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How Variable Speed Drive (VSD) Rotary Screw Air Compressors Save You Money
April 10, 2024Energy Efficiency Unleashed: The Advantages of Rotary Screw Air Compressors
Kaishan USA | April 3, 2024 | Uncategorized
Rotary screw air compressors are a natural for oil and gas exploration settings because they are energy efficient and properly designed compressed air systems do not introduce ignition sources into an already hazardous environment.
While the drive to conserve energy and control costs isn’t new, more and more companies are looking to rotary screw air compressors to help cut energy use and cost and reduce their carbon footprint.
Of course, compressed air is not the most energy-efficient power source, but it is indispensable, especially when it is unsafe to introduce electricity. Air-powered tools run cooler and are much lighter (helping with worker fatigue). They don’t generate sparks or fires. You can use them in environments where conductive materials and flammable liquids are present. And heat, dust and debris make a typical industrial plant a hostile environment for electric tools.
That’s why compressed air and pneumatic tools have become the preferred alternative in challenging environments like metalworking, shipping, oil and gas sites, power plants and petrochemical facilities. They handle temperature extremes, as well as other harsh environments. You don’t want to introduce sources of ignition in mines.
Rotary screw air compressors are often used in power plants because of their energy efficiency and their ability to handle demanding environments.
And, as the preferred source of compressed air in most industrial settings, rotary screw air compressors are a mainstay in the modern industrial environment—a fourth utility, joining water, electricity and gas.
Energy Advantages of Rotary Screw Air Compressors
Rotary screw air compressors appear in so many industrial applications because of a wide range of advantages, especially in their use of energy.
Energy Performance
Rotary screw air compressors deliver more compressed air per horsepower, giving you more power than other types of compressors and enabling you to run equipment and tools with high horsepower requirements (up to 600 HP). Plus, they have a simple, time-tested design that enables impressive efficiency.
They operate continuously and work best with a 100% duty cycle. We recommend setting up your compressed air system so that it operates as close to full load as possible.
Improving Energy Savings
Several significant developments are enhancing the energy savings rotary screw air compressors can achieve, including the application of variable-speed drives and the use of multi-stage compressors.
Variable-Speed Drives
A VSD air compressor has a variable-frequency drive or inverter that adjusts its motor speed or RPM (and thus its CFM) to match the real-time demand for compressed air. When the demand drops, the inverter reduces the motor operation to a lower speed (and lower CFM). It thus consumes proportionately less energy (and money), creating a relatively linear output-to-input efficiency curve.
VSDs are an extremely energy-efficient way to address rapid cycling, which occurs when your air compressor switches back into the loaded state before the transition to the no-load state is complete. Usually, an indication that your compressor is oversized.
If rapid cycling happens too frequently, it can cause increased wear and reduce compressor reliability and lifespan.
We recommend VSDs when the compressor operates at a load between 40% and 80% of its total capacity most of the time. Conversely, we advise against using VSDs when your compressor is running at less than 20% or more than 80% load most of the time. The most efficient rotary screw air compressors, of course, run fully loaded, so a VSD will not offer any savings there.
They are valuable as a trim compressor complementing a base load unit and a backup system in a three-compressor configuration that optimizes pressure, flow, energy use and uptime.
A fixed-speed compressor still consumes 30-70% of full-load energy when operating with no load. A VSD air compressor, on the other hand, scales back power consumption proportionately, requiring almost no energy input when no load is required.
That can add up to real money:
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- Annual energy usage will drop by 33% on average, according to the Compressed Air & Gas Institute, with individual manufacturers placing the savings as high as 70%.
- Annual cost savings can be as much as $17,208, according to a recent American Society of Mechanical Engineers study analyzing case studies across multiple industries.
- Payback periods can be as low as two years although the ASME estimated average VSD paybacks at two to five years.
For more on VSD compressors, see our blog post, “Variable-Speed vs. Fixed-Speed Air Compressors.”
Two-Stage Compressors
A two-stage compressor divides the compression cycle into two steps, reducing the work done across each stage. The compression ratio is then just 2.8-to-1 in each stage, whereas a typical one-stage 100-PSI system usually has a 7.8-to-1 compression ratio.
Kaishan’s KRSP2 two-stage rotary screw air compressors are some of the most energy-efficient machines on the market.
Since the second stage builds on the pressure created in the first and some cooling occurs between stages, a two-stage compressor will generate more compressed air for less energy (more CFM per HP).
The bottom line? A two-stage air compressor will generate up to 15-20% more flow in the same size air compressor. That’s a payback that will generally recoup the price difference quickly.
Other Advantages of Rotary Screw Air Compressors
Rotary screw air compressors provide clean, high-quality air. And food processors can even use oil-free machines, like our new KROF two-stage rotary screw air compressor, in areas where the air comes in direct contact with food.
In addition to their energy efficiency, rotary screw air compressors offer many other advantages, including their ability to provide a steady flow of high-quality air and handle temperature extremes and variations in demand.
They are known for their steady air flow. They minimize fluctuations, enhance overall efficiency and give you a smoother operation.
In addition, they can handle variations in demand and temperature extremes. Compressed air systems are relatively safe, an essential concern in any environment.
Rotary screw air compressors have a compact footprint and occupy relatively little floor space.
And, compared to other types of compressors (especially reciprocating machines), rotary screw air compressors are less noisy.
Because they have long-term reliability built-in, they have a longer lifespan and a relatively low total cost of ownership.
In addition, rotary screw air compressors generally have better warranties than other types of air compressors because of their reliability, efficiency and long life. Kaishan USA backs its KRSP and KRSP2 premium rotary screw air compressor with an unmatched lifetime warranty on the airend.
Kaishan USA backs its KRSP and KRSP2 premium rotary screw air compressor with an unmatched lifetime airend warranty, thanks to their reliability, efficiency and long life.
Disadvantages
Admittedly, rotary air compressors have some disadvantages. They have a higher initial cost than a comparably sized recip (up to 25 HP). But are priced less than a centrifugal of comparable horsepower. And while they don’t need service often, they occasionally require the skills of advanced maintenance professionals.
And they are not designed for intermittent use. If your compressor cycles on and off too much, water accumulates and starts attacking the bearings.
Local Help
If you need help maximizing the energy efficiency of your rotary screw air compressor or the compressed air system in your facility, we can help. Kaishan works with a nationwide network of independent distributors, who can provide on-site help and consultation as needed. And help you find the right solution to any issue.
Key Takeaways
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- Rotary screw compressors deliver more compressed air per horsepower than other types of air compressors.
- Their simple design enables impressive efficiency.
- Rotary screw compressors work best at a 100% duty cycle.
- You can improve your energy savings by using VSDs (in applications with varying demand) and two-stage rotary screw air compressors.
- Other advantages of rotary screw compressors include their ability to provide a steady flow of high-quality air from a compact footprint.
Let Us Help
Having your rotary screw air compressor operating at peak energy efficiency can be a game changer for the operation of your compressed air system and all the processes that rely on that system. If you need assistance optimizing your system, get in touch with the experts at Kaishan. Contact us today.
