Companies that sell screw air compressors know that compressed air is used in thousands of applications, and that their machine is, of course, the most reliable, efficient, and durable of them all. The range is bewildering to say the least – and definitely not a simple choice to make selecting the right or more suitable type of compressor for your business is anything but easy.
Consequently, irrespective of your industry, whether it is a plant for dry ice or manufacturing goods, a pharmaceutical facility or a construction site, this comparison of attributes is bound to assist you to understand the discrepancies between different types of compressors to choose the most suitable compressor.
We hope this guide helps to demystify the topic.
What is a Rotary Screw Compressor?
The rotary screw compressor consists of two rotors (helical screws). Rotary screw compressors work quite differently from reciprocating air compressors which feature a piston to compress air. Because of the intermesh of rotors (screws), they compress or decrease the air volume with rotation, which results in increasing the air pressure. The design of the rotary screw compressor ensures that it runs continuously and it suits applications requiring a constant air supply.
What are the benefits of theirs? Besides the reliability, quality and universality, rotary screw air compressors have many other advantages:
- Those motors won’t be very noisy, and the equipment footprint will be tiny. That means you can put them in more places.
- Unlike piston compressors they don’t need to cool down the oil after each cycle, so they can run endlessly and very little maintenance is required.
- Oil-lubricated rotary screw compressors have a minimal oil carry-over, as low as 3 ppm (parts per million).
How to Choose the Rotary Screw Compressor that Fits Your Facility?
Making the choice between oil-injected and oil-free rotary screw compressors depends on your air purity requirements.
The presence of oils in the compressor can make it produce air impurities. Oil-free compressors on the other hand produce air of the utmost quality, so referred to in the medical field as surgical-grade air. This is precisely the reason why oil-free units are much favored in the food processing industry as well as in the pharmaceutical industry. Oil-injected models make up the majority, especially for more general industrial use, where air purity is not so important.
You already chose between an oil-injected engine compressor and an oil-free one, now it’s time for a drive type. Furthermore, belt-driven compressors are cheap, simple to install, operate and maintain and are therefore suitable for small operations. Such models are quieter and more energy efficient, using less power to cool larger hot water cylinders for more demanding applications. They have a slightly higher initial outlay. But because they are more energy efficient and trouble free, compressors featuring gears will cost less to run, and you will soon recoup that higher cost.
It is said that the choice between the fixed-speed and variable-speed rotary screw air compressor would depend on a single factor, that is, your air demand. The fixed-speed compressor would run continuously at a higher rotation speed, applicable for those applications with steady demand. But VSD (variable speed drive) compressors would run only when the demand is fluctuating.
Contrary to this popular notion, compressors that are fixed-speed are not necessarily the right answer for never-ending air demand.
Compressors with variable speed drives (VSD) are just as good, changing their speed to follow demand and provide air whether the need is stable or variable. In this latter case, either design will result in the same energy use and, so, efficiency. Basically, as with anything else in life, price becomes a critical factor beyond all technical considerations.
Another option is dual-speed technology, which is more energy efficient than a fixed-speed compressor, but investment cost is lower than for a VSD compressor. Dual-speed increases free air delivery at any pressure setting, unlike a fixed speed, but with greater investment cost. Dual-speed is best suited for applications with higher flow at varying pressure.
Overall, even though the variable-speed rotary screw is more expensive to purchase and install than a fixed-speed or dual-speed compressor, it is truly the best for applications with both steady and variable demand, it is also earth-friendly as it helps you save energy.
The Right Air Compressor Size
Another important factor to note is the rotary screw compressor and its correct flow of compressed air. If the compressor is too small, it will not supply the right quantity of compressed air and too large a compressor will increase energy consumption. That’s why a compressor has to be from a trusted brand name because in general sizes differ and this helps you pick out the right size in order to work your compressor in an effective manner in a way to decrease the energy.
Summary
It is a well known fact that screw compressors are far more economical compared with piston compressors which are used by operations with negligible compressed air needs. They are cheaper to run, thus saving you money and creating less of an environmental footprint, while running 24/7 will ensure they can keep up with any increase in demand. Lastly, an electric fixed-speed rotary screw compressor will drastically drop the oil content within your compressed air system – something that a reciprocating compressor might not be capable of achieving.