Unwetted wall fire case - Tube side on Exchanger

[Bill3752]

I have several exchangers that are processing gas on both the tube and shell side. Should I consider fire case for tube side? I searched this on a couple of boards, and found that I definitely would NOT look at a fire case if the shell contained liquid. Phil L also seemed to indicate in a post that since a fire would pretty destroy the exchanger from the shell side in, I should not consider the tube side a valid case. By logic, that would indicate don't worry about the tube side regardless of the material?
Thanks in advance.

 

[gr2vessels]

Bill,
First off all, there is a specialized personnel who provides the mechanical department with information over the fire protection requirements for particular equipment potentially exposeded to fire damage. They will advise the extent of protection required for your equipment, so you don't have to look for fire cases out of your control.
The fire case you mentioned is affecting the whole equipment, tubeside and shellside, the fire does not discriminate.
If you have been told to provide fire protection for the mentioned equipment, they will also tell you the expected heat flux, duration of exposure, expected time for the fire exposure or the expected time for the complete or parts of the equipment to reach critical failure temperature, etc...Then you will assess the best protection you could provide, by means of active or passive protection (deluge cooling water, fire resistant paint or refractory or other means). Please, the internet is not the best source of protection for your exchangers. You also have to work together with piping and valving people, to assess the need for depressuring of the exchangers, emergency shut-down procedures, etc...
You could get some valuable help from this forum, provided you start with the beginning, like what is a fire case?
cheers,
gr2vessels

 

[pleckner]

@Bill3752: I don't know where you get the idea you shouldn't take fire into account for a PSV scenario on a S&T exchanger. If the shell is an ASME code vessel then it must have a PSV on it (with some specialized exceptions). Even if it is gas filled, it still must have a PSV. A fire would destroy the exchanger in time but the object of the PSV is to prevent a catastrophic failure, aka:bomb.

I have yet to be convinced that the tubes of a S&T exchanger need PSV protection against an external fire. I've argued this case many times and don't want to get into details in this post. Those interested can search both this Forum and the one at Cheresoures.com and decide for yourselves. Being conservative is good....to a point.

 

[Bill3752]

Phil, not sure where you got the impression that I did not think the shell side needed RV protection. I have been defaulting to doing fire calc for both shell and tubes. Then I had found some of your earlier posts, which indicated not to provide tube side fire case protection. I was attempting to confirm/clarify, since I have several situations with gas on both sides and felt the tubes were not "so protected" in those cases. Sorry for the confusion.