Metal Working, Lubricant, Refrigerant, Compressor, Compatibility
Metal working fluids (MWF) are basically two types, metal removal (chip making) and metal forming (chip-less). MWF are used in all aspects of production fabrication of refrigeration systems. Metal removal applications typically include turning followed by finish lapping of crankshafts and piston connecting rods, also milling and finish grinding of screw compressor vanes. Metal forming applications include deep drawing of compressor housings, wire drawing, tube forming and stamping of electric motor laminations. MWF are not always completely removed before final assembly. The MWF residuals may get mixed into the refrigerant and compressor lubricant affecting system life and efficiency. Â To date, very little compatibility testing of residual MWF in refrigeration lubes and refrigerants has been investigated. Â Unlike most lube oils, MWF are typically water-based and traditionally make very high usage of extreme pressure (EP) additives. EP additives help remove metal during the cutting process and actually increase wear.Â EP containing MWF mayÂ interfere with compressor lube oil performance. EP are additives are known to be somewhat acidic and corrosive. Â Due environmental persistence concerns, the EPA will restrict the use of chlorinated alkanes as EP additives. Chlorinated alkanes will be being phased out over the next few years and replacements are needed. It has been proven that preformed emulsions are capable of replacing traditional EP additives in MWF. Preformed emulsions allow non-traditional base â€œoilsâ€ to be used in MWF. These non-traditional base oils are generally very high in viscosity and viscosity index. Some of these base stocks exhibit very high film strengths under high pressures encountered in metal removal operations. These high VI and high film strength synthetic base stocks can replace corrosive EP additives without loss of machining or drawing (stamping) performance. Residual films remaining after machining are non-reactive and oil like, providing corrosion protection of in process metal parts prior to assembly.Â Additionally, high viscosity synthetic base stocks provide low pour points, lower volatility and less vapor interaction within a refrigeration system. Better compatibility with mostly non-polar water insoluble refrigeration lubricants are a benefit. In the future, new refrigerants are likely to be more reactive to reduce environmental persistence. Interactions and effects of various classes MWF with traditional compressor lubes and refrigerants are examined and reported.