Rapid response cuts expensive dry-dock costs

A rapid response from James Walker engineering teams ensured an early return to service for the ferry MF Euregia when marine propulsion system manufacturer Voith Turbo identified a risk of leakage from a competitor's seals on one of the Euregia's propulsion units.

The vessel is one of a large number of passenger and vehicle ferries in daily operation on Lake Constance that use the Voith Schneider Propeller (VSP) system. The VSP system's unique design provides both steering and propulsion in a single unit — allowing thrust to be generated in any direction, quickly and in a continuously variable manner. This provides the levels of extreme control and manoeuvrability required for docking operations — keeping docking times to a minimum whilst also using the minimum of energy.

Lake Constance is a very ecologically sensitive body of water, being a source of drinking water for the surrounding population, so in addition to leakage being detrimental to the operation of the propeller system, preventing any leakage of oil from the system into the lake was of the highest priority.

In May 2010 the vessel was dry-docked for repairs and Voith Turbo asked James Walker to examine seal designs to prevent the possibility of leakage occurring from the steering column immediately below the propeller main bearing. When no definitive cause could be found for problems with the competitor's fluoroelastomer seals, James Walker applications engineers approached the task from a fresh perspective. The seals supplied by James Walker were self-retaining M6/D6/M Walkerseles of 800mm diameter in a nitrile (NBR) material. Ultraglide HNBR material was also considered, but for this application the shaft temperature didn't require the higher temperature performance offered by Ultraglide.

Following initial testing on the James Walker rotary test rigs, the final seal designs were subjected to a 100 hour test on a VSP unit at Voith Turbo before the actual customer seals were manufactured and fitted to the MF Euregia. James Walker engineers attended both testing and final installation to ensure that no unanticipated factors would be likely to compromise the seals' performance.

The vessel's owners were so impressed with the repairs carried out to the first unit that, during the ferry's next scheduled dry-docking, they specified James Walker seals be used on the second propulsion unit as preventative maintenance. Once again James Walker provided a rapid turnaround, even modifying the existing tool moulds to accommodate required design changes before manufacturing the new seals and delivering to Germany. The rapid response allowed Voith to complete repairs ahead of schedule, putting the vessel back in service earlier than expected and making significant savings.

21 April 2011

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