Search and rescue vessels require reliable sealing solutions
Wärtsilä article 26 June 2014
When it comes to designing a search and rescue vessel, it is important to select the right kind of shaft seal. A poor choice could inhibit the vessel's performance, increase the lifecycle costs or in the worst case make the vessel inoperable.
Demanding sea conditions can lead to excessive propeller shaft movements. These radial and axial movements may only be a few millimetres but the consequences of the seal being unable to tolerate this can be dramatic. Wärtsilä Enviroguard’s partially split seal (PSE) has a unique bellows design which means the seal can accommodate up to 5 mm of radial and 8 mm of axial movement without damaging either the seal or the shaft. This means the vessel can successfully operate in all sea conditions.
The seal’s performance is why the world’s oldest lifesaving charity, the Royal National Lifeboat Institution (RNLI), chose to install Wärtsilä Enviroguard seal on their Tamar and Severn classes of all-weather lifeboats. “Following extensive trials the seals proved to be reliable with minimal maintenance requirements,” states Spencer Johns, Senior Engineer, RNLI.
In the ten years since its launch, the Wärtsillä Enviroguard seal has been proven the most reliable seal available in its class. Wärtsilä’s face seal design also eliminates the possibility of shaft wear and incorporates silicon carbide material interfaces that will work effortlessly even in the gritty waters found in coastal regions. The combination of corrosion resistant aluminium bronze and chloroprene used in its construction further enhance its reliability. Thanks to its robust design the Wärtsilä Enviroguard seal is capable of operating in excess of five years without scheduled maintenance in standard operating conditions.
Royal National Lifeboat Institution’s Kilmore Quay Tamar lifeboat uses Wärtsilä Enviroguard seal
Zero pollution seals required
Developments in environmental legislation are leading to a growing demand for higher performance seals that offer better reliability, biodegradable lubricants, as well as water lubricated systems that guarantee zero pollution. “Sea water as a lubricant means zero risk of pollution which in turn ensures the Wärtsilä Enviroguard seal is proofed against any future environmental legislation. With no outboard seal requirement there is no chance of entanglement with ropes or fishing lines which can cause propulsion failures during operation. This dramatically reduces the chance of unplanned maintenance for the vessel,” comments Simon Kill, IWW & Coastal Sales Manager, Wärtsilä Seals and Bearings.
The Wärtsilä Enviroguard seal is suitable both for new build or retrofit of existing installations and available for shaft sizes between 70‒450 mm and 3”‒18”. Wärtsilä also offers a number of variants that provide easy access for maintenance especially when dry docking is not an option and can cater for much larger (up to 1200mm) bespoke applications using Wärtsilä’s in-house face seal design team based in the UK.