Rotary screw compressors provide an extremely reliable supply of clean, dry compressed air.
When deciding between rotary and piston compressors, it is important to consider duty cycle, performance, energy efficiency, air quality, maintenance, and installation costs.
Piston compressors are still the most common choice for many small compressed air system users.
For many of these applications, the relatively low air demand and quality needed make the piston a cost effective choice.
There is, however, a segment of compressed air users that may require a higher level of air quality. A collision repair shop, for example, would typically use much more compressed air and have higher air quality needs than other automotive service businesses.
Duty Cycle and Flow
An important difference between piston and rotary compressors is their duty cycle.
Duty cycle is the percentage of time a compressor may operate without the risk of overheating and causing excessive wear.
A piston compressor may provide adequate flow for a short period, but its allowable duty cycle must be considered. Most small piston compressors have an allowable duty cycle of 60-70%. For this reason, piston compressors are usually oversized to allow the compressor to periodically shut down and cool off because of the relatively high operating temperatures.
Even with adequate air storage this can cause capacity problems during peak operating hours. Further, if the shop expands or business increases, lack of air capacity can become even more of an issue.
Rotary screw compressors have a 100% allowable duty cycle and operate continuously if the need arises. This is possible because rotary compressors are fluid cooled. The fluid performs four important functions:
• Lubricates the bearings in the pump
• Removes contaminants from the air
• Forms a non-wearing seal between rotors and casing
• Removes the heat generated by compression as part of a thermostatically controlled fluid circuit.
Heat and Moisture
All of these benefits are important, but this last point is very relevant to the air quality. Piston compressors operate at internal temperatures of 300°F - 400°F, while a rotary screw compressor runs at much lower internal temperatures (between 170°F and 200°F). Just as hot summer air holds more humidity, hotter compressed air can hold more moisture and requires additional components to dry and clean it. A rule of thumb is that every 20 degree (F) increase in temperature doubles air’s ability to hold moisture.
Diesel Screw Compressor
The advantage of a diesel screw compressor is reducing the dependancy on an electrical power source, and, the ability to be mobile.
The ABLE diesel screw compressor can be moved between locations much the same way as our ABLE diesel generators using a forklift, HIAB, tilt tray, telehandler, or sling for example.
Being a mobile unit makes the diesel screw compressor perfect for service vehicle applications on farm, mine and building sites.