Coastal tanker ASPERITY

According to The Motor Ship June 1997

The double-hulled coastal tanker ASPERITY was built by Singmarine Dockyard and Engineering, Singapore. A major feature of the cargo tank arrangement is the elimination of the centreline bulkhead to reduce discharge time to halve the number of tanks to pump. In the result, the ship has five cargo tanks of varying size, which allow small parcels of differing product grades to be transported. Each cargo tank is equipped with the Wärtsilä Svanehoej variable speed deepwell pump with a capacity of 550 m3/h at 90m liquid column. Loher 174 kW explosion proof motors are sited on the trunk top and drive the pumps using Cardan shaft.

All cargo lines and tank fittings are made of stainless steel. Cargo valves are stainless steel high-performance butterfly valves. Cargo stripping and tank washing valves are stainless steel ball valves.

The cargo control system comprises a loading computer, tankradar and temperatures probes, ballast, bunker, fresh-water and draught gauging and an independent hi-hi tank alarm system.

Two computer monitors with light pens control the five deepwell cargo pumps, the slop pump and ballast pumps. Other details monitored are cargo tank ullages and pressures, slop tank ullage and pressure, tank temperatures. The control system has mimic diagrams and monitors the control plan and two-valve segregation parameter. Dynamic colouring of pipelines indicates flow and the opening of valves. Continous information of tank levels is provided to the Kockumation loading computer for a continuous update of tank status and ship stability.

A main engine develops 2000kW at 825 rev/min. It drives a 3.3m diameter CP propeller at 160 rev/min through a gearbox. An arrangement of clutches allows the shaft alternator to be used as the emergency propulsion, providing a “get-you-home” speed of 9 knots.

Length, oa: 88.76m, Length, bp: 82.20m, Breadth, moulded 16.50m, Depth, moulded: 7.65m, Draught: 5.60m, Displacement: 5490t, Lightweight: 1712t, Deadweight: 3778dwt, Service speed: 12.5 knots, Cargo capacity: 4266m3.

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