Buying Rotary Screw Air Compressors

Written By Steve Thompson

If you're looking for an air compressor that provides a continuous output over a long period of time, consider rotary screw air compressors. These machines are designed for constant use in a wide variety of demanding applications.

How rotary screw air compressors work
Traditional reciprocating compressors compressed air with one or more pistons that use an up-and-down motion to force air through the cylinder. Rotary compressors use dual counter-rotating screws to continually draw compressed air into specially designed cavities. The main advantage is that the rotary compressor allows for continuous, uninterrupted use, rather than having to rest after a specific period of time.

Rotary screw air compressors are generally more practical for industrial use and are frequently found at construction sites and in manufacturing plants. Since the mechanisms are continually cooled and use fewer moving parts to operate, they have a 100% duty cycle. While a high-end reciprocating compressor might have a 90% duty cycle, meaning it has to rest 10 percent of the time, a rotary compressor needs no such break.

Although rotary compressors are more expensive than their reciprocating counterparts, they boast a much longer operating life. Furthermore, buying used rotary screw air compressors can provide the same lifespan as a reciprocating machine and the cost will be about the same. In many cases, small businesses or fledgling business owners are more likely to buy used to save money while still maintaining the same level of operation.

Sizing the rotary compressor
Buying the right rotary screw air compressor is a matter of finding the ideal combination of performance and air yield. Sizes and performance are displayed on web sites or product literature, but not always in the clearest ways, so be sure to ask dealers about your exact requirements.

For example, let's say that you know you need a compressor that operates at 74 cubic feet per minute (CFM), which is good information to have. You also need to know the optimum pounds per square inch (PSI) for your machinery or tools to work most effectively. Generally speaking, you'll want to leave room for growth in the CFM figure, should you require higher performance in the future. It is best to err on the side of caution.

Additionally, you'll find that these compressors are most frequently listed according to horsepower rather than any other guideline. For example, a compressor might run at 20 HP with 74 CFM at 125 PSI. Ideally, you'll want a machine that runs at the lowest possible horsepower for the other requirements you have. In most cases, you won't find a rotary compressor that operates at under seven HP.

Start your search for the perfect rotary screw air compressor by submitting a free request for rotary air compressor price quotes. We'll match you to suitable dealers in your area.