Case study - SAIPEM

Cutting unproductive time in dock for specialist vessels is vital for the owners that operate them. Saipem, who operate worldwide and provide oil and gas contracting services are no exception. When the regular overhaul of specialist heavy lift vessel Saipem 3000 and diving support vessel Bar Protector were scheduled for early 2008, the planning started early.

“As the Saipem Rotterdam office was undertaking the planning for the work on both ships it was logical for the Rolls-Royce Benelux service centre to take the lead on our activities,” explains Country Manager Fred Mast. “Additional technical support was provided throughout from our centres of excellence in Ulsteinvik and Kristineham. The close proximity of Rolls-Royce and Saipem here in Rotterdam simplified communications and ensured our activities were fully integrated into the project plan.”

The 162m Saipem 3000 displaces over 31,000 tonnes and is classed to DP3 standard. Due to the arduous operating conditions where the thrusters can be operating 24/7 for long periods, their regular overhaul is required under class rules. The four Rolls-Royce retractable TCNRQ 105/75-220 azimuth thrusters rated at 2,073kW and 2,684kW were installed in 1992. They were first overhauled in 2000, before the vessels’ conversion from crane ship to a self propelled heavy lift crane vessel with the addition of the 2,400 tonne crane and 3,500 tonne stern section.

Due to the global nature of the Saipem business, Cape Town was selected as the best place for the docking, working with the DCD Dorbyl shipyard. All parts plus the special tooling required were supplied by Rolls-Royce and shipped in a special container by Saipem from Europe.

“To complete the overhauls in the time available we brought together a team of 16 service engineers and worked in two 12 hour shifts, using additional manpower support from the shipyard as required,” says Marcel de Visser, project coordinator for Rolls-Royce on site. “Our work was on the critical path and as the vessel and ballast tanks were being blasted and painted at the same time, the conditions we had to work in were challenging. As this was the first time the thrusters had been overhauled since the ships conversion, we had the added complication of satisfying both ABS and DNV class rules.”

In parallel at the Sobrena shipyard in Brest, another team of 20 Rolls-Royce service engineers were upgrading the propulsion control system on the 112m Saipem diving support vessel Bar Protector. The vessel, that first entered service in 1982 is equipped with Rolls-Royce propulsion equipment comprising two 1,120kW azimuth thrusters, two 1,120kW tunnel thrusters and controllable pitch propellers, and was still operating with its original analogue controller. It was successfully updated to the latest digital specification within the planned docking period.

Exchange thrusters set to shorten docking.

The drillship Saipem 10000 went into service in 2000, equipped with six large underwater-mountable azimuth thrusters from Rolls-Royce, each unit rated at 4,000kW. The vessel operates in dynamic positioning mode most of the time and is classed to DP3 standard. Rated for drilling to 30,000ft in water depths down to 10,000ft, Saipem 10000 is 228m long and displaces over 96,000 tonnes.

These thrusters have given good service, and since Saipem 10000 will be undergoing a major survey and overhaul, the question was how best to conduct the work and limit the time spent off hire. Following discussions between Saipem and Rolls-Royce the answer to reducing overhaul time for the thruster underwater sections, which can be significant when six large units have to be handled, was to decouple the exchanging process from the overhauling process.

Saipem is therefore buying six new TCNP 156/M-380 underwater units. Each thruster takes 2-3 days to exchange, cutting the total time to between two and three weeks. As part of the agreement Rolls-Royce will hold four of the drillship’s existing thrusters in its ownership in Ulsteinvik. Saipem will retain ownership of the other two, and Rolls-Royce will overhaul them at a site of Saipem’s choice so they can be kept as spares for quick exchange in the future. A turnkey agreement covering the process of taking out the old thrusters and installing the new ones is also under discussion.

At the same time as the thruster exchange, there will be some upgrading, in particular of the steering gear to take account of product improvements in the upper part of the thrusters that have been introduced in the past ten years. The contract also includes provision of spares, and some long lead-time steering components on a just-in-case basis.