Moving Rod to comply with Temperature Class T3

[patchlam]

Hi all,

Let me briefly illustrate the constraint that I am facing.

Basically, I have an equipment which is required to comply with temperature class T3, at 200 deg C. My equipment will have the hot flue gas to flow through at the temperature around 540 deg C. There is not any trouble for my equipment's outer surface to comply with that temperature class as internal insulation is applied.

However, the equipment has a moving stroke rod, which will move in and out of the equipment constantly throughout the operation. When the rod is within the equipment, it will be exposed to high gas temperature (540 deg C). Thus, when the rod moves out from the equipment, I believe the surface of the rod will be higher than 200 deg C due to heat soak when it is inside.

So, can I say that my equipment now does comply with that particular temperature class? If yes, what kind of measure that I should do such as sealing to ensure that kind of compliance?

Thanks!

 

[7anoter4]

First of all it is not an electrical problem, at all.
The rod will get heat from the hot gas and will discharge in the outside air.
The heat will be transferred from the gas to the rod through 3 ways:
1)conduction-if there is a contact between rod and the inner hot part of the equipment
2)convection-Qc=kc*Aria*(Tgas-Trod)*time
3) radiation Qr=krad*(Tgas^4-Trod^4)/100*Aria*time
If we could consider no conduction and neglecting the radiation then
a*Aria*(Tgas-Trod)*dt=M*thcap*dTrod
where a=convection transfer factor, Aria it is the exposed surface of the rod, M=rod mass, thcap=thermal
capacity of the rod material.
Let’s say A=a*Aria/M/thcap*Tgas and B= a*Aria/M/thcap, x=Trod then
dx/dt=A-B*x
The solution will be Trod=Tgas-(Tgas-Trod0)*exp(-B*t) [if t=infinite then Trod=Tgas and if t=0 Trod=Trod0]
Outside the rod is cooled in the same way Trod0=(Trodinside-Tambiant)*exp(-B*t)+Tambiant where
Trodinside=rod temperature when it immediately gets out.See the attached [possible] diagram.
The rod inside temperature may reach a temperature not far from Tgas.
In my opinion, you have to consider this will be more than 200 degrees and to proceed accordingly.