Leak Testing of Valves - Power Plant 4

[Bottle]

When purchasing valves from a valve company is leak testing of valves by a supplier usual practice or a requirement of a standard? (Not pressure testing, just checking if there is any leakage over the valve seat at MAWP or MOP).

If it is normal practice to leak test valves, would it be satisfactory to test a full batch or only a sample.

On a separate point, has anybody any good or bad feedback on the following types of valve manufacturers:

Bollfilter
Bray
Camau
Friulco
Jasta
Krombach
LVF
Neway
S+S
Sisto
Zwick

 

[JLSeagull]

I have used Zwick and have seen Bray. I am unaware of problems with either.

It is a normal practice to require API STD 598 compliance certification for seat leakage. Some project require testing a sample. Some may test all critical valves. Testing costs time and money. Neither leak testing nor certification assure that the valve won't leak after plant hydrostatic testing.

 

[Bottle]

How does API STD 598 fit in with ASME/ANSI. Is there any requirement under ASME B31.1 or 31.3?

 

[greg1950]

API 598 is a stand-alone document and has no relationship with ANSI/ASME B31.1 or B31.3 construction codes. API 598 is referenced as the testing standard for valves made to API downstream valve standards such as API 600 (gate valves) and others. The only ANSI/ASME standard that comes close to API 598 is B16.34, which specifies testing procedures but does not address leakage rates. API 598 does address leakage rates.

 

[NGiLuzzu]

Bottle,
there are already discussions about the same issue within this Forum: see, for example, thread408-23297 and thread408-192222.

About Zwick (and other Manufacturers of the same type of valve) please take a look at thread408-135872.

Hope this helps, 'NGL

 

[JimCasey]

Certainly the manufacturer should test the valves at assembly.

There are many standards for testing. "Bubble Tight" is not one of them although it is mentioned frequently and is completely meaningless unless a procedure is also involved.

Other useful specs are MSS-SP61 and API 6D.

FCI 70.2 is most frequently invoked for control valves but it is important to understand that 70.2 is merely a measure of the machining and assembly. The procedure (except for Class V) specifies testing at nominal 50 psi.
There is no relaible procedure to extrapolate what the leakage will be at other pressures, temperatures, or with other ladings.