PRESSURE TEST FOR SEA CHEST COVERS

Cover plates are fitted externally to the sea chests on a Floating Production Facility by divers or ROV's in order to seal them off and allow them to be pumped dry for maintenance purposes.

The steel plate covers currently used are thick and consequently heavy to handle both on deck and subsea. This project was to replace the existing covers with lighter covers made from glassfibre reinforced plastic (GRP).

To prove that the GRP was a sufficient replacement material a pressure test was deemed necessary. GRP Aberdeen Ltd. manufactured the replacement sea chest covers from a calculated laminate make up consisting of layers of CSM (chopped strand mat) and Woven Rovings. A steel test rig was also fabricated to which two cover plates could be bolted to in order to simulate the actual connection and sealing details.

In conjunction with a local testing facility the completed test rig and covers were subject to an external hydrostatic pressure of 4.5bar for a duration of one hour.

The GRP covers performed excellently with no leaks or structural issues. The weight saving offered was also considerable, 20kg lighter than the steel versions in air and 32kg lighter in water.