Plant Engineering - June 15, 2006
Electrostatics: another way to get the gunk out of oil
Another aspect of a lubrication program to evaluate is filtration. While mechanical filtration, which employs strainers to remove particulates from lubricant and is based on particle size, has been the dominant method for years, it’s not the only way to keep your lubrication system free of contaminants. Electrostatic filtration goes a step further by removing substances that are either too small or are otherwise difficult—if not impossible—for mechanical filters to handle.
“The key difference from other contamination control strategies is that electrostatics are able to pull particulate out of the oil regardless of size,” explained Jon Prescott, Kleentek Technical Sales. “What electrostatics does is it pulls all insolubles out of the fluid, regardless of their size and composition. It doesn’t remove additives and soluble components of the oil system, but it pulls out all of the dirt and all of the degraded additives that are floating around in an insoluble state. These substances [if not removed] can plate out on surfaces everywhere. ”
Electrostatic oil filtration allows users to remove contaminants all the way down to the molecular level, Prescott said. Because it’s not dependent on a screen, as mechanical filters are, it slows down or stops the catalytic degradation mechanisms in the oil.
“There’s always going to be oxidation. But if you pull the oxidation products out of the fluid early, they don’t get into these catalytic loops,” said Prescott. “You never get that ‘hockey stick’ growth of contamination problems, where the problem builds over extended periods of time, and then all of a sudden, all of your problems magnify. ”
The use of electrostatic filtration can also serve to eliminate problems caused by the physical process of mechanical filtration.
“Recent research talks about the damaging effects of mechanical filtration at very small micron sizes and high velocities,” Prescott continued. “That is the predominant problem that we see in contamination control these days. You use tighter and tighter mechanical filtration. Unfortunately, the point of diminishing returns on those types of systems was reached a long time ago, and so now you’re getting a lot of oil degradation as a result of additive depletion and spark discharge. It is the top cause of the majority of downtime in gas turbines these days. ”
Prescott suggests implementing a hybrid system as an option for more effective filtration of lubricants. By combining mechanical and electrostatic methods, users can reduce the overall velocity and shearing forces of fluids as they pass through the mechanical filters.
“They’re going to be taking the micron levels up—not down—going from the 3-micron filter that they’ve been using up to a 15-, 20- or 25-micron filter,” he said. Then, by implementing an electrostatic unit, they can remove any spark discharge and smaller particulates and oxidation products that “the mechanical filters are not touching at all,” and which can cause multiple problems over time.
“That’s a key change that is going to become more and more prevalent over the next five years or so,” Prescott said.
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