Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/1123345
10 | May - June 2019 | www . machinerylubrication.com MPC method may have a higher patch weight if the system has excessive varnish, since the solvent used can force semi-soluble contaminants to precipitate and be collected on the patch along with the submicron debris. is method primarily uses a color scale to identify the fl uid's condition and does not include patch weight. When soot is in the system, a black patch is already assumed, so while color is important, the weight of the patch will be the more valuable information. erefore, be sure your lab can weigh the patches. Electr ostatic Filtr ation Since changing the fi nal fi lter from a 3- to 1-micron element was impractical, electrostatic fi ltration was tried. is type of fi ltration had previously been used with excellent results but was not deemed cost-ef- fective for the old, degraded fl uid. One thing to consider when using electrostatic fi ltration is the fl uid's water content, as it does not function properly when the water level is more than 500 parts per million (ppm). With phosphate-ester fl uids being hydrophilic, they can solubilize up to 4,000 to 4,500 ppm water at operating temperature, which can create problems. In this case, the system had dry headspace purge air installed many years ago. is utilizes a device that dries the air to a dew point of minus 40 degrees F. e air is then blown into the headspace of the reservoir and exits through the existing vent. Phase equilibrium allows the water to be pulled out of the fl uid into the dry air and then blown out the vent. is has worked very well. Even in the hot, humid summers of Florida, water levels below 500 ppm have been maintained. Two types of electrostatic fi ltration are available for lubricants: balanced charge agglomeration (BCA) and the collector type. BCA initially was tried on the second unit. It consists of a pre-fi lter and a mixing chamber that charges particles and starts the agglomeration process. Larger agglomerated particles are fi ltered out in a fi nal or post fi lter. Although this method reduced the patch weight, no color change was noted in the fl uid. Next, the collector type of electrostatic fi ltration was employed. With the fi ltration in service, it took a few months for the oil to begin changing colors and for the patch weight to decrease. A problem then occurred with the fi ltration unit, which was not fi xed for a couple months because of a unit shutdown. Fortunately, during the same shut- down, accumulators were installed on the second unit. is allowed for one-pump operation. Now, not only was the reservoir residence time increased for air release, but the soot generation was also lessened due to adiabatic compression of bubbles within the pump. When electrostatic fi ltration was placed back into service on the second unit, the cleanup time to clear oil was greatly reduced. e air-release time also decreased by two minutes. e hope is this was due to the reduction of generated debris rather than the system being cleaned with new oil. Contr olling System Pr oblems As with most mechanical things, when something goes wrong, it usually is not just one issue but several compounded problems. e quick fi x is often just to change the oil, but this case is a perfect example of the oil not being the issue. Instead, it was the system that was causing the trouble. While many of the easy fi xes have been made, only time will tell if they are enough to solve the problems that seem to plague EHC systems. Electrostatic fi ltration appears to be the best technology for removing submicron debris from the fl uid in this system. Although it is always nice to have fl uid you can look through, your primary concern should be to reduce and control the problems within the system that create submicron debris, as this can be very detrimental to properly maintaining your oil. ML Electrostatic fi ltration was not deemed cost-eff ective for the old, degraded fl uid. COVER STORY PENETRATES. LUBRICATES. PROTECTS. Unlike ordinary rust solvents, Penetro's exclusive oil-based formulation not only breaks through rust, it coats metal surfaces with a lubricating film that won't wash off. • Triple protection against rust. • Triples the life of hoist chains and sprockets. • Prevents thread stripping. schaefferoil.com 314.865.4100