14 replies to this topic

[Vegeta]

Team, 

 

I am working on the relief valves of an equipment at which the relief load of the non-fire scenarios is extremely higher than the fire scenario (approximately 100 to 3, respectively).   I'm thinking of providing two relief valves: one for the non-fire scenarios and the other for the fire scenario.   I have the following questions: 

 

1. Is this doable in the context of ASME & API (does this fall under multiple devices installation in API 520?)? 

 

2. If yes, what can be the set pressure values of each PSV? 

 

Your feedback is highly appreciated...

 

 

Regards,  

[latexman]

Why?  If the non-fire scenarios >> fire scenario, just provide a PSV for the worst non-fire scenario and it will easily relieve the fire scenario, right?

[Vegeta]

The view has been that the big PSV can relief the pressure in the fire scenario but it is going to re-close extremely fast and the cycle will repeat again (hopefully not quickly). That is the driver of the idea of two PSVs - big and small.

[Bobby Strain]

Forget it. How likely is the equipment to experience a fire when it is blocked in?

 

Bobby

[snickster]

If there is a fire who cares if the relif valve chatters.

[Vegeta]

For my knowledge,

What if there have been another operational scenario which requires a small capacity as the one for fire?
For example, there are three scnarios such that:

Operational scenario 1: 100%
Operational scenario 2: 3%
Fire scenario: 3%

How many PSVs (in category) shall be there? and how to set their set pressure?

[Vegeta]

Forget it. How likely is the equipment to experience a fire when it is blocked in?

 

Bobby

 

Very unlikely 

[latexman]

That may make more sense. It depends on the frequency of occurrence of OS2 versus that of OS1? Staged set pressures would be needed to make it work. Do you have enough room above normal operating pressure and below MAWP?

A fire is a rare event.

[Vegeta]

The operating pressure is 290 psig and the MAWP is 360 psig

[Vegeta]

Dear team,

Any guidance?

[latexman]

Are all scenarios vapor?

[seuenergy]

Hi, Can you give some data about the bigger scenario requires ? for example, 10 inches? or 12 inches? 

[shvet1]

@Vegeta

See quotes here

https://www.eng-tips....cfm?qid=504687

[Vegeta]

Are all scenarios vapor?

 

In fact I posted this topic because I got several PSVs of the same concept.  In general, most of these PSVs have only vapor relief scenarios with few which have both vapor and liquid relief scenarios. 

 

Is the idea behind your question the blowdown of the PSVs?

[Vegeta]

Hi, Can you give some data about the bigger scenario requires ? for example, 10 inches? or 12 inches? 

 

In this particular example I picked, the big PSV is 4"P6".