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Design pressure of hydrotest vessel question.

Design pressure of hydrotest vessel question.

Design pressure of hydrotest vessel question.

(OP)
We are having made two hydrotest vessels for our workshop, but I am confused over what the design pressure should be. The vessels are 12" OD, horizontal with ten x 2" class 2500 LWN flanges on the top.

Flange class is ANSI class 2500, max rating is 425 bars, at 37 degrees C.

We will be using the vessels to test up to 655 bar, regularly.

My problem is, should it have an operating pressure / design pressure of 655 bar?, and be tested to 1.43 x this = 936bar?

The flange rating would be exceeded at the vessel's normal operating pressure!

Or do we have the design pressure set to the flange rating, 425 bars, and just consider that it will be hydrotested regularly to 655 bar?

It will be in a concrete / steel lined test pit, and we have an external company doing the risk assesments and blast doors etc.

I do not want to go down the route of having class 4500 connections, as we would still be using 2500 flanges to bolt the signallers onto.

Any advice would be welcome.
 

RE: Design pressure of hydrotest vessel question.

AndyBass

I note you have a 1.43 multiplier, suggesting PED 97/23/EC. Opening paragraph '8' allows rthe use of non-CE vessels if they '...do not present any signifiant hazard due to pressure...'.
If you are using it as test equipment, in a manner that test conditions will allow for safe failure of the equipment under pressure, then that would seem applicable.

Bickers

RE: Design pressure of hydrotest vessel question.

(OP)
Thanks for that, I hadn't seen that before. I think we have figured out a solution to the class rating as well. Instead of standard geometry class 2500 flanges, we will make special forged connections with the same bolt circle and RTJ groove dimensions as the class 2500 flanges, but "beefed up" on wall thickness and flange thickness so they are designed for the pressure they will see as an operating pressure. This will mean I have to do justifying calcs on the new flange designs but thats not a prob.

We'll have special beefy blinds made for the vessel's hydrotest, and in normal service the standard class 2500 flanges of the items on test will bolt straight on with longer studs.

I might need some exotic RTJ seal rings for the vessel test though.

We're looking into using a high strength duplex for the shells on these vessels (2 of them)

Andy Cassidy

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