Couplers and connectors are to compressed air and air compressor plumbing, what a wall plug and wall socket are to electricity.
To further that metaphor, the wall socket performs a similar function for electricity as the coupler does for compressed air. Both require something to be plugged into them for flow to take place.
The cord plug performs a similar function for electricity as the compressed air connector does for the flow of compressed air. By inserting them into the appropriate receptacle, flow can take place.
Like their electrical counterparts, the couplers and connectors you will acquire for plumbing your compressor, air hose and air tools have certain standards. Not paying attention to them may create problems, not as serious as trying to plug a 120 volt plug into a 220 volt socket for sure, but problems with air leaks, poor air flow and so on.
Compressed Air Couplers
A discharge coupler, one of which is shown in the photo, is the device at the end of the pipe from the air tank on your air compressor.
The discharge coupler keeps the air pressure in the tank until you need to use it. It can do this because most couplers are “checked”. This means that the air coupler has an internal one-way valve that could be spring, air-pressure or both, forced closed to stop the compressed air from flowing through it.
You will normally see a compressed air coupler on one end of each air line as well as on the discharge from your air compressor. The air line coupler will be checked as well.
Compressed Air Connectors
The compressed air connector is the other half of the compressed air connection team.
When an air connector is inserted into a mating discharge coupler on the air compressor, the connector unseats the coupler’s internal check valve. This allows the compressed air to flow from the compressor tank, through the discharge coupler, through the connector, and into whatever the connector is attached to.
Usually the connector is attached to an air hose. By inserting the connector into the discharge coupler, air flows into the air hose.
At the other end of the air hose there is typically another compressed air coupling. This stops the air from flowing out of the air hose to atmosphere, as this coupling will be checked too.
Couplers and Connectors Make Air Extension Cords
Compressed air is power. Just like you would use an extension cord to conduct electrical power over a longer distance, air hoses provide the same function. If we use the electrical model for comparisons sake, the air connector would emulate the plug on the electrical extension cord, and the coupler would emulate the socket. If there is nothing plugged into the socket on the extension cord, power does not flow, even if the plug is connected to the wall socket.
Installing Couplers and Connectors
Odds are good that the discharge coupler on your air compressor is one equipped with a female thread. The end that turns onto the pipe from the tank has internal threads, and the pipe has a male thread that matches the internal thread in the coupler.
Or, less likely, your discharge coupler has a male thread – one that sticks out of the end of the coupler – and the coupler is turned into a female thread on a bushing on the compressor discharge pipe.
That covers two the most common attachment configurations for air couplers.
Air connectors also have male thread and female thread configurations, and they, too, come also with a barbed fitting.
The barbed fitting allows the barb to be inserted into an air hose, and with a gear clamp or compression clamp on the outside of the hose over the barb, the connector is firmly connected to the hose.
The air connector can come equipped with a barbed end as well, also for inserting into an air hose.
Air hoses often come equipped with male threaded fittings on each end, so the connector and the coupler would need to be female threaded to be installed.
Regardless of the choice of fitting – female / male / barbed – when you wish to install a new coupler, it is necessary to ensure that the thread on the receptor end is the same as the thread on the inside or outside of the coupler or connector.
Incompatible Couplers and Connectors
Your air compressor came with a discharge coupler already installed. When you wish to use air from your compressor, you will want to plug an air connector into that coupler. Which one?
Unfortunately, there are a number of standards for couplers and connectors. If you purchase connectors for your compressor and they are not of the same standard as your coupler, they may not insert.
Or, if they insert, they may not be firmly installed, and may blow out when least expected.
If the connector isn’t correct, even if installed and locked in, it may not open the check valve all the way, thus impeding flow of compressed air to your air tool.
In the connector photo, an ARO 210 connector is shown. That style of connector may not fit your coupler. There are military specifications for some couplers and connectors, and different companies have their own designs and standards. It can be a bit confusing.
Coupler and Connector Kits
One solution to the confusion over which connector fits which coupler is to buy coupler and connector kits.
In the kit depicted in the image above – and looking at the contents from the left – the kit has one coupler with a female thread, one connector with a female thread, one connector with a male thread, and one bushing to allow connecting two items with female threads together.
This kit contains couplers and connectors with an “M” style configuration, as can be noted at the top of the package. This means that as long as you acquire couplers and connectors that have this “M” style designation, they will work together, regardless of where you acquire them.
Other coupler and connectors kits may contain just one coupler and multiple connectors, since you will likely use more connectors than couplers, so that’s why some kits have only one coupler but many mating connectors.
Using your couplers and connectors
If you are not familiar with how the coupler and connector works, and particularly when you decouple one of them, be prepared for a blast of air from the connector.
Depending on what the connector is threaded into, that blast of air might be just a bit, or if it were a large air cylinder or long hose, that blast of air can be quite long and violent. When you decouple a coupler connector, keep the connection away from your face, and hold firmly to both parts until the pent up compressed air has dissipated to atmosphere.
Item one on the sketch is the coupler, and it is equipped with a knurled ring. Typically something that comes equipped with a knurled part is meant to be manipulated by hand.
To connect the connector (item two) to the coupler, you need only to insert the probe into the female opening on the coupler. Savvy users know that if you move the knurled ring to the left as you insert the connector, and then release the ring as the connector bottoms out, that this makes the process easier.
Regardless, forcing the connector into the coupler should allow the two to connect.
I always push the knurled ring on the connector towards the connector after the two have mated, just to be sure they are connected securely. One or two air hose “blow offs” when you are connecting will help you understand why I do that.
To decouple, hold both sides securely and away from your face. Pull the knurled ring to the left with a couple of fingers on the left hand, and make sure you hold on particularly tight to the connector side, as compressed air will bellow out of there.
Hope this helps you better understand couplers and connectors.
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