Lubricant Realizes Long Air Compressor Service Life

Francis Y.D. Hou, Anderol Jacky Fang, Anderol Jacky Fang, Analysts
Tags: compressor lubrication, synthetic lubricants

Selecting the right lubricant for machinery operations positively impacts the plant's bottom line. By providing processing equipment with correct lubrication, companies can extend equipment life, increase productivity and avoid unnecessary repair work related to mechanical degradation. What should companies consider when employing a lubricant? The key is to look for a lubricant that meets the requirements of plant operations.

One gas manufacturer understands the importance of selecting the right lubricant. The company converted to Anderol BDC 68 polyolester (POE) synthetic compressor oils to reap significant performance benefits.

Shanghai Shidongkou Gas Making Co. Ltd., a subsidiary of Shanghai Fuel Gas Group, is a gas supply plant built to implement Shanghai's five-year development plan for domestic and industrial gas production. The company utilizes four Frick/York RWB II-856 oil-injected, twin-screw compressors, each with a discharging capacity of 6,020 m3/hr (3,700 CFM) at a maximum discharge pressure of 1.4 Mpa (203 psi) and discharge air temperature between 110 to 120°C (230 to 248°F).

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Figure 1. Shanghai Shidongkou Gas Making Facility

Throughput Concerns
During a production peak at the end of 2004, maintenance engineers noticed an abnormal reduction of compressed air capacity. The unit production volume dropped drastically from normal startup figures of 5,100 to 5,200 m3/hr of air to as low as 2,000 m3/hr. With the compressor capacity reduced to less than half of its potential, the gas manufacturer had to operate three compressors to generate the output normally achieved by one machine. The company tried both polyalphaolefin (PAO) and diester-based synthetic products, which failed due to premature oxidation after only 300 hours of operation. The engineers also noticed that the lube oil had darkened. Through used oil analysis testing, Anderol was able to detect this problem, which was severely undermining compressor performance.

"Detailed checks revealed that the cause of capacity fluctuation was premature thermal-oxidative breakdown of the lubricant," said a Shanghai representative. "We tried other synthetic compressor oils including products from the original manufacturer and several other lubricant companies, but unfortunately, the problem persisted."

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Figure 2. Conventional Horizontal Double-barrel Lube Oil Cooling Tank

Solving the Problem
To solve the problem, the gas manufacturer approached Anderol Specialty Lubricants to implement an effective long-term lubrication strategy.

"Using inappropriate synthetic compressor oil could lead to complications such as heat exchange deficiencies or compatibility issues regarding seal, gaskets and quality of discharge air. Ignoring these problems could imply a safety threat, especially to equipment operators," points out Francis Hou, general manager, Asia Pacific, Anderol. "We had to be selective in helping Shidongkou choose the right compressor oil."

To maximize operational efficiency, it was necessary for the gas manufacturer to select a new synthetic compressor oil with qualities that promised not only enhanced performance but also safety and reliability during use. The lubricant must have high viscosity/temperature stability, high degree of thermal oxidative stability, extended service life, and excellent thermal conductivity properties. After careful matching and consideration, the lubricant supplier recommended its synthetic compressor oil, which met all of the company's requirements.

But before integrating the new compressor oil into the production process, the lubricant supplier assisted the gas manufacturer in its changeover procedure to eliminate residual oil, carbon deposit and rust inside the compressor system to ensure equipment cleanliness.

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Figure 3. Frick/York Compressor

The Right Lubricant Saves the Day
The synthetic base oil, made from technical-grade PE-polyolester, was highly compatible with the company's consumable parts. Exhibiting high thermal stability, the oil was especially suitable for use in screw compressors operating under high discharged air temperatures above 95°C (203°F). After application of the synthetic oil onto all four compressor units, they were able to consistently operate at a smooth air-discharging capacity of 5,000 to 5,300 m3/hr.

"The outstanding thermal oxidative stability of the oil virtually eliminated the deleterious by-product of oxidation, resulting in extended service life of our equipment," said a Shanghai representative. "This led to substantial cost savings on our resources. Effectively, we were able to do more for less."

On top of these benefits, the compressor oil's natural detergency and dispersing capabilities not only remove internal deposits to ensure smooth functioning, but also help keep the system clean. While its biodegradable properties make it an environmentally friendly product, its high flash point ensures a higher level of operational safety.

The combination of the right lubricant and proper maintenance strategies has proved to be fruitful for the gas manufacturer. After application, the company was able to maintain its production efficiency at 5,000 to 5,300 m3/hr.

"The oil's high-quality viscometrics, high-temperature stability and sealing capabilities have brought out the best performance in our compressors," a Shanghai representative said. "We know that the lubricant supplier has helped customers achieve business goals for many years. It's great to see that success replicated with Shidongkou air compressors."

About the Company 
Anderol, Inc., a Chemtura Company, is a supplier of specialty synthetic lubricants. For more information, go to www.anderol.com or e-mail info@anderol.com.