Among the latest vessels to benefit from the retrofit of MacGREGOR Flexipad hatch cover bearing pads is P&O Nedlloyd's 4,230 TEU container ship Jervis Bay, which had all steel pads replaced by Flexipads in June

Schedule reliability is vital for long-haul container ships and any risk of disruption has to be addressed. A project to retrofit Flexipad hatch cover bearing pads to the 1992-built Jervis Bay project was initiated when, during a Rotterdam call in February, P&O Nedlloyd reported to MacGREGOR the appearance of cracks at the hatches and coaming surrounding the steel bearing pads. Traditional steel-to-steel pads often wear to a state that they no longer support the full load of a hatch cover and its cargo.

The cracks were caused by heavy loading and movement of the hatch covers. The steel pads were worn out and due for renewal at the planned drydocking in June. Similar problems were evident on the eight other Bay-class sisterships.

MacGREGOR was not the original hatch cover supplier but because of its experience was requested to study the bearing pad arrangement by P&O Nedlloyd, which sought a solution for avoiding problems in the future. Cracking is a great safety risk. Any significant cracking might call for unscheduled repairs, threatening an off-hire period since it is difficult to carry out welding in most container terminals.

Eliminating structural damage

A modernisation project using its Flexipad hatch cover bearing pads was subsequently proposed by MacGREGOR and accepted by the owner in early May. Flexipads have demonstrated their ability in numerous installations to eliminate damage often associated with heavily loaded container ship hatch covers, protecting the coaming from the high horizontal friction forces.

Some 574 Flexipads were installed on Jervis Bay in June during a planned drydocking at the Unithai yard in Thailand. Installation was executed on schedule by the yard during the 20-day docking period under the supervision of a MacGREGOR Rotterdam-based engineer. The satisfied owner has commissioned a similar project at the yard on a second Bay-class container ship but with a completion time of only 12 docking days. Experience gained by MacGREGOR and the yard from the first project will be applied to meet this challenge. Three more ships in the series, Repulse Bay, Newport Bay and Singapore Bay, are being retrofitted with Flexipads during dockings between October and December. "We are a satisfied customer concerning this project, and if the Flexipads perform as suggested over the coming years, then our satisfaction can only increase," said Tony Greener, P&O Nedlloyd Fleet Superintendent.

Evenly distributed forces

Flexipads exploit a sandwich construction of alternate laminates of rubber and steel bonded together, ensuring that forces applied to the pad are distributed more evenly than with other bearing pad types. This feature reduces high peak loadings on coaming structures, which can be the cause of structural damage such as cracking. Structural repairs are expensive both in terms of direct costs and indirect off-hire costs.

Significant long-term cost benefits result from reduced wear to hatch cover components and better weather protection of the cargo. Flexipads ensure that the designed distance between covers and coamings is maintained at all times, thus eliminating over-compression in the packing.

[picture available from Steve Labdon]