Vol. 227 No. 12

Rig floor equipment

Electric motors drive 2,000 hp mud pumps

When the world’s two largest semisubmersible rigs, Aker H6 design, come in to operation in 2008, they will be equipped with the biggest mud pumps ever installed on one rig. The pumps are of triplex-design, and each has a 2,000 hp rating. Four pumps will be installed on each rig, giving a full pumping capacity of 8,000 hp.

The pump package has a total weight of 200 t per rig and the height is four meters. They will be speed-controlled by frequency converters via specially-designed electric motors from Schorch in Germany. These EExe motors are watercooled, double shafted and have a special arrangement for insulating the motor bearings to avoid current damage from the PWM-type inverters.

EExe motors from Schorch will drive four 2,000 hp mudpumps on each new Aker H6 rig.

According to Hallvard Slettevoll, director of Schorch Norge, Schorch now makes electric motors as large as 25 MW and up to 15 kV in voltage, and in the EExd motor up to more than 10 MW. The company has extensive experience building motors for the offshore market, and many EEx motors, similar to the eight new motors for Aker, have been installed on rigs in the North Sea. Most of them are EExe design, built in accordance with Norsok requirements, and are DNV approved.

The Schorch factory in Mönchengladbach, Germany, is one of the world’s biggest and most experienced electric motor manufacturers. Established in 1882, it has a unique test-bunker for explosion testing EEx motors. This capability certifies them to make their own safety approvals in cooperation with PTB. This is one of the reasons for the company’s design flexibility and short delivery times, even in custom-designed motors.