Replacing a tank washing system can save considerable time and money, according to Mats Marklund, vice president sales at Polarmarine in Sweden.

Speaking at Tanker Shipping & Trade's annual conference in November 2016 he described a retrofit carried out on the 47.000 dwt crude tanker Oaktree that cut its owner's fuel bill and saved many manhours for the crew.

The ship had been fitted with 18 twin nozzle machines, 16 of them used for cargo and tank cleaning. These were run for six hours during each of 10 annual cleaning operations. Operating them two at the time, this required 48 hours of tank washing.

Polarmarine replaced these with PolarJet 30 (PJ30) ECO washing units which could complete each washing in four hours, bringing the annual total down to 32 hours. With the boiler burning 0,333 m3/hr this has saved 55 m3 of fuel, reduced pump running time and cut manhours to operate them. It also reduced chemicals and slops.

These savings are made possible by the PolarJet ECO's design, which take account of a tank's shape to spread the cleaning media evenly. Tank cleaning machines are mounted closer to the top of a tank than the bottom, which usually means that the top is over-cleaned. But by using a "clever geometry in the gear box" Polarmarine's units accelerate the nozzle rotation at the top of the cleaning cycle and slow it at the bottom, reducing the cleaning time by 25 percent, leading to the described savings.

Vessels that have Polarmarine's standard PJ15 and PJ30 washing units can upgrade them to the ECO version by adding the cleaning head without lifting the main pipe out of the tank.

Polarmarine also offers the Washmaster software. This has been designed to monitor and report on tank cleaning processes as they take place and to generate post tank cleaning reports.