Sep. 02, 2024
Air compressors are used everywhere, from fuel stations to construction sites, domestic refrigerators to heating systems, workshops to factories. They play a vital role in all sorts of processes, supplying power for applications and environments where electrically powered tools can&#;t be used because of fire and operator electrocution risks.
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So how do you choose?
There is a bewildering array of compressor choices in terms of size and power supply, from low-pressure options suitable for inflating tyres and hobby applications up to powerful, heavy-duty units used to power major manufacturing processes.
Air-powered tools are usually lighter and smaller than batter or mains powered options &#; batteries and motors can weigh heavily on the hand! They&#;re safer because they have no electrical components or mains connections, protecting the operators. If there are combustible gases or moisture in the working environment, air tools and a compressor are the safest options.
Air-powered tools are usually cheaper than the alternatives too, and air systems and easier and less costly to install than hydraulic systems. Add to these low maintenance requirements and therefore reduced downtime, the advantages are really stacking up.
Air compressors are used to transform motive power into compressed air by compressing the air into a tank then releasing this to create power. Power is then generated until the pressure in the holding tank drops to a certain predetermined level. A pressure switch then triggers the motive power source and refills the holding tank, generating more pressure.
Compressor power ratings are calculated in cubic feet per minute (CFM). All compressor-powered tools and processes will have a CFM requirement, which will be stated in the user guide. Multiplying this by 1.2 will indicate the required CFM for the compressor matched to the task, ensuring enough capacity to complete the work without overextending its capabilities and thereby reducing efficiency levels and operating life. Remember that if you&#;re running more than one tool at once, you&#;ll need a compressor capable of handling the combined CFM ratings of all these tools.
The same consideration should be given to choosing the tank size in order to achieve optimum performance. This is the deciding factor in how much-pressurised air the compressor can hold at any one time to power the pneumatic processes. The larger the air tank, the longer your compressor will run so choose the right tank for the job(s) at hand.
To complicate things even further, there are different types of compressors too, and it&#;s best to speak with a specialist to decide which is right for your application. Our team of engineers is always pleased to help!
Reciprocating or piston air compressors are positive displacement machines that increase the pressure of the air by reducing its volume. The machine takes in a volume of air that is compressed by a piston, raising the pressure. The compressor can be either air or water-cooled and are available in a wide variety of sizes and capacities.
ShopRotary screw compressors can be single-stage helical or spiral lobe oil flooded screw air compressors. They operate via two rotors in a casing that compress the air internally. Rotary screw compressors are oil-cooled.
ShopCentrifugal or rotary vane air compressors are dynamic machines using the transfer of energy from a rotating impeller to the air. This gives a continuous flow through the compressor, making it ideal for higher capacities. Centrifugal air compressors are oil-free.
ShopYour required flow rate will determine the size of the compressor and receiver that you will need (most tools have a stated consumption in either CFM m3/min or Litre /Sec). Don&#;t forget that if you have multiple air tools running simultaneously, there is a multiplication factor for any additional tools and you should choose your compressor accordingly.
What level of power will your application require? See table below.
What pressure does your application require? See table below.
In other words, how often is the machine going to run? Smaller budget machines offer circa 30-40% duty, which means they typically run for just 20 minutes in every hour. 100% duty machines, such as Hydrovane and Champion screw machines, are better suited for light to medium industrial applications.
For applications such as workshops and garages where floor space may be limited, compressor footprint is a major consideration. Many of the machines available to purchase from ACE Group are compact enough to be installed on a smaller footprint.
For lighter industry applications, we understand that there might not always be a large budget for compressed air equipment. Our range includes a selection of extremely cost-effective options. We also have a finance option to allow you to spread the cost, should you wish. If you already have a machine that is out of warranty you may decide to contact us about our alternative service kits and parts when it comes to maintaining your equipment.
Do you need oil-free air? Do you need 100% dry air? All compressors produce water condensate and you may need to consider an oil-free compressor or additional auxiliary equipment such as filtration and dryers to give you the air quality your application requires. Choosing a filter is dependent upon the degree of contamination you need to remove. Talk to our specialists for advice.
The compressor you select will also depend on the electrical power you have available on your premises in relation to the electrical input required by the compressor requires. You should consider whether the machine you select will be single-phase or three-phase, how many amps the machine will draw and also the fuse size in your electrical board. We typically suggest D-rated fuses as start-up currents hugely exceed the general running current. As an example, heavy-duty compressors use a 220-volt current and require special wiring and outlets. A 220-volt compressor drawing 15 amps consumes 3,300 watts (220 volts x 15 amps).
When purchasing a compressor, the cost doesn&#;t just stop when you buy the machine. There are maintenance costs and spares to weigh up too. Fortunately, many of our range of compressors are designed to have low maintenance requirements and costs and are efficient in operation too. ACE Group also have a team of service engineers, so we&#;ve got your ongoing maintenance covered.
By choosing a reputable distributor such as ACE Group, you will benefit from qualified advice and support during the purchasing process and into the future. If you have any questions our team are here to listen, advise and assist you, so you can be confident we will help you to select a machine that matches your needs.
For points 2 and 3 see the table below. Different air-powered tools will require different CFM and pressure. The table will help you identify the kind of power and pressure you&#;ll need to run your tools and equipment.
Something you must consider from the start is how you plan to maintain your equipment. Some applications will have the benefit of in-house engineers who have the expertise and knowledge to maintain compressed air systems correctly, but otherwise, you may not know where to start looking for professional and reliable compressor maintenance engineers.
Fortunately, here at ACE Group, we have a dedicated Service Team able to meet all your maintenance requirements, from minor services to major overhauls.
Our team of qualified engineers has years of expertise in the field and is supported by a knowledgeable office team. Our engineers attend sites all over the UK and further afield.
Some customers choose to enter into a service contract for the many benefits involved, such as 24-hour breakdown call out &#; essential where the machine plays an integral and vital role in your production processes.
In addition to this, we also have a dedicated parts department stocking up to £1,000,000 worth of spare parts and service kits to support all your maintenance requirements. Some of our more popular service kits are available to purchase online.
Installation is also something we offer in-house and our team is able to offer bespoke projects for all sizes of applications, fully managed from quote to commissioning.
ACE Group only works with industry-leading suppliers at the forefront of technological development. Our supply chain is regularly reviewed and we are certified to ISO , ensuring the highest standards of quality control.
Our online shop offers a comprehensive list of some of our most popular products, best suited to light/medium industrial and workshop applications.
If you are looking for a larger compressor then our sales team will be pleased to assist and guide you through the many options. We have a huge range of compressors, dryers and auxiliary equipment to suit every application, and our sales consultants carry out exhaustive site surveys to assess which machine would be the best fit and to advise on installation.
With well over 20 years of expertise in the field and hundreds of satisfied customers nationwide, ACE Group provides the best choice and qualified professional support for all your compressed air needs.
We hope you&#;ve found this air compressor buying guide useful. Feel free to ask any questions or make suggestions on information to add to the guide.
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Rotary Screw Versus Vane Compressors- which one is a good choice?
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MVPs
(Mechanical)
(OP)
20 Jul 11 12:18Hi Folks,
Just a basic question about rotary compressors:
what are the advantages or distadvantages of a rotaty screw compressor over a rotary vane compressor or vice versa? we are using it for plant instrument air application and need to decide on one type? Apparently, a vane unit is quite economical than a screw unit.
I would like to get feed back on performacne, machine life, maintenance issues, noise and ability to handle solid particles(although the application is air however would like to know if the service was for natural gas VRU applications)
Thanks for your time.
Jfarid
Replies continue below
(Mechanical)
20 Jul 11 14:04You are probably going to need to provide more details to get much value from the response. The terminology is not always consistent between different industries and in different countries. So, please be specific.&#; If this is an air machine, what capacity range are you looking for? Some machines are more economic when they are large. What discharge pressure do you require? Some machines work very, very well, but are limited to relatively low pressures.&#; Are you asking specifically about dry screw or flooded screw technology? Perhaps you don't care. I have never heard of anyone using a dry screw compressor for air. But, if you had a great need for oil-free air, someone might consider it.&#; Are you talking about sliding vane or some other vane technology? We only have one sliding vane unit in air service, but it is a very specialized non-lubricated model.In plant air (instrument air) service, we use all of the following:&#; Oil lubricated reciprocating piston compressors.&#; Oil flooded screw compressors&#; High speed centrifugal compressors (multi-stage)&#; One non-lubricated sliding vane compressorWe have dry screw machines in off-gas service. We have liquid ring machines in vacuum service. We have oil lubricated sliding vane machines in flare gas recovery service. We have many multi-stage centrifugal compressors in variety of services.
Johnny Pellin
(Mechanical)
(OP)
20 Jul 11 17:08Here are specific details on the unit:
capacity: 50 scfm.
Discharge pressure: 125 psig
I am refering to an oil-injected compressor and the compressor is a sliding vane unit.
Thanks
Jfarid
(Mechanical)
20 Jul 11 18:46Johnny,
The only place I've ever seen dry screws is in air service, it is funny to me that you've never seen them in that service. I guess "normal" really is a function of the path you've taken.
Jfarid,
50 SCFM for an air compressor is less than 15 hp, or about $10/day in electric cost. I wouldn't spend a lot of time chasing much effeciency improvement.
VRU's are the single hottest topic in my world right now. It is an amazingly complex subject and probably should be its own thread.
David
(Mechanical)
20 Jul 11 22:14We have a number of oil flooded screw machines in plant air service running at about 125 psig. In general, they all run very well and have been trouble free. They are package units that came in complete, so installation was relatively simple. There is a certain about of routine maintenance required for the filters, coolers and coalescers. However, it seems to me to be a small price to pay. The oldest of these machines has probably been running for about 15 years with no major repairs.We do not have any oil lubricated sliding vane machines in air service. But the ones we have in other services are much more trouble. We tend to see wear on the vanes which requires a rather intensive PM program. We have to remove and measure the vanes for wear and replace them frequently. This has improved since we changed to Kevlar vanes. We tend to see wear in the bores of the cases (wash-boarding) that cannot be fully repaired. After some number of years, the vibration and vane wear caused by the worn cases requires us to completely replace the case. Our sliding vanes machines were not purchased as package units, so the installation was quite complex. We have a circulating glycol system for cooling, an oil injection system for lubrication of the compressors and bearings. We have gearboxes to achieve the needed speed which required another circulating oil system for the gearbox and motor.The flooded screw machines are much quieter than the vane machines. The building that houses our largest pair of sliding vane compressors is one of only two areas in the plant that requires double hearing protection (plugs plus muffs). The noise level is too high for ear plugs alone.Given my experience, I would much prefer the flooded screw option for air service rather than the sliding vane machine. I am not sure I know what you refer to as VRU, so I can't comment on that service.
Johnny Pellin
(Mechanical)
20 Jul 11 23:16VRU is "Vapor Recovery Unit". As state and federal governments are tightening the restrictions on outgassing from tanks, people are starting to get serious about stabalizing liquid hydrocarbons in a place where the vapors can be recovered.
I get questions about VRU's every day. The solutions range from amazingly ineffectual, to ok.
David
(Industrial)
20 Jul 11 23:23For longevity at 125 psi the oil flooded screw would be my choice. In a low volume and low discharge pressure I.e. less than 50 psi the rotary vane is ok but efficiency over time is not one of its best atributes
(Chemical)
23 Jul 11 06:56
Sliding vane compressors are noisy.
(Chemical)
1 Aug 11 18:06My experience with rotary vane are that the vanes break and the unit is down all the time. That was in nat gas service. The large differential pressures cause lots of problems with the vanes too.
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