Bed Temperature Thermocouple for CFB Boiler


Thread Starter


Hi guys,

I’™m engineer in power plant CFB boiler and for a long time have faced problems in bed temperature thermocouple sensors which is every shutdown. The unit we found a lot thermocouples were damaged, and the protection tube also completely corroded.

My thermocouple specification:

Type: K
RANGE: 0-1100 C
Standard: ANSI MC96. 1
Sheath material: 316SS Ǿ8
With protection tube
Well material: standard
Proc Conn size: 1³ NPT
WEAR resistance length(L2): 200mm
WELL total length (L1): 600mm

It’™s a Chinese standard. I want to change it by European standard, but I don’t know the equivalent can someone know that?

Or give me some suggestion about this problem?

My Best regard
These are all too common in many industries, and none of the current standards cover such applications.

Right off, 316ss is not suitable for 1100C, there are several options

1. ceramic
2. special alloys
3. Infrared measurements (analyzer) of the process fluid.

In any case a good deal of detail engineering and design work is required. It won't be cheap.

Type K is notorious for high temperature failures. Type N has somewhat better resistence at those temperatures, but some resort to infrared temperature temperature measurement of the gas with special purging of the optical connection.

There are a number of engineering /consulting firms that can further identify the failure mechanisms and reolve the meaurement issues.

Thank you Mr Dave for your response.

and i wonder why you suggest type N not type R or S. secondly i want some known manufactures have like this style and industrial protection tube ceramic type if it possible.

Best regard
Type R or S will work too, if your plant can afford it. As you are currently using Type K, N- is a bit more robust and affordable.

Any supplier of your thermocouples, will also have a selection of well materials that are compatable with the sensor to chose from.

the salesman may be able to take early retirement!
I was just sitting in a presentation for a thermal imaging camera. It was claimed that these have superseded tube temperature thermocouples. The lens was installed right in the furnace, check for LumaSense

Hope this helps
The ones for process measurements cannot allow direct exposure as you suggest. Thus the rather significant installation design issues.

There are two types. Those sighting down a protection tube, and those with direct view of the process gases.

>I was just sitting in a presentation for a thermal imaging
>camera. It was claimed that these have superseded tube
>temperature thermocouples. The lens was installed right in
>the furnace, check for LumaSense
Yes, the projection tube as you say isolates the camera from the heat. I assumed the projection tube was fitted with a lens.

The presenter claimed you can monitor hundreds of different spots in a furnace with one fixed camera. I have no first hand knowledge of the system.