Hi:
I need to rerate a vessel with operating pressure of 60 Psig and 35 F and design p=150 Psig to design P=200 Psig.
The PSV which is set at 150 Psig popps up at summer time due to high ambient and we have NH3 relief .
The issue is that I think the PSV will have higher capacity once we change set point from 150 to 200 Psig but my co worker thinks the capacity will stay same.
the over pressure is 10% on PSV and capacity as of now is 37 #/hr with size 3/4 x1.
Another problem is that I think the header size for ammonia relief should be reviewed once we change the set point pressure, this is for two PSV 's , there are over 20 PSV connected to a 3" header, plant was designed for lower production but later product type changed and no one really looked at PSV header sizing again.
The relief header size is 3 inch now I think it should be 6" as the biggest PSV can relief 110 #/min NH3 , I used biggest PSV in system and considered back pressure of sparge tank to be 5 Psig, hysys simulation shows pressure drop on 3" relief header to be quite high around 14 Psig,,,total drop=14+5=19 Psig).
19 Psig is 10% of set point of lowest PSV set point in system.we have PSV;s set at 250, 300 and 200 Psig all connected to same header, pipe length is over 80 ft .sch 40
How can I convince my manager to consider re sizing header?
Does vessel re rating and change to PSV set point cause PSV capacity increase, can I change spring size
what are the resources available.api 520 or articles?tx
Edited by ziba, 03 December 2016 - 10:14 PM.