Back seat test in gate valve

[VYTR56]

Hi,
Is any one with experience with gate valve pressure testing. what is the best practice for back seat test and air tightness test in end of manufacturing process?

[Kelly_Bramble]

Welcome to EE!

Depending on the valve end-requirements... I've seen valves bubble tested under water to being placed in a test fixure and pressurized to 150% of operational load.

[PinkertonD]

What level of leak is acceptable?

As Kelly suggests a bubble test may suffice but if we are talking rocket fuel or something where even vapor-leak is a danger, then and upstream gas (non volatile, Argon etc) chamber and gauge for a 24-hour or better test would be the starting point. Check building codes for gas plumbing testing to get you started with how to go about testing.

You need to give us more information if you want more specific information. I failed Mind Reading 101. Either that or I have forgotten how to make it work.

[VYTR56]

Thanks for your replies, the test must be done based API 598 standard. I find something by search, this is the summery for these kinds of tests: Every valve shall be subjected to a hydrostatic test of the body shell at 1.5 times the maximum permissible working pressure at 100°F (38°C) The body should remain tight for the test duration. The test shall show no leakage, no wetting of the external surfaces, and no permanent distortion under the full test pressure. No device shall be used in testing the valve that will reduce the stress in the body. The valve shall be set in the partially open position for this test, and completely filled with test fluid. Any entrapped air should be vented from both ends and the body cavity via either a) The upper test flange with the valve axis vertical.
b) The body vent connection with the valve axis horizontal. After venting the body, vent plugs should
be replaced.
The gland or bellows and any body jointing shall be deemed as part of the pressure envelope. Where a bellows is fitted, the stuffing box packing & gland shall not be fitted.
The valve shall then be brought to the required test pressure. All external surfaces should be dried and the pressure held for at least the minimum test duration. There shall be no visible leakage during the test duration.Normally the these tests must be witnessed by vendor inspection agency hired by purchaser. The purchaser will deliver inspection and test plan to agency and vendor is responsible to notify inspection agency to attend to the vendor facility and witness "hold" points in inspection and test plan.