Achieving improved thruster performance in offshore supply vessels

Electric motors and variable speed drives deliver numerous benefits to the vessels that serve the offshore rigs.

My experience working with electric motors and variable frequency drives (VFDs) began while I was working for Baldor out of the Atlanta office, prior to the ABB acquisition of Baldor. In my current role as a product and application sales manager for ABB Baldor out of the same office, I have seen many times where the pairing of Baldor motors and ABB VFDs has elevated the performance of whatever system it powers well beyond the existing benchmarks.

One application I have been involved with for over ten years particularly sticks out in my mind. It involves Master Boat Builders Inc. of Bayou La Batre, AL, founded in 1979, and known today for being a leading builder of highly sophisticated offshore supply vessels to serve the oil industry.

Transitioning from hydraulic to electronic thrusters

Up until approximately 2006 the oil supply vessels featured mechanically operated bow and stern thruster systems driven with hydraulic motors. The thrusters were relatively complex and inefficient, incredibly loud while engaged, and poorly suited for the harsh marine environment.

Boat owners began to demand a change, and Master Boat helped solidify its niche by being one of the first builders to design supply boats with electric thrusters powered by electric motors and VFDs.

I became involved several years prior while Master Boat was first investigating the electric motor and drive packages that would power the thrusters. A call came in to our office with very little application information, so I went down to the shipyard to evaluate the opportunity. It turned out to be a good fit for us, and we pulled together a Baldor motor and drive package.

The electronic thrusters delivered substantial benefits over the hydraulic units including far greater environmental and operational safety, easier installation, and cheaper, more efficient operation. Plus they were uniquely capable meeting the challenges presented by the rough conditions of the open sea.

Larger vessels require more advanced electric motor and drive technologies

In 2011, or thereabouts, Master Boat began building larger, more sophisticated vessels. It didn’t take long for us to realize that pairing the ABB ACS800 VFD with the Baldor RPM AC motor, both newer, more advanced technologies, would provide some additional longevity and performance benefits. So we made the switch.

The new thruster packages provide enhanced performance on the larger vessels, with the direct torque control (DTC) technology in the ABB drive and the low inertia aspects of the Baldor AC motor providing excellent control throughout the entire speed range, from 2 rpm to 1,800 rpm. This provided highly efficient acceleration, deceleration and full reversals, while reducing generator load and increasing the overall performance of the system.

Better Dynamic Positioning System performance

One of the biggest benefits, however, is how smoothly the thrusters interface and respond to the sophisticated Dynamic Positioning (DP) system required of offshore supply boats.

A DP system is an automatic operational mode that triangulates between GPS satellites to maintain a vessel‘s position within a 1 to 3 meter radius. It is used while a ship is in very close proximity to an oil rig, controlling the bow thrusters, the main propulsion and steering system to hold the ship in place, no matter the wind, current or wave action. The ability of the ABB drive and Baldor motor pairing to execute very quick and rapid accelerations and decelerations greatly enhances the system performance.

Gulf Coast Air & Hydraulics – an expert partner

Early in the relationship Gulf Coast Air & Hydraulics, a full service distributor serving the heavy industry and marine markets located in Mobile, Alabama, became an important partner. Despite the presence of “hydraulic” in their name, they have become experts in electronic thruster technology, and have worked closely with Master Boat and ABB Baldor as the thruster systems have become more sophisticated, and the applications for electric motors and drives have expanded.

When the bow thrusters increased to 800 horsepower on the 220 ft vessels we collaborated on a compact cabinet design that saved five feet of space so the two cabinets could sit side by side in the limited bow quarters. And based on success of the motors and drives on the thrusters, further pairings have expanded to other onboard systems, powering ventilation systems and mud, fire and deluge pumps.

Future challenges

There are 60 plus Master Boat built vessels floating around the Gulf of Mexico with ABB/Baldor drive systems powering the thrusters and other onboard systems. As we look to the future there are certainly more challenges ahead. Boats will continue to get bigger and require more power, and the motor/drive units will need to be further customized to provide the necessary performance in increasingly confined spaces.

As long as the established model of innovative supplier, expert distributor and open-minded end-user stays in place, we should be up to the challenge!

In case you are interested to read the full story and watch a video of how Master Boat Builders improved the thruster performance, please visit the case site here.