Page 15: of Maritime Reporter Magazine (October 1996)

EUROPEAN UPDATE

Emergency Propulsion

Systems

During the anniversary celebra- tion, Schottel employee Uwe

Gragen, a naval architect and pro- ject manager, provided an update concerning IMO's Design and

Equipment Subcommittee's thoughts on the subject of emer- gency propulsion systems, particu- larly for ships carrying hazardous cargoes. He cited a number of recent incidents where he sup- posed vessel losses would have been prevented, had Schottel pump jets been installed at vessel bows.

Pump jets, which provide 360 degree steerable thrust, are avail- able in a range of sizes to accept an input power of up to 3,500 kW, and the Manovriertechnishes Institut (MTD in Hamburg has reportedly calculated that many environmen- tal disasters could have been pre- vented with an emergency propul- sion system requiring less power than this.

IMO has concluded that an inde- pendently powered pump jet installed at the bow has no effect on the efficiency of the vessel being flush with the hull and can increase maneuverability during normal operation. Moreover, the unit's position, situated at a dis- tance from the engine room — the most likely source of a vessel-crip- pling fire — is in the best position for guaranteeing maximum maneuverability with the lowest power requirements.

Interestingly, the IMO

Subcommittee has commented on the fact that many tankers are under-motorized. A combination of advanced shiplines and improved propulsion enables these vessels to achieve their service speed in calm water at very low power. At

Beaufort wind and Sea States 10 and 11, however, the speed attain- able by these vessels is hardly enough to give the rudder any effect, and at Beaufort 12, full power is insufficient to keep sta- tion. A pump jet used in conjunc- tion with the main engine would also reportedly solve this problem.

The Schottel pump jet comprises an impeller, diffusor assembly and bottom plate. The impeller, driven through a right angle gear, sucks water via an intake funnel and dif- fusor into a pressure casing which is connected to the bottom plate.

The water is expelled through three symmetrically arranged out-

October, 1996 let nozzles in this plate, and as the whole pressure casing can be turned through 360 degrees, thrust may be directed without losses in any direction. The unit can be installed flush at any point on the ship's hull and driven by any power source.

Mr. Gragen conceded that addi- tional safety for ships carrying hazardous cargoes cannot be real- ized at zero cost. "The environmen- tal disasters caused by tanker acci- dents and our responsibility to future generations, however, force us to react immediately to mini- mize these risks," he said. Bearing in mind that a double hull is a sec- ondary means of protection and often only provides a delay before the cargo starts to pollute, fitting an independent emergency propul- sion system such as the Schottel pump jet seems a step in the right y Hoogovens Aluminium

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