Leaking Bonnet Cap

Nature of Defect

The natural gas Housing filter was weeping from the valve bonnet. At 26barg, minor leaks had been detected. Leaks from the bonnet cap were more evident as the pressure increased to 32barg. The client requested a composite repair to seal the leaks or at least improve the current situation and reduce the chance of the leaks worsening.


Metalyte Pipeworks solution was to form a shuttering around the bonnet cap to form a seal of resin. This would then be wrapped into the body of the filters below the cap.

Repair method

Metalyte technicians began by removing all coatings and rust from the area. The surface was prepared to gain an adequate roughness to allow the resins and composite to adhere to. A pre-fabricated shuttering was fitted around the bonnet cap and was filled with an epoxy resin. Once cured, the line was re-started and the area tested for leaks. With no leaks present the team where given the go ahead to continue with the composite overwrap. A bonding resin was applied over the filter body and resin cap. Metalyte Pipeworks technicians then applied the Dragon composite system. The repair was finished off with a UV and Chemical resistant coating.