Case Study: Oil & Gas: Offshore Platform Pumps
Five production pumps on this offshore platform feed oil into a pipeline taking the product to onshore facilities. Three of the 2,250 hp pumps were under control of adjustable speed drives to adjust the total flow to demand, and the other two were on fixed speed. The original drives were obsolete and spare parts were difficult to obtain. In addition, the older drives required power factor correction and power line filters to keep the power clean. These filters were very noisy for employees working in the equipment room for long periods.
The Oil production company wanted to:
- Replace the old drives with new maintainable drives.
- Obtain high drive reliability backed by a five-year warranty.
- Obtain better system power factor without the use of correction.
- Eliminate the noisy power line filters by using drives with inherent low harmonic distortion.
- Have the ability to perform synchronous bypass.
- Reduce the component count to increase reliability and reduce maintenance.
In making its selection for the new drives, the company regarded experienced, local service support from the New Orleans office as important. Throughout the process, strong application support from the TMEIC GE engineering office in Virginia provided strong application support.
The first of the three old drives was replaced with a Dura-Bilt5i MV. After evaluation, a second Dura-Bilt was installed on the second pump. Each drive is equipped with the components for synchronous bypass in the future, although the actual bypass contactors were not initially included. A power study performed by TMEIC showed that the remaining old drive could operate without any filters since it represents a small portion of the load on the platform.
Benefits of the Dura-Bilt5i MC Pump System
High Reliability
Low Harmonic Distortion
High Power Factor
Compact Drive
Pump System One-Line Diagram
In this diagram, Drive 1 is shown with a synchronous bypass option, which can be added in the future.
This option will allow the drive to:
- Start Motor 1 with low current inrush.
- Bring the motor up to synchronous speed.
- Synchronize the motor with the supply bus.
- Put the motor across the line and disconnect the drive from the supply.
- Allow Drive 2 to control Pump 2 flow as required by the flow demand.
This configuration allows Motor 1 to run at full speed without the heat losses in the drive. The synchronous option can be extended to the second drive if required.
Future Improvements
The customer has the option in the future to retire the last old drive and install contactors on all motors and the two drives. With appropriate PLC control logic, the system will allow either Dura-Bilt to start and run any of the five motors, and put them across the line.
This future system improvement will provide:
- The maximum flexibility to operate the pumps under a wide range of situations.
- Soft starting available for all motors to minimize system impact and deterioration of the windings caused by inrush current.
- Reduction in the impact of drive downtime since no motor is dedicated to any drive.