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The Safe Application of 3-Position Pneumatic Valves

Many pneumatic valves are fairly straightforward things — they’re open, or they’re shut, and it’s pretty clear when they should be in each position. But 3-position pneumatic valves with double-acting cylinders can be confusing.

3-position pneumatic valves are able to stop an attached pneumatic cylinder in mid-stroke, either ceasing motion or — their intended purpose — ‘jogging’ the cylinder for a heartbeat in mid stroke before continuing to extend or retract normally.

Often, such complexities are requested when they’re not needed, because the engineer designing the system believes that such a three-position valve is needed as an emergency response: if, for example, power cuts out in mid-job, they believe the third position is a useful way to prevent damage to the system.

In fact, that’s not the case; instead, two-position, detended pneumatic valves should be used on clamps and other devices to maintain cylinder position if power is unexpectedly removed. A spring-return, two-position valve will also work if no pinch point exists or the cylinder is moving in a guarded action and can return to its normal position safely.

The problem with using 3-position pneumatic valves as ’emergency response’ is that there is no position in which such a valve is actually safe during an extended power cut.

  • If the valve is in the all-closed position, the cylinder will be pressurized on both sides, which can lead to drift if the cylinder isn’t perfectly sealed.
  • If the valve is in the ‘let air in’ position, the cylinder will immediately move toward the extended position because of the higher surface area on the can end of the piston than the rod end.
  • If the valve is set to ‘let air out’ position, the cylinder will immediately move toward the retracted position because there will simply be no pressure present to maintain the extension.

There is a fourth scenario — if the 3-position valve is set to ‘let air out’ position and the circuit has a dual pressure system designed to provide ‘make-up’ pressure to overcome any leakage (which almost always comes with check valves in place to keep the cylinder pressurized against unexpected loads), the 3-position pneumatic circuit doesn’t suffer terribly in an emergency outage. However, this is an incidental byproduct of a system created for other purposes, and using a system like this as an emergency measure is expensive and less reliable than the aforementioned system of detended two-position valves and spring-return valves.

Anodized Aluminum Framing for Industrial Applications

It’s been almost a hundred years since aluminum framing revolutionized the world of industrial metal. Since those days, aluminum has allowed new architectural possibilities and industrial functions. At the same time, advanced in coil anodizing have allowed for a wide variety of textures, finishes, and designed that are versatile, functional, and environmentally responsible.

Anodized aluminum can be laser engraved, stamped, roll-formed, perforated, laminated, welded, embossed, silk-screened, and otherwise customized in a mind-boggling variety of ways. Recent breakthroughs in coloring techniques allow aluminum to be created with almost the same variety and richness of color as latex paints. Anodized aluminum appears in roofing, architectural exteriors, doors, window frames, fixtures, and of course in a huge variety of industrial applications.

Why Anodized?
Anodized aluminum is aluminum that has undergone an electrochemical conversion — an electrically charged solution alters the chemical structure of the aluminum. The surface layer of the aluminum is oxidized — which, if it were steel, would mean rusting, but aluminum works quite differently. Aluminum oxide isn’t at all like rust; instead, it’s a hard, protective layer that adheres better to paint or other coatings and can absorb dyes as well.

Industrial Applications
Anodized aluminum is 1/3rd the weight of stainless steel while maintaining the same approximate hardness and resistance to the elements. That makes it absolutely ideal for a huge variety of framework applications. Whether you need a tiny little clip to hold a heat sink onto a microprocessor or you’re building a superstructure that will hold a conveyor belt cleaner under the terminus of an industrial coal conveyor, anodized aluminum framing is always a good choice for the job.

Anodized aluminum is the functional, versatile, and environmentally responsible choice for industrial applications. Strong, corrosion-resistant, and easy to maintain, anodized aluminum does not chip, flake, peel, or lose color. Continuous-coil anodizing technology allows the creation of pieces featuring uniform color, surface and edge consistency, and even colors that imitate natural materials without degrading. Coil anodized aluminum framing can get the job done — all you need to do is figure out what exactly you need and which fabricator is the best one to get your job done right.