Which type of reducer to be designed downstream of a relief valve?

[bobansmech]

I would like to know, which type of reducer (Concentric or eccentric) to be designed downstream of a TZV / PZV (relief valves).

If concentric be in place for above query, in which position shall it be designed - vertical or horizontal?

Could someone help with any reference, rather than thumb rules?

 

[BigInch]

It's not very often you'd want a reducer downstream of a relief valve, as the object is usually not to restrict relief lines in any unnecessary manner. You can buy big relief valves, but not pipe, or what?

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[racookpe1978]

Are you asking perhaps about which direction an "expander" would best be placed as the outlet pipe from a PV valve expands from one size to the next larger? (Flat side down vs flat side up so water/condensate/rainwater can't get trapped in a horizontal run and block flow?)

As above, you do not want the outlet of any RV to be restricting flow.

 

[TD2K]

I'm assuming the reducer is to match the PSV outlet flange size to the main header size, such as a 2" PSV flange to a 3" tailpipe. I wouldn't reduce down, that in my opinion is just poor practice.

I've normally seen concentric reducers used on PSVs. I wouldn't have a problem with an eccentric if it made sense to use one, I'd orientate it such that I couldn't create a liquid pocket. Which orientation makes sense for your application depends on the piping isometric.

 

[bobansmech]

Thanks for all the posts!!
More precisely, my relief vale is a TZV (Temperature) It has an inlet of 1" and outlet also as 1" but I need to connect outlet 1" to a 3/4" flange in Tank Nozzle.

So I need a reducer downstream / outlet of TZV 1" X 3/4".

If I use Concentric Type, what is the problem? I dont think any pocket formation will happen, as TZV outlet will not regularly operate, but only in worse case if there is any temperature raise.

Please have your say dudes!

 

[GHartmann]

Please note that what folks have suggested is that it is not a good idea to reduce down in size exit a relief valve.

You may need to check the backpressure created by the smaller line size and if it is greter than 10% of the set pressre your will need to size the valve differently.

 

[Drexl]

I don't know what a PZV/TZV is but if you are protecting pressure equipment with a safety valve then you should not reduce size in the outlet piping. At least in the standards I work with.

 

[TD2K]

API 520 or 521 I know prohibits a smaller inlet line than the PSV inlet but I recall at least the older versions didn't prohibit a smaller outlet line than the PSV discharge flange if the resulting backpressure was within the allowable limits. That may no longer be the case, I don't recall. That said, I think it's poor practice.

What sort of required flow are you talking about? If I have to relieve a flow that is a significant capacity of the PSV, I wouldn't do it regardless of the outlet pressure drop and resulting backpressure calculations. If I'm looking at a typical thermal relief where my required relieving capacity is 0.002 gpm and the PSV capacity is 50 gpm, I'd be more likely to consider it versus insisting the 3/4" tank connection had to be replaced.

Expect a LOT of people to be coming to you pointing out the mistake.