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Category: Pneumatic Fitting

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.


Quick-Disconnect Pneumatic Fittings – Modern and Legacy

It’s a pretty basic concept: you have something that moves air, and you need to attach it to something that has to have air pressure in order to do its job. You need to be able to detach that tool quickly, so you can’t use screws or other complex machinery. Enter the standard thumb-latch connector, and your problems are solved! Seems like there’s not much there that needs changing — but pneumatic fittings have in fact evolved in recent years.


The Old Guard: Metal Latch Couplings

More than 55 years ago, when pneumatics were first becoming industry standards across the world, the metal latch coupling was born. Cast of strong metals with as few moving pieces as possible, they held up against the extreme changes in internal air pressure easily. After a few years of trial-and-error to establish what the standardized sizes would be, metal latch couplings became so ubiquitous that they seemed to be a foregone conclusion. You need to connect pneumatics, you use a metal coupling, done deal.

But then, along came plastic and changed everything.


Plastic Latch Pneumatic Fittings

Plastic is lighter — significantly lighter — than metal, and its ability to remain strong even when more thinly sculpted allows for a more ergonomic fitting. Furthermore, plastic is resistant to corrosion in a way that metal isn’t, which made the plastic coupling much more durable under a variety of different industrial conditions.

And plastic wasn’t done yet.


Plastic Twist-Lock Connectors

Twist-lock connectors were the logical extension of the Luer-taper fittings of the previous century: simple pneumatic fittings that could be slipped together and locked tight with a mere quarter-turn. Because they are nearly as durable as a plastic latch fitting but don’t require a latch or button to activate, twist-lock connectors can be used in smaller spaces, or in implements like sphygmomanometers (blood pressure cuffs) where the much heavier plastic latch would cause usability problems.


With quick-disconnect pneumatic fittings evolving from the near-indestructible and extraordinarily reliable metal latches that are still industry standard after more than half a century of use to the the very small, very light, and easy-to-operate plastic twist-lock, there are very few places where pneumatic connections are an engineering challenge these days — and we’re all better off for it.


How to Improve the Life Expectancy of Your Gas Springs, Pt. I

The number one determinant of the life expectancy of a gas spring is, perhaps without much surprise, the manufacturer. Choosing a manufacturer whose representatives will offer you assistance choosing the best design for your job — and then actually listening to the reps — is a great step toward a long-lasting gas spring. Also, talking to your supplier about performance guidelines — specifically, operating temperature, speed, and charging pressure — can help you understand how to stay within a spring’s operating parameters, which will help it last.

The decision of which gas spring to use should be based on several criteria. The spring must match the task it’s intended for, it’s location in the die, and the mounting method most appropriate for the task.

Tool Build and Die Design
Die design is one of the most important parts of optimizing gas spring life. Such springs have standard operating specifications — for example, a spring may be charged to a maximum pressure of 150 bar (2175 psi), and reach a maximum operating temperature of 160 degrees Fahrenheit. Exceeding either of those guidelines will rapidly slash the life expectancy of that spring.

Futhermore, unless there is no other option, you should never use more than 90% of the stroke of a gas spring — and a rod travel of 75% to 80% is even better, as it reduced both in-cylinder pressure rise and the amount of heat produced per stroke. Further, aiming to distribute loads evenly between springs so that no one spring outworks the others and none are approaching full capacity goes a long way toward keeping a spring functioning in the long term.

Accessorizing for Lifespan
Gas spring accessories like nitrogen-gas surge tanks added to a piped system will add volume so as to maintain a lower pressure rise. Piping gas springs together with pneumatic fittings can give you the ability to monitor and control force from outside the die, giving you the ability to manually modify a spring’s operations based on external conditions like load, which further enhances the lifespan.

This is still only scratching the surface — come back next week for part II of our guide to maximize gas spring lifespan.

Centralized Pneumatic: Fitting For Industry

Centralized pneumatic air tools (not to be confused with Central Pneumatic, a brand name) offer quite a bit in terms of pricing, variety, durability, and efficiency. The concept behind central pneumatic is simple: you acquire a single, powerful pneumatic pump that sits quietly in one corner of your facility. Long, airtight pneumatic lines extend from that central pump out to wherever the work needs to be done; on the far end, those lines connect to a wide variety of possible tools with pneumatic fittings.

The big advantage of having a central pneumatic system is that the individual tools that you attach to the end of each pneumatic line are significantly less expensive than the same tools that work using a battery or other ‘on-board’ power supply. As long as you maintain and upkeep the central pneumatic unit properly, it will last for decades under normal circumstances. Between the long-lasting central unit and the inexpensive end-tools, a central system can save you a lot of money.

Similarly, the ability to power virtually any tool that uses a pneumatic fitting means that as your needs change or one-off situations crop up, you can always just go get the tool you need for the job. If it’s a one-time thing, you can generally find a place to rent a tool — if it’s something you’ll need again soon, buying is naturally the better option.

When properly maintained, a central pneumatic pump can function with minimal trouble for dozens of years, even in a high-particulate environment like many industrial settings. Depending on the quality of the tools you purchase, you can find tools that are cheap and need frequent replacement, or that are quite costly and will also last for decades. Which is the better choice for your business model is up to you.

Because all of your pneumatic power comes from a single source, but the end points are several, you gain efficiency. Specifically, you gain cost efficiency because you don’t have to replace the entire pneumatic system when an individual tool breaks. It’s much more common for a tool, which takes beatings and gets handled daily, to break down compared to the central unit that sits in the corner pushing air day after day.

Pneumatic Fittings In Everyday Life

Most often when we think about a factory that fabricates products like our cars, coffee grinders, and computer boards, we envision a robotic environment where dozens of computerized arms whirr on electric motors, bustling efficiently about creating product. Truth be told, that vision is often wrong in a few way. For one thing, ‘arms’ aren’t nearly as prevalent as you might think. For another, most of the power in fabrication labs these days comes from pneumatics, not from electric motors. The sound in a plant is much less ‘whirr, whirr’ and much more ‘psshh, hiss’.

But it’s not just in the fabrication plant that we come across pneumatics. A surprising amount of everyday objects use pneumatics to get their jobs done. Most jackhammers must be attached to an external air compressor via a pneumatic fitting, for example. Many larger trucks and buses have pneumatic brakes. But what about in your daily life?

How about:

  • Tire pressure gauges
  • Vacuum cleaners
  • Some nail guns
  • Bicycle/ball pumps
  • The device that slows your screen door down so it doesn’t slam shut when you let go of it
  • The handicapped-access button that opens door for you
  • Some car’s shocks
  • Those capsules you use to give and receive money from the farther-away of the two bank teller drive-ups

The list is long and sometimes surprising. There are far and away more industrial applications than household ones for pneumatics, of course: pneumatics see use in almost every kind of factory, whether they’re fabricating DVDs or deburring cast metal tools before they’re ready for sale. The most common difference between industrial and home-use pneumatics is the likelihood that a given tool will be self-powered or be required to hook to a central pneumatic compressor that provides power to a variety of different units.

Thus, while pneumatics might be common in everyday life, you rarely see pneumatic fittings outside of industrial applications. Unless you happen to have or use a sandblaster, air compressor, or vacuum pump for craft projects or as a part of the work you do from home, chances are much greater that you’ll come across a hydraulic fitting at home than a pneumatic one.