Couplers and air tool connecting!

(Last Updated On: October 2, 2020)

This post is prompted by a questioner about “non-relieving” couplers not being used on air nailers.

I hadn’t  heard the term “non-relieving” couplers, but I have heard of “checked” couplers. The checked coupler, I think – in principle, is the same as the non-relieving kind, only allowing air to flow when it has a connector inserted.

couplings on an air compressor

The insertion of the connector into the checked coupler unseats a ball check inside the coupler, and as long as the connector is inserted, compressed air can flow through them both. Pull the connector from the coupler, and the ball re-seats inside the coupler, and the air flow stops.

I think the concern is that some folks may thread a male coupler into their air tool supply port. If the air tool is a nailer, and the coupler is non-relieving or a checked type (and most are) then when the mating connector is pulled from that coupler, compressed air can be trapped inside the air nailer. Unbeknownst to the user, that air nailer can still fire a nail, even though there is no air line attached. A very dangerous situation indeed.

air coneccting tools

I guess I just assumed that folks would always use a connector in the supply port of an air tool, and attach a coupler on an air line to that connector when they wanted to power the tool.  A connector is fully open to air flow. So, when the coupler is removed from the connector that is  threaded into the tool supply port, any air in the tool will bleed back to atmosphere immediately upon removal of the coupler, rendering the air tool powerless.

If you have air tools with couplers in the tool instead of connectors, may I suggest you change them out?

Hello, I am Bill, the Compressed-Air-Man. I have years of experience in industrial and residential compressed air applications, air compressors and general pneumatics. I created this site to help professionals, students, and DIYers understand and properly implement and maintain compress3ed air systems.


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