Wear and Friction performance of lifeboat launch slipways
Start date: 11 May 2010
The Royal National Lifeboat Institution provides search and rescue cover along the United Kingdom and Republic of Ireland coast using a variety of lifeboats and launch techniques. In locations where there is no natural harbour it is necessary to use an inclined slipway to launch the lifeboat into the sea. Slipway stations consist of an initial section where the boat is held on rollers followed by an inclined keelway lined with low friction composite materials, the lifeboat is released from the top of the slipway and proceeds under its own weight into the water. The lifeboat is subsequently recovered to the top of the slipway using a winch line. With the introduction of the new, larger ‘Tamar’ class lifeboat it is necessary to upgrade existing boathouses and standardise slipway operational procedures to ensure consistent operation. The higher contact pressures and launch velocities associated with the new lifeboat have led to issues of high friction and wear on the low friction composite linings and a number of methods have been adopted to mitigate this effect. This paper presents a methodology for assessing slipway lining performance so that friction and wear conditions along the slipway can be monitored to ensure consistent operation. A multidisciplinary approach using tribometer testing in conjunction with finite element analysis and real world slipway condition surveys is adopted to extend the scope of investigation to incorporate common real world effects such as panel misalignments. Various lubricants are assessed for their suitability with regard to friction and wear performance in addition to sustainability considerations using the methodology, and modifications to the design of slipway panels, guidelines for lifeboat operation procedures and suitable panel installation tolerances are developed. Finally, new slipway condition monitoring procedures are proposed incorporating slipway panel failure and replacement criteria and recovery winch based condition monitoring.