Dear Process Experts

I want to reintroduce an old problem within this topic: Design Temperature of Flare Network. As I checked there are some old topic within the site for this issue without clear conclusion.

Problem: During Relief Load Calculation based on API 521, high temperature up to 300-350 C have been reported! Therefore such high temperature may be used for design temperature of Flare Network. It is clear that carbon steel can work with such high temperature without problem. But expansion loop should be designed for flare header with corresponding capital cost!

Major shortcome for such high temperature prediction is boiling point of heavy component of liquid within a given liquid filled or partially liquid filled vessel. In real world for such high temperature long time (I think more than 20-30 min) is required to heat up vessel content during fire scenario.

Therefore we can ask that if such high temperature is real (e.g. 300 C) we should report it for vessel also. But such high temperature design due to fire case is not available in process design criteria of different projects!!

At same time we should note that when a vessel work in 40-50 C and then got high temperature around 300-350 C (after 20-30 min expose to fire) vessel expected to mechanically fail before PSV action.

I got some recommendation from well known companies to consider fire case design temperature as 180-220 C without any technical backup (Just Experince).

I shared all issues related to this problem here. Please complete it with valuable points. Some designer proposed to design only PSV tail pipe for fire case (e.g. 300 C) and then flare header only for 80-100 C. I prefer reply with some technical and clear backup such that new user can use it for their design.

Ghasem Bashiri