/13/2011 7:32:48 PM EDT
[#33]
Quoted:
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Great post! I blown down once a week. My chemical salesman checks my pH once/year. I don't think they've ever done a conductivity analysis. I usually do a wet close too. Bottom blowing once a week (open knife valve, then open slow, close slow, close knife valve, open and close slow, most open the "fast" valve and dump it hard, not the right way, I apologize if you already know this procedure), is what is recommended by ASME for lower pressure steam like at your plant. The same is true of your water columns, however, I would do those daily. As for chemicals, the plants I see with good water quality and no scale at the end of the year have their maintenance check the water quality on a weekly or semi-weekly basis and constantly tweak on the pumps until it's just right. Every month or every couple of months is not enough of a sample size for accurate water control. I would recommend you get with the chemical man about getting a test kit and some test procedures as well as an explanation of which test tells you what. Since you have low pressure and cannot run a deaerator, you will be using a chemical to remove oxygen, it has to be 24ppm or higher to function, so you check it a few times a week and if it's getting low, turn the pump up just a little, if it's getting high, turn it down a little. The difference in results that this gets is just night and day. Conductivity is based on your total dissolved solids and if it gets out of balance (high) you will see foaming/surging and probably trip ALWCO. This is controlled by blowdowns, if it starts getting above 3000, increase frequency/duration of blowdowns, if below 2000 back off on it a little. Watching your makeup water softeners is also important as this is what can cause scaling of the boiler quick, it's a very easy test and if pink instead of blue, there's a problem with your softener. Thanks dude. I dump mine fast and hard. Boiler shuts down and re-fires. I thought that was sufficient? I will do it the way you suggest from now on!
Believe it or not, we don't soften our water, we used to. I have ran anti-corrosive and anti-sludge chem. My chemical is injected whenever I take on city water. I know we are cutting corners and not doing things "by the book", but the state fire marshall and insurance inspectors pass us, so the administrators give us minimal budget to maintain. He is talking about blowing down the boiler itself. You are describing blowing down the low water cut off. That can be opened fast no problem. Fresh water with oxygen is the enemy. My boiler reps say not to soften as the cast iron wants the minerals. On blow downs, yes. There are generally two valves at the bottom, one that's a knife type valve and one that's a slow wheel opening valve. This is not necessarily how yours is piped in as low pressure follows different requirements, but the principle of allowing the bottom blowdown to start and end slowly still applies, this allows the pipes to heat up and won't kick sludge back into the middle of the boiler as water rushes toward the drain opening. On LWCO, yes, just cranking it open is generally fine, but I still do it a little slow. Not common for a float to flatten, but I've seen it happen. As for soft water on cast iron... I haven't heard that, but I don't generally work on cast iron units, I generally don't work on low pressure steam either, I'm primarily involved with high pressure steam in plants running 100-125 psi. Soft water will increase your ph which is a barrier against corrosion from carbonic acid though, and any scale on the heating surface will decrease efficiency and increase thermal stress on the heating surface. I'm going from memory right now (and a couple of drinks ) but I think all I have on the bottom of mine are ball valves. I also run my steam boilers in tandem, by that, I mean that they are not isolated. The head and pressure are the same in both no matter which one is running. What is your opinion of that? It is acceptable practice, right? What situation (if any, besides major problems) would call for isolating them?I have never isolated a boiler. Even if you do get that old, crusty gate valve closed it won't hold pressure to test the block. To test a boiler, I flood a cold boiler and look for leaks. As for running them together, that is fine but when I have 2 or more boilers serving the same header, I drop one off before the other to save $$. If both are needed it will take some time to get to pressure. If both are not needed (shoulder seasons, oversized boilers) when one drops off close to ideal pressure, the other will take it to your pressure setting or it will drop until #2 fires back up. I do this with 3 sitting side by side, saves $ and works well. Water hammer is a sign of something wrong. Steam passing water, bad slope, bad traps, too high pressure, no main insulation, and so on... |
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Posted: 4/13/2011 7:34:32 PM EDT
[#34]
Quoted: Quoted: Quoted: Quoted: Quoted: Quoted: Great post! I blown down once a week. My chemical salesman checks my pH once/year. I don't think they've ever done a conductivity analysis. I usually do a wet close too. Bottom blowing once a week (open knife valve, then open slow, close slow, close knife valve, open and close slow, most open the "fast" valve and dump it hard, not the right way, I apologize if you already know this procedure), is what is recommended by ASME for lower pressure steam like at your plant. The same is true of your water columns, however, I would do those daily. As for chemicals, the plants I see with good water quality and no scale at the end of the year have their maintenance check the water quality on a weekly or semi-weekly basis and constantly tweak on the pumps until it's just right. Every month or every couple of months is not enough of a sample size for accurate water control. I would recommend you get with the chemical man about getting a test kit and some test procedures as well as an explanation of which test tells you what. Since you have low pressure and cannot run a deaerator, you will be using a chemical to remove oxygen, it has to be 24ppm or higher to function, so you check it a few times a week and if it's getting low, turn the pump up just a little, if it's getting high, turn it down a little. The difference in results that this gets is just night and day. Conductivity is based on your total dissolved solids and if it gets out of balance (high) you will see foaming/surging and probably trip ALWCO. This is controlled by blowdowns, if it starts getting above 3000, increase frequency/duration of blowdowns, if below 2000 back off on it a little. Watching your makeup water softeners is also important as this is what can cause scaling of the boiler quick, it's a very easy test and if pink instead of blue, there's a problem with your softener. Thanks dude. I dump mine fast and hard. Boiler shuts down and re-fires. I thought that was sufficient? I will do it the way you suggest from now on! Believe it or not, we don't soften our water, we used to. I have ran anti-corrosive and anti-sludge chem. My chemical is injected whenever I take on city water. I know we are cutting corners and not doing things "by the book", but the state fire marshall and insurance inspectors pass us, so the administrators give us minimal budget to maintain. He is talking about blowing down the boiler itself. You are describing blowing down the low water cut off. That can be opened fast no problem. Fresh water with oxygen is the enemy. My boiler reps say not to soften as the cast iron wants the minerals. On blow downs, yes. There are generally two valves at the bottom, one that's a knife type valve and one that's a slow wheel opening valve. This is not necessarily how yours is piped in as low pressure follows different requirements, but the principle of allowing the bottom blowdown to start and end slowly still applies, this allows the pipes to heat up and won't kick sludge back into the middle of the boiler as water rushes toward the drain opening. On LWCO, yes, just cranking it open is generally fine, but I still do it a little slow. Not common for a float to flatten, but I've seen it happen. As for soft water on cast iron... I haven't heard that, but I don't generally work on cast iron units, I generally don't work on low pressure steam either, I'm primarily involved with high pressure steam in plants running 100-125 psi. Soft water will increase your ph which is a barrier against corrosion from carbonic acid though, and any scale on the heating surface will decrease efficiency and increase thermal stress on the heating surface. I'm going from memory right now (and a couple of drinks ) but I think all I have on the bottom of mine are ball valves. I also run my steam boilers in tandem, by that, I mean that they are not isolated. The head and pressure are the same in both no matter which one is running. What is your opinion of that? It is acceptable practice, right? What situation (if any, besides major problems) would call for isolating them?It's ok as long as you're not overfilling your offline boiler, which you may well be, see water hammer stories for why that's bad. If you have no manway in the boiler you can get away with less isolation than if you had a manway. Whenever you start one up cold, if it modulates, keep it in low until it's warm then bring it up a little more, then a little more and let it run after that. |
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Posted: 4/13/2011 7:36:35 PM EDT
[#35]
Quoted: We had a water heater at an elementary school explode about 30 years ago. Killed a bunch of kids and a teacher. http://www.esmagazine.com/Articles/Feature_Article/8b110b674dda8010VgnVCM100000f932a8c0____ "It was shortly after noon in the busy cafeteria. Children were seated at tables, enjoying lunch when a concrete wall, which separated the lunchroom from the kitchen, blew in. An 80-gallon water heater had exploded and launched itself skyward. The children seated nearest the wall were crushed and killed as concrete and steel were propelled from the epicenter of the blast. It was a horrific scene. In all, seven were killed and 36 lay injured." Anytime water exists above 212 degrees F, there is the potential for catastrophic damage, and it must be treated with respect. |
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Posted: 4/13/2011 7:41:50 PM EDT
[#36]
Quoted:
Quoted:
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Great post! I blown down once a week. My chemical salesman checks my pH once/year. I don't think they've ever done a conductivity analysis. I usually do a wet close too. Bottom blowing once a week (open knife valve, then open slow, close slow, close knife valve, open and close slow, most open the "fast" valve and dump it hard, not the right way, I apologize if you already know this procedure), is what is recommended by ASME for lower pressure steam like at your plant. The same is true of your water columns, however, I would do those daily. As for chemicals, the plants I see with good water quality and no scale at the end of the year have their maintenance check the water quality on a weekly or semi-weekly basis and constantly tweak on the pumps until it's just right. Every month or every couple of months is not enough of a sample size for accurate water control. I would recommend you get with the chemical man about getting a test kit and some test procedures as well as an explanation of which test tells you what. Since you have low pressure and cannot run a deaerator, you will be using a chemical to remove oxygen, it has to be 24ppm or higher to function, so you check it a few times a week and if it's getting low, turn the pump up just a little, if it's getting high, turn it down a little. The difference in results that this gets is just night and day. Conductivity is based on your total dissolved solids and if it gets out of balance (high) you will see foaming/surging and probably trip ALWCO. This is controlled by blowdowns, if it starts getting above 3000, increase frequency/duration of blowdowns, if below 2000 back off on it a little. Watching your makeup water softeners is also important as this is what can cause scaling of the boiler quick, it's a very easy test and if pink instead of blue, there's a problem with your softener. Thanks dude. I dump mine fast and hard. Boiler shuts down and re-fires. I thought that was sufficient? I will do it the way you suggest from now on!
Believe it or not, we don't soften our water, we used to. I have ran anti-corrosive and anti-sludge chem. My chemical is injected whenever I take on city water. I know we are cutting corners and not doing things "by the book", but the state fire marshall and insurance inspectors pass us, so the administrators give us minimal budget to maintain. He is talking about blowing down the boiler itself. You are describing blowing down the low water cut off. That can be opened fast no problem. Fresh water with oxygen is the enemy. My boiler reps say not to soften as the cast iron wants the minerals. On blow downs, yes. There are generally two valves at the bottom, one that's a knife type valve and one that's a slow wheel opening valve. This is not necessarily how yours is piped in as low pressure follows different requirements, but the principle of allowing the bottom blowdown to start and end slowly still applies, this allows the pipes to heat up and won't kick sludge back into the middle of the boiler as water rushes toward the drain opening. On LWCO, yes, just cranking it open is generally fine, but I still do it a little slow. Not common for a float to flatten, but I've seen it happen. As for soft water on cast iron... I haven't heard that, but I don't generally work on cast iron units, I generally don't work on low pressure steam either, I'm primarily involved with high pressure steam in plants running 100-125 psi. Soft water will increase your ph which is a barrier against corrosion from carbonic acid though, and any scale on the heating surface will decrease efficiency and increase thermal stress on the heating surface. I'm going from memory right now (and a couple of drinks ) but I think all I have on the bottom of mine are ball valves. I also run my steam boilers in tandem, by that, I mean that they are not isolated. The head and pressure are the same in both no matter which one is running. What is your opinion of that? It is acceptable practice, right? What situation (if any, besides major problems) would call for isolating them?It's ok as long as you're not overfilling your offline boiler, which you may well be, see water hammer stories for why that's bad. If you have no manway in the boiler you can get away with less isolation than if you had a manway. Whenever you start one up cold, if it modulates, keep it in low until it's warm then bring it up a little more, then a little more and let it run after that. LWCO doubles as a pump control. Everytime I look at the sight glass on each, they appear to be about the same. Both tend to run just a few inches above the min. water line. |
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Posted: 4/13/2011 7:44:51 PM EDT
[#37]
Quoted:
Quoted:
Quoted:
Quoted:
Quoted:
Quoted:
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Great post! I blown down once a week. My chemical salesman checks my pH once/year. I don't think they've ever done a conductivity analysis. I usually do a wet close too. Bottom blowing once a week (open knife valve, then open slow, close slow, close knife valve, open and close slow, most open the "fast" valve and dump it hard, not the right way, I apologize if you already know this procedure), is what is recommended by ASME for lower pressure steam like at your plant. The same is true of your water columns, however, I would do those daily. As for chemicals, the plants I see with good water quality and no scale at the end of the year have their maintenance check the water quality on a weekly or semi-weekly basis and constantly tweak on the pumps until it's just right. Every month or every couple of months is not enough of a sample size for accurate water control. I would recommend you get with the chemical man about getting a test kit and some test procedures as well as an explanation of which test tells you what. Since you have low pressure and cannot run a deaerator, you will be using a chemical to remove oxygen, it has to be 24ppm or higher to function, so you check it a few times a week and if it's getting low, turn the pump up just a little, if it's getting high, turn it down a little. The difference in results that this gets is just night and day. Conductivity is based on your total dissolved solids and if it gets out of balance (high) you will see foaming/surging and probably trip ALWCO. This is controlled by blowdowns, if it starts getting above 3000, increase frequency/duration of blowdowns, if below 2000 back off on it a little. Watching your makeup water softeners is also important as this is what can cause scaling of the boiler quick, it's a very easy test and if pink instead of blue, there's a problem with your softener. Thanks dude. I dump mine fast and hard. Boiler shuts down and re-fires. I thought that was sufficient? I will do it the way you suggest from now on!
Believe it or not, we don't soften our water, we used to. I have ran anti-corrosive and anti-sludge chem. My chemical is injected whenever I take on city water. I know we are cutting corners and not doing things "by the book", but the state fire marshall and insurance inspectors pass us, so the administrators give us minimal budget to maintain. He is talking about blowing down the boiler itself. You are describing blowing down the low water cut off. That can be opened fast no problem. Fresh water with oxygen is the enemy. My boiler reps say not to soften as the cast iron wants the minerals. On blow downs, yes. There are generally two valves at the bottom, one that's a knife type valve and one that's a slow wheel opening valve. This is not necessarily how yours is piped in as low pressure follows different requirements, but the principle of allowing the bottom blowdown to start and end slowly still applies, this allows the pipes to heat up and won't kick sludge back into the middle of the boiler as water rushes toward the drain opening. On LWCO, yes, just cranking it open is generally fine, but I still do it a little slow. Not common for a float to flatten, but I've seen it happen. As for soft water on cast iron... I haven't heard that, but I don't generally work on cast iron units, I generally don't work on low pressure steam either, I'm primarily involved with high pressure steam in plants running 100-125 psi. Soft water will increase your ph which is a barrier against corrosion from carbonic acid though, and any scale on the heating surface will decrease efficiency and increase thermal stress on the heating surface. I'm going from memory right now (and a couple of drinks ) but I think all I have on the bottom of mine are ball valves. I also run my steam boilers in tandem, by that, I mean that they are not isolated. The head and pressure are the same in both no matter which one is running. What is your opinion of that? It is acceptable practice, right? What situation (if any, besides major problems) would call for isolating them?It's ok as long as you're not overfilling your offline boiler, which you may well be, see water hammer stories for why that's bad. If you have no manway in the boiler you can get away with less isolation than if you had a manway. Whenever you start one up cold, if it modulates, keep it in low until it's warm then bring it up a little more, then a little more and let it run after that. LWCO doubles as a pump control. Everytime I look at the sight glass on each, they appear to be about the same. Both tend to run just a few inches above the min. water line. Does the water prime or surge (bounce) in the sight glass? should be steady with some movement. I pipe simple swing check valves on the returns of my steamers that sit next to each other so there is no pressure from the boiler that is firing getting into the one that I dropped off. |
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Posted: 4/13/2011 7:49:17 PM EDT
[#38]
Quoted: LWCO doubles as a pump control. Everytime I look at the sight glass on each, they appear to be about the same. Both tend to run just a few inches above the min. water line. If there is not a working non-return valve in the line, the steam will slowly travel into the offline boiler, condense and overfill. It is more common for this in addition to a slightly leaking modulating feedwater valve to cause the offline boiler to overfill, but is still something to look for. Always fire one up cold in manual low fire, and then slowly bring it up a little at a time in firing rate. If you have an automatic hot standby via a temp sensor and thermostat, or a temperature switch in the water side of the boiler that cuts the modulation circuit, that would be beneficial to use. |
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Posted: 4/13/2011 7:49:39 PM EDT
[#39]
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Great post! I blown down once a week. My chemical salesman checks my pH once/year. I don't think they've ever done a conductivity analysis. I usually do a wet close too. Bottom blowing once a week (open knife valve, then open slow, close slow, close knife valve, open and close slow, most open the "fast" valve and dump it hard, not the right way, I apologize if you already know this procedure), is what is recommended by ASME for lower pressure steam like at your plant. The same is true of your water columns, however, I would do those daily. As for chemicals, the plants I see with good water quality and no scale at the end of the year have their maintenance check the water quality on a weekly or semi-weekly basis and constantly tweak on the pumps until it's just right. Every month or every couple of months is not enough of a sample size for accurate water control. I would recommend you get with the chemical man about getting a test kit and some test procedures as well as an explanation of which test tells you what. Since you have low pressure and cannot run a deaerator, you will be using a chemical to remove oxygen, it has to be 24ppm or higher to function, so you check it a few times a week and if it's getting low, turn the pump up just a little, if it's getting high, turn it down a little. The difference in results that this gets is just night and day. Conductivity is based on your total dissolved solids and if it gets out of balance (high) you will see foaming/surging and probably trip ALWCO. This is controlled by blowdowns, if it starts getting above 3000, increase frequency/duration of blowdowns, if below 2000 back off on it a little. Watching your makeup water softeners is also important as this is what can cause scaling of the boiler quick, it's a very easy test and if pink instead of blue, there's a problem with your softener. Thanks dude. I dump mine fast and hard. Boiler shuts down and re-fires. I thought that was sufficient? I will do it the way you suggest from now on!
Believe it or not, we don't soften our water, we used to. I have ran anti-corrosive and anti-sludge chem. My chemical is injected whenever I take on city water. I know we are cutting corners and not doing things "by the book", but the state fire marshall and insurance inspectors pass us, so the administrators give us minimal budget to maintain. He is talking about blowing down the boiler itself. You are describing blowing down the low water cut off. That can be opened fast no problem. Fresh water with oxygen is the enemy. My boiler reps say not to soften as the cast iron wants the minerals. On blow downs, yes. There are generally two valves at the bottom, one that's a knife type valve and one that's a slow wheel opening valve. This is not necessarily how yours is piped in as low pressure follows different requirements, but the principle of allowing the bottom blowdown to start and end slowly still applies, this allows the pipes to heat up and won't kick sludge back into the middle of the boiler as water rushes toward the drain opening. On LWCO, yes, just cranking it open is generally fine, but I still do it a little slow. Not common for a float to flatten, but I've seen it happen. As for soft water on cast iron... I haven't heard that, but I don't generally work on cast iron units, I generally don't work on low pressure steam either, I'm primarily involved with high pressure steam in plants running 100-125 psi. Soft water will increase your ph which is a barrier against corrosion from carbonic acid though, and any scale on the heating surface will decrease efficiency and increase thermal stress on the heating surface. I'm going from memory right now (and a couple of drinks ) but I think all I have on the bottom of mine are ball valves. I also run my steam boilers in tandem, by that, I mean that they are not isolated. The head and pressure are the same in both no matter which one is running. What is your opinion of that? It is acceptable practice, right? What situation (if any, besides major problems) would call for isolating them?It's ok as long as you're not overfilling your offline boiler, which you may well be, see water hammer stories for why that's bad. If you have no manway in the boiler you can get away with less isolation than if you had a manway. Whenever you start one up cold, if it modulates, keep it in low until it's warm then bring it up a little more, then a little more and let it run after that. LWCO doubles as a pump control. Everytime I look at the sight glass on each, they appear to be about the same. Both tend to run just a few inches above the min. water line. Does the water prime or surge (bounce) in the sight glass? should be steady with some movement. I pipe simple swing check valves on the returns of my steamers that sit next to each other so there is no pressure from the boiler that is firing getting into the one that I dropped off. I don't notice any "surge" in my glass. I have a condesate pit, it pumps into a holding tank. The holding tank has dual pumps, each one has it's own check valve. |
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Posted: 4/13/2011 7:53:01 PM EDT
[#40]
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Great post! I blown down once a week. My chemical salesman checks my pH once/year. I don't think they've ever done a conductivity analysis. I usually do a wet close too. Bottom blowing once a week (open knife valve, then open slow, close slow, close knife valve, open and close slow, most open the "fast" valve and dump it hard, not the right way, I apologize if you already know this procedure), is what is recommended by ASME for lower pressure steam like at your plant. The same is true of your water columns, however, I would do those daily. As for chemicals, the plants I see with good water quality and no scale at the end of the year have their maintenance check the water quality on a weekly or semi-weekly basis and constantly tweak on the pumps until it's just right. Every month or every couple of months is not enough of a sample size for accurate water control. I would recommend you get with the chemical man about getting a test kit and some test procedures as well as an explanation of which test tells you what. Since you have low pressure and cannot run a deaerator, you will be using a chemical to remove oxygen, it has to be 24ppm or higher to function, so you check it a few times a week and if it's getting low, turn the pump up just a little, if it's getting high, turn it down a little. The difference in results that this gets is just night and day. Conductivity is based on your total dissolved solids and if it gets out of balance (high) you will see foaming/surging and probably trip ALWCO. This is controlled by blowdowns, if it starts getting above 3000, increase frequency/duration of blowdowns, if below 2000 back off on it a little. Watching your makeup water softeners is also important as this is what can cause scaling of the boiler quick, it's a very easy test and if pink instead of blue, there's a problem with your softener. Thanks dude. I dump mine fast and hard. Boiler shuts down and re-fires. I thought that was sufficient? I will do it the way you suggest from now on!
Believe it or not, we don't soften our water, we used to. I have ran anti-corrosive and anti-sludge chem. My chemical is injected whenever I take on city water. I know we are cutting corners and not doing things "by the book", but the state fire marshall and insurance inspectors pass us, so the administrators give us minimal budget to maintain. He is talking about blowing down the boiler itself. You are describing blowing down the low water cut off. That can be opened fast no problem. Fresh water with oxygen is the enemy. My boiler reps say not to soften as the cast iron wants the minerals. On blow downs, yes. There are generally two valves at the bottom, one that's a knife type valve and one that's a slow wheel opening valve. This is not necessarily how yours is piped in as low pressure follows different requirements, but the principle of allowing the bottom blowdown to start and end slowly still applies, this allows the pipes to heat up and won't kick sludge back into the middle of the boiler as water rushes toward the drain opening. On LWCO, yes, just cranking it open is generally fine, but I still do it a little slow. Not common for a float to flatten, but I've seen it happen. As for soft water on cast iron... I haven't heard that, but I don't generally work on cast iron units, I generally don't work on low pressure steam either, I'm primarily involved with high pressure steam in plants running 100-125 psi. Soft water will increase your ph which is a barrier against corrosion from carbonic acid though, and any scale on the heating surface will decrease efficiency and increase thermal stress on the heating surface. I'm going from memory right now (and a couple of drinks ) but I think all I have on the bottom of mine are ball valves. I also run my steam boilers in tandem, by that, I mean that they are not isolated. The head and pressure are the same in both no matter which one is running. What is your opinion of that? It is acceptable practice, right? What situation (if any, besides major problems) would call for isolating them?It's ok as long as you're not overfilling your offline boiler, which you may well be, see water hammer stories for why that's bad. If you have no manway in the boiler you can get away with less isolation than if you had a manway. Whenever you start one up cold, if it modulates, keep it in low until it's warm then bring it up a little more, then a little more and let it run after that. LWCO doubles as a pump control. Everytime I look at the sight glass on each, they appear to be about the same. Both tend to run just a few inches above the min. water line. Does the water prime or surge (bounce) in the sight glass? should be steady with some movement. I pipe simple swing check valves on the returns of my steamers that sit next to each other so there is no pressure from the boiler that is firing getting into the one that I dropped off. I don't notice any "surge" in my glass. I have a condesate pit, it pumps into a holding tank. The holding tank has dual pumps, each one has it's own check valve. No surge is good. Means the surface of the water in the boiler does not have too much oil or contaminates floating around and interrupting the smooth flow of steam off the water. The 'holding tank' is likely a condensate pump, two pumps is a duplex setup. |
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Posted: 4/13/2011 7:59:32 PM EDT
[#41]
Quoted: http://i868.photobucket.com/albums/ab250/Timcohydronics/PA120091.jpg I absolutely LOVE what I do.... Gotta love a boiler that rolls out... |
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Posted: 4/13/2011 8:02:16 PM EDT
[#42]
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http://i868.photobucket.com/albums/ab250/Timcohydronics/PA120091.jpg I absolutely LOVE what I do.... Gotta love a boiler that rolls out... 400k rolling out......we can fix this. 64 mil btu rolling out....boiler room and building melted...or level 7. |
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Posted: 4/13/2011 8:05:02 PM EDT
[#43]
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Great post! I blown down once a week. My chemical salesman checks my pH once/year. I don't think they've ever done a conductivity analysis. I usually do a wet close too. Bottom blowing once a week (open knife valve, then open slow, close slow, close knife valve, open and close slow, most open the "fast" valve and dump it hard, not the right way, I apologize if you already know this procedure), is what is recommended by ASME for lower pressure steam like at your plant. The same is true of your water columns, however, I would do those daily. As for chemicals, the plants I see with good water quality and no scale at the end of the year have their maintenance check the water quality on a weekly or semi-weekly basis and constantly tweak on the pumps until it's just right. Every month or every couple of months is not enough of a sample size for accurate water control. I would recommend you get with the chemical man about getting a test kit and some test procedures as well as an explanation of which test tells you what. Since you have low pressure and cannot run a deaerator, you will be using a chemical to remove oxygen, it has to be 24ppm or higher to function, so you check it a few times a week and if it's getting low, turn the pump up just a little, if it's getting high, turn it down a little. The difference in results that this gets is just night and day. Conductivity is based on your total dissolved solids and if it gets out of balance (high) you will see foaming/surging and probably trip ALWCO. This is controlled by blowdowns, if it starts getting above 3000, increase frequency/duration of blowdowns, if below 2000 back off on it a little. Watching your makeup water softeners is also important as this is what can cause scaling of the boiler quick, it's a very easy test and if pink instead of blue, there's a problem with your softener. Thanks dude. I dump mine fast and hard. Boiler shuts down and re-fires. I thought that was sufficient? I will do it the way you suggest from now on!
Believe it or not, we don't soften our water, we used to. I have ran anti-corrosive and anti-sludge chem. My chemical is injected whenever I take on city water. I know we are cutting corners and not doing things "by the book", but the state fire marshall and insurance inspectors pass us, so the administrators give us minimal budget to maintain. He is talking about blowing down the boiler itself. You are describing blowing down the low water cut off. That can be opened fast no problem. Fresh water with oxygen is the enemy. My boiler reps say not to soften as the cast iron wants the minerals. On blow downs, yes. There are generally two valves at the bottom, one that's a knife type valve and one that's a slow wheel opening valve. This is not necessarily how yours is piped in as low pressure follows different requirements, but the principle of allowing the bottom blowdown to start and end slowly still applies, this allows the pipes to heat up and won't kick sludge back into the middle of the boiler as water rushes toward the drain opening. On LWCO, yes, just cranking it open is generally fine, but I still do it a little slow. Not common for a float to flatten, but I've seen it happen. As for soft water on cast iron... I haven't heard that, but I don't generally work on cast iron units, I generally don't work on low pressure steam either, I'm primarily involved with high pressure steam in plants running 100-125 psi. Soft water will increase your ph which is a barrier against corrosion from carbonic acid though, and any scale on the heating surface will decrease efficiency and increase thermal stress on the heating surface. I'm going from memory right now (and a couple of drinks ) but I think all I have on the bottom of mine are ball valves. I also run my steam boilers in tandem, by that, I mean that they are not isolated. The head and pressure are the same in both no matter which one is running. What is your opinion of that? It is acceptable practice, right? What situation (if any, besides major problems) would call for isolating them?It's ok as long as you're not overfilling your offline boiler, which you may well be, see water hammer stories for why that's bad. If you have no manway in the boiler you can get away with less isolation than if you had a manway. Whenever you start one up cold, if it modulates, keep it in low until it's warm then bring it up a little more, then a little more and let it run after that. LWCO doubles as a pump control. Everytime I look at the sight glass on each, they appear to be about the same. Both tend to run just a few inches above the min. water line. Does the water prime or surge (bounce) in the sight glass? should be steady with some movement. I pipe simple swing check valves on the returns of my steamers that sit next to each other so there is no pressure from the boiler that is firing getting into the one that I dropped off. I don't notice any "surge" in my glass. I have a condesate pit, it pumps into a holding tank. The holding tank has dual pumps, each one has it's own check valve. No surge is good. Means the surface of the water in the boiler does not have too much oil or contaminates floating around and interrupting the smooth flow of steam off the water. The 'holding tank' is likely a condensate pump, two pumps is a duplex setup. It's kind of a screwy deal. I had a Kewanee Type "C" that was in service since 1952 (when the place was built) until just about 3 years ago. Now I have 2 smaller, waaaay more efficient boilers. The Kewnaee was set up so that the condensate pit float switch would send condensate back to the boiler. My new boilers call for condensate return via LWCO. The float switch in the pit was now configured to call for make up water. Because of this, I would have tons condensate running out of the overflow and down the drain before the LWCO would ever call for it. Eventually, it would go into a LWCO condition and have to bring on make up water. I had a major sludge problem because of this, not to mention expensive treatment going down the drain. The "holding tank" after the pit has solved that problem. Now, the float switch in the pit is configured to send the condensate to the holding tank. The make up water float switch is inside the holding tank. |
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Posted: 4/13/2011 8:10:06 PM EDT
[#44]
Steam boiler explosions were not only common in the old days up to the early 1900's, they were the number two cause of most steamboat losses, exceeded only by loss by fire.
The boilers were made of uncertain quality iron, built to last about 3 years which was the expected lifespan of a boat, and safety devices were either not yet invented, were defective, or were wired down by the engineers. All this was compounded by inept, poorly trained, incompetent, or drunken crews. In a famous steamboat boiler explosion on a boat just above Memphis, Mark Twain's brother was horribly scalded and blown overboard in the blast, dying in agony a week later. In one explosion above St Louis the blast was so violent the boat's purser was found hung up in the trees on the Illinois side of the river, and the mud clerk was found in the middle of a cornfield in Iowa. In one explosion above New Orleans a boiler blew with such force, huge bails of cotton were blown hundreds of yards. |
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Posted: 4/13/2011 8:12:57 PM EDT
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Great post! I blown down once a week. My chemical salesman checks my pH once/year. I don't think they've ever done a conductivity analysis. I usually do a wet close too. Bottom blowing once a week (open knife valve, then open slow, close slow, close knife valve, open and close slow, most open the "fast" valve and dump it hard, not the right way, I apologize if you already know this procedure), is what is recommended by ASME for lower pressure steam like at your plant. The same is true of your water columns, however, I would do those daily. As for chemicals, the plants I see with good water quality and no scale at the end of the year have their maintenance check the water quality on a weekly or semi-weekly basis and constantly tweak on the pumps until it's just right. Every month or every couple of months is not enough of a sample size for accurate water control. I would recommend you get with the chemical man about getting a test kit and some test procedures as well as an explanation of which test tells you what. Since you have low pressure and cannot run a deaerator, you will be using a chemical to remove oxygen, it has to be 24ppm or higher to function, so you check it a few times a week and if it's getting low, turn the pump up just a little, if it's getting high, turn it down a little. The difference in results that this gets is just night and day. Conductivity is based on your total dissolved solids and if it gets out of balance (high) you will see foaming/surging and probably trip ALWCO. This is controlled by blowdowns, if it starts getting above 3000, increase frequency/duration of blowdowns, if below 2000 back off on it a little. Watching your makeup water softeners is also important as this is what can cause scaling of the boiler quick, it's a very easy test and if pink instead of blue, there's a problem with your softener. Thanks dude. I dump mine fast and hard. Boiler shuts down and re-fires. I thought that was sufficient? I will do it the way you suggest from now on!
Believe it or not, we don't soften our water, we used to. I have ran anti-corrosive and anti-sludge chem. My chemical is injected whenever I take on city water. I know we are cutting corners and not doing things "by the book", but the state fire marshall and insurance inspectors pass us, so the administrators give us minimal budget to maintain. He is talking about blowing down the boiler itself. You are describing blowing down the low water cut off. That can be opened fast no problem. Fresh water with oxygen is the enemy. My boiler reps say not to soften as the cast iron wants the minerals. On blow downs, yes. There are generally two valves at the bottom, one that's a knife type valve and one that's a slow wheel opening valve. This is not necessarily how yours is piped in as low pressure follows different requirements, but the principle of allowing the bottom blowdown to start and end slowly still applies, this allows the pipes to heat up and won't kick sludge back into the middle of the boiler as water rushes toward the drain opening. On LWCO, yes, just cranking it open is generally fine, but I still do it a little slow. Not common for a float to flatten, but I've seen it happen. As for soft water on cast iron... I haven't heard that, but I don't generally work on cast iron units, I generally don't work on low pressure steam either, I'm primarily involved with high pressure steam in plants running 100-125 psi. Soft water will increase your ph which is a barrier against corrosion from carbonic acid though, and any scale on the heating surface will decrease efficiency and increase thermal stress on the heating surface. I'm going from memory right now (and a couple of drinks ) but I think all I have on the bottom of mine are ball valves. I also run my steam boilers in tandem, by that, I mean that they are not isolated. The head and pressure are the same in both no matter which one is running. What is your opinion of that? It is acceptable practice, right? What situation (if any, besides major problems) would call for isolating them?It's ok as long as you're not overfilling your offline boiler, which you may well be, see water hammer stories for why that's bad. If you have no manway in the boiler you can get away with less isolation than if you had a manway. Whenever you start one up cold, if it modulates, keep it in low until it's warm then bring it up a little more, then a little more and let it run after that. LWCO doubles as a pump control. Everytime I look at the sight glass on each, they appear to be about the same. Both tend to run just a few inches above the min. water line. Does the water prime or surge (bounce) in the sight glass? should be steady with some movement. I pipe simple swing check valves on the returns of my steamers that sit next to each other so there is no pressure from the boiler that is firing getting into the one that I dropped off. I don't notice any "surge" in my glass. I have a condesate pit, it pumps into a holding tank. The holding tank has dual pumps, each one has it's own check valve. No surge is good. Means the surface of the water in the boiler does not have too much oil or contaminates floating around and interrupting the smooth flow of steam off the water. The 'holding tank' is likely a condensate pump, two pumps is a duplex setup. It's kind of a screwy deal. I had a Kewanee Type "C" that was in service since 1952 (when the place was built) until just about 3 years ago. Now I have 2 smaller, waaaay more efficient boilers. The Kewnaee was set up so that the condensate pit float switch would send condensate back to the boiler. My new boilers call for condensate return via LWCO. The float switch in the pit was now configured to call for make up water. Because of this, I would have tons condensate running out of the overflow and down the drain before the LWCO would ever call for it. Eventually, it would go into a LWCO condition and have to bring on make up water. I had a major sludge problem because of this, not to mention expensive treatment going down the drain. The "holding tank" after the pit has solved that problem. Now, the float switch in the pit is configured to send the condensate to the holding tank. The make up water float switch is inside the holding tank. Get rid of the pit. Have your returns dump into the condensate pump. Add a makeup line (fill) to the condensate box. No need for all that water in the pit. If the wet return is piped right, no condensate pump even needed. Gravity return is best, no moving parts to fail. |
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Posted: 4/13/2011 8:13:15 PM EDT
[#46]
Quoted: Quoted: Quoted: http://i868.photobucket.com/albums/ab250/Timcohydronics/PA120091.jpg I absolutely LOVE what I do.... Gotta love a boiler that rolls out... 400k rolling out......we can fix this. 64 mil btu rolling out....boiler room and building melted...or level 7. It would be entertaining to see someone try to make an atmospheric burner that big. Those ones that are up at 63MMBH, low nox...well...lets talk rumbling...it's a little unsettling when it starts shaking the control panels on 50 ton boiler. Go farther and the 125 hp motor starts going up and down a few inches. Normal to encounter during tuning... Not so normal is the few that push the California emmisions standards and shear the limit tree off during startup, the water columns, the stack, the concrete floor, etc. heh... Or...a watertube that has individual servos controlling gas and air...and the gas goes from 30% to past full open, dumping 40+ mmbh beyond stoichiometric limits into the boiler operating at a steam pressure of 400 psi. That's a rush I'd rather not have again. *all that happened was post purge, but the other boiler barely caught the load before problems in the plant would have occured. |
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Posted: 4/13/2011 8:18:34 PM EDT
[#47]
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Great post! I blown down once a week. My chemical salesman checks my pH once/year. I don't think they've ever done a conductivity analysis. I usually do a wet close too. Bottom blowing once a week (open knife valve, then open slow, close slow, close knife valve, open and close slow, most open the "fast" valve and dump it hard, not the right way, I apologize if you already know this procedure), is what is recommended by ASME for lower pressure steam like at your plant. The same is true of your water columns, however, I would do those daily. As for chemicals, the plants I see with good water quality and no scale at the end of the year have their maintenance check the water quality on a weekly or semi-weekly basis and constantly tweak on the pumps until it's just right. Every month or every couple of months is not enough of a sample size for accurate water control. I would recommend you get with the chemical man about getting a test kit and some test procedures as well as an explanation of which test tells you what. Since you have low pressure and cannot run a deaerator, you will be using a chemical to remove oxygen, it has to be 24ppm or higher to function, so you check it a few times a week and if it's getting low, turn the pump up just a little, if it's getting high, turn it down a little. The difference in results that this gets is just night and day. Conductivity is based on your total dissolved solids and if it gets out of balance (high) you will see foaming/surging and probably trip ALWCO. This is controlled by blowdowns, if it starts getting above 3000, increase frequency/duration of blowdowns, if below 2000 back off on it a little. Watching your makeup water softeners is also important as this is what can cause scaling of the boiler quick, it's a very easy test and if pink instead of blue, there's a problem with your softener. Thanks dude. I dump mine fast and hard. Boiler shuts down and re-fires. I thought that was sufficient? I will do it the way you suggest from now on!
Believe it or not, we don't soften our water, we used to. I have ran anti-corrosive and anti-sludge chem. My chemical is injected whenever I take on city water. I know we are cutting corners and not doing things "by the book", but the state fire marshall and insurance inspectors pass us, so the administrators give us minimal budget to maintain. He is talking about blowing down the boiler itself. You are describing blowing down the low water cut off. That can be opened fast no problem. Fresh water with oxygen is the enemy. My boiler reps say not to soften as the cast iron wants the minerals. On blow downs, yes. There are generally two valves at the bottom, one that's a knife type valve and one that's a slow wheel opening valve. This is not necessarily how yours is piped in as low pressure follows different requirements, but the principle of allowing the bottom blowdown to start and end slowly still applies, this allows the pipes to heat up and won't kick sludge back into the middle of the boiler as water rushes toward the drain opening. On LWCO, yes, just cranking it open is generally fine, but I still do it a little slow. Not common for a float to flatten, but I've seen it happen. As for soft water on cast iron... I haven't heard that, but I don't generally work on cast iron units, I generally don't work on low pressure steam either, I'm primarily involved with high pressure steam in plants running 100-125 psi. Soft water will increase your ph which is a barrier against corrosion from carbonic acid though, and any scale on the heating surface will decrease efficiency and increase thermal stress on the heating surface. I'm going from memory right now (and a couple of drinks ) but I think all I have on the bottom of mine are ball valves. I also run my steam boilers in tandem, by that, I mean that they are not isolated. The head and pressure are the same in both no matter which one is running. What is your opinion of that? It is acceptable practice, right? What situation (if any, besides major problems) would call for isolating them?It's ok as long as you're not overfilling your offline boiler, which you may well be, see water hammer stories for why that's bad. If you have no manway in the boiler you can get away with less isolation than if you had a manway. Whenever you start one up cold, if it modulates, keep it in low until it's warm then bring it up a little more, then a little more and let it run after that. LWCO doubles as a pump control. Everytime I look at the sight glass on each, they appear to be about the same. Both tend to run just a few inches above the min. water line. Does the water prime or surge (bounce) in the sight glass? should be steady with some movement. I pipe simple swing check valves on the returns of my steamers that sit next to each other so there is no pressure from the boiler that is firing getting into the one that I dropped off. I don't notice any "surge" in my glass. I have a condesate pit, it pumps into a holding tank. The holding tank has dual pumps, each one has it's own check valve. No surge is good. Means the surface of the water in the boiler does not have too much oil or contaminates floating around and interrupting the smooth flow of steam off the water. The 'holding tank' is likely a condensate pump, two pumps is a duplex setup. It's kind of a screwy deal. I had a Kewanee Type "C" that was in service since 1952 (when the place was built) until just about 3 years ago. Now I have 2 smaller, waaaay more efficient boilers. The Kewnaee was set up so that the condensate pit float switch would send condensate back to the boiler. My new boilers call for condensate return via LWCO. The float switch in the pit was now configured to call for make up water. Because of this, I would have tons condensate running out of the overflow and down the drain before the LWCO would ever call for it. Eventually, it would go into a LWCO condition and have to bring on make up water. I had a major sludge problem because of this, not to mention expensive treatment going down the drain. The "holding tank" after the pit has solved that problem. Now, the float switch in the pit is configured to send the condensate to the holding tank. The make up water float switch is inside the holding tank. Get rid of the pit. Have your returns dump into the condensate pump. Add a makeup line (fill) to the condensate box. No need for all that water in the pit. If the wet return is piped right, no condensate pump even needed. Gravity return is best, no moving parts to fail. My returns come out of a pipe chase that was below the level of the old Kewanee. She set on top of a refractory fire box a good 3 1/2'. |
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Posted: 4/13/2011 8:34:47 PM EDT
[#48]
Quoted: My returns come out of a pipe chase that was below the level of the old Kewanee. She set on top of a refractory fire box a good 3 1/2'. Your way of manually adding make-up water is a definite problem. If you have one or two tanks with enough capacity for your condensate running back, and a float valve or some other way to automatically send more water into the tank when it goes down in level will keep things nicely in a steady state, and chemical controls possible to meter. Edit: just reread your posts and it seems you already have a system like this. |
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Posted: 4/13/2011 8:45:45 PM EDT
[#49]
Quoted:
Between the OP and this guy I think this thread wins the "WAAAAYYYYY over some member's heads" award. Why do you say that? Not that its over my head, it's not something I've ever had too much interest in. Quoted:
You should have just stuck with the first part.
I'm thinking of a pirate phrase, with the word 'down' omitted. Quoted:
Nuclear power is in effect a boiler. Very efficient. You have two seperate systems. The reactor makes steam in a closed loop. The super heated steam from that goes to a heat exchanger which in turn boils water in the secondary loop. That steam powers turbins that in turn spin generators. I'm familiar with this concept; using steam combined with a turbine. I'm guessing it's still in some industrial and maritime applications. I just wonder about agriculture applications from around the turn of the century, smaller applications. Quoted:
OK. Lets break this down. I will do an overview of 99% of the residential boilers (houses) and commercial (large apartment buildings) Steam. All cast iron, natural draft. The Empire State building runs on 5lbs of steam. I run my 5 story apartment buildings on maybe 1/2lb of steam. If several vents or traps are bad, it could take 2lbs of steam to do the job. Google a Hartford Loop. This is the safety mechanism piped into the returns of any steam boiler so if the wet return ruptures, the boiler's water does not just dump out. It is the connecting point and the 'loop' you see which is also part of the equalizer. http://i868.photobucket.com/albums/ab250/Timcohydronics/DSC00561-2.jpg Steamers are cast iron boilers. no tubes, just cast iron sections. They have 2 low water cut offs by code, and both can be a float or one can be a probe. One has to be a manual reset. They kill the gas. All steamers also have two pressuretrols, one controls boiler pressure and one is a high-limit manual reset. They also have a relief valve equal to the boiler's BTUs and that valve is set for 15lbs. Hot water gives you infinite designs, copper, stainless steel, cast iron, and so on. These are 30lbs max. Typically they are set to 12lbs. In tall structures (the tallest I maintain is 14 stories) they run at 80lbs to get the water to the top floor. http://i868.photobucket.com/albums/ab250/Timcohydronics/DSC00979.jpg http://i868.photobucket.com/albums/ab250/Timcohydronics/DSC00763-1.jpg http://i868.photobucket.com/albums/ab250/Timcohydronics/DSC00266.jpg FIXED pics.. Thanks for the info. Now, are these units used to supply hot water or steam for heat? I'm thinking the old cast iorn radiators for long ago, |
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Posted: 4/13/2011 8:54:50 PM EDT
[#50]
Quoted:
Thanks for the info. Now, are these units used to supply hot water or steam for heat? I'm thinking the old cast iorn radiators for long ago, They can do both! Hydronic and steam heat can both be used for climate control and hot water. Heat exchangers in the heat loop can heat water for lavatory and showers. Some systems can reverse for cooling purposes (I'm not that lucky). This is achieved by sending the medium (usually glycol instead of water) through chiller units. The same heater units that heat will blow cool air when chilled. |
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