Application and Problem
A U.S. food processing plant in the Midwest employs hydraulic drive systems to operate meat conveying equipment called “dumpers". These are used in material handling applications throughout the facility. Mineral oils were originally used as lubricants in this equipment. The mineral oil product contained a zinc additive and was rated at 20W (46 ISO) with a viscosity index (VI) of 98.
During daily washdown, pressurized water from spray cleaning equipment would contact oil reservoirs located under the dumpers. Some of the water would mix with the oil and form a thick, sticky emulsion. It was not unusual for the plant to shut down for the evening with the oil appearing OK, only to discover at start-up the next day that the lubricants had emulsified during the night. Before work could proceed, the oil would have to be changed due to the water contamination. Because the emulsion degraded lubricating performance and the lubricant’s ability to circulate properly in the hydraulic system, this plant typically performed oil changes at 30-day intervals, well before the product’s rated lifetime.
In an effort to prevent costly formation of emulsion in the oil, the maintenance manager switched to MOLYKOTE® L-1346FG Synthetic Blend Hydraulic Oil, a DuPont product. This oil features a viscosity of 20W (46 ISO) with a VI of 112. The synthetic oil’s anti-wear (AW) additives meet ASTM D 2882, the standard for piston and vane pumps used for pressures lower than 2000 psi. Unlike the original oil, which is made in conventional fractionation processes, the synthetic oil is engineered by combining smaller molecular “building blocks” to meet targeted performance specifications and to minimize impurities.
During a trial period, the L-1346FG was sampled and analyzed at regular intervals. The results indicated that the fluid remained in good condition for the duration of the test.
Installation of the synthetic hydraulic fluids followed thorough draining of the old oil. The MOLYKOTE® Oil was monitored monthly using a vendor-provided sample analysis. The lubricant ran successfully for 6 months before the anti-oxidant additives were depleted; that's 500% longer than the previous lubricant. No special flush fluid was used. No signs of emulsification occurred during the life of the MOLYKOTE®. Samples revealed the presence of zinc additives, which were left over from the original product. Residual acid zinc additives typically shorten the lifetime of the anti-oxidant used in synthetic oils. After the initial changeout of the L-1346FG, the product lifespan increased as the amount of residual zinc declined.
The plant saw annual cost savings of 57% due to the extended life of the hydraulic oil used in the dumpers. The former hydraulic fluids were consumed at a rate of 180 gallons/year for an annual cost of $1,044 per dumper. $720 for product and $324 for disposal. The new synthetic hydraulic oil was consumed at a rate of 30 gallons/year for an annual cost of $450 per dumper. $396 for product and $54 for disposal. In addition to the $594 per dumper direct cost savings, labor costs incurred by frequent maintenance dropped by 80%. Furthermore, processing interruptions for oil changes declined by a factor of five. The food grade hydraulic equipment operated more reliably and safely because there were no sudden premature changes in viscosity due to emulsification.
Synthetic Product Simplifies Compliance
Use of the new synthetic hydraulic oil reduced inventory required to meet the plant’s MRO needs. Fewer oil changes and the food grade hydraulic oil formulation simplified the plant’s compliance with Hazard Analysis and Critical Control Point (HACCP) reporting. This grade of Molykote® conforms to USDA requirements applicable to meat and poultry plants and is qualified for direct food contact under FDA regulations. Plant management has adopted a policy of using only food grade lubricants made from synthetic polyalphaolefin (PAO) for its MRO needs. Although these products typically exceed the unit cost of the conventional mineral oils they replace, their superior lubrication performance and lifespan more than make up for the difference. Standardizing on food grade products eliminates the possibility that plant workers will confuse one type of hydraulic oil with another.
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