Washdown Challenge

Harsh environments call for specially formulated lubricants, and every application dictates the necessary properties for the ideal lubricant. Dusty environments lend themselves to solid lubricants that will not dry out and will not trap dust and dirt. On the other hand, extreme temperatures and frequent washdowns — as found in food processing facilities and other applications — call for lubricants that can withstand water, maintain their viscosity, control rust and corrosion, and will not be washed away.

Research indicates that synthetic lubricants can provide superior performance to mineral oils in extreme-temperature and wet environments. Mineral oils are produced using a solvent-based refining process. Due to the manufacturing process, they tend to retain a signifi-cant number of impurities, such as sulphur or aromatics, that result in decreased thermal and oxidative stability, leading to premature degradation of oil.

In addition, impurities such as sulphur-containing species lend polarity to mineral oils, which can generate an increased rate of emulsification when compared to synthetics.

Synthetic lubricants are produced through chemical engineering and designed to meet certain performance parameters. Compared to mineral oils, synthetic fluids are inherently more chemically inert. Certain synthetics such as polyalphaolefi ns (PAO) lack polar sites, which means they offer no inherent attraction to water, allowing free water to separate from the oil and go to the lowest point in a system, where it can be easily drained off.

PAO greases used in the food and beverage industry possess the same properties as PAO fluids and can be formulated to be extremely tacky in order to resist water washout and spray off. For example, Molykote G-1502FG Synthetic Chain and Open Gear Grease has proven successful in washdown environments in food and beverage applications. It has demonstrated the ability to reduce the amount of grease used to lubricate washdown-application bearings. The grease stays in the bearing after repeated washdowns, reducing the ability of water to enter the bearing housing.

Polyolesters (POE) are synthetic lubricating fluids that possess excellent thermal and oxidative stability and can tolerate water very well. POE oils are often biodegradable. Due to these facts, POE lubricants, such as Molykote L-4646 Synthetic High Temperature Compressor Oil, are a good choice in rotary screw compressor applications. POE oils have demonstrated greater than 14,000 hours of service life on a single fill. Unlike hydrocarbon-based lubricants, polyolester lubricants will not form varnish and sludge deposits.

Silicone fluids can be used to formulate greases that perform extremely well over a wide range of temperature extremes (-73C to 288C). Silicone fluids have an inherent viscosity index of 400-500, which means that in comparison to other lubricating fluids, the viscosity of the oil will not alter much over differing operating temperatures.

Operating efficiencies may be increased as a result of lower viscosities of silicone lubricants at extremely low temperatures, since less energy is required to create motion and operate bearings and other mechanical components, leading to cost savings and lower carbon dioxide emissions.

For more information about Dow Corning’s Molykote brand lubricants, visit www.molykote.comor e-mail industrial@dowcorning.com.

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