Piston compressor or reciprocating compressors and rotary screw air compressors are two of the most popular compressor technologies available today. But do you know which one would be better suited for your specific needs and applications? Understanding the difference between piston and rotary screw air compressors and the capabilities of each technology is key. That’s why we’re covering the basics below!
Advantages & disadvantages of piston vs screw compressors:
When comparing piston and rotary screw compressors, it's important to understand their operational differences and how these relate to their suitability for specific tasks. Piston compressorsare typically used for applications that require short, intense bursts of air. In contrast, rotary screw compressors are designed for applications that need a steady flow of air over extended periods.
Energy efficiency
Rotary screw compressors are typically more energy-efficient than piston compressors, delivering more air per unit of input energy. For example, piston compressors generally deliver 3-4 cubic feet per minute (cfm) per horsepower (hp), while rotary screw compressors deliver 4-5 cfm per hp. This efficiency is particularly beneficial where electricity costs are high.
Operating costs and energy efficiency
Rotary screw compressors generally have lower operating costs and are more energy-efficient in the long run, especially for continuous use scenarios. However, piston compressors might offer savings for smaller or less frequent applications.
Operational differences
Piston compressors work by drawing air into a cylinder and compressing it with a reciprocating piston. They are generally best for lower volume air needs and have a duty cycle of about 60-70%, meaning they need to shut down periodically to prevent overheating.
Rotary screw compressors, on the other hand, use two interlocking rotors to compress air and are fluid cooled, allowing for 100% duty cycle and continuous operation without the risk of overheating.
Air quality
The quality of compressed air is another consideration. Piston compressors operate at higher internal temperatures, which can lead to more moisture in the compressed air. This may require additional drying and cleaning components. Rotary screw compressors run at lower temperatures and often come with built-in aftercoolers to reduce the air temperature, resulting in better air quality.
Maintenance and durability
Rotary screw compressors have fewer moving parts than piston compressors, which translates to less wear and tear and lower maintenance requirements. While piston compressors are simpler in design and may be easier to maintain, they typically require more frequent service due to more moving parts.
Noise and space requirements
Rotary screw compressors operate more quietly and require less space compared to piston compressors, making them suitable for closer proximity to workspaces.
Total Cost of Ownership
The initial cost of a rotary screw compressor may be higher, but the total cost of ownership can be lower due to its increased efficiency and lower maintenance costs over time. This includes the purchase price, energy consumption, maintenance and downtime costs.
Atlas Copco's GA series with VSD technology is recommended for its energy efficiency. The GA 5-37 VSDˢ model, in particular, can achieve significant energy savings and has a design that minimizes energy consumption.
What Factors Should I Consider?
Initial and operating costs, energy efficiency, duty cycle, and service intervals are important factors to consider when determining whether your business will benefit most from a piston or a rotary screw compressor. Noise levels is an additional factor to take into consideration.
- Initial Cost vs. Operating Costs. Budgeting for a compressor shouldn’t only include how much you pay for your compressor upfront; you also need to consider how much you’ll pay for your compressor in the long run (i.e. your overall operating costs). As much as 70-75% of a compressor’s lifetime operating costs are spent on energy usage, so keep that in mind when selecting a compressor technology. Pistons have a lower initial cost than screws, but screws cost much less to operate over time.
- Energy Efficiency. If both a piston and a screw were running the same amount of hours, the screw compressor will be much more efficient and have lower operating costs than the piston over the lifetime of the compressor. When selecting a technology, ask yourself: Is the initial or lifetime cost more important to you and your business?
- Duty Cycle. Because piston compressors are limited in their duty cycles, they’re ideal for applications with low duty cycle requirements and low daily running hours. Screw compressors, however, have long duty cycles. In fact, screws are engineered to run 100%, all day, every day!
- Service Intervals. There are more moving parts in a piston compressor than in a screw, which results in increased machine wear and tear. Screw compressors don’t have as much wear; hence, they have reduced maintenance needs. But keep in mind that it’s important to keep any type of compressor on a consistent maintenance schedule! This will help ensure machine efficiency and optimal system performance.
- Noise Levels. Piston compressors are loud – especially in comparison to screw technology. If you’re looking for a lower-noise machine or a low noise level is required, you may want to consider a screw compressor.
In brief
Piston compressor a great option as an entry level compressor, but it's common for facilities outgrow the unit. If you need a consistent and or increased flow (CFM) and are looking for something that is compact, efficient, reliable and quiet, going with a rotary screw would be a great option. It’s quite normal for a company to start out with limited need for compressed air, but as production and customer demand increases, so does the need for increased output and the need for a larger compressor that can adequately handle the demand and increased duty cycle!
Still struggling with which technology is right for you? Our compressed air experts are always available to talk you through the decision! Give us a call or email us
