Manifold problems solved on MAN marine diesels

Customised seals and technical expertise from James Walker have overcome damage problems on the inlet manifolds of MAN's high-efficiency V28/33D marine diesel engine.

This engine in its V12, V16 and V20 configurations was designed by Alstom Engines in the UK, and purchased with the company by MAN Diesel in June 2000. The 20-cylinder variant is reputed to be the most powerful and efficient 1000rpm marine diesel on the market. Rated at 9000kW, it meets the rigorous EPA 2007 and IMO emission standards, making it an excellent choice for high-speed ferries and naval patrol vessels.

In 2008, Michael Strietzel of James Walker Deutschland and Colin Moody of James Walker Technology Centre, were invited by MAN Diesel at Augsburg, Germany, to investigate seal leakage on the engine's inlet manifolds.

Each cylinder has two circular seals on its manifold. One of 129mm OD for the ozoniferous charge air at 60°C and 500kPa; the other of 69mm OD for water/glycol coolant at 90°C and 500kPa.

Examination of the engine showed the steel-spring anti-extrusion elements of the original seals were pushing into the face of the aluminium-alloy manifold and creating leakage paths. It appeared that the seal housing depths varied from the original specification and the seals no longer fitted properly.

Armed with this information, James Walker Technology Centre swiftly set to work. Explained Colin Moody: "Special seals were designed with a horizontal U-ring profile to work without the problem-atical spring reinforcement. We also redesigned the housings to work more efficiently within the engine assembly tolerances."

The seals were manufactured in James Walker's Elast-O-Lion® 175 hydrogenated nitrile. This has excellent sealing qualities at the temperatures involved, and resists ozone, water/glycol, heavy fuel and lubricants. Two new sets of seals were developed - one for retrofitting to existing engines, and the other for use with the redesigned housings on new engines.

Reported Michael Strietzel: "Engine trials with the new seals were completed successfully in early 2009. These demonstrated that the new seals are easy to install and operate perfectly, without leakage."

With between 12 and 20 sets of seals on every MAN V28/33 engine the demand for these custom-designed products will last for many years.

27 October 2009

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