:: Air Compressor Parts ::

Compressors fall into three general areas; Small portable units like the Porter-Cable “Job Boss” often with one pancake or two small storage tanks, Mid-size units like Campbell-Hausfield, which normally have wheels, and large compressors have fixed bases for shops and industrial sites. In terms of capacities, smaller units start around 1.5 horse and larger unites can exceed 6 horse power motors. The pumps themselves are either oil-less or oil-lubricated and the pumps are one or two cylinder and singe of two-stage compressors …. and this last statement is the reason most wood workers don’t have an air compressor, because they sound complicated.

Some of the useful terms that you should know about when looking for a compressor include: PSI - Pounds per square inch, CFM - Cubic feet per minute, Duty Cycle - is the amount of time a compressor can run compared to the amount of rest time (storage tank) over a 30 minute period … such as it can operate for 10 minutes, then rest for 20 without creating significant head wear, Single Stage - is where the compression piston compresses all the air in one stroke, Two Stage - is where there are two pistons that work together to compress the air. (Generally a two stage requires less horse power, and produces less heat).

As a rule, the types of tools that are harder on air volumes are those which run continuously like sanders, and grinders and cutters. Tools that require less cycling are tools that run intermittently like nailers, staplers and in some cases drills or even sprayers.

If you are planning on running some continuous tools like sanders, buffers, grinders and so on you will want to consider something in the mid-size or even large shop size of compressors like. In a case like this you should probably have a 25 gallon storage tank and around a 4 horse rating like a Makita or Craftsman. You will probably be looking at a 220 Volt version as well.

If you are planning on using a number of tools, some of them continuous draw, like grinders, sanders and buffers, you will want to consider a large fixed base compressor like Campbell - Hausfeld or Ingersoll-Rand. These will have around 6 horsepower and a storage tank of 50 gallons or more.

If you are a hobbyist woodworker, who is looking for a nailer or stapler, one of the small portable compressors is probably ideal. Manufacturers like Porter-Cable or Delta will work fine.

The real trick to buying a compressor is to know ahead of time what you are going to use it for and what the air-tool rating is in PSI and CFM. This will give you a better indication the duty cycle you will need. But this isn’t end all either, because your need to look CLOSELY at the air tools you are considering because the same tool an vary widely in the amount of compressed air it will consume. For example a series of six inch random-orbital sanders have cfm differences of of 8 to 24. That’s huge, and it means the difference between buying a mid-size compressor or large fixed compressor. It pays to examine the tools you will be using and select the appropriate ones.

A compressor and associated air powered tools can be a real time saver, even for the hobbyist’s work shop. In many cases a simple brad nailer is almost like having a second set of hands around in assembling and gluing projects together. The other consideration in selecting a compressor is, what other uses will you find for it? For example if you do select one of the portable units, it is conceivable that you can carry this around to odd jobs, in the house, for friends or other areas. This is less of an option of the mid-size and out of the question for the large units … but then the portables will not likely be suitable for sander/buffers … SO … in the end you will have to make that tough decision, but what ever you do, make sure you make sure get a nice selection of tools designed for your compressor. It will make your woodworking more fun, quicker and even more enjoyable than it is now.

Copyright Colin Knecht of WoodWorkWeb.com. This article may be freely distributed and reprinted as long as you leave the article fully intact, including the links.
Visit Woodworkweb.com - woodworking resource for more great woodworking information.

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There is a lot of confusion out there about selecting the right size air compressor to run your air tools. Basically, there are several factors to look at when choosing the proper air compressor for your shop or garage.

The first criteria is horse power rating. Most people assume the higher the horsepower rating on the box, the better the air compressor. However, all horse power ratings are not created equal and can easily be misrepresented. What I mean is, you go to your local giant hardware retailer to pick out a new air compressor to run your impact wrench. They have a 5 hp unit that is priced really cheap. Why is that 5 hp industrial unit cost so much more? 5 hp is 5 hp, right? Not necessarily. Let me explain. Look at how much power the hardware store unit draws. It probably needs around 15 amps from a normal 110 volt circuit. At this rating, you are really getting only 2 hp. The 5hp rating on the box is inflated. To really produce true 5 hp you need at least 24 amps from 220 volt circuit to get it. If you are looking for 5 hp electric compressor, buy the industrial unit and stay away from the cheaper unit at your local hardware store. I am not saying that every air compressor at your local hardware is junk. A lot of times one of those units is all you need. Just be aware of the true horsepower rating.

The next consideration when purchasing a new air compressor is, “How much PSI will I need?” For the newbies, PSI is short for “pounds per square inch” and this is how most compressors in the US are rated. In Europe, you will see them measured in bars. PSI is all you need to worry about on this side of the Atlantic. Most of the commonly used air tools require about 90 PSI to operate correctly. However, you will still need a compressor with a higher shut-off pressure. Most air compressors that you find at the local hardware giant are “single-stage” and shut off at 125 - 135 PSI. Don’t let that fool you. You might think all you need is 90 psi, so that should work just fine. Generally, these light duty compressors shut off at 100 psi and don’t forget about pressure loss in the line. The little light duty compressor will barely run an impact wrench. It might be fine for light duty garage use, but if you really intend use your air tool, more is definitely better. Many industrial compressors are “two-stage,” which means they build up to shut-off pressure in two stages. The first stage builds to about 90 PSI and the second stage builds to 175 PSI.

The next rating criteria for air compressors is CFM. CFM stands for “cubic feet per minute”. It is a measurement of volume. Basically it is how much air is being moved. Air tools require a certain amount of air volume to run on. PSI is just part of equation. Don’t be confused by different CFM ratings at different pressures. Every manufacturer is trying to make their product look better by giving higher CFM ratings at different pressures. The only real concern is how much CFM you will get at 90 PSI. Remember 90 PSI is what most air tools require to operate. To find out what your air tool needs to run, just look on the box for the manufacturer’s specs. Generally, air tools require 4 - 6 CFM. A good rule of thumb on air compressors is you should get 3 -4 CFM per real HP at 90 PSI.

The final factor to consider is tank size. Tank sizes are generally stated in US gallons. For example, 30 gallon is a common tank size. So the question remains, how large a tank do I need? First of all, don’t confuse a large tank with more run time for your air tools. If you use your impact intermittently, a large tank is fine. However if you have need for continuous use, you will need a small tank with big enough pump and motor. If the pump and motor are powerful enough, you shouldn’t run out of air. You can save some dollars by purchasing an air compressor with a large tank and smaller motor for intermittent use. If you need to run a 1″ impact wrench (about 20 CFM) intermittently, and have a small compressor with a large tank, you might have enough air stored in the tank to do the job. However, if you are constantly running your air tool, you will need to invest in a more powerful air compressor to do the job.

You should be able to select the air compressor armed with this information. Basically, you need to decide ultimately what you going to use the unit for and pick the appropriate model.

Jason is the webmaster for Red Hill Supply - Online Air Tools

Air Impact Wrenches,Air Tools, and More - Red Hill Supply

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If you purchase a “do-it-yourself” type air compressor, or if you purchase any type of air compressor for that matter, check to make sure that it comes with an Air Regulator. If not, purchase one. You will be glad you did!

An air regulator is a device that lowers the downstream air pressure. Downstream air is the air that’s moving from the regulator towards your application.

Compressed air will flow from the compressor reservoir into the air regulator (this supply is called upstream air) and through a system of an internal diaphragm and springs, the regulator will maintain a constant downstream air pressure level, despite changes in the upstream supply pressure from the tank.

Recognize that you can only use a compressed air regulator to increase the downstream air pressure up to the level of the upstream supply air pressure. An air regulator will not enable you to “dial up” the downstream air pressure higher than the upstream level.

However, if you can figure out how to do that, do let me know, and we’ll both get rich! ;-}

You will want to set the downstream air pressure from your regulator at a pressure level that is below the lowest air pressure that will be incoming from your air compressor. Here’s why.

The compressor maximum pressure set point is the pressure level inside the compressor receiver at which the compressor shuts itself off. This is also known as the “cut out” pressure.

When the cut out pressure is reached, the compressor stops compressing air. When you start to use compressed air from the compressor tank, the pressure inside starts to drop, and eventually the compressor will start again. This is the “cut in” pressure point.

As a result, your application, be it an air tool or an air brush, will “see” varying pressures from the tank as the compressor cycles on and off between the two set points.

For most applications, a varying air pressure supply isn’t satisfactory and it is particularly problematical for folks that use compressed air to spray paint. Despite your best efforts with the air brush, if the supply air pressure is constantly changing, so too will the quality of your work.

This brings us back to the why you will always want to have an air regulator installed in the line between the compressor and your application.

If you set the downstream air pressure at a pressure level BELOW the cut in pressure level of the air compressor, in theory, the air pressure to your application should never change. As the air compressor goes through its normal cut-in and cut-out cycle your air regulator ensures that your downstream device will see a steady, non-fluctuating, supply of compressed air.

This is theoretical only, unfortunately. If your application consumes more compressed air than your compressor can generate, even though you have set your air regulator at a “safe” level, eventually the air pressure from the tank will fall below the level your regulator is set for, and the downstream device will see a steadily diminishing air pressure supply too; this even though your compressor may have cut-in, and is trying desperately to build up a supply of compressed air inside the tank.

This is why you really want to know how much air you need for your application to ensure that your air compressor has enough capacity to oversupply your needs. Check out details of this at ABOUT-air-compressors. com!

Know that air pressure regulators come with different levels of accuracy with the least accurate being, as you might guess, the least expensive.

Most general purpose compressed air regulators will have an accuracy of 3-5 PSI, meaning that the actual air pressure that your device is being supplied through the regulator will vary within that range, despite what it says on the gauge.

If you need more accuracy, opt for a precision regulator, and depending on the manufacturer, you may be able to get a downstream air pressure within a .5 PSI accuracy of the pressure reading on the gauge.

General purpose air pressure regulators normally have an operating range in the area of of 0 - 120 PSI. Others will be rated for pressures of 0-100 or 0-150 PSI.

You can also get air regulators with a narrower and more specialty oriented range of pressures such as: 0-10 PSI, 0-20, 20-60 PSI and so on. At the other end of the scale, you can purchase regulators that can safely handle many thousands of PSI.

For most do-it-yourself types, a general compressed air regulator with a range of 0-100 PSI will do just fine.

Bill Wade’s experience in compressed air and other industries spans decades; from field sales positions through to the corporate presidential office. His sales agency represents a select group of industrial firms. Mr. Wade writes about all facets of compressed air at http://www.about-air-compressors.com

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