4 replies to this topic

[phoenixmoca]

In the latest version of API 521 SUPERHEAT LIMIT TEMPERATURE(SLT) is applied to the overpressure scenario of entrance of volatile material into the system.
My question is if it is necessary to conduct SLT calculation to determine whether PRD is suitable for the overpressure scenario?
Thank you in advance.

[latexman]

It depends on the credibility/probability of your scenario attaining SLT, right? If probable, yes. If not probable, no.

[phoenixmoca]

Tanks,latexman.
It should follow the guidance shown in the API 521 to check the possibility of the scenario. If so how to design the PRD?

[latexman]

It should follow the guidance shown in the API 521 to check the possibility of the scenario. If so how to design the PRD?

 

You should re-read API 521, section 4.4.6.1, "Because of the shock wave potential, PRDs do not provide any mitigation against a superheat limit explosion."  Therefore, API 521 is saying one cannot design a PRD for the scenario.  It is not practical.  Re-read all of section 4.4.6.

[mark_84]

There is an excellent article about the background of the updated SLT section of API-521 entitled "API Standard 521 Guidance on Mixing of Hot / Cold Liquids and Prevention of Superheat Limit Explosions" by E. Zamejc, published in the Journal of Loss Prevention in the Process Industries, v 70.  It's available through Science Direct.