Valve passing at site
Valve passing at site
(OP)
Dear members,
Based on API 589 closure test requirements, some passing (leakage) is permitted during manufacturer shop closure test.
However what about the passing at construction site during line hydrotest?
Is there any international code or standard for that case?
You know that the test pressure during line hydrotest at site may be lower than that during shop closure test.
Thanks in advance..
Based on API 589 closure test requirements, some passing (leakage) is permitted during manufacturer shop closure test.
However what about the passing at construction site during line hydrotest?
Is there any international code or standard for that case?
You know that the test pressure during line hydrotest at site may be lower than that during shop closure test.
Thanks in advance..





RE: Valve passing at site
I'm not aware of any International Standards dealing with line hydrotests of newly constructed plants (and I would be curious to read one...), but I believe every Engineering and End-User Company has own its own Specification.
You will not find an answer to your specific question, but you can probably read some stimulating hints about the same subject within thread408-150132: "Zero Leakage" conept and EN 1779 std....
Regards, 'NGL
RE: Valve passing at site
RE: Valve passing at site
These valves are block valves to be installed in inlet of spare-pumps. It means that these valves are normally closed. What about this case? In this case, should the blank be used instead of valve?
RE: Valve passing at site
RE: Valve passing at site
Many system hydro tests are done at 150% rated and will lift (open) the seats on most of our valves (some are over designed). Likewise, other valves from other valve manufacturers if they are building to the same standards will also have their seats lift or open.
RE: Valve passing at site
I will echo the previous posts for EN standards and confirm the viewpoints presented.
There is always a limit to what the valve manufacturor will allow as maximum for a valve at a line test. This is partly given by the valve standard, wich will be higher for the housing (open valve housing test 1,5 times pressure class (or more depending on pressure class, dimension and producer and valvetype)) than the seat (operating pressure equal to pressure class normally 1,1 times (again also depending on valve type - for instance will often smaller valves (ball valves for instanca) over-qualify) on allowed seat pressure.
Under line pressure tests there is always a risk of something malfunctioning and giving water hammer, which in addition to overpressure of seats can damage (permanently) the valve sealing or valves.
Generally: blinds should be used and all valves be left open under line tests.
Or (the world is not always ideal) if valves are closed under line-tests, all care should be taken, the valve manufacturor to allow in writing the given pressure.
Two buts: For some types of resilient seated gate-valves for instance, a somewhat higer seat pressure will have less impact than for other constructions.
Secondly: anything going wrong and valves not operating properly or leaking after a (too high) test the responsibillity and guarantee that everything was done properly lies on the test executing side.