Marine engineering and propulsion company Royston said Monday it had completed the overhaul of diesel generators on board Stena Drilling's semi-submersible offshore drilling rig ‘Stena Spey’.

The work saw cylinder heads, pistons, and conrods overhauled as part of a 12,000 running hour service of one Rolls Royce Bergen KVGB12 Diesel generator by Royston engineers onboard the rig while it was located at Orkney.

Royston has previously overhauled diesel power units onboard other Stena Drilling rigs, including the Stena Don semi-submersible drilling rig, and the Stena IceMAX and Stena Carron drillships.

According to Royston, the engines were stripped down to allow engineers to carry out maintenance and repair work on the 12-cylinder heads, two-unit inspections, main bearing inspection, camshaft inspection, timing chain, and drive inspection. Other work, which included repairs to water leaks in No.3 generator, involved removing of the cylinder head, piston, and connecting rod and renewing the cylinder liner.

The Stena Spey is a drilling, completion, and workover rig capable of undertaking drilling operations to depths of more than 8,000 meters.

The rig was built in 1983 by Daewoo in South Korea. The Stena Spey is a Friede & Goldman L907 (enhanced Pacesetter) twin-pontoon, column-stabilized, self-propelled, semi-submersible offshore drilling rig. Since entering service in 1983, the rig has undergone several upgrades.