Whether you’re a seasoned fleet operator or just curious about how air compressors work and how to best maintain them, understanding them is essential. These versatile machines come in a variety of types and sizes; each suited to different tasks. But, with so many options and technical terms, it’s easy to feel overwhelmed. In this article, we’ll tackle frequently asked questions about both reciprocating and rotary screw air compressors.
Why does non-detergent oil for my reciprocating air compressor matter?
While reciprocating compressors may be similar to internal combustion engines, they typically don’t have any oil filtration. Detergents in oil are designed to clean and maintain dirt or debris suspended in the oil so it can be captured in filtration. Non-detergent oil allows the debris to settle at the bottom of the air end, ensuring that debris flushes out when draining the oil during service. When draining the reciprocating compressor oil, the debris is more likely to exit with the old oil when using a non-detergent oil. Debris in detergent oils tend to float to the top, and can be left behind when servicing the compressor, similar to draining a bathtub when the debris is left on the side after draining.
Why do I have condensation in my receiver tank or coming out the air discharge hose?
A byproduct of compressed air is condensation, or a formation of water droplets from the atmosphere. While the air is compressed it creates heat, and as the air cools, condensation forms. This event occurs with any compressor.
What is emulsification, and how does it affect my rotary screw air compressor and air/oil separator tank?
Emulsification occurs when two liquids, such as oil and water, are forced together into a stable blend. In rotary screw compressors, oil is injected to lubricate and cool the system, but normal moisture from the air condenses and mixes with the oil, forming an emulsion. This emulsion forms a milky or cloudy substance that is thick and difficult to separate back into water and oil. This milky/cloudy oil can be caused by:
- High humidity
- Cooling system failure
- Low load rates
- The presence of moisture in the compressed air
Some machines include an air/oil separator element, such as Vanair’s patented UltraLife® 6,000 Hour Air/Oil Separator , designed to remove oil from the compressed air. But once the oil is emulsified, it’s much more difficult to separate from the air. Emulsified oil can clog or reduce the effectiveness of the separator’s filter elements or coalescing media. This potentially requires more frequent replacement or cleaning. When this happens, the compressor works harder, raising energy costs, risking overheating, and risking normal production. Maintenance becomes more frequent and expensive, with separator elements wearing out faster, and potentially corroding internal parts.
To prevent emulsification:
- Select a high quality compressor oil, such as Vanguard™ Rotary Screw Compressor Oil.
- Drain your machine’s condensation regularly after use to prevent rust and corrosion, protect internal components, and ensure cleaner air output.
- Monitor your ambient temperatures and ensure proper ventilation. Hot, humid air drawn into the compressor traps in moisture, leading to potential emulsification.
- Maintain and regularly clean your aftercoolers for maximized efficiency and moisture control.
- Always adhere to proper and frequent maintenance schedules, so you can avoid downtime and maintenance issues.
Will an air aftercooler help with moisture issues & temperature concerns when using pneumatic pumps or other tools?
Yes, an air aftercooler with a moisture trap removes roughly 75% of moisture and gives an air discharge approach of about 20°F of ambient temperature. This means if the ambient temperature is 80°F, your compressor/discharge temperature would be about 100°F.
Does it matter what size (diameter) air hose I use with my compressor?
The short answer is yes. The flow (CFM) of an air compressor will always leave the tool end of the hose, but the pressure (PSI) may significantly reduce at, say, 50 feet away, depending on the size of the hose. It is a good rule to match the hose size to the discharge connection size to keep any pressure drop minimal. Reducing the hose diameter will not increase the pressure.
If a reciprocating compressor has more than one cylinder, does that make it a two-stage air end?
No, reciprocating air compressors can have many cylinders and still only be a single-stage air end. Single-stage air compressors typically have a maximum pressure of 150 PSI, whereas two-stage air ends typically reach 175 PSI. Two-stage air ends have an initial stage(s) that compress and discharge to a secondary cylinder(s) that will compress the air to a higher pressure before it is discharged to an air receiver tank for operation.
To learn more and check out other frequently asked questions, visit our FAQ videos page here.
