Wool lube oil filters claimed to perform better than centrifuges

31 Dec 2014
A GreenOil filter unit

A GreenOil filter unit

Danish company GreenOil reports on a collaboration with ship operator Torm involving using filtration rather than centrifuges to clean lubricating oil in the auxiliary engines of two ships, by Joel Goodstein.

A six-month trial of Greenoil’s filters onboard two Torm vessels is said to have resulted in lower power consumption, reduced service hours and lower maintenance costs.

Some Torm ships were experiencing turbocharger problems on their auxiliary engines. This was apparently caused by poor lubrication, thought to result from insufficient cleaning of the lubricating oil in the centrifuges. Consequently, Torm investigated alternative cleaning methods, and the company decided to undertake trials of filter solutions from GreenOil and a competitor. GreenOil says that its filters were installed on two Torm ships in January 2014.

“After six months of testing, our experience with using oil filtration instead of centrifugation is very good. GreenOil filters are a very simple and user-friendly solution, ensuring the same quality of oil purification at less than half the annual operating cost of a centrifuge,” says Lars Skov Nielsen, chief engineer at TORM.

Six oil filters in total from GreenOil were installed by Torm, one for each of the three auxiliary engines on two ships. This provides dedicated cleaning for each engine, as opposed to the centrifuge that is used to clean the lubricating oil from all three auxiliary engines.

GreenOil claims that its oil filters from GreenOil are designed for efficient operation and simple maintenance. They absorb a negligible amount of power, while a filter cartridge can be changed in a matter of minutes, without any human contact with the oil. The company suggests replacing the cartridges after 500 hours of operation. The need for maintenance is shown on a pressure gauge – when the pressure reaches 5 bar it is time to change the cartridge.

“When the filter cartridge needs to be replaced, you just turn off a switch, change the cartridge and press the switch again. The whole process takes only a couple of minutes, and should be undertaken approximately every six weeks,” says GreenOil sales manager Tomas Skjærris.

The primary filtration medium in the GreenOil filters is sheep wool, and the filtration of unwanted particles in the oil is said to be equally as effective as in a centrifuge. "We do not claim that the GreenOil filtration itself is better than in a centrifuge, but the acquisition cost as well as the operating and maintenance costs are lower and therefore worth considering instead of centrifuges," says Mr Skjærris.

He adds that the power consumption in the oil filters is minimal compared to the centrifuge, while there is virtually no oil spill when the filter is changed. “A centrifuge must heat the oil to 90° C and use thousands of kilowatt-hours in the process. A GreenOil filter is operated at 245W for both filtration and water separation,” he says.

On the two Torm vessels, the annual operating cost for a centrifuge servicing the three auxiliary engines on each ship has been calculated at around €13,500 Euro. In comparison, the annual operating cost for the three oil filters doing a similar job is estimated at about €6,000.

“The payback period for the GreenOil filter is one year. After that, you have an annual gain of €7,500 – for every consecutive year,” says Mr Nielsen.

Technically, centrifuges are more demanding than oil filters - and more time consuming. In addition, the centrifuge has a large oil consumption. “Operating a centrifuge puts special demands on the crew, for example, when the flow or temperature needs to be changed. In some cases, you have to take the centrifuge apart to change the settings. For the crew, it can be both technically demanding and time-consuming to keep the centrifuges running optimally. With filters from GreenOil, this is not an issue. Crews can easily install the filters, and you just need to keep an eye on the filter pressure. The replacement of the filter cartridge is quick and easy and does not require any special technical knowledge. Everybody on board can do it,” says Mr Nielsen.

“A centrifuge is only as good as the crew who operate it. If the operation of the centrifuge is not optimal, you do not get the necessary purification of the oil. This was evident in the oil samples we received from some of our ships. The centrifuges did not have enough operating hours, and the settings were not optimal in relation to flow, temperature and pressure, which can be a demanding task. Some crews stop the centrifuges at the end of the day, so they do not get alarms at night. Some crews stop them to save power. Overall, this will cause the oil quality to decline, and this again requires more frequent oil changes than with a better operation of the centrifuge. The additional cost for extra oil is an important part of the calculation when you compare operating costs between a centrifuge and oil filters,” Mr Nielsen adds.

According to GreenOil, many new ships are designed and built for operation on distillate fuels only, and thus have no centrifuges on board, but filter solutions instead. With main propulsion engines burning HFO, centrifuges are still necessary for cleaning the lubricating oil in the main engine. This is because filters are less able to deal with separating excess water from the fuel oil, as can occur accidentally.

“I think you can get by with fewer centrifuges using oil filters and settle for a single centrifuge for the main engine and a centrifuge for the auxiliary engines, so you are sure to have an adequate water separation in case of an accident. Regarding the daily particle filtration and removal of condensed water from the oil, the filters can handle these tasks,” says Mr Nielsen.

Claimed benefits of GreenOil filters

  • Low energy consumption
  • Easy installation - carried out by the crew itself
  • Water separation - patented solution that removes 250ml/day of water
  • Filter cartridge change in 1-2 minutes - without oil spillage and without physical contact with the oil
  • Filter cartridge change every 500 hours - equivalent to a change approximately every six weeks
  • Stainless steel design with low maintenance costs

Torm and GreenOil collaboration

  • GreenOil filters tested on board Torm Moselle and Torm Rosetta since January 2014
  • Three auxiliary engines per ship: Daihatsu 5GB-20, each rated 522kW at 720rpm
  • One GreenOil filter per auxiliary engine
  • GreenOil filter unit: WP1-B1-100
  • Oil circulation, capacity: 150litre/h (running at 60Hz)
  • Power consumption: 245W
  • Filter cartridge consists primarily of sheep wool

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