Wärtsilä is supplying air/oil lubricated sterntube seals and bearings to Chinese shipyard Shanghai Waigaoqiao Shipbuilding (SWS) for a series of new tankers under construction by SWS for Singapore-based Ocean Tankers.
A complete Wärtsilä package of JMT Airguard seals, sterntube bearings, and shaftline bearings, was ordered in October and December 2006 for installation in the first of 12 Aframax tankers.
"We have established a very good relationship with Shanghai Waigaoqiao Shipbuilding, which today is the largest commercial shipyard in China. Since 2001 we have supplied seals and bearings to SWS for 32 bulk carriers and 16 crude oil tankers," said Wärtsilä Seals and Bearings regional sales manager
The Airguard sterntube seal system, part of Wärtsilä's EnviroSeal range, is an anti-pollution lip seal that uses compressed air to prevent the ingress of seawater and the seepage of oil.
The aft sterntube seal is a multi-barrier lip-type seal with three seal rings: two rings face the sterntube oil side to provide active double security against oil spill, while the third faces and seals off the water side.
All seal rings run on a shaft liner
to avoid grooving of the shaft. They are supplied as a ready-to-install cartridge, which includes the shaft liner, without the need for any further assembly work.
Since Wärtsilä-owned Japan Marine Technologies Ltd began marketing this unique system in the latter half of the 1980s, its popularity has steadily expanded to include large containerships, VLCCs and LNG carriers
. As a result, the Airguard system has grown to become the mainstream technology for oil-lubricated sterntube seals supported by a solid reputation for pollution and trouble-free reliability.
The first 108,000 dwt Aframax tanker will be delivered in 2007, and the rest of the vessels are scheduled for delivery at intervals through to 2008.