Managing a ship requires to be on top of various tasks such as handling the content for shipping and supplies, registrations and visas, leading and managing staff, technical management and maintenance. The amount of responsibility is as vast as the ocean and the time at hand limited to a few droplets. Unlike the engine, propeller, battery, bilge pump, electrical lines, oil and filter, other fluid levels and hull; seals for ship’s propulsion shafts, thrusters, gearboxes, tidal turbines and pump shafts seem lesser at top of mind when considering the concerns of maintenance. However, in emergency cases seals can become worrisome – pinky toes are small but paralyzing when broken. Naturally, preventing unforeseen circumstances or being prepared with a safety net when those occur can provide you with a peace of mind.
Lagersmit developed the inflatable seal for emergency cases or in-situ maintenance. Being able to change seals while afloat saves you time and costs of not needing to get into the dry dock. Take for example the Supreme Hydrofuse (fig. 1). This seal is especially developed to prevent water leakage from your open water-lubricated stern tube system into your engine room. It is equipped with the inflatable seal, so that the contents of the stern tube can permanently be sealed-off and maintenance can be done in-situ.
With EAL oils already being quite expensive, mineral oils are also increasing in price due to worldwide developments. Therefore, the inflatable seal now also finds its purpose in oil lubricated stern tube applications. Once in dry dock the shipowner can decide to inflate these seals and keep the oil inside the stern tube, whilst maintaining the aft and fwd stern tube seals. It is unnecessary to change the lube oil in the stern tube when the lubricant is still in good condition. With the inflatable seal from Lagersmit installed you ensure a real money saver.
The inflatable seal assembly itself consists of two parts: an NBR seal profile and a plastic support ring which fits inside the cross section of the rubber seal (fig. 2). This support ring ensures air tightness at the interface surfaces. The inflatable seal is fitted in a seal housing (ring) together with a closing (adaptor) ring (fig. 2).
Having the inflatable module enables in-situ maintenance. Bonding divisible lip seals in situ is a cost-effective alternative of seal replacement without disassembling / removing the shaft or propeller. In this way an unnecessary dry dock can be prevented, and maintenance can be postponed safely.
Under normal circumstances, during operation, the inflatable seal will be in its deflated state (fig. 2, left). The inflatable seal makes no contact with the (rotating) shaft. In case of emergency or if maintenance is due while afloat the seal can be inflated (fig. 2, right). For static sealing against an idle shaft the seal is inflated using a pressurized medium provided by an external pump. After inflation the pressurized seal will contact the opposing shaft surface, providing a radial acting static seal. The inflatable seal is designed to handle a maximum pressure difference between inside and outside pressure of 10 bar.
A great effort is made in the inflatable seal design to make it suitable for applications that suffer from large bearing wear or applications that are coping with large shaft to bore misalignments. Radial eccentricity up to 2 mm is allowed, making this inflatable seal ideal for in-situ maintenance for open water lubricated stern tube systems or respectively tidal turbines or any other application that needs to deal with large radial bearing play, giving you a reliable sealing solution for years to come.
For the most common stern tube seal applications the inflatable seal can be added to the existing Supreme Aft seal and Supreme Fwd seal. The interface dimensions of the inflatable seal can be engineered to the required dimensions, making the seal suitable for retrofitting the existing seal. The Lagersmit inflatable seal can be supplied for shaft diameters 70 up to 890 mm.
Lagersmit has been based in the Netherlands since 1856 and has one mission: to deliver Peace of Mind with the best sealing solutions for ships, pumps and tidal turbines. Whether you choose to operate your vessel with air-type sealing systems or with water lubricated systems, Lagersmit is here to help you!
Get in touch for more information about our products or a no-obligation quotation.