In the application of unbonded flexible pipes in offshore oil and gas field locations, the top riser supports might be located in the splash zone or just below the water line. At this location, both the vent valve and the end fitting are in a region which is prone to marine fouling, which may lead to blocking and damage to valves and consequently the riser itself.

The recommended practice for these types of pipe, API 17B, requires verification of the performance of the venting equipment, and clearly informs that the objective of this test is to verify the continued operation of venting valves after a long-term exposure to sea water - subjected to a sea water bath with a water column of 10 meters. After a 6-month exposure period, valve opening, and resettlement tests shall be performed to confirm serviceability, as intended, however no reference is made to marine growth assessment.

Some clients however have complained about the execution of the seawater long term exposure test in a laboratory, indicating that this test was meant to assess the effects of marine growth on the valves.

It is expected that in future some clients may amend their technical specifications and tender requirements to incorporate a new marine grow requirement for the vent valve qualification. As a result we are proactively proposing to address the issue of marine fouling around vent valves located at this position with various mitigating solutions.

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