How to Detect Boiling Water inside a Tank? Page 5 UPDATE WITH FINAL DESIGN

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[ARCHIVED THREAD] - How to Detect Boiling Water inside a Tank? Page 5 UPDATE WITH FINAL DESIGN (Page 1 of 3)

Posted: 2/23/2006 3:01:38 PM EDT

Does anyone know of a method to detect boiling water inside a tank? Somehow detecting the turbulance of the water? Or just a way to detect if the tank is full or empty.

Conductivity detection cannot be used and floats cannot be used.

I was thinking of using halleffect detectors through the tank but I don't want to penitrate the tank if possible.

Posted: 2/23/2006 3:03:30 PM EDT

[#1]

Open the valve for a second.

Posted: 2/23/2006 3:04:43 PM EDT

[#2]

Touch it and see if it's Hot

Posted: 2/23/2006 3:07:18 PM EDT

[#3]

Quoted:
Touch it and see if it's Hot

That won't work. The presence of water must be detected, not heat. The water just happens to be boiling.

Posted: 2/23/2006 3:07:48 PM EDT

[#4]

audio?

Posted: 2/23/2006 3:07:55 PM EDT

[#5]

Sound or thermometer

Posted: 2/23/2006 3:08:11 PM EDT

[#6]

Ask the crew when they climb out.

What's boiling water doing in a tank anyway?

Edit to add: open a hatch and look inside.

Posted: 2/23/2006 3:10:47 PM EDT

[#7]

Quoted:
Ask the crew when they climb out.

What's boiling water doing in a tank anyway?

Edit to add: open a hatch and look inside.

The device has to be left alone. There is not someone there to look at it.

Posted: 2/23/2006 3:11:44 PM EDT

[#8]

Is this an open top tank or a pressure tank?

Posted: 2/23/2006 3:12:28 PM EDT

[#9]

Quoted:
Sound or thermometer

A thermometer will not work. The level of the water must be detected. When the water boils off (no more turbulence) the device must shut off.

Posted: 2/23/2006 3:12:55 PM EDT

[#10]

Quoted:
Quoted:
Ask the crew when they climb out.

What's boiling water doing in a tank anyway?

Edit to add: open a hatch and look inside.

The device has to be left alone. There is not someone there to look at it.

Is it in the motor pool? How did it get filled with water?

what kinda tank is this?

Posted: 2/23/2006 3:13:39 PM EDT

[#11]

What class is this homework problem for?

Posted: 2/23/2006 3:13:43 PM EDT

[#12]

Quoted:
Is this an open top tank or a pressure tank?

The tank is inclosed but the pressure difference between it and the outside is negligible.

Posted: 2/23/2006 3:16:11 PM EDT

[#13]

Quoted:
Quoted:
Is this an open top tank or a pressure tank?

The tank is inclosed but the pressure difference between it and the outside is negligible.

Not if you are expecting it to boil.

Posted: 2/23/2006 3:17:13 PM EDT

[#14]

Quoted:
Quoted:
Is this an open top tank or a pressure tank?

The tank is inclosed but the pressure difference between it and the outside is negligible.

If the tank is enclosed then the pressure inside will be higher than outside unless there is a way for pressure to release. If there is a way for pressure to release then there is a way to check the temp/level. If the tank is fully enclosed but with a pressure release valve you could catch the steam being released and cool it back down to water and then use that as a mesure on how much water is left in the tank.

Posted: 2/23/2006 3:18:04 PM EDT

[#15]

Quoted:
Quoted:
Quoted:
Is this an open top tank or a pressure tank?

The tank is inclosed but the pressure difference between it and the outside is negligible.

Not if you are expecting it to boil.

It is not completely inclosed. Steam escapes out of the top of it.

It is not pressurized like a tea kettle.

Posted: 2/23/2006 3:19:15 PM EDT

[#16]

Quoted:
Quoted:
Quoted:
Quoted:
Is this an open top tank or a pressure tank?

The tank is inclosed but the pressure difference between it and the outside is negligible.

Not if you are expecting it to boil.

It is not completely inclosed. Steam escapes out of the top of it.

It is not pressurized like a tea kettle.

steam escapes out of the top?

So watch the steam. When it stops your tank is dry.

Posted: 2/23/2006 3:19:28 PM EDT

[#17]

Quoted:
Quoted:
Quoted:
Is this an open top tank or a pressure tank?

The tank is inclosed but the pressure difference between it and the outside is negligible.

If the tank is enclosed then the pressure inside will be higher than outside unless there is a way for pressure to release. If there is a way for pressure to release then there is a way to check the temp/level. If the tank is fully enclosed but with a pressure release valve you could catch the steam being released and cool it back down to water and then use that as a mesure on how much water is left in the tank.

Won't work because the tank is sometimes not completely full before starting the machine. There is no way to quantify how much water you start and end with.

Posted: 2/23/2006 3:19:49 PM EDT

[#18]

Quoted:
Quoted:
Is this an open top tank or a pressure tank?

The tank is inclosed but the pressure difference between it and the outside is negligible.

As you raise the pressure, the temp that it takes to make the water boil also rises. You could use a thermostat that kills the heat source......that is simple. Figuring out the temp you need to set it at will be more of a challenge. (someone where will know the formula to figure out how much temp rise is needed with how much pressure)

There are switches that make conections when submurged(sp?) this will be a problem because I don't know how many heat cycles they could survive. Plus boiling water doesn't have a steady level.

Posted: 2/23/2006 3:20:04 PM EDT

[#19]

Quoted:
Quoted:
Quoted:
Quoted:
Quoted:
Is this an open top tank or a pressure tank?

The tank is inclosed but the pressure difference between it and the outside is negligible.

Not if you are expecting it to boil.

It is not completely inclosed. Steam escapes out of the top of it.

It is not pressurized like a tea kettle.

steam escapes out of the top?

So watch the steam. When it stops your tank is dry.

By that time the heating element is ruined.

Posted: 2/23/2006 3:20:16 PM EDT

[#20]

you'd need sensors of some sort pressure and temp, from those 2 plus the volume of the tank and knowning the volume of the water you could probably detect boiling. Just my guess.

Posted: 2/23/2006 3:21:25 PM EDT

[#21]

n/m just got caught up.

Posted: 2/23/2006 3:22:03 PM EDT

[#22]

Quoted:
Quoted:
Quoted:
Is this an open top tank or a pressure tank?

The tank is inclosed but the pressure difference between it and the outside is negligible.

As you raise the pressure, the temp that it takes to make the water boil also rises. You could use a thermostat that kills the heat source......that is simple. Figuring out the temp you need to set it out will be more of a challenge. (someone where will know the formula to figure out how much temp rise is needed with how much pressure)

There are switches that make conections when submurged(sp?) this will be a problem because I don't know how many heat cycles they could survive. Plus boiling water doesn't have a steady level.

Thermostats will not work.

Pressure dectection will not work.

Posted: 2/23/2006 3:23:59 PM EDT

[#23]

tell us why thermostats or pressure sensors will not work. Just saying something will not work does not give enough info for a work around.

Posted: 2/23/2006 3:24:45 PM EDT

[#24]

Not an easy answer without a lot more info...

If the water is going to boil off then we must think that the tank is vented to the outside.. If the tank were closed then for ever 1psi increase in pressure the boiling point of the water would go uo by 3*F.

Do you want to detect if the water is at a boil or not... or just the presence of water?

If you are just looking for the presence of water then you can use a optical prisim sensor. I don't know what the temature limits of these are but they work very well.. This would be the best bet for the low water sensor.

Posted: 2/23/2006 3:24:53 PM EDT

[#25]

Quoted:
tell us why thermostats or pressure sensors will not work. Just saying something will not work does not give enough info for a work around.

The pressure difference between the outside and inside is not great enough for cheap, pratical detection.

Posted: 2/23/2006 3:25:13 PM EDT

[#26]

Quoted:
Quoted:
Quoted:
Quoted:
Is this an open top tank or a pressure tank?

The tank is inclosed but the pressure difference between it and the outside is negligible.

As you raise the pressure, the temp that it takes to make the water boil also rises. You could use a thermostat that kills the heat source......that is simple. Figuring out the temp you need to set it out will be more of a challenge. (someone where will know the formula to figure out how much temp rise is needed with how much pressure)

There are switches that make conections when submurged(sp?) this will be a problem because I don't know how many heat cycles they could survive. Plus boiling water doesn't have a steady level.

Thermostats will not work. I wonder why?

Pressure dectection will not work. I wonder about this as well

What exactly are you trying to accomplish?

Because to detect boiling water in a tank.......either a thermostat or pressure detection if properly calibrated will work.

Posted: 2/23/2006 3:26:04 PM EDT

[#27]

Quoted:
Not an easy answer without a lot more info...

If the water is going to boil off then we must think that the tank is vented to the outside.. If the tank were closed then for ever 1psi increase in pressure the boiling point of the water would go uo by 3*F.

Do you want to detect if the water is at a boil or not... or just the presence of water?

If you are just looking for the presence of water then you can use a optical prisim sensor. I don't know what the temature limits of these are but they work very well.. This would be the best bet for the low water sensor.

BLUE: This is preferable

RED: I want to avoid penitrating the tank wall.

Posted: 2/23/2006 3:27:20 PM EDT

[#28]

So basically you have a pot of water and want to turn off the heat before all the water has boiled away. Right?

Why can't floats be used?

I guess I'd rig up some kind of microphone/stethescope up the side of the tank and see if you can hear a difference when the water drops below the level of the mic.

Posted: 2/23/2006 3:27:54 PM EDT

[#29]

Quoted:
Quoted:
Quoted:
Quoted:
Quoted:
Is this an open top tank or a pressure tank?

The tank is inclosed but the pressure difference between it and the outside is negligible.

As you raise the pressure, the temp that it takes to make the water boil also rises. You could use a thermostat that kills the heat source......that is simple. Figuring out the temp you need to set it out will be more of a challenge. (someone where will know the formula to figure out how much temp rise is needed with how much pressure)

There are switches that make conections when submurged(sp?) this will be a problem because I don't know how many heat cycles they could survive. Plus boiling water doesn't have a steady level.

Thermostats will not work. I wonder why?

Pressure dectection will not work. I wonder about this as well

What exactly are you trying to accomplish?

Because to detect boiling water in a tank.......either a thermostat or pressure detection if properly calibrated will work.

Detecting the water in a water distiller.

The tank is the incomming water that is boiled off and then purified.

The tank holds about a gallon of water.

Posted: 2/23/2006 3:28:21 PM EDT

[#30]

Quoted:
Quoted:
Not an easy answer without a lot more info...

If the water is going to boil off then we must think that the tank is vented to the outside.. If the tank were closed then for ever 1psi increase in pressure the boiling point of the water would go uo by 3*F.

Do you want to detect if the water is at a boil or not... or just the presence of water?

If you are just looking for the presence of water then you can use a optical prisim sensor. I don't know what the temature limits of these are but they work very well.. This would be the best bet for the low water sensor.

BLUE: This is preferable

RED: I want to avoid penitrating the tank wall.

Is this a still?

The tank is already penetrated if there's away for the steam to boil off.

Posted: 2/23/2006 3:29:14 PM EDT

[#31]

Quoted:
So basically you have a pot of water and want to turn off the heat before all the water has boiled away. Right?

Why can't floats be used?

I guess I'd rig up some kind of microphone/stethescope up the side of the tank and see if you can hear a difference when the water drops below the level of the mic.

BLUE: Yes, that is exactly what I want to do.

Floats can be fouled.

Also, the tank is stainless steel. Everything in the tank should be stainless.

Posted: 2/23/2006 3:29:15 PM EDT

[#32]

Quoted:
Quoted:
Quoted:
Quoted:
Quoted:
Quoted:
Is this an open top tank or a pressure tank?

The tank is inclosed but the pressure difference between it and the outside is negligible.

As you raise the pressure, the temp that it takes to make the water boil also rises. You could use a thermostat that kills the heat source......that is simple. Figuring out the temp you need to set it out will be more of a challenge. (someone where will know the formula to figure out how much temp rise is needed with how much pressure)

There are switches that make conections when submurged(sp?) this will be a problem because I don't know how many heat cycles they could survive. Plus boiling water doesn't have a steady level.

Thermostats will not work. I wonder why?

Pressure dectection will not work. I wonder about this as well

What exactly are you trying to accomplish?

Because to detect boiling water in a tank.......either a thermostat or pressure detection if properly calibrated will work.

Detecting the water in a water distiller.

The tank is the incomming water that is boiled off and then purified.

The tank holds about a gallon of water.

OK, measure how much water you put into the thing, and then shut it down and refill when about half of that comes out the other end.

Posted: 2/23/2006 3:29:53 PM EDT

[#33]

The boiling water carries away heat. A thermostat or thermistor placed near the heat source, presumably near the bottom of the tank, will detect the heat rise when the water drops below that level and the temperature starts to run away.

Posted: 2/23/2006 3:30:35 PM EDT

[#34]

Quoted:
Quoted:
Quoted:
Not an easy answer without a lot more info...

If the water is going to boil off then we must think that the tank is vented to the outside.. If the tank were closed then for ever 1psi increase in pressure the boiling point of the water would go uo by 3*F.

Do you want to detect if the water is at a boil or not... or just the presence of water?

If you are just looking for the presence of water then you can use a optical prisim sensor. I don't know what the temature limits of these are but they work very well.. This would be the best bet for the low water sensor.

BLUE: This is preferable

RED: I want to avoid penitrating the tank wall.

Is this a still?

The tank is already penetrated if there's away for the steam to boil off.

Yes, it is a still.

I know it is penitrated. I just don't want to penitrate it with electronic equipment.

Posted: 2/23/2006 3:32:28 PM EDT

[#35]

Quoted:
The boiling water carries away heat. A thermostat or thermistor placed near the heat source, presumably near the bottom of the tank, will detect the heat rise when the water drops below that level and the temperature starts to run away.

Won't work. The device needs to be stopped before the water is boiled off. The device needs to be stopped when the water level is low but not lower than the heating element.

Posted: 2/23/2006 3:32:31 PM EDT

[#36]

A heat element that is boiling water will cycle on and off as it gets to a certain temp. Put a volt meter on the voltage to the heater element and have it do a auto shutdown when the heater element stays on too long. Preferable do this before it burns out. Will take some experamenting to get the heat cycles down before letting it run on its own.

Example: say your heater element stays on for 5 seconds during a normal heat cycle. Have a relay trip when said voltage is present for say 10 seconds. This will allow a small leeway during water adds. If you have to add water manually then hook up a override switch so you cna leave the heater element on until the water reaches boiling point.

Posted: 2/23/2006 3:32:54 PM EDT

[#37]

Quoted:

OK, measure how much water you put into the thing, and then shut it down and refill when about half of that comes out the other end.

Dammit.....that is too simple......we need a complicated solution.

PS put the float in the condensate tank.

Posted: 2/23/2006 3:34:20 PM EDT

[#38]

check for condensation?
.
ETA: Check for a condensation line?

Posted: 2/23/2006 3:38:20 PM EDT

[#39]

Ultrasonic or capacative level detection?

You would need to put some penetrations in the tank but there would be no float.

Ultrasonic Level Detection

Capacitive Sensor

Posted: 2/23/2006 3:39:01 PM EDT

[#40]

Quoted:
Ultrasonic or capacative level detection?

You would need to put some penetrations in the tank but there would be no float.

Nope, I can't use electricity inside the tank.

Posted: 2/23/2006 3:41:15 PM EDT

[#41]

Quoted:
Quoted:
Ultrasonic or capacative level detection?

You would need to put some penetrations in the tank but there would be no float.

Nope, I can't use electricity inside the tank.

Seriously, can you measure the condensate?

Posted: 2/23/2006 3:43:08 PM EDT

[#42]

You need to come up with a device that works on the weight of the tank. The tank will get lighter as water boils off.

When it gets to a preset weight have it shut off.

Posted: 2/23/2006 3:43:18 PM EDT

[#43]

.

Posted: 2/23/2006 3:46:00 PM EDT

[#44]

Quoted:
Quoted:
Ultrasonic or capacative level detection?

You would need to put some penetrations in the tank but there would be no float.

Nope, I can't use electricity inside the tank.

The hall effect solution will require electricity too.

You need to give us all of the requiremets up front, it will help us find you a solution.

Posted: 2/23/2006 3:50:52 PM EDT

[#45]

Use some of those evil armor piercing rounds... Duh.

Posted: 2/23/2006 3:51:20 PM EDT

[#46]

WTF IS THIS THREAD ABOUT???!!!!

Posted: 2/23/2006 3:54:34 PM EDT

[#47]

Quoted:
WTF IS THIS THREAD ABOUT???!!!!

He is building a still and don't want to burn out his electric heater element.

Posted: 2/23/2006 3:54:49 PM EDT

[#48]

How about a machine vision solution?

You can place a camera at the top of the tank looking down and use machine vision to analyze if the water is boiling or not.

You would have trouble with condensation on the lense, thats why an ultrasonic transducer looking down from the tank to measure the level would be best.

One penetration at the top of the tank is not much. You can get the ultrasonic transducers in pharmacutical and food grades, so no need to worry there.

You could measure the flow rate of the water coming in and how long the valve letting the water in is open to calculate the volume of water in the tank, measure inlet temperature. Then knowing how large the heating element is you could calculate how long to boil the water.

Posted: 2/23/2006 4:04:35 PM EDT

[#49]

folks have suggested a lot of solutions.

Here is a fool proof one. Buy a high quality coffee maker that has auto-shutoff (like when the pot gets empty) and see how they do it.

Posted: 2/23/2006 4:07:47 PM EDT

[#50]

Quoted:
You need to come up with a device that works on the weight of the tank. The tank will get lighter as water boils off.

When it gets to a preset weight have it shut off.

I am with this guy. You should have your incoming water supply linked to the weight of the tank.

[ARCHIVED THREAD] - How to Detect Boiling Water inside a Tank? Page 5 UPDATE WITH FINAL DESIGN (Page 1 of 3)

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