Demand for faster cargo pumping from MR tankers has prompted design of a larger-capacity pump that has already won orders.
Over the past couple of years, medium range (MR) tankers have been ordered and delivered in growing numbers, introducing a new generation of ships whose cargo pumping arrangements are subject to more rigorous demands.
Operators are demanding an increase in cargo pumping rate. In the past, rates of 500 m3/h were sufficient, but now rates around 600 m3/h are requested, says MarFlex technical & QHSE manager Peter Raaijmakers.
Although pumps can operate at up to 20 per cent above their rated throughput, previous pump models have often achieved only via reduced efficiency. MarFlex has responded by extending its MarFlex Deepwell Pump Double (MDPD) range with a higher capacity model: the MDPD-200, which is designed to provide a flow of 600 m3/h at its best efficiency point, with a discharge head of 130m.
Its design and manufacture break new ground, Mr Raaijmakers says. During the engineering process, MarFlex used computational fluid dynamics (CFD) to calculate the most efficient cargo flow. This showed an optimal streamlined shape for the pumphead, which can only be achieved by casting it in one piece, he explains.
Normally, only the lower part of the pumphead would be cast, with other parts (such as the flange) welded into place. This reduces welding during its manufacture and makes it more robust: making it in one piece avoids introducing potential weak spots at the welds. It also removes the possibility that welding imperfections will alter the flow that has been optimised during the CFD process, in which fluid velocities have been predicted.
Other improvements claimed for the pump include designing the entrance to its impeller to be smaller than its discharge. Mr Raaijmakers explains that this is to reduce damage from debris in the fluid that is drawn into the pump. If the exit is smaller than the entrance, items could be drawn in and then be unable to escape, causing damage to the impeller.
The pump was introduced to the market towards the end of last year and had secured its first order. It is understood to be a sizeable contract from a major Asian yard.
Source: Tanker Shipping &Trade - February/March 2016