Alimak has supplied rack and pinion lifts to rigs and platforms since 1974. One of its earlier installations was for the semi-submersible Actinia, now owned by Transocean.
Until recently, the rig was still in active service, working on contracts in the Mediterranean, and so was the original lift system. However, Transocean needed to refurbish the rig to extend its working life by another 20-30 years. The extent of the planned overhaul meant that the two passenger lifts would have to be removed and replaced with newer models. Transocean contracted Alimak to manage this program.
According to Alimak Offshore Division Opera-tions Manager Steve Williams, space available for the new lifts could not be increased, due to physical constraints associated with the internal structure of the columns.
The Actinia outside drydock in Malta.
"One of the challenges was to provide a new system within these confines, while also offering improved service through use of the latest design technology and components," Williams said.
Another important consideration for Trans-ocean was the need to limit the normal schedule for a program of this nature by ensuring that critical milestones were achieved while the rig was briefly in port at various locations in the Mediterranean. This would help Transocean minimize disruption to its own operations. The rig's general overhaul was being performed in stages at quayside in Spain and Malta between a series of 90-day assignments offshore Egypt and Tunisia.
Initial contract planning and design meetings were held at Alimak's head office in Skellefteå, Sweden. Design queries and planning issues were resolved quickly, enabling a fast-track program to be agreed. Alimak then proceeded according to the agreed timescale, sending equipment and manpower to Spain for the removal and new installation work and subsequently manpower to Malta for the final commissioning phase.
"Through improved planning and communication with Transocean in Aberdeen, we completed the design and delivery of both lifts in just under six months," Williams says, "20% ahead of a typical schedule for this type of equipment."
Early in the program, Williams explains, "our project coordinator visited the rig offshore, not only to perform surveys, but also to assess potential safety risks or hazards that could arise during the contract period. Job-specific risk assessments were then compiled and agreements reached with Transocean before any installation work started, reflecting both companies' commitment to the safety of the offshore personnel.
"It turned out that since the original installation, the customer had had to put in steelwork under the lifts, plus other fabrications, to meet new requirements concerning impact loads," Williams says. "Through close liaison with Transocean's structural engineer in the UK, load calculations and stress analysis were carried out, leading to design of additional steelwork to dissipate the loads that the new lifts would impose on some of the existing structures.
"We agreed a full spec with Transocean, including new communications systems. For instance, we introduced a programmable logic control system for the landing operation, designed and manufactured by us in-house. Previously, for every landing stage, we had had to install curves to let the lift 'know' where it was. The new system incorporates digital measurements to determine the lift's position in the shaft. An Alimak overspeed governor was factory tested under full load conditions and fitted to the lift car for safety."
The new lifts have been designed to carry passengers or goods weighing up to 400 kg, as dictated by best use of the limited space available within the existing columns. The lifts serve three levels from the deck down to the pump rooms. A two-way communication facility has also been installed in the lift cars to enable passengers to communicate with other rig crew outside the lifts.
Alimak prepared manuals for the crew of the Actinia concerning proper use of the new lifts. "There is a need for written documentation to support operational safety. Otherwise, offshore personnel are at risk from incidents such as dropped objects on feet. In this case, we are also translating our documentation into different languages to accommodate the different nationalities working on the Actinia." Alimak can also offer Transocean's personnel safety/operational training in the lifts, both on the rig and at its training facilities in Skellefteå and Rushden, UK. These have been used to train certification staff from ABS and DNV, among others.
"One of Transocean's reasons for selecting Alimak for this contract was the level of our support service. We design, manufacture, and provide warranty to our lifts, and can therefore guarantee a stable source of supply of genuine spare parts."
Alwyn North and others
Elsewhere, Alimak has just signed a contract with TotalFinaElf North Sea in Aberdeen to refurbish the goods passenger lift on the Alwyn North platform. Other recent deliveries include two access lifts with 500 kg transport capacity for Maersk's new deepwater drilling semisubmersible for the Caspian Sea, and two access lifts with 12,000 kg lift capacity for BP's new Valhall platform in the Norwegian sector.
Alimak has adapted its lifts to offset pitch and roll motions on FPSOs.
"We're also looking at solutions for Spar platforms," Williams says. "The benefits of rack and pinion lifts in confined spaces may have been overlooked by the operators, but we think Spar crews are struggling with stairways and consequently limited access for both goods and passengers. Admittedly, Spars have space restrictions, but solving this is our forte. A small compact rack and pinion lift wouldn't add that much to the overall load, and it would improve access to the tight confines of a Spar platform for maintenance personnel."
For more information, contact Steve Williams, Alimak. Tel: +46 910 87000, fax: +46 910 56690, email: Steve.Williams@alimak.se.