Rotary screw air compressors are a type of rotary volume compressor and thanks to their reliability, long lifetime and
versatility, they are widely used in a lot of different industries. Compared to piston compressors, they are overall more efficient and
flexible. Find out the working principle of a screw drive compressor.
The working principle of a screw compressor
First of all, let us take a look at the rotary screw compressor element. The element consists of two rotors that look like helixes, each
with a different shape and number of 'grooves'/'teeth' (usually one with 4 and one with 6 teeth). To put it simply, atmospheric air is
sucked into this screw element and as the air progresses along the rotors, it gets compressed.Â
The screw element (block) consists of two rotors that are similar to a helix with a large climb with a different number of teeth. The most
usual ratio of teeth is usually 4:6. As the air progresses along the rotors the air is compressed as the volume space between the rotor
teeth decreases in the direction from the suction to the outlet.
The most widespread type of screw compressors are lubricated compressors with oil injection. For sensitive processes regarding the quality
of compressed air non-lubricated compressors are used. The compression process, in case of a lubricated compressor, proceeds as follows:
The working principle of a lubricated screw compressor
The air circuit: Air is drawn through the filter and an open inlet valve, into the compressor element and gets
compressed. A mix of compressed air and oil flows into the air receiver/oil separator via a check valve. The air is discharged through an
outlet valve via a minimum pressure valve and the air cooler. During loaded operation, a minimum pressure valve keeps the pressure in the
separator tank above a minimum value, required for lubrication. An integrated check valve prevents the compressed air downstream the valve
from being vented into the atmosphere during unloaded operation. When the compressor is stopped, the check valve and inlet valve close,
preventing compressed air (and oil) to be vented into the air filter.
The oil circuit:
In the air receiver/oil separator, most of the oil is removed from the air/oil mixture by centrifugal action. The remaining oil is removed
by the oil separator. The oil is collected in the lower part of air receiver/oil separator, which serves as an oil tank. The oil system is
provided with a thermostatic bypass valve. When the oil temperature is below its set point, the bypass valve shuts off the supply to the oil
cooler and the oil cooler is bypassed. Air pressure forces the oil from the air receiver/oil separator through the oil filter and oil stop
valve into the compressor element. The bypass valve starts opening the supply from the cooler when the oil temperature has increased to the
set point. At approx. 15 ËšC (27 ËšF) above the set point, all the oil flows through the oil cooler. An oil stop valve prevents the compressor
element from flooding with oil when the compressor stops.
Talk to the team today to see how we can help you minimise costs and maximise efficiency.
Your business performance is what we strive for. Ash Air offers a full range of Chicago Pneumatic and Alup air compressors, tools and
on-site solutions. We also provide oil-free compressors and food-grade oil to suit your needs. Ash Air are specialists in vacuum
pumps, blowers, and medical gas solutions. Ash Air offers complete quality air solutions as well as advanced piping systems for the
performance and efficiency of your compressed air system.
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Who we are and how Ash Air can help your business!
Ash Air has been around in New Zealand since 1979, and we’ve grown into a nationwide company with international support and a
reputation for quality and reliability.We look after all things compressed air for your business!
Reciprocating, Screw, air compressors
Vacuum pumps
Nitrogen
An extensive line of air treatment components
Ash Air's range of Chicago Pneumatic, Alup, Pneumatech, and Quincy compressors are used extensively around the world in industries
ranging from oil and gas to food, automotive and farming, and we bring you these world class compressors here in the land of the long white
cloud.Our technicians are compressed air equipment experts and are dedicated to addressing customer needs. Supported by a 13 locations
nationwide, Ash Air offers one of the widest selections of compressed air equipment and parts available today in New Zealand.
Reliability and Efficiency
With Ash Air compressors, you can count on reliability and high performance for even the most demanding applications. We focus our
efforts on the following:
Air compressors come in many types, rotary screw, piston, scroll, reciprocating, some are oil-free and other air compressors require oil
lubrication. Like many businesses, an efficient air compressor is at the heart of their operations. So, which type of compressor should you
choose? What makes a compressor, like a rotary screw, unique? Here are some clear cut benefits of equipping your business with a rotary
screw compressor. Â
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In the world of compressors, there are often significant and unutilized energy-saving possibilities including energy recovery, pressure
reduction, leakage reduction and optimization of operations through correct choice of a control and regulation system as well as the choice
of compressor size.We are going to take a look at some of the opportunities for minimizing the compressor’s operating costs.Â
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Many installations that produce compressed air offer significant and frequently unutilized energy
saving possibilities in
the form of waste energy recovery. In large industries, energy costs can amount to 80% of the total cost of compressed
air production.
However, a lot of this energy can be recovered, which in turn will save you a lot of money.Â
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Liquid water in compressed-air systems can lead to rusted equipment and unresponsive controls. Anyone who uses compressed air will, at some
point, find liquid water in the air distribution system. This can be anything from a nuisance to a serious problem, depending on the
application. If water might corrode equipment or introduce bacteria, removing it is critical.Â
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Liquid water in compressed-air systems can lead to rusted equipment and unresponsive controls. Anyone who uses compressed air will, at some
point, find liquid water in the air distribution system. This can be anything from a nuisance to a serious problem, depending on the
application. If water might corrode equipment or introduce bacteria, removing it is critical.Â
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Whenever most people think about a compressor, they probably have a piston compressor in mind. You might already know there are two basic
principles of air compression. One of those is the principle of displacement compression. There are a lot of compressor types that classify
as a displacement compressor. The piston compressor is one of them, oil-lubricated or oil-free.Â
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Once you have the size and type of
compressor figured out, one last question remains, should I go with an oil lubricated or oil-free air compressor. To not overcomplicate the
answer, your choice should be based on the application and process that the compressed air will be utilized in.
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Like all compressor types, rotary screw models do require periodic maintenance. Thanks to the simplicity of the internal components,
maintenance is relatively easy on most rotary air compressors. As long as you stick to a rotary screw compressor maintenance schedule, you
will likely be rewarded with many, many years of optimal productivity from your machine.Â
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Did you know, the biggest part of the air we breathe is nitrogen? Everyone needs oxygen to survive, however air is made up of 78% nitrogen,
only 21% oxygen and tiny amounts of other gases. Although, the human body does not use this nitrogen, it is very helpful in various
industrial applications. There is an unlimited source of nitrogen readily available, allowing you to achieve needed purity at a fraction of
your current annual nitrogen cost.Â
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If you notice that your compressor is getting hot and bothered, there may be heating issues affecting your air compressors performance. Did
you know that an overheating compressor is top of the pops for being the most common cause of compressor failure.Â
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A rotary-screw compressor is an air compressor that uses a rotary-type positive-displacement mechanism, typically used replace piston
compressors where large volumes of high-pressure air are needed, either for large industrial applications or to operate high-power air
tools.Â
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Have a look around and what do you see? What are you thinking about? Your next holiday to Queenstown maybe? You might go snowboarding with
the kids or have some alone time at the Day Spa. Whatever holiday you choose, compressed air is involved in some way, without you even
realising it! Â
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There are crucial reasons why you should service and maintain your compressor regularly, with the most common issues being piston failure
caused by wear of components, increased friction, corrosion, reduced cooling, overheating bearings and components, clogging of air filters.Â
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Our passion for energy efficiency and cost saving derives from the concern for our children’s future. Analysing the efficiency of your
system is a brilliant way to start saving.
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Compressed air is all around us, from the air in a balloon to pumping up tires on your bicycle. In this article we will explain what
compressed air is and how it is created. Whether you know it or not, compressed air is involved in every aspect of our lives, from the
balloons at your birthday party to the air in the tires of our cars and bicycles. It was probably even used when making the phone, tablet or
computer you’re viewing this on.Â
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One of the biggest challenges is to correctly size your new air compressor. Similarly to everything else, new compressors available on the
market are more efficient and employ better technology, therefore you have to understand the application and usage to size the machine
correctly. Choosing the wrong air compressor for your facility can lead to problems with production and or increased costs due to wasted
energy.Â
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Once you have the size of the air compressor figured out, the
next thing to do is to decide on the type of compresor you will need for your application - piston, rotary screw compressor etc. Let us take
a look at two of the most popular options available. When choosing the right type of compressor, you should ask yourself the following
questions:
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​Which vacuum pump do I need? - this is one of the most frequent questions we receive and this is understandable, because there are number
of technologies which can provide the same vacuum level and pumping speed. Here is quick advice on how to choose the best vacuum pump for
your needs.Â
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You may be asking, why does my air compressor start, then stop? Allow us to take the guessing out of it. We understand your pain. We know
that a compressor problem can quickly result in hours (if not days) of production downtime and loss of revenue. When your compressor
continuously shuts off from on, we refer that as a short cycle. There are a few reasons that a short cycle may be happening with your
compressor.Â
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Air compressor leaks are very common in all applications, but can be very costly and difficult to find. On average, 20-30% of the compressed
air used in a manufacturing plant is wasted as leaked air. Finding and fixing these leaks can save your business thousands of wasted dollars
a year.Â
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When installing a compressed air system into a business, people often look to PVC piping as an option to build a piping system because it is
cheap, versatile and easy to install. However, using PVC pipe in any compressed air application is extremely dangerous and NOT recommended
by multiple associations and manufacturers.Â
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Changing the oil and oil filters on your compressor is one of the most common routine maintenance tasks to perform to keep your compressor
running efficiently. After you remove your old oil and oil filter, you may find yourself wondering, “Where do I dispose of these?”, or “Can I
just throw them in the trash?”. Because oil is toxic and a pollutant, disposing of your old oil and filters is not as simple as just tossing
them in the trash.Â
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