5 replies to this topic

[Engineer87]

Hi Members,

 

I have a Process diagram showing the location of PSV's. I have one pressure safety valve attached to the air eliminator that is sized for fire.Other 2 are connected to nitrogen bottles via 3/8'' hose which is afterward connected to 4'' hose line.I'm little confused are those 2 PSV sized for blocked flow? Can anyone tell me the reason for having PSV there?

 

 

I'm talking about PSV-1001 and PSV-1002.

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Edited by Engineer87, 05 March 2014 - 10:41 PM.

[Bobby Strain]

I'm like you. I'm confused, too.

 

Bobby

[aroon]

hi,

 

PSV-1001 should be sized for two cases:

1. Blocked flow, as it should be applicable due to Nitrogen cylinders (very high pressure during initial stage).

2. Failure opening of pressure regulating valve (PRV-1000 and PRV-1001).

Ensure that you have considered maximum operating pressure of the Nitrogen cylinder.

 

However, as per my knowledge, there is no need of PSV-1002 if it really set at 150 psig. Either location or the set pressure is misleading and need to be field verified.

[fallah]

Engineer87,

 

The PSV-1001 is there to protect the 3/8" and 1/2" hose lines whose design pressure seems to be 150 psig. The overpressure scenario would be one of PRV-1001/1002 failure as stuck in wide open position.

The PSV-1002 seems to be additional based on the info provided, other than the design pressure of the 1/2" hose line would be lower than 70 psig, then the set pressure of PSV-1002 should be lower and equal to design pressure of 1/2" hose line...If so, the overpressure scenario for PSV-1002 sizing would be PRV-1002 failure to be stuck in wide open position...

Edited by fallah, 06 March 2014 - 01:15 AM.

[Engineer87]

Thanks Bobby,Aroon and Fallah.

 

 

Can anyone of you please explains the utilization of Nitrogen at facilities.I think it used to purge tanks,vessels and pipelines of vapors and gas.is that right?

Edited by Engineer87, 06 March 2014 - 02:00 AM.

[aroon]

Yes. In your case, this is for flushing and venting of unloading line, strainer and pump to avoid inventory of flamable material during non operational case.