Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/1206285
24 | January - February 2020 | www . machinerylubrication.com Test Frequency and Limits Table 1 shows recommended action limits for monitoring phos- phate ester fluids. Proactively managing the fluids can help reduce the cost to maintain them in the long term and extend the life of the machine. Additional tests, such as viscosity, chlorides, particle count, air release and foaming, can provide further insight into the health of the fluid and the system. Contamination Control Different contamination control technologies, such as electro- static filtration, acid-scavenging media and air-membrane drying, are commonly used to remove degradation compounds or contaminants from phosphate ester fluids. Figure 5 shows these technologies and their target applications. Electrostatic Filtration Electrostatic filtration technology is used to remove soot and incomplete combustion products. It works on the principles of elec- trophoresis and dielectrophoresis. Electrophoresis is the motion of dispersed particles under the influence of a spatially uniform electric field relative to a fluid. Dielectrophoresis is the phenomenon of a non‐uniform electric field exerting a force on a dielectric particle. e spatially uniform electric field charges the particle. e charged particle agglomerates, and the filter removes the particles. Acid-Scavenging Media Ion-exchange media technology is a modern means of treating in‐service phosphate ester fluid for acid reduction. ere are multiple benefits of ion-exchange technology over traditional techniques like fuller's earth media. e ion-exchange treatment removes several types of contaminants, including stronger acids (phosphoric acid deriva- tives), weaker acids (alkylphenols), organic soluble varnish (carboxylic varnish), metal soaps and some polyphosphate gels. In addition, the ion-exchange media can restore a fluid's resistivity. Different media combinations have shown varying rates of acid removal and acid saturation, depending on the condition of the phosphate ester fluid. Some media remove only stronger acids, while others eliminate mostly weaker acids. erefore, it is essential to use customized media blends. Acid titration curves can serve as a useful tool in assessing the performance of the media by identifying the nature of the acids, adsorption and acid saturation. Air-Membrane Drying An air-membrane dryer sweeps dry air across the headspace of an EHC reservoir. e dry air lowers the moisture content of the fluid via mass transfer. Air-membrane dryers can be effective for maintaining low moisture levels in the field and may be less expensive and main- tenance-intensive than vacuum dehydration systems. Maintaining Phosphate Ester Fluids You now should have a better understanding of the most signifi- cant problems users face in managing phosphate ester fluids and why standard oil analysis tests may not always identify certain issues. is information should also provide a roadmap for testing the condition of phosphate esters as well as recommended actions to help ensure years of trouble-free performance. ML 2,500 2,000 1,500 1,000 500 0 1 11 21 31 41 51 61 Water (%WT) Days In-service Fluids OEM Maximum Limit Recommended Limit Figure 6. A reduction in moisture content is shown after application of an air-membrane dryer. CONTAMINATION CONTROL