Oil serves as a lubricant, aiding in minimizing friction among the parts within an air compressor’s pump. It also acts as a sealant, preventing gas leaks from the compressor, and assists in regulating temperature during operation. Less heat from friction means less energy is consumed and a longer machine life is achieved. Monitoring and managing lubricant viscosity can prevent costly breakdowns and affect energy efficiency.
This article will teach you about compressor oil viscosity and why oil viscosity is so important.
What is Oil Viscosity?
Viscosity refers to an oil’s resistance to flow/shear. It decreases (thins) with increasing temperature and increases (thickens) with decreasing temperature. An oil’s viscosity is determined by measuring the time (in seconds) required for a fixed volume to flow a known distance (by gravity) through a capillary within a calibrated viscometer (an instrument for measuring the viscosity of liquids) at a closely controlled temperature.
Viscosity is reported in a unit called the centistoke (cSt). The viscosity of an oil is the first and most important consideration when selecting an oil for a specific application. The viscosity needs to match the speed, load, and temperature requirements of the parts being lubricated.
What is the Viscosity Index?
Some oils contain the ability to resist changes in viscosity due to a change in temperature. This property is referred to as the oil’s viscosity index or VI. The higher the VI, the less the oil’s viscosity is altered by temperature changes and the better the protection provided at higher temperatures. As the VI decreases, the viscosity of the oil is more prone to change with variations in temperature.
Types of Compressor Oils
The oil and gas industry utilizes different types of compressor oils to ensure the smooth and efficient operation of compressors:
- Mineral-based compressor oils. These oils are derived from refined crude oil and are suitable for general-purpose applications in compressors. They offer good lubrication properties and thermal stability, making them suitable for a wide range of operating conditions.
- Synthetic compressor oils. Synthetic oils are engineered to provide superior performance and stability compared to mineral-based oils. They offer excellent thermal and oxidative stability, as well as enhanced lubrication properties, making them ideal for high-temperature and high-pressure applications.
- Semi-synthetic compressor oils. Semi-synthetic oils are a blend of mineral-based and synthetic oils, combining the benefits of both types. They offer improved performance and stability compared to mineral-based oils, while still providing cost-effectiveness.
- Ashless compressor oils. These oils are formulated without ash-forming additives, making them suitable for compressors where ash deposits can cause issues. Ashless oils offer excellent cleanliness and are often used in sensitive applications where contamination must be minimized.
- High-performance compressor oils. For demanding applications such as offshore platforms or critical industrial processes, high-performance compressor oils are used. These oils are engineered to withstand extreme conditions, including high temperatures, pressures, and corrosive environments, while still providing reliable lubrication and protection.
Choosing the right type of compressor oil depends on factors such as operating conditions, equipment specifications, and industry regulations. Conducting thorough research and consulting with lubricant experts will help ensure that the right oil is selected for each specific oil and gas application. The specialist will also advise on the compressor oil viscosity.
Why is Compressor Oil Viscosity Important?
Compressor oil viscosity is important and here’s why:
- When oil viscosity deviates from the specified range, it results in compressor bearing failure, leading to rotor assembly wear
- Insufficient lubrication results in production downtime and revenue loss
- Loss of proper lubrication leads to high repair costs
- Proper oil viscosity reduces energy use
- Viscosity governs the sealing effects of oils and the rate of oil consumption
- Oil viscosity determines the ease with which machines are started and/or operated under varying temperature conditions
- Proper oil viscosity increases the life of a compressor
Choosing the right compressor viscosity oil can also improve energy efficiency. Oil that is too thick may require more energy to pump through the compressor system, while oil that is too thin may result in increased friction and energy loss. Optimal viscosity ensures efficient oil circulation and minimizes energy consumption.
What Factors Affect Oil Viscosity?
Many factors affect oil viscosity:
- Oxidation. When compressor oil churns and foams, it exposes more of the oil to surface air, leading to oxidation. This process can lower viscosity and diminish the useful life of the lubricant, compromising its ability to provide adequate lubrication and protection to compressor components.
- Dilution. Compressor oil may become diluted with gas, such as methane, during operation. This dilution decreases the viscosity of the oil, potentially reducing its lubricating properties and effectiveness in maintaining proper equipment operation.
- Foaming. The churning action of compressor oil can create bubbles as it interacts with the screws or vanes of the compressor. This foaming process can cause a drop in viscosity, impairing the oil’s ability to provide sufficient lubrication and protection to compressor internals.
- Contamination. Hydrocarbon vapors from the compression process may mix with the compressor oil, leading to contamination. This can alter the oil’s viscosity and degrade its performance, potentially causing issues such as increased wear and reduced efficiency in the compressor system.
- Temperature changes. Significant fluctuations in temperature, particularly during startup, can affect the viscosity of compressor oil. Cold temperatures can cause the oil to thicken, while high temperatures can cause it to thin. These viscosity changes can impact the oil’s ability to flow adequately and provide effective lubrication to critical components.
Regular oil analysis, proper maintenance practices, and selecting the right oil viscosity grade for the operating conditions can help mitigate the effects of these factors and ensure reliable compressor operation.
Criteria for Compressor Oil Selection
The following factors are considered when selecting compressor oil for the oil and gas industry:
- Operating conditions. The operating conditions of the compressor, including temperature, pressure, and humidity levels, play a crucial role in determining the appropriate oil viscosity and performance characteristics needed to ensure proper lubrication and protection of compressor components.
- Equipment compatibility. It’s essential to choose compressor oil that is compatible with the materials used in the compressor system, including seals, gaskets, and other components. Incompatibility can lead to premature wear and damage, as well as potential leaks or failures.
- Environmental regulations. Compliance with environmental regulations is a key consideration when selecting compressor oil. Certain oils may contain additives or properties that could have adverse environmental impacts if released into the environment. Choosing environmentally friendly oils helps mitigate these risks and ensures compliance with regulations.
- Application specificity. The specific application and function of the compressor within the oil and gas industry influence the selection of compressor oil. Factors such as the type of gas being compressed, the level of contamination present, and the criticality of the compressor’s operation all impact the choice of oil.
- Performance requirements. Different compressor systems may have unique performance requirements, such as high temperature or pressure capabilities, extended service intervals, or compatibility with specialty gases. Selecting compressor oil that meets these performance specifications ensures optimal performance and reliability of the equipment.
- Maintenance considerations. Ease of maintenance, including oil change intervals, oil filtration requirements, and compatibility with existing maintenance procedures, should also be taken into account when selecting compressor oil. Choosing oils that simplify maintenance tasks can help reduce downtime and maintenance costs.
- Cost-effectiveness. While performance and quality are essential considerations, cost-effectiveness is also a factor when selecting compressor oil. Balancing performance requirements with budget constraints ensures that the chosen oil provides the best value for the investment.
By taking these factors into account, it is possible to select a compressor oil that meets the specific requirements of compressor systems, ensuring optimum performance, reliability and environmental compliance.
How Can You Protect Your Compressor and Ensure Good Performance?
Monitoring and managing compressor oil viscosity can prevent costly breakdowns due to bearing failure. Refineries commonly perform monthly lab checks but these checks are insufficient to prevent bearing failure and subsequent plant downtime. Protect your compressor(s) by adding in-line oil viscometers to all new and existing units. In-line viscosity monitoring provides plant operations with real-time data on the lubricant viscosity. This saves lab and technician time and reduces the chance of damaging equipment.
While the goal is a lubricant with a long and useful life, harsh environments, contaminants and even humidity in a refinery’s external environment can greatly reduce lube oil’s useable lifespan. Controlling the viscosity of the compressor oil is the best way to prevent bearing wear and compressor failure.
Experiencing wear and tear on your compressor? GasPro’s qualified service technicians inspect and service all our compressor units. We provide “Same Day Service” to guarantee maximum uptime and efficiency for our clients. Our fully stocked service trucks handle all our client’s needs and our focused team takes pride in their work. We aim to offer reliable products and swift service to all our customers.
We are constantly enhancing and innovating our products to align with evolving industry needs. GasPro Compression is a leading provider of compressor packages in Canada. Contact us to request a quote, get answers to questions about compressor oil viscosity, and more. Call 403-443-8886 or email us at clint.praski@gaspro.ca.