Periodic cleaning of engine room equipment is part of the USS Great Lakes Fleet preventative maintenance program. To do a thorough job, it involves the use of cleaning compounds which dissolve lube oil and grease.
Carl Walker, engineer – maintenance planning at USS Great Lakes Fleet, specifies these compounds, and one of his major concerns is what happens when they enter the bilge water – as he also has to ensure that the fleet’s oily water separators reduce the oil content of bilge water to a negligible amount, even in the presence of these chemicals. As Mr. Walker said, “Separators need help in the form of auxiliary equipment, and they benefit greatly from planning that considers the type of cleaning compounds used.”
The company has found an oil skimmer to be a piece of auxiliary equipment which greatly enhances the performance of an oily water separator. In many separators, filter element efficiency is affected by oil concentration in the water being processed. By reducing floating oil before it gets into the separator, the equipment performs more efficiently and filter elements last longer. The cost of the oil skimmer is quickly repaid through reduced element replacement cost and less time spent giving special attention to monitoring and reprocessing water whose oil content remains high.
On many USS Great Lakes Fleet bulk carrier vessels, Mr. Walker has installed an oil skimmer made by Abanaki Corp. of Chagrin Falls, Ohio, which helps when removing oil from water and reducing oil content of bilge water before it gets to the separator. The Abanaki Model 4 Oil Grabber specified by Mr. Walker uses a stainless steel belt operating on a motor and pulley system. This design makes use of differences in specific gravity and surface tension between oil and water to pick up grease, oil and other hydrocarbon liquids as the belt passes through the water. The unit can start removing oil from water at a rate of 20 gallons of oil per hour.
Still, peak skimming efficiency can more quickly be achieved through good installation practices, and by being selective in the types of cleaning compounds used. For example, some cleaning compounds have emulsifiers which help loosen oil and grease, but subsequently may cause the oil to form a tight emulsion in the bilge water.