PAG Lubricant Revolution
PAG (Poly Alkylene Glycol) lubricants offer excellent lubricity, a high natural viscosity index and very good temperature stability. PAG base fluids are available in both water soluble and insoluble forms, and in a wide range of viscosity grades. They offer low volatility in high-temperature applications and can be used in high- and low-temperature environments. They are commonly used as quenchants, metalworking fluids, food-grade lubricants and as lubricants in hydraulic and compressor equipment.
PAGs were one of the first synthetic lubricants to be developed and commercialized. They were created under mandate from the U.S. Navy in response to hydraulic fluid fires on ships resulting from ordnance strikes during World War II. In 1942, and for the next 30 years, the Navy began to exclusively use PAG-based water glycol hydraulic fluids that were fire-resistant and could operate over a wide temperature range. Later, PAGs began to see extensive use as textile lubricants, quenchants in metal heat treating, and lubricants for use in equipment in the food processing industry.
Because of the properties that make up PAG lubricants, they are uniquely suited for a number of industrial and manufacturing applications. Their water solubility allows for easy clean-up of equipment. PAG lubricants offer high viscosity indexes, and are shear stable. PAGs are also valued for their low volatility in high-temperature applications, and for resistance to formation of residue and deposits. Their biodegradability makes them ideal for environmentally sensitive applications.
PAGs are best known as compressor lubricants. PAGs are also the lubricant of choice in high-pressure natural gas and ethylene compression, where the viscosity stability of hydrocarbon-based lubricants is adversely affected due to solubility of the gas in the fluid. In refrigeration compression, PAG and polyol ester-type lubricants are used almost exclusively with the current generation of environmentally friendly HFC refrigerants such as R-134a and R-152a. The two largest U.S. air compressor OEMs have used PAG lubricants as the standard factory fill in rotary screw air compressors for almost 20 years. More recently, a third compressor OEM has begun to offer PAG as an optional fluid.
PAG’s are also useful in industrial equipment operating year-round without seasonal changes. Their superior heat transfer characteristics and thermal and oxidation stability make them ideal for use as heat transfer fluids in large, open vented systems and for process fluids in the production of plastics, elastomers, threads or fabricated parts where compatibility of the fluid with the processed part is important.
Textile fiber production is another industry that benefits from the use of PAGs. These lubricants do not stain or discolor fibers, and are easily removed during the scouring process. PAGs are also the lubricant of choice for many high-speed, high-temperature fiber processes where shear stability is a requirement. In addition, they are often used as lubricants in textile manufacturing equipment as extreme-pressure gear lubricants.
A renewed emphasis on energy conservation has increased interest in energy-efficient gear lubricants. For example, the extreme demands of gear lubrication in wind turbines are being met by PAGs. The low velocities and high surface loadings on the gears in these units have resulted in micropitting problems with conventional hydrocarbon oils that have been overcome with PAG-based fluids. In other gearbox applications, especially worm gears, the naturally low coefficient of friction found in PAG fluids results in energy savings, lower temperatures and lower wear rates.
For more than 60 years, synthetic lubricants have provided a viable alternative to traditional hydrocarbon lubricants. Each type serves unique roles, with PAGs performing in both high- and low-temperature environments, in areas of extreme pressure and where water solubility is desired.
PAGs can be designed to form a wide variety of polymers. The design of the polymer can be tailored to the lubricant application to provide, for example, the desired viscosity, pour point, solubility and other attributes. This versatility and the applications in which they are used shows that PAGs account for about 24 percent of the entire synthetic lubricant market. Low pour points, a wide range of viscosities, resistance to varnish formation, increased solvency and a wide range of solubility all add to PAG lubricants’ reputation as a high-performance synthetic lubricant on the market. With continuing emphasis on environmentally acceptable lubricants in industry, these qualities will continue to push PAGs to the forefront of the synthetic market.