Repair of DC motor for Seadrill

Start date: 18.1.2011

The use of DC motors offshore is decreasing. DC motors are no longer being installed on new rigs, but there are still a lot of DC motors on the old rigs. Because of the motors being outdated the competence within DC is vanishing from the market. Karsten Moholt still has a lot of competence in this field, and is a strong resource to the industry.
Karsten Moholt has overhauled a DC motor (GE 785US2)  after breakdown for Seadrill. At the initial inspection there was discovered rust inside as well as on the outside covers and motor casing. The rotor and stator windings were in poor condition, and bearings were worn on both ends. Brushes, commutator and brush rocker needed repair. The brush rocker was renovated, and new brushes were made and mounted. It was stated that worn down brushes was the cause of breakdown. The windings in rotor and stator were repaired, and the imbalance in rotor was corrected. The machine was tested before being delivered back to the customer.
In general it will often pay off for the customer to repair a DC machine instead of buying a new one. DC machines are hard to get hold of, with delivery time often surpassing a year. On offshore installations it is critical to keep production going. A quick repair will often be preferred, even though the costs may be high.