Reverse Integrity Testing

TPC Clamp Connector seal ring for reverse integrity testing

The purpose of the reverse integrity test ring (or a back seal test ring) is to verify that assembly of the TPC Clamp Connector has been successfully performed, and that seal surfaces are good and well sealed, all without having to pressurize the whole piping system that the clamp connectors is a part of.

Two O-ring grooves are machined into the web of the ring and the cavity between the O-ring and the seal lips is pressurized through a small diameter pipe exiting between the hubs and in-between two clamp ears. Before assembly, the O-ring contact surfaces on the hubs must be properly cleaned and may need polishing for the O-ring to function properly. Before pre-loading the bolts, the clamp should be rotated to the most convenient orientation for performing the test.

The actual test

The test medium will normally be air or nitrogen. The pressurized volume is very small which provides a safe test as well as a sensitive test. A small leak is immediately seen as a significant pressure drop.

Since the seal is pressurised from the reverse side, the contact pressure between seal and the hubs in the test, will always be lower than during operation since the internal pressure in operation provides a strong pressure energized effect. The reverse integrity test pressure can therefore be low, and the test is typically 10 bar for 10 minutes.

Higher test pressure can be used, but this does not provide any better confirmation of the seal functionality for internal pressure. Using too high pressure will push the seal off the seat and create a leakage. A condition which has no relevance to the actual use. A reverse integrity test pressure higher than 150bar should not be applied, except in the case of testing to verify external pressure capacity.

It is only in the case of using the TPC Clamp Connector subsea that a higher external pressure than 150bar needs to be applied. The actual external pressure capacity is depending on seal ring material strength and the seal ring.