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Choosing the Right Pneumatic Fitting

There are a few different kinds of pneumatic fittings on the market, and choosing the right one isn’t always easy. You need to know the tubing being used, the operational air pressure, the thread type on the receiving fitting (if any), the amount of vibration the fitting is expected to endure, and more.


The Most Common Fittings

  • A Compression Fitting relies on a nut or other similar device being screwed down over a ferrule, compressing it. The compression of the ferrule causes it to bow inward, compressing the tube, the fitting, and the receiving fitting together to form a tight seal. Compression fittings are appropriate for copper, aluminum, and plastic tubes, and are themselves usually made of brass.
  • Specialty Compression Fittings such as Compress-Align, Metru-Lok, Poly-Tite, and so on use a similar mechanism to a generic compression fitting, but generally have preassembled parts that are designed to ‘play nice’ with a wider variety of tubing, allowing the use of tubes made of TFE, PFA, PEA, thermoplastic, steel, and so on to be used.
  • Hi-Duty Flareless Fittings are a kind of compression fitting made specifically for high-pressure applications (exceeding one thousand PSI.)
  • Push-Connect Fittings use a similar mechanic to Compression Fittings, but instead of a metal ferrule, they use a (usually vulcanized rubber) O-ring that will regain its original shape when released. This allows the fitting to be undone as easily as it was created, but creates fittings that are by necessity used for lower-pressure applications. They are generally made from nickel-plated brass, though some composite fittings made of glass-reinforced nylon are available as well. Push-connect fittings are easy to disconnect and reconnect, making them excellent for any environment where frequent changes are necessary. They are usable with copper, brass, steel, thermoplastic, nylon, polyurethane, and some less common tube types.
  • Barbed Fittings don’t rely on anything outside of simple friction to keep the tube attached; as such, they tend to be used for very low-pressure jobs only — anything higher would pop the tube off of the fitting!  Barbed fittings are generally made of either brass or thermoplastic, and are only used with tubes that have a little bit of ‘give’ to them: polyethelene, rubber, or GPH.

There are several other types of fitting available, naturally — the more exotic the job conditions, the more unusual the fitting. These are only the most commonly available, but they are appropriate for the vast majority of jobs.


The Power of a Hydraulic Power Unit

Lumberjacks. Miners. Search and rescue crews. What do they have in common? Well, they’re obviously some of the most hardcore people in America, but other than that, they also all work some with extreme machinery in their daily jobs. But where does a man find enough power to lift a massive tree, move huge volumes of earth, or drag a car out of a canyon? The answer is that the machinery they use are almost universally driven with a hydraulic power unit — a motor that converts the motion of liquid into mechanical force.

A hydraulic motor, at its essence, is fairly simple: a reservoir of hydraulic fluid, a power unit, and a machine that can be moved by any form of rotation. The power unit — usually a small electric device — pressurizes the fluid. Because fluid cannot be compressed, any amount of pressure from the pump causes the fluid to move, usually through a series of valves designed to make sure that the fluid can’t move backwards and harm the pump.

At the far end of the line, the fluid moves into a piston, which extends as it fills up, and voila! — a log is lifted easily off of the earth, swung about, and dropped onto a waiting truck. Or, perhaps, the fluid moves through a propeller, which generates a rotational force that is then fed into a series of gears that slows the rotations-per-minute but adds a huge amount of torque, and the winch on the far side of those gears pulls a truck out of a lake. The number of potential applications is huge.  After the fluid has done its job, it returns back to the reservoir along a different line, ready to be used again the next time the pump comes online.

Electric motors can only generate more power by being built bigger — so to get an electric motor to haul a ton of earth directly, you need one that is absolutely massive. But by using a hydraulic power unit — which is, ultimately, an electric motor, just used in conjunction with a hydrostatic system — the same job can be accomplished with a much smaller device.