Leakage rates for valves

[raton]

Hi there.
I have a question regarding the admissible values for leakage rates during a tightness pressure test.
I was given the rates for internal leakages in valves for sea water based on the DN as:

DN litres/h
6 0.05
8 0.08
10 0.08
15 0.15
20 0.2
25 0.32

I wonder if there is any standard or best engineering practice where I could find if the above values are correct.

Thank you very much in advance.

Jaime

 

[mlanc]

What kind of valve? What type of seal is in the valve?

 

[DLite30]

See if this helps you.

http://www.engineeringtoolbox.com/control-valves-leakage-d_484.html

 

[raton]

Thanks guys.
The valve is a ball valve.
The seal is metal.

Thank you for your help


Jaime

 

[Cockroach]

Bubble tight at the time of manufacturing release means less than 3 bubbles per minute when tubed to water. This is usually a Class 6 allowance as called out by the industry. Third party inspectors usually are tempermental about placing the tube to a glass of water so that the tube makes contact with the liquid, i.e. submerging it creates a hydrostatic head which defeats the purpose of the test.

It's an old trick by valve manufacturers, old as slice bread.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[raton]

Thank you very much Cockroach.

Jaime

 

[CostasV]

Normally the tube is submerged in a glass of water not deeper than 3-4 cm, so how can this cancel the test?

The tube (and the rest of air volume) can accept a little (0,4% of the volume, for 4 cm of water) more leaking air until it starts to bubble, but if the valve is leaking, then it will bubble with the same rate as it would, without the glass of water.

Do I miss something?