Integrated technology solutions provider SKF has supplied bearings for gearboxes designed by Korean diversified solutions company Hyosung Corporation for oil rig drilling platforms.

SKF reports that oil rig drilling platforms are high-cost capital investments and that the designers and end-users of these massive structures require reliability and availability in the components of critical equipment.

Jack-up platforms are designed to float to a location and then have the drilling platform jacked up off the surface of the sea. In this platform, the jacking gearbox is a piece of critical equipment. 
Jacking gearboxes provide the power to lower the platform legs onto the sea floor and then lift the significant weight of the drilling platform high enough above the water to 
ensure there is no interference to drilling 
operations from wave motion, even in stormy conditions.

Hyosung Corporation, of Korea, reports that its jacking gearboxes provide reliability and power. SKF supplied the 23 bearings in each of Hyosung’s latest gearbox designs, 
including the SKF CARB toroidal roller bearing, which delivers the highest carrying power in the smallest package of any bearing type.

Hyosung Industrial Machinery senior 
designer Won-Cheol Hong started a project to design a smaller, lighter, more powerful jack-up gearbox for oil drilling platforms. A significant component in the design was the bearings that supported the shafts and gears as they lifted the weight of the platform at 1,5 ft/min. The weight of the platform and the demanding operating conditions meant that minor deflections of the shafts could not be avoided. To prevent premature bearing failure in gearbox applications, the bearings selected needed to accommodate these deflections in all conditions throughout the life of the gearbox.

Hong’s final selection included SKF 
tapered roller bearings, spherical roller bearings and CARB bearings for the demanding load carrying in the planetary gears. This selection, says SKF, resulted from thorough advanced modelling of the gearbox together with sophisticated bearing life and load calculations carried out by SKF.

When the project was completed, Hong’s design was selected for the highest award at Hyosung for innovative product development. 
More than 500 sets have been delivered for use in offshore drilling and will be incorporated in new platforms being commissioned in the next few years.

The first drilling platform equipped with these gearboxes started drilling off the coast of China, in January 2009, and will remain there for three years. The oil rig, operated by a US company, uses 54 Hyosung reducers to jack up the drilling platform, having 18 gearboxes on each of its three support legs.

The rig platform has a maximum drilling variable deck load of 3 673 t, which requires reliability and power from the gearboxes. Further, the oil drilling platform is expected to be active for 20 years, and the gearboxes need to last as long as the platform, especially if the operator is to have efficient and trouble-free operation during the anticipated total 2 000-hour 
period of lifting and lowering the platform 
once it is positioned. 
The first gearboxes produced have a lifting capacity of 220 t and a holding capacity of 350 t in normal conditions, extending to 500 t in severe-storm conditions. 
Later models have a 225-t carrying capacity with proportionally more holding and 
severe-storm capacities.

“I am pleased with the technical support I received from SKF in this project. As well as full support from local SKF Korea engineers, I was visited by European SKF engineers who had applied CARB bearings in other heavy industry applications, such as steel mills, pulp and paper plants and wind turbines. 
“They provided deep technical presentations that gave us the confidence to move forward with the development. The use of CARB, and its self-aligning ability allowed us to design low-profile gears that are wider, stronger and give greater torque capacity, compared with previous designs. 
“This provided us with the confidence to downsize the gearbox, which was proven in tests, when we loaded the gearbox planetary gears to three times the expected loads with no problems. CARB’s ability to take up minor misalignments and heavy loads improves the gear meshing, which also improves the gearbox efficiency,” says Hong.

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