Thermocouples in Crude Vacuum Furnaces 1

[KazakhJeff]

I seek advice for the use of tube skin thermocouples in crude vacuum furnaces. Is the intention normally to check the furnace tubes in normal process operation, or decoking, or both? Does anyone have practical advice for how they work? How many should we place, and where?

 

[hacksaw]

tube skin t/c are specialty items. most t/c manufacturers make them.

they are weld-on. one manf. uses a radiant shield over the sensor to insure that you get a ture metal temperature.

 

[akd9305]

Dear KazakhJeff
The skin thermocouple which are welded to the tubes, should be located at the radiant and convection section of the heater to check the TMT so that it does not exceed the design value in case of low fluid flow in the tubes and flame impingement on the tubes during normal and decoking operation. These are located on the either side of the radiant zone up to the flame height on all the coils. Simillarly on the convection zone on all the coils.

 

[aybee]

All the previous threads are valid plus try to put them where you can see them so that a) you can check that they are still thereb) check their validity by doing thermoscan as well
also put in 50% more than you need as they have a habit of failing. Wrap the tail (the wire which goes back through the wall) in ceramic fibre (Kaowool or similar)as this si usually the bit that fails.
You will probably have to stress relieve the welding when you weld them on..I am presuming the tubes are better than carbon steel. check out the Gay (thats a trade name ) web page for thermocouples ,.they also do a good information section

 

[kaypeegee]

Further to aybee's thread. I have had very good experience with Gayeso Refracto-pad thermocouples in oil refinery crude and vacuum furnace skin-point service.

http://www.gayesco.com