PED- Allowable pressure dropp (pressure loss)

[Jezovuk]

Hallo to everyone!

I would like to hear an expert opinion about permissible pressure loss according to PED 97/23?
We tested a vessel (V=20L) with O-ring at a pressure of P1= 5 bar and after 2 hours the pressure drop was 2 bar (P2=3bar). I just can´t find a reference in Pressure equipment directive to determine if this pressure loss is permissible or not. Or is generally any pressure drop allowed.

 

[XL83NL]

The PED generally isnt specific on issues like these. Your design code may however.
What is the design code of the vessel?

 

[EmmanuelTop]

If EN 13445-5 the acceptance criteria is as follows (10.2.3.9): "During the proof test the vessel shall show no signs of general plastic yielding. Local deformation which is identified by visual inspection and which is cause for concern shall be referred to the designer for reconciliation against the design specification. During the proof test no leaks are permitted from the pressure envelope."

Dejan IVANOVIC
Process Engineer, MSChE

 

[Jezovuk]

Thank you for your answers!
XL83NL- The design code is German PV Code: AD2000
EmmanuelTop- "During the proof test no leaks are permitted from the pressure envelope". - I was hoping to find something similar in AD2000 but i didn´t have any luck.

 

[racookpe1978]

The water went somewhere: or the vessel leaked past a bad seal or valve, or the vessel yielded to either failure, or to expansion. 20 liters is very small, but if the test pressure was 5 bar, and dropped to 2 bar, you lost about 60% of your fluid volume that raised the pressure from "full" at atmospheric pressure, to 5x atmospheric pressure. Did you measure how much you pumped in?
Did you gather ALL of the possible fluid leak paths to see if a valve or seal brke?
Did you record original, at intial test, at final test, and at empty ambient temperatures?
Was the PV actually at the ambient temperature you measured? (No sunlight or power sources, or heater turning on or off?)

 

[Jezovuk]

Hallo racookpe1978!
Thank you for usefull tips!
We didn´t fill the vessel with water, we just made a pressure test with air.
I think that our problem is the O-ring. The O-ring we use now is encapsulated FEP O- ring which is very hard and thus can not be commpressed enough because our lid is screwed just with 4 fast opening bolts (tightened with hand).