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Temperature Indicator

temperature instrumentation

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#1 Max Domingues

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Posted 18 April 2017 - 08:52 AM

Please, does anybody has any tip about a temperature indicator using a range of 0-1200 Celsius?

I mean supplier, manufacturer, etc.

 

I have a system (furnace) and the operator needs to know the temperature when the equipment is down (energy fails, trip, etc)  and 'de-energized'. All of my manufactures/suppliers  are not able to provide this instrument who works at this high temperature.

 

Reinforcing: temperature transmitter is not acceptable because we are adopting no energy at this case.

 

Thank you all!

 

Max



#2 MTumack

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Posted 18 April 2017 - 11:07 AM

I don't think this is possible.

 

All TI's use what is called a bimetallic strip. Essentially two metals bound together and a strain gauge is used to measure the amount of distortion causes due to the differences in thermal expansion. That being said, there is a limit to how much temperature difference you can tolerate as while the expansion is natural and causes no strain, the resistance due to the other metal trying to pull or push the first one causes some large stresses; at some point your strip just fails as either the connections between the metals or the metals themselves break. Based on what is available, I'd estimate that range of feasibility is maybe half the temperature range that you are suggesting.

 

https://en.wikipedia...imetallic_strip

 

I would suggest utilizing the expansion of the furnace itself in order to provide some sort of marker on the floor or something if able; I assume the furnace expands quite a bit from 0 degrees to 1200 degrees, in the order of inches. When it is heated from 0 C to 1200 C, the typical piece of steel would expand somewhere between 0.01 to 0.0144 meters/meter of length. or 10 to 14 mm per meter of length, assuming a coefficient of thermal expansion of around 10 to 12x10^(-6) m/(m K). If your appliance is a couple meters long you might have up to 3 inches of possible expansion to work with.

 

I also imagine you might be able to find hydraulic temperature valves to operate some sort of pneumatic system (IE, a globe valve of sorts with an expanding stem.) although that is just me guessing.

 

If I might ask, what is the rational behind not using energy in the building? Certainly there is tons of energy being used considering that the process is being heated some 1200 degrees! I'd find it hard not to justify the energy required for proper operations alarms, personally.


Edited by MTumack, 18 April 2017 - 11:08 AM.


#3 MrShorty

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Posted 18 April 2017 - 11:24 AM

Is there some reason that a simple thermocouple would not work? Type K's list an upper temperature of 1260 C, Type S and Type R go up to 1400 C, and Type B claim to go to 1700 C. A simple multimeter/voltmeter can read the thermocouple data, and, if you can get a battery operated voltmeter with data logging/storage ability, then you should be able to keep a record of your oven temperature without an external power source.

 

I don't know if Amazon is considered a suitable source for a professional engineer, but I can put "thermocouple data logger" into the search engine at Amazon and get several handheld units that claim to read Type K thermocouples and that can log data.



#4 Max Domingues

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Posted 18 April 2017 - 12:32 PM

Dear Mr Mtumack, the reasons of not using energy are the following:

 

1) When you turn down the oven (in our case, the oven is an RTO - regenerative thermal oxider) and the operator must to enter inside the chamber to verify something, how could him knows the temperature inside the RTO (considering the energy is down and all the instruments are off)? 

 

2) critical situations when the energy is down for several reasons. We do not have a 'hotbypass' and either no generator of electricity and , again, the operator must to go inside the chamber to verify something specific (i understand it will be very rare but i must to admit in case of security).

 

We have a lot of critical instruments for security (including two temperature transmitters SIL 2 and 2 temperature transmiters SIL 0) but we are considering everything is off and there is a necessity to go inside the chamber.

 

Thanks for your reply!

 

I don't think this is possible.

 

All TI's use what is called a bimetallic strip. Essentially two metals bound together and a strain gauge is used to measure the amount of distortion causes due to the differences in thermal expansion. That being said, there is a limit to how much temperature difference you can tolerate as while the expansion is natural and causes no strain, the resistance due to the other metal trying to pull or push the first one causes some large stresses; at some point your strip just fails as either the connections between the metals or the metals themselves break. Based on what is available, I'd estimate that range of feasibility is maybe half the temperature range that you are suggesting.

 

https://en.wikipedia...imetallic_strip

 

I would suggest utilizing the expansion of the furnace itself in order to provide some sort of marker on the floor or something if able; I assume the furnace expands quite a bit from 0 degrees to 1200 degrees, in the order of inches. When it is heated from 0 C to 1200 C, the typical piece of steel would expand somewhere between 0.01 to 0.0144 meters/meter of length. or 10 to 14 mm per meter of length, assuming a coefficient of thermal expansion of around 10 to 12x10^(-6) m/(m K). If your appliance is a couple meters long you might have up to 3 inches of possible expansion to work with.

 

I also imagine you might be able to find hydraulic temperature valves to operate some sort of pneumatic system (IE, a globe valve of sorts with an expanding stem.) although that is just me guessing.

 

If I might ask, what is the rational behind not using energy in the building? Certainly there is tons of energy being used considering that the process is being heated some 1200 degrees! I'd find it hard not to justify the energy required for proper operations alarms, personally.



#5 Max Domingues

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Posted 18 April 2017 - 12:44 PM

Another thing: sorry for my fault! I didnĀ“t mentioned before about the style of oven - RTO (regenerative thermal oxidizer). Inside this equipment are two bed of ceramics who retain the heat. The heated ceramics are other reason to check and re-check the temperature inside the oven even when the energy is down.



#6 MrShorty

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Posted 18 April 2017 - 04:04 PM

but we are considering everything is off and there is a necessity to go inside the chamber.
for a scenario like that, what about using one of those non-contact infrared (IR) thermometers? Once the oven door is open, the operator can simply point the thermometer at the desired surfaces inside of the oven to see temperature. Amazon again lists a few IR thermometers that will measure above 1000 C. these measure surface temperature rather than air temperature, so it could depend on exactly what temperatures you want to be able to measure inside of the oven when you need to enter.

#7 breizh

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Posted 19 April 2017 - 04:50 AM

Hi ,

I will try a pyrometer or IR camera . These days you can find companies renting this type of equipment .

 

I used these technologies on Kilns and electrical contact ( hot spot on Electrical cables )

 

 

Good luck

 

Breizh






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