Gas release from Shut Down Valve (SDV) Grease Injector Fitting

During routine plant maintenance routine function testing of SDV, central control room informed the instrument technician that valve had not met its function stroke limits. Valve has been in service since 1992.

Upon investigation, an instrument technician heard audible noise coming from the grease injector fitting on the valve stem. The system was then shut down and isolated for further examination.

The valve was removed from service and sent to vendor to simulate the exact site process test conditions. During the test the “official leakage rate” was recorded from the grease injector fitting, which indicated failure of lower stem seal, allowing gas to pressurise behind the grease injector fitting.

The valve was then stripped down and the valve components were found to be in good condition. However, closer inspection indicated that the lower stem seal had ‘collapsed’ and the grease injector NRV check-valve exhibited corrosion on the check-valve seating faces.

A full engineering report was compiled by the vendor, which indicated the root cause as being “injection of grease in a reverse flow direction, causing the lower seal lip seal to collapse”. Secondary component failure of the grease injector fitting found “Corrosion on the check valve seating faces, probably due to the length of time in service, and the environment location of the valve”.

Post Incident – ALL valves in hydrocarbon service were inspected (visual & FLIR Camera) and checked for signs of leakage through injector fittings.