How AMSOIL helps extend the life of your rotary-screw compressor

Rotary-screw compressors are known for their reliability, longevity and infrequent maintenance. As such, key industries, such as molded plastics, rely heavily on these nonstop workhorses for blow molding, extrusion molding and injection molding. While renowned for their reliability and durability, rotary-screw compressors are complex pieces of machinery that require specific maintenance practices to function optimally. Proper maintenance starts with using the correct lubricant. Beyond that, significant gains can be made by using a specialized oil designed specifically for the unique operating environment found in rotary-screw compressors.

In this article, you will see how AMSOIL Industrial PAO Rotary Compressor Oil reduced oil consumption by 50% compared to a leading competitor brand oil. We will also cover how using the wrong oil can result in varnish buildup, premature wear and unforeseen failures.

Over the years, rotary-screw compressors have made substantial technological advancements. Designed to meet the demanding schedules of production lines, today’s compressors are quieter, smaller and more energy efficient than ever. As innovative new technology replaces the old, additional factors must be accounted for.

Smaller units contain smaller sumps but are still expected to run similarly to a full-size unit, meaning the same oil is exposed to higher heat. This puts a greater strain on a reduced amount of oil, which can result in rapid oxidation.

Suggested manufacturer maintenance protocols work well to meet general requirements — checking filters, hoses, leaks, belts and oil levels — but preventive maintenance cannot account for unseen issues forming inside the compressor as a result of using inferior oil, like varnish and wear.

Plastics manufacturing plants expose rotary-screw compressors to extreme environments, requiring a lubricant engineered to withstand high operating temperatures, air-demand fluctuations and contamination risks.

An elevated ambient climate combined with heat generated from compression cycles can negatively impact a compressor’s thermal management system. A superior synthetic lubricant with thermal stability will withstand high operating temperatures and prevent thermal breakdown. This is important in plastics manufacturing plants as compressors experience periods of continuous high usage. Lastly, contamination risks in the form of moisture and particulates can make their way into the compressor’s air intake. To combat these contaminants, compressor oil must be filtered and possess demulsification capabilities.

The right rotary-screw compressor oil combats environmental challenges, fights varnish and minimizes oil consumption — all essential for optimal machine life, lower maintenance costs and boosted productivity.

Varnish is a major threat to the longevity and performance of rotary-screw compressors. Varnish forms when a lubricant breaks down due to excessive heat or oxidation. The result is a thick substance that wreaks havoc on essential compressor components. Some indications you may have varnish include:

• Increased Friction: Varnish deposits increase friction between components, resulting in higher operating temperatures, reduced efficiency and increased wear.
• Restricted Oil Flow: Varnish can clog oil passages and filters, hindering the compressor's ability to circulate oil effectively and cool critical components.
• Premature Component Failure: Varnish deposits can restrict heat transfer away from bearings and rotors, leading to premature wear and potential component failure as well as higher oxidation rates.

“Systems that turn on and off can create varnish problems. The key is to keep varnish from forming in the first place. Once varnish occurs, it's extremely expensive to eliminate. We’ve committed over a decade to testing the efficacy of our compressor oils. Our testing showed a significant reduction in varnish buildup compared to a leading competitor. When it comes to providing solutions for our customers, data-driven analysis is the catalyst for determining which lubricant is best suited for their needs. We provide customers with lubrication solutions that yield superior results, optimizing the life of their equipment and reducing operating costs. It's what we do," says Jim Pezoldt, AMSOIL Industrial Sr. Business Development Manager, Lubrication Engineer, STLE CLS#59235 .

The Membrane Patch Colorimetry (MPC) Varnish Potential Test (ASTM D7843) determines a lubricant’s propensity to form varnish. The lubricant is filtered through a patch and the resulting color is measured against a control patch. The darker the patch, the higher the potential for damaging varnish. 

To analyze high-temperature performance, a leading competitor’s synthetic compressor oil and AMSOIL Industrial PAO Rotary Compressor Oil were run in industrial rotary-screw compressors with oil discharge temperatures of 200°F.

The leading competitor’s compressor oil showed critical varnish potential after only 6,228 hours of service. AMSOIL Industrial PAO Rotary Compressor Oil continued to exhibit minimal varnish potential after 16,000 hours, indicating its superior resistance to varnish at extended service intervals.

• Synthetic Lubricants: Provide superior resistance to thermal and oxidative breakdown compared to conventional mineral oils. This translates to a significant reduction in varnish formation within the compressor.
• Antioxidant Additives: Neutralize free radicals, the primary culprit behind lubricant oxidation. This reduces varnish formation and extends the oil's service life.
• Detergent and Dispersant Additives: Help suspend contaminants, preventing them from settling and forming deposits within the compressor. Regular oil changes and proper filter maintenance are crucial for removing suspended contaminants before they can contribute to varnish buildup.

AMSOIL Industrial Synthetic Rotary Compressor Oil and AMSOIL Industrial PAO Rotary Compressor Oil offer excellent foam resistance and air-release properties, reducing oil consumption in field testing.

"We dedicated extensive time and effort to testing, and the results are clear: AMSOIL Industrial Synthetic Rotary Compressor Oil requires 35% less top-off oil, and AMSOIL Industrial PAO Rotary Compressor Oil requires 50% less than the leading competitor. The collaboration between our mechanical lab and chemistry lab for this field trial demonstrates our commitment to our products and devotion to engineering the best solutions for our customers," says Kat Guillen, AMSOIL Sr. Product Development Engineer.

Over an 8,000-hour period, both AMSOIL Industrial compressor oils required less make-up oil than a major original equipment manufacturer’s (OEM) synthetic compressor oil, saving time and resources, while providing peace of mind that compressors remain protected.

Learn more about AMSOIL Industrial Rotary-Screw Compressor Oil testing. 

Using the right lubricant for your compressor is the first step. Ensuring the oil is delivering optimum performance to extend the life of your compressor requires additional strategies.

1. Regular Oil Analysis: Schedule regular oil analysis to monitor lubricant condition and detect the presence of contaminants or signs of degradation. This prevents problems before they arise. The excellent cleaning action of AMSOIL Industrial synthetic compressor oils can loosen or remove performance-robbing deposits left by the previous oil. To ensure good changeover results, monitor your equipment with oil analysis.
2. Proper Oil Levels: Maintaining the correct oil level in the compressor is crucial. Running the compressor with insufficient oil can lead to overheating and component damage. Overfilling can cause foaming and reduce efficiency.
3. Oil Changes: Follow the recommended oil change intervals outlined by your compressor manufacturer and lubricant supplier. These intervals will vary depending on factors such as operating conditions and the specific lubricant used.
4. Air Filtration: A clean and efficient air-intake filter is essential. Contaminants like dust and dirt can accelerate lubricant degradation and cause excess wear on screws and bearings. Regularly inspect and replace air filters as recommended by the manufacturer. 
    

Investing in the right lubricant for your rotary-screw compressor not only increases the life of your machine it also increases sustainability in the following ways:

• Extended oil change intervals mean less oil to dispose of.
• Improved efficiency of compressors translates into lower energy use.
• Proper lubrication reduces the risk of equipment failure and the need to replace it.
   

Rotary-screw compressors play a critical role in the success of plastics manufacturing operations. By prioritizing proper lubrication practices, plastics manufacturers can ensure their rotary-screw compressors operate at peak performance for years to come.
AMSOIL application engineers can provide guidance for developing a maintenance plan, performing fluid analysis and interpreting the results. After evaluating the fluid analysis report, we can determine the oil’s remaining life and recommend the best options to help slow oxidation and prevent varnish, helping you increase efficiency and profitability.

Learn more about Industrial solutions engineered specifically for plastics manufacturing plants.