:: Air Compressor Parts ::

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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Recently, I published an article on this site titled: What’s a 2/2 compressed air valve? Here, in the next installment in this series, is information on a slightly more complex air valve; the 3/2 style.

The first number in the 3/2 air valve, the three, refers to the number of “working” air ports that are found in the valve body. That is, the number of ports that supply air to the valve, and channel the compressed air to whatever it is that the valve is supposed to do.

Most 3/2 valves will have numbers or letters etched, cast or painted near each of their three “working” air ports. If there are numbers near the ports, the number 1 would be the supply port to bring the compressed air to that valve.

Port number 2 would be the working port from which air would flow to accomplish whatever task that you wanted that valve to do.

The third port in a 3/2 air valve is an “exhaust” port and if numbered, it could be a 3 or a 5. If the port designations in a 3/2 valve are letters, then port ‘A’ would be the supply port and port ‘B’ the working port, with the third port normally being an ‘E’.

As in the 2/2 valve there may be one or two additional ports in the ends of the 3/2 valve to allow an air signal line or lines to be connected. If this is the case, this 3/2 valve will either be single, or double air piloted.

The 2 in a 3/2 air valve indicates the number of positions that the internal valve mechanism has. In this case, two. When this valve is operated or actuated, it will either open or close and air will either flow to the application upon actuation, or it will be prevented from flowing.

Most 3/2 compressed air valves will be NC, or normally closed. When the valve is not actuated, it’s normal state is closed, and compressed air cannot pass through it.

If your application calls for air to flow through the valve when it’s not actuated, that the circuit needs air to be flowing through this valve when it is at rest, then a NO or normally open configured valve would be selected.

All 3/2 valves have actuators that will operate or ’shift’ the air valve. An external button, or toggle, or perhaps a solenoid actuator would be the visible actuator. Inside, there will likely be an internal actuator - a spring - which will shift the valve to the off position when the external actuator is not being used.

If the external actuator is ‘detented’, then when the valve is operated, it will stay in it’s last selected position until an operator changes it. Detented means it will stay where it’s put! This is useful when an operator needs to actuate the valve, and then manually perform another operation while the air valve feeds air to the application.

Unlike it’s less complex 2/2 valve cousin, the 3/2 valve is used when a compressed air supply is needed to an application or device that uses compressed air to power it, yet in itself has no integral air pathway to atmosphere. Therefore, when the device has performed it’s function, and it’s time to ‘deflate’ it or to let the compressed air back out, the third port in the 3/2 valve comes into play.

When the compressed air supply through the valve is shut off internally, a pathway back through the valve to atmosphere will be opened, to allow the compressed air to escape. The air supply is shut, so the compressed air flowing to the valve cannot flow through it, and the compressed air that was formerly in the device or application can now bleed back down the air line through the valve to exhaust.

So, what type of devices are these?

Usually they are single acting type actuators. One comes to mind immediately; “Air springs”.

Both Firestone and Goodyear (among others) manufacture “air springs”. These are devices that look like tires, but rather than have an opening in the middle of the doughnut where the rim goes, they are closed on both sides with steel plates. In one side there will be an air port to which an air line from a 3/2 valve can be connected. These “air springs” are mounted on their sides, picture a tire lying flat after you’ve taken it off your car, and can generate huge actuation forces. Force equals pressure times area, and the “piston” size inside an air spring can be huge. The application of air springs mirrors that of typical air cylinders, yet offer large capacity at a fraction of the cost of an air cylinder of a necessary size to generate the same force as the air spring.

Another application for 3/2 valves is single acting air cylinders. Whether they are spring extend or spring retract, an air supply is required to operate the SA cylinder. A 3/2 valve is designed to do just that.

A couple of more points; the 3/2 valve can have the exhaust port plugged, and voila, you have a 2/2 valve.

If the cost of the valve is the same, you can use a 3/2 air valve anywhere you might use a 2/2 valve. Since 2/2 valves always have to have the “working port” ultimately plumbed to atmosphere, that there is an exhaust port in a 3/2 valve offers no obstacle to it’s use.

If you have a double acting air cylinder, and you don’t have a 4/2 or 5/2 (more on these valves next article) available, you can use two 3/2 valves to operate any cylinder that requires two supply lines in order for it to extend and retract.

At ABOUT-air-compressors.com my e-book entitled All About Air Valves - Volume One is now available. If you are interested in more information about air valves, do visit the site and download a copy. This first e-book is an introduction to air valves, and focuses on the 2/2 iteration. Future volumes will focus on 3/2 valves, and then the 4/2 & 5/2 configurations.

And as always, if you have any questions, please send me a message from the contact screen at my web site.

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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It’s really easy to pick up a low cost air compressor at the local store anymore. But, how do you get the air from the compressor to your application? Folks that are plumbing up compressed air lines for their garages or workshops at home, as well as the professional plant person, have a variety of options with which to do connect the various air-lines available to them.

Usually the air compressor will come with a rudimentary kit which will include a PVC (Polyvinyl Chloride) or RVC (Rubber Vinyl Chloride) air hose. If not, these kits are available as accessories.

Rather than having a clutter of air hose running across the floor (a trip hazard) consider emulating the factory installation. Have the discharge air line from the compressor run up to the ceiling in the garage or workshop, and then install “drop lines” down to the various locations on the bench where compressed air might be used.

The discharge from the compressor should have, at the very least, a compressed air filter where the air exits the receiver / tank, and the smaller home-compressors will often have a regulator there as well. Compressing air causes water problems, and you can read more about this in my article in this E-zine entitled “Why does water run out my compressed air lines…”. The regulator is necessary too, and you can read about this in an article titled “Why use a compressed air regulator” also on this site.

Commercial installations of compressed air will have a large general purpose compressed air filter at the compressor discharge, and then a filter, regulator and sometimes an in-line lubricator (oiler) at each of the points where the compressed air is to be used, to help deal with compressor generated water.

The regulator will provide the ability to control the pressure of the air to that particular application. You might want 90 PSI of air to run a grinder at one drop line, but farther along the bench you might only want 12 PSI for an air brush paint set up. Individual regulators give you this capability. If you are installing a regulator at each drop location, remove the regulator at the compressor to ensure you have full pressure and flow to the air main overhead and the drop lines.

The oiler use is dependant on what it is that the compressed air is running.

On your work bench, at the bottom of each drop line, you can install a coupler. A coupler is a device into which you can insert a connector. The coupler will be “checked”, meaning that compressed air is trapped at that point until a connector is inserted into the coupler which opens the “check” and allows air to flow.

Compressed air can then be supplied to the air tool or whatever you wish to drive with compressed air via an air-line extension cord. You can purchase ready made or you can make your own. They are lengths of air hose or tube with a connector at one end and a coupler at the other. The air tool will have a connector in it’s air port. When ready to supply compressed air to your tool, you simply insert your air-line extension cord connector into the drop line coupler, and the other end, which will be a coupler, has the air tool connector inserted into it.

Connectors and couplers are not all the same. Different manufacturers have differing styles and they are not usually interchangeable. When you first start purchasing couplers and connectors for your air line, make a note of the brand first purchased, and purchase the same brand as your needs continue.

I remember the difference between a coupler and a connector by making a mental image of a “cup” into which I insert the connector. The “cup” is the coupler.

If it were me installing an “air main” and drop legs down to my workbench in my garage, I would use soldered copper pipe. Copper pipe won’t rust, and there are more than sufficient adapters available to convert from the soldered (sweated) copper to a thread.

If opting for an overhead main, know that the longer the supply line to the application, the more pressure loss there will be. Each elbow and every turn creates a loss in available pressure at your application, so make the air main as large as practical. How big? Why not 3″‘ copper pipe at the ceiling and 3/4″ copper drop lines for the home workshop?

Remember that PVC or RVC air hose size is measure on the I.D. A 1/2″ air hose will have a 1/2″ I.D., regardless of the O.D. of the line. Different air line manufacturers will have hose with different wall thickness, so the outer diameters will vary.

To connect PVC or RVC air hose together, you can use the aforementioned couplers and connectors. Usually the coupler and connector has a “barbed” male protrusion, though other styles are certainly available. Make sure the “barb” size of the coupler / connector corresponds with the internal diameter of your air hose. A gear clamp (do yourself a favour and purchase stainless steel clamps over carbon steel. A few pennies more, but much longer life) is installed on the hose first, and then the barb is inserted into the I.D. of the hose. After insertion of the “barb” the gear clamp is brought up the air hose, over the area where the “barb” is inserted, and tightened firmly. Using a small wrench to tighten the clamp is preferable over a slotted screw-driver which have a tendency to distort the nut.

There are a variety of other fittings available to join air hose. “Barb” to “barb” connectors, “barbed” elbows, “barbed” T’s, and so on.

If you are planning on using a lot of compressed air, hours worth of tool use at time for example, your drop legs should have a manual valve at the bottom of them and the supply to your tool should be taken about six inches from the bottom. The manual valve will allow you to drain the water that will accumulate there. See ABOUT-air-compressors.com for more extensive information on plumbing for compressed air.

As to the smaller air lines themselves, perhaps running to an air valve, joining an air valve to a cylinder, or even a small air brush or air tool, P.E. (polyethylene) is the air tube of choice. It is chemically inert, won’t rust with air-borne water, has a variety of fittings available, and is inexpensive.

P.E. tube has a variety of fitting styles available.

It can be connected with compression-ring (ferrule) type fittings. A nut, and then the ring fits over the tube, and once the tube is inserted into the fitting, the compression-ring is brought down over the tube and then the nut is tightened onto the thread, compressing the ferrule and created a seal. This type of fitting is available in many configurations including straight fitting, elbow, ‘T’ and so on.

The easiest fitting for plumbing P.E. tube is the “instant” variety. There will be a hole, correctly sized for the O.D. of the tube, into which the tube, after it is cut squarely, can be inserted into the fitting. Inside the hole will be an “O” ring type seal, and then a collar of small metal fingers through which the tube passes. When the air is turned on, the P.E. tube swells a bit, and these “fingers” dig into the surface of the tube, holding it in. The “O” ring prevents escape of the compressed air. There will be a small ring on the exterior of the fitting which, when depressed, will “bend” the fingers out of the way, allowing the tube to be removed from the fitting when necessary. This should only take place if the air is off.

“Instant” type fittings may not work on soft air-line tube, such as polyurethane. Copper tube may present a problem too, as the “fingers” cannot easily grab the smooth surface of the tube.

There are some manufacturers that offer a line of miniature barbed fittings for tube. If you are installing many fittings in your application, they may offer a lower cost solution. The downside is that they significantly reduce the air flow through the smaller I.D. plastic tube.

For a good selection of air line couplers, connectors, hose, tube and fittings, consider locating and visiting your local industrial supplier of fluid power or compressed air components, rather than your local hardware or department store. Not only will the industrial supplier likely have everything you need in one location, undoubtedly, they too will have the expertise to provide the advice that will not necessarily be available at the other retail outlets.

If you have questions, please don’t hesitate to visit my site and send me an email through the contact page there.

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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