In industries such as agriculture, manufacturing and mining, compressed air is as essential as electricity and water. Unlike those utilities, however, compressed air must be produced on-site — which is what makes an air compressor a critical asset. Without compressed air, hand tools and machines won’t run; liquids and powders can’t be conveyed; and some agitation and ventilation systems will be unable to function.
Efficiency, reliable operation, long life and low lifecycle costs: These are what industrial users want from their air compressors. While maintenance plays a part in attaining these goals, the single biggest contributor to the performance of your air compressor is the model you choose. Here is a comparison of the most common types of air compressors, with a discussion of the features that are relevant to industrial users.
UNDERSTANDING COMPRESSOR TYPES
The primary types of air compressors are:
- Rotary screw
Here’s a closer look at each:
ROTARY SCREW COMPRESSORS
These units use a pair of interlocking helical scrolls to draw in and compress air before delivering it into the distribution system. In most designs, the scrolls run in an oil bath. This ensures a good seal, helps reduce wear and removes the heat that results from compression.
Rotary screw compressors tend to produce more airflow per unit horsepower than other designs and do so with less space. They are capable of operating at 100% duty cycle, plus they run quieter than other designs and require little maintenance.
Rotary screw compressors are available from 5 to 500hp. Smaller models are typically belt-driven, while more the powerful units use direct drive. These two-stage compressor designs can also increase efficiency.
Reciprocating compressors use either an electric motor or an engine to turn a crankshaft that drives a piston up and down in a cylinder. Air is sucked in as the piston moves down, then the intake valve closes, and the piston compresses the air on the up-stroke.
Air produced by a reciprocating compressor exhibits pulses in pressure which can cause speed and/or performance problems in many applications. To counteract this, air from a reciprocating compressor is usually distributed from a storage reservoir. Bringing this tank to pressure can cause delays in the startup of downstream processes and equipment.
As they have a lot of moving parts, reciprocating compressors tend to require more maintenance than rotary screw designs. They also typically run louder. Reciprocating compressors are a popular choice in small-scale applications, especially when portability is desired. However, lower efficiency and higher maintenance demands make them a poor choice for most industrial users.
An axial compressor is similar in design to a jet engine. Spinning fan blades draw in air, and successive rings of blades compress it. This design can efficiently produce very high amounts of air but is only suitable for the highest volume industrial applications. In addition to their large physical size and high output, another reason that axial compressors are used only in industrial settings is that they are significantly more expensive than other models.
The centrifugal compressor uses a single ring of rotating fan blades. These suck in air along the fan axis and funnel it 90 degrees through the unit. As it moves out to the housing around the blades, the air is compressed.
This design produces a lot of compressed air in a relatively small space, which makes it useful in high-volume industrial applications. However, these machines are usually less able to handle fluctuations in air demand. Additionally, purchase costs are typically higher than for similar capacity rotary screw designs. They also generally need more frequent maintenance, so lifecycle costs may be greater.
CHOOSING THE RIGHT COMPRESSOR FOR YOUR APPLICATION
When compressed air plays a vital role in business operations, it is important to choose the best model for your application. Kaishan USA has been in the air compressor industry for many years. We are proud to produce a range of rotary screw compressors that satisfy the expectations of our industrial clients.
Our highly experienced product specialists can help you evaluate the various air compressors and determine which type can best meets your needs for efficient, reliable and low cost compressed air production. Contact us today to get started.