Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/1032074
ML www . machinerylubrication.com | September - October 2018 | 41 filtration requirements and limitations defined by the manufacturer of both the equipment and the hydraulic fluid. en, make any appro- priate adjustments to these recommendations to satisfy the cleanliness targets established by your reliability program. Considerations During Changeovers A lubricant changeover in any application should not be completed without careful consideration of the degree of cross-compat- ibility and amount of residual fluid in the system. Upgrading to a system with a fire-re- sistant fluid or changing to a different type of base oil will require additional attention. Always drain the fluid while the system is still warm and make every effort to purge all fluid from any low pockets, nooks and crannies. Replace all filters and any other components that have saturated amounts of residual fluid. When changing to a different fluid, always consider the compatibility of the seal mate- rials, paints and other coatings, especially for synthetic-based fluids. It's generally advisable to circulate an appropriate flushing fluid under minimal to no load to pull as much remaining oil from the previous fill. Afterward, fill the system to the correct fluid level with the spec- ified fire-resistant fluid. e ISO 7745 standard provides general flushing and changeover procedures as well as specific change considerations for viscosity, lubrication, densit y a nd compatibilit y concerns for every base oil combination of fire-resistant hydraulic fluid. Also, always check with the f luid manufacturers for compatibility information. Benefits and Disadvantages Hydraulic fluid requires a unique lubri- cating ability that can work under pressure and mitigate an array of risks, including fire. ese risks and the mode in which the fluid operates at higher pressures can make it easy to justify the use of a fire-resistant fluid. e base oil will be crucial, whether it is a synthetic such as a phosphate ester, which naturally resists combustion, or a water-based fluid, which relies on water vaporization to create steam and smother any imminent fire potential. Nevertheless, it remains the responsi- bility of the individual selecting the fluid for the application to carefully consider all the necessary factors. ese most certainly will include viscosity, viscosity index, oxidation stability, thermal stability, and anti-wear and anti-corrosion protection. Hydraulic systems that operate with fire-resistant fluids will often need a few modifications, such as shortening or enlarging inlet lines to avoid cavitation or employing certain types of filters for water- based fluids. In any case, the selection of fire-resistant hydraulic fluids has proven to be a critical decision in minimizing fire risks and avoiding catastrophic equipment failures. ML References Townsend, F. and Baker, P. "Factors Relating to t he Selection a nd Use of Fire-Resistant Fluids in Hydraulic Systems." Hydraulic Pneumatic Power, April 1974. ISO Standard 7745. Hydraulic f luid power – Fire-resistant fluids – Requirements and guidelines for use. Jagger, S., et. al. "Assessing Hydraulic Fluid Fire Resistance." Machinery Lubrication, September 2007. FM Global Technologies LLC, Factory Mutual, Approval Standard for Flammability Classification of Industrial Fluids. Class Number 6930, January 2002. About the Author Bennett Fitch is the director of product development a nd lubrication progra m development (LPD) ser vices for Noria Corporation. He is a mechanical engineer who holds a Machine Lubricant Analyst (MLA) Level III certification and a Machine Lubrication Technician (MLT) Level II certi- fication through the International Council for Machinery Lubrication (ICML). Contact Bennett at bfitch@noria.com to learn how Noria can help you select the right lubricants for your application.