Compressed Air Pressure Switch

The Compressed Air Pressure Switch will generate an electrical or pneumatic signal when it senses that the pressure in the air line to it has reached the set point.

Applications vary. Any circuit that requires a specific compressed air pressure to work properly would benefit from having the supply line to the circuit monitored by a pressure switch, and only when the pressure in that line is at the level it’s supposed to be, would compressed air flow to the circuit and the subsequent application commence.

More information on using compressed air here. 

Don’t worry about how much air…..

As many of you know, I write an information web site known as About-Air-Compressors.com . One of the questions I get frequently is how to get more air from a small air compressor.

The simple answer is….you can’t.

If you are one of the many hundreds of thousands with a 1 to 3 HP home compressor, the discharge rate (the amount of compressed air coming out of the compressor) is limited by the horsepower of the electric motor running the compressor head. Rule of thumb, if your compressor is under 10 HP, you’re likely only going to see about 2 CFM of air at 90 PSI for each HP of electric motor, and that’s the max.

The proliferation of relatively low cost air tools means that many of us, including me, have stocked up on air consuming devices that draw huge amounts of compressed air to run properly. And, like many of us, our little compressors can’t keep up.

What to do?

Don’t sweat it. Run the tool for the few seconds that your small reservoir can provide compressed air for, and when the compressor kicks in to recharge the receiver, put the tool down and relax.

Sure, you can buy a bigger compressor. Sure you can put a couple of compressors in parallel to provide more air, and yes, you can overuse your little compressor and ultimately cause it damage. Why?

For most of us, we are not earning a living from our home compressors. As a result, that it takes longer to do an air tool type job with a small compressor doesn’t make our project unprofitable, or tie up talented staff (that’s us) so long that we lose money on a job, since by and large, the home jobs are just for fun.

Take it easy, let the little compressor do the job for you that it will do for years if you treat it right.  And don’t worry that you don’t have enough compressed air to run the air tool continuously.

Give yourself and your little compressor a break.

Air gauges fail…

When I’m using my at-home compressor, doing an odd job around the house, the needle in the air gauge may move a few hundred times a day as the air pressure fluctuates through compressed air use and the compressor cycling. This is low cycle rate for an air gauge.

Compare that to the air gauge on a system, perhaps containing dozens of air cylinders or air tools, all cycling at a high rate of speed 24/7/365. The mechanical components in the air gauge may cycle hundreds of thousands of times a day.

Eventually, mechanical fatigue will cause the moving parts of the gauge to fail.

You can lengthen the functioning life of an air gauge in high speed circuits by using a liquid filled gauge.  Normally filled with glycerine, the viscosity(liquid thickness) of the filling tends to slow by a small degree the speed with which the gauge’s internal mechanical parts  and the needle moves with air changes, reducing mechanical wear and impact damage as the internal parts of the gauge return to zero when the air is repeatedly exhausted.

If you have an application where compressed air gauge failure occurs, consider using a liquid filled unit to extend the life of your compressed air gauge.

What’s PSIG?

When you read about using compressed air, and here’s a good site to do so, there are many references to the force generated by compressed air. It’s usually measured in PSI (Pounds of force per Square Inch of surface area).

The gauge on your compressor or regulator will show the air pressure of your air system. Though it’s not generally referred to, the readings on your compressed air gauge are almost always PSIG (Pounds of force per Square Inch of surface area, Gauge adjusted to zero).

If the pressure gauge wasn’t adjusted, at sea level, it would show 14.7 PSI, which is the pressure of the earth’s atmosphere at sea level. You would have to deduct 14.7 PSI from your gauge reading each time you wanted to know what the actual pressure of your compressed air system was.

The gauge manufacturer’s (and here’s a source for gauges if you need one) adjust the gauges to zero, even though the actual pressure they are reading at sea level is 14.7. Therefore, it’s easier for the gauge user to read the actual pressure of their system.

You can assume, unless you specify otherwise, that gauges you buy are PSIG and have already been adjusted to zero to account for the ambient air pressure of our atmosphere.

One compressor, one air line, many tools…

One solution to using multiple tools with one compressor and one air line, is to bring that air line to a manifold on your work bench.

A manifold is usually a block of machined aluminum, with an in-port on one or both ends for plumbing your supply line into, and multiple outlet ports along one or more sides into which you can install a coupler, or even just an instant fitting if you are using polyethylene tube to supply components on your bench with compressed air.

Other manifold styles are made of brass, or steel, depending on their manufacturer, design use and how many outlets are included.

Unused outlets can be plugged and reopened later if additional compressed air sources are required for your bench.

The in-port on the end of the manifold will normally be at least one size larger than the outlet ports, and sometimes larger, depending on the number of outlets.

In you install checked couplers into the distribution ports, then you can quickly attach any number of tools or compressed air components with mating connectors.

Here’s info on fittings, and here’s a source for manifolds, including one with a 2″ NPT inlet, a self-contained reservoir, and 7 outlets for the serious compressed air user.

If you need to move a load within the length of the air cylinder….

then you’ll need either a cable, band or magnetically coupled cylinder.

All of these types are considered “rodless”, meaning that the carriage to which the load is attached, moves along the cylinder barrel as opposed to a “rodded” cylinder that moves a rod in and out of itself.

A footprint for a 12″ stroke rodded cylinder will be at least 24″, while the footprint of the same stroke in a rodless type cylinder will be only slightly more than the 12″, just enough extra length for the cylinder end caps.

Here’s lots more information on cylinders of all types.

ISO 6431 air cylinders

ISO 6431 air cylinders are the European standard for a series of air cylinders that, regardless of the manufacturer, will have common port sizes, rod diameters, rod threads, mounting styles, and so on.

In North America, the standard for similar air cylinders is NFPA.

Buying a cylinder that meets a standard means that when you need a replacement, specifying one of that same standard, regardless of source, should mean that the new is interchangeable with the old, with little or no difficulty.

Here’s more information on air cylinders.

Oscillating air cylinders;

There are applications for small air cylinders that require fairly rapid and adjustable oscillation. Things like imparting a vibration to a conveyor or bin to help keep product flows or for moving small sifting screens.

You can design an oscillating circuit yourself. I’ve done so, but it’s a bit awkward to get true adjustability in a self-designed cylinder oscillator circuit.

Never fear, some manufacturers of compressed air equipment can provide an air cylinder oscillator that you simply plumb into the air line before the cylinder to be oscillated. Turn on the air, and the cylinder starts extending and retracting, and these units are infinitely adjustable as to oscillation speed.

Other manufacturers may have their standard unit, but I know for sure that Festo has one. Ask for their VLG-1/8 or VLG-1/4 if you contact them for further information. Or, contact me through this site, and I’ll get you more information.

Don’t forget air saws….

Like most power saw, those powered by compressed air are generally, size for size, more powerful than their electric cousins.

Air saws can be used where flammability is an issue, as their power source is air, not electricity. They don’t create sparks through their operation.

When the air saw stalls in a heavy cut, it stops. Period. No problem. Pull the saw out of the cut and you’re back in business. When an electric saw stalls, the motor will start to burn out and possibly the electrical fuse or breaker will trip.

Lubricator settings….

I’ve had a lot of questions at www.about-air-compressors.com about setting the drips on an in-line lubricator.

First off, I’ve always been told that 2-3 drips per minute on a continuously used air circuit is ample lube for all but the fastest cycling cylinders or high-volume air tools.

Most applications could get away with 1 drop per minute, or maybe less. Folks tend to over lubricate.

If you’re not sure about your air tool or application, either contact the tool manufacturer to get their recommendation, or the air actuator supplier for theirs.

Once you start lubricating a tool or air actuator, don’t stop doing so. Lube oil you’ve introduced via your lubricator will tend to wash away any factory-installed lubrication, and if you stop adding lube to the circuit, your air tool or cylinder will suffer as a result. There’s more information on compressed air lubricators on this site both to use and if you need one, to buy.