Alarm setting for Tube Wall Temperature in a Fired Heater

[Dendrobium1975]

Dear members,

I need information related to Tube Wall Temperature (TWT) or tube skin monitoring in Fired Heater operation. When we consider to set a high temperature alarm for the TWT in a fired heater, what temperature should (or commonly) be used as the setting? Currently, we are considering some ideas such as:

1) Maximum TWT calculated as mentioned in the heater specification sheet (usually there are 2 maximum TWT mentioned in the specification sheet: calculated and design)
2) Creep temperature or Limited Design Temperature (refer to API Std 530 table 4) for the corresponding tube material
3) Certain temperature below Limited Design Temperature as mentioned in the point 2

Any idea or sharing of experience in such issue will be highly appreciated .

Best regards

Dens

 

[dh328]

Dendrobium 1975,
It depends on the function of the heater. is it a cracking/reaction furnace? or a simple heater for warm up?
I think you should set the TWT for the lowest one between design temperature and creep temperature (if you have free carbon in the coils).

 

[Dendrobium1975]

dh328,

Thanks for your helpful response. You said that the alarm setting could depend on the function of the heater. Could you please share further information about that statement?

Have a good day.

 

[rustbuster]

API Standard 530 offers calulations / methods to detemine TMT API 560 is the standard for fired heaters.