Compressed air is often referred to as the "fourth utility", and like electricity, water and natural gas, is critical to most manufacturing operations. The prevalent type of air compressor used today to produce this utility is the oil-flooded rotary screw. These compressors are favored for their low capital cost, yet are quite expensive to operate and maintain. A rotary screw compressor's annual operating costs are a result of high energy consumption, expensive replacement fluids and parts, labor intensive maintenance and repairs, and hazardous waste oil handling and disposal, which typically exceeds its original purchase price.

The Hidden Problem
The hidden enemy of rotary screw air compressors, and the root cause of most of their operation and maintenance costs, is fluid contamination. Compressor fluid contamination reduces the service life of the oil and every component it contacts by accelerating oil degradation, wear, corrosion and fouling. Unlike other rotating equipment, rotary screw compressors have a forced-contamination design that continuously ingests solid and vapor contaminants, forcing them directly into the oil. Inside the compressor, these contaminants chemically react with the oil to accelerate oxidation, produce acids and permanently change the oil's physical, chemical and performance properties.

The most destructive contaminants are the acids and ultra-fine or clearance-size solids that are not removed by the compressor's standard, full-flow oil filter. These contaminants continuously accumulate in the oil, deteriorating the oil's ability to lubricate, cool and protect expensive compressor internals. Unfortunately, compressor users pay a high price for fluid contamination because of unnecessary fluid and separator purchases, wasted energy consumption from high separator pressure drop, frequent maintenance and repairs, needless compressor downtime and excessive waste oil handling and disposal.

Traditional preventive maintenance treats the symptoms of fluid contamination; however it does not address the root cause of the problem. The time-based practice of regularly replacing compressor fluids, separators and filters is expensive and labor intensive, and leaves compressors vulnerable to the persistent attack of aggressive contaminants.

A Proactive Solution
After witnessing the problems caused by fluid contamination, Fluid Metrics developed the Compressor Oil Purifier (COP), specifically designed for oil-flooded rotary screw air compressors. The COP is a proactive maintenance contamination control system that combines proven ion exchange acid adsorption and ultra-fine filtration technologies to remove harmful acids and clearance-size solids that accumulate in compressor oils.

Fluid Metrics turned to the world leader in rotary screw compressor lubrication and ion exchange technologies, The Dow Chemical Company, for assistance in developing the purifier. Dow conducted nearly three years of testing on the most common synthetic compressor fluids used today, and determined the type of ion exchange media used in the COP to be "extremely effective at removing acids and controlling TAN and pH in these lubricants." Dow's testing also proved the ion exchange media was completely safe and "did not contaminate or otherwise harm the treated lubricants in any way."

Innovative Design 

The heart of the COP is the patent-pending dual-core cartridge that combines state-of-the-art mechanical and chemical separation technologies. As a small slip-stream of contaminated oil flows through the purifier's cartridge, ultra-fine clearance-size solids are removed down to three microns absolute. The prefiltered oil then passes through the ion exchange media bed which adsorbs and neutralizes both weak and strong acids present in the oil. By continuously removing these harmful contaminants, the purifier helps maintain the oil's original physical, chemical and performance properties.

The COP is ideally suited for today's most common synthetic compressor fluids including PAGs, PAOs, hydrotreated hydrocarbons and ester-based fluids. The purifier is available in three standard sizes to suit any make, model and horsepower rotary screw air compressor. An installation kit is also provided to simplify installation in an auxiliary bypass loop to the compressor's main oil circuit.

Key Benefits
Continuously removing the acids and ultra-fine solids produces several key benefits proven to save compressor users time and money while improving reliability. These benefits include:

  • Extending Oil Life - The COP extends compressor fluid life up to five times the manufacturer's rated oil life, and reduces oil purchases as much as 80 percent.

  • Extending Separator Life - The COP extends compressor separator life up to three times the manufacturer's rated life, and reduces separator purchases as much as 60 percent.

  • Reducing Energy Consumption - The COP reduces compressor energy consumption by as much as three percent by reducing the fouling and energy-robbing pressure drop of compressor separators.

  • Reducing Maintenance Labor - The COP cuts routine maintenance labor costs by as much as 50 percent through extending compressor fluid and separator change intervals.

  • Extending Air-end Bearing Life - The COP reduces the number of ultra-fine solids less than 15 microns by as much as 97 percent. Studies by SKF Bearing Company illustrate that improving lubricant filtration from the standard compressor's oil filter performance of 25 microns absolute down to three microns absolute, performance of the purifier can extend bearing life by a factor of four.

  • Reducing Hazardous Waste Oil Generation and Disposal - The COP lowers oil handling and disposal costs and reduces environmental impact by reducing the generated volume of hazardous waste oil.

Practicing proactive maintenance and eliminating the root causes of component failures is proven to be a superior method for reducing costs and improving reliability of critical equipment. Ion exchange and ultra-fine filtration technologies now give compressor users the ability to proactively maintain rotary screw air compressors.