Reducer in PSV discharge

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10 years 3 weeks ago - 10 years 3 weeks ago #8413 by Er.piping
Reducer in PSV discharge was created by Er.piping
Hi everyone..
I have worked on many projects and in every other project process or client seems to have different philosophies for.
1. Type of reducers used in PSV discharge (Conc. or Ecc.)
2. Orientation of Ecc. reducer in PSV discharge FSU or FSD.

Jop sir , 11echo can you please shed some light on the factors that govern the type (CONC. or ECC.) and orientation of ECC. reducer in PSV discharge.

Thanks

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10 years 3 weeks ago - 10 years 3 weeks ago #7073 by Jop
Replied by Jop on topic Re: Reducer in PSV discharge
Q1. Type of reducers used in PSV discharge (Conc. or Ecc.)
A1. You can use either a Concentric or Eccentric Reducer in the discharge of a PSV if and only if you are going from the smaller PSV discharge nozzle size to a larger discharge line size to reduce the back pressure.

Q2. Orientation of Ecc. reducer in PSV discharge FSU or FSD.
A2. The choice of BF (Bottom Flat) or TF (Top Flat) depends on where you choose to install the Reducer. The choice of one over the other will not make a measurable difference to the flow. What matters more is the rule for PSV discharge lines, "Do Not Pocket".

Do it once and Do it Right

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10 years 3 weeks ago - 10 years 3 weeks ago #7080 by 11echo
Replied by 11echo on topic Re: Reducer in PSV discharge
I see no advantage in using an eccentric reducer on the discharge of a PSV ...other then trying to avoid some obstacle, and that is usually accomplish by correctly locating the PSV away from an such obstacles. The function of the reducer is to help decrease velocity of the discharged commodity, and as JOP pointed out you do NOT want to have pockets in your discharge piping to collection any condensate.
From my experience PSV’s either discharge to atmosphere or into a common discharge header. When discharging to the atmosphere the discharge is normally directed “up”, which acts as a bucket to catch any liquids available …i.e. rain, condensate, & etc. To avoid this a ¼” diameter hole is drill about an inch from the bottom weld on the elbow, this is a bleed hole to drain any accumulation.
PSV’s discharging into a common header has the same problems, hence you don’t pocket the line to catch any liquids …but carrying that idea farther, you need to slope the main header slightly to enhance this non-pocketing effect. IF the main header was run “flat” the slight bending of the header between support would catch small amounts of liquid …doesn’t sound like a big deal but now multiple that by the number of supports on this common header and this “small amount” starts to add up …which could now slug the header and with the pressure if a PSV discharge could create some severe water hammer!

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