Thruster Guidelines

THRUSTER GUIDELINES SUB-COMMITTEE

Chair – Dietmar Deter, Nautex

Committee Objective

To provide practical and informative guidelines for thruster users, as well as professionals specifying and /or purchasing thrusters.

Mission Statement

The subcommittee on thrusters is intended to provide a consistent forum for exchange of information, discussion of technology, education, improvement of reliability and efficiency, review of existing regulations and/or guidelines, and the generation of new guidelines or recommended practices for the

• Design
• Manufacturing
• Testing
• Procurement
• Operation
• Maintenance

of thrusters in DP service. The new guidelines shall supplement existing ones (mainly rules of classification societies and gear manufacturer’s standards).

Statement of Need:

Thrusters are an important part of a DP system. Their costs and maintenance requirements by far exceed those of the DP control system. The consequences of failures of thrusters affect directly the DP performance of the vessel.

Thrusters evolved into the largest right-angle gear drives in the history of mechanical engineering using state-of-the-art gear cutting technology, extremely highly-loaded gears. Nevertheless, they are typically inaccessible for conventional maintenance tasks. Unlike any other gear drives, they operate in an extremely hostile environment, are supported by non-rigid structures, and are frequently operating in pulsating load conditions (while exposed to the wake of a second thruster). Some of the mechanical problems, for example, successfully sealing the propeller shaft over an extended period of time to prevent seawater intrusion into the oil-filled gear housing, are far from being solved.

The existing design rules provide some basic information for the design engineer, but leave too many gaps and ranges open for subjective interpretation.

The specific hydrodynamic tasks of thrusters in DP service are relatively young. Before the advent of DP, subjects such as propeller-hull interaction, propeller-propeller interaction, and their impact on the performance of the thruster were of no interest to the naval architect. The DP technology opened a new area of hydrodynamic concerns and research. The influence into the practical operation and efficiency of a DP drill vessel should be emphasized.

Despite the above mentioned problem areas and the high costs involved with the selection and procurement of thrusters, decisions regarding the purchasing of thrusters are often made by personnel with a sincere lack of information. While it would be unthinkable that the selection of the drilling-related equipment of a 350 M DP drilling unit be made by personnel without prior expert knowledge and experience, this is practically the norm in the selection of the thrusters. The selection is too often made based on brand name recognition or preference, and cost, and not based on a sound engineering evaluation.

The guidelines of the thruster subcommittee are:

• To offer assistance to engineering personnel in select the right thrusters for specific applications
• To offer assistance in the safe and efficient operation and maintenance of thrusters
• Assist in optimizing the life of the selected thrusters while minimizing costs.

 

TASK ASSIGNMENTS

The work of this committee is in progress and results will be published to this web site as they become available.

Contact

In case of suggestions, interest in volunteering, or other interest in the subcommittee please respond by clicking here.