Ship safety is put at risk if low-friction bearing pads on hatch covers are not renewed when worn, and if they are not replaced by the correct type of pad
Low-friction bearing pads are one of the important features enabling modern container ships to get bigger. These pads ensure the operational functionality of hatch covers throughout the lifetime of the vessel.
In spite of their benefits and good features, low-friction bearing pads do wear, however, says Rauno Rajalampi, technical manager for container ship hatch covers. The wear of an individual pad depends on its location and the actual loading it has been subjected to. Therefore pads need to be changed gradually depending on their wear not the whole shipset at once.
There are serious consequences if maintenance is neglected, or if changes are made to the originally specified features of the system when replacing pads. Mr Rajalampi says that the two most common mistakes are:
- the pads are not changed when they ought to be
- the pads are replaced by another type, for example pads with higher friction coefficient.
Increased friction or using the wrong pad material can cause the non-replaceable stainless steel mating plates to be permanently destroyed, which would prevent the correct bearing pad type being fitted later. This damage, or increased friction, could lead to cracks in the ship hull and/or hatch covers. The same effect will be caused if the bearing pads are not changed on time and the steel holders of the bearing pads then contact the mating plates. In addition, the service life of a replacement pad of the wrong type is considerably shorter than the lifetime of a genuine and functionally compatible spares component.
Crack in a hatch cover longitudinal girder
Crack in a hatch cover side plate close to a bearing pad
Worn pad to be replaced before the sliding surface has been worn down to the steel holder level
For further information:
Esko Karvonen, General Manager, Container Ship Process, MacGREGOR (FIN) Oy,
Hallimestarinkatu 6, FI-20780 Kaarina, Finland
Tel: 358 2 4121 314, Fax. 358 2 4121 390