Only a Short Burst of Air – 2

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If you have just landed on page only a short burst of air – 2, the first page can be found here. The issue being discussed on these pages is: when an air tool is operated, sometimes there is only a short burst of air out of the air hose, and then the compressed air supply dribbles down to almost nothing. We are working on diagnosing the causes and recommending a cure.

On page one in this discussion, and referring to the same drawing as you see below, we have determined that the compressed air path from the tank to the regulator is normally unobstructed. It is safe to assume that compressed air is flowing freely from the tank to the regulator in all small air compressors unless, of course, you have the one where someone installed another air component in that path. That we cannot address unless we know what that air equipment is, and you can tell us that using the form at the end of this page.

On page one of a short burst of air we also talked about a quick check to see if the regulator appeared to be working.

In this next step, we will talk about the discharge coupler.

In the sketch you can see that the compressed air flows from the tank, through the regulator – where the downstream pressure is set – and then to the discharge coupling. The discharge coupling is checked, meaning that air cannot flow out of it and on downstream until a mating connector is inserted.

Is your compressed air connector the problem?

Your air compressor came with a checked discharge coupler installed. That air coupling is one of the things that keeps the compressed air in the compressor tank until you need to use it.

Quick question… is the connector on the end of the air hose that you are plugging into the discharge coupler compatible with the discharge coupling?

Unfortunately, there are many manufacturers of compressed air couplings, and there are also many different manufacturing standards. That means that unless you are confident that the connector you are inserting into the discharge coupler is compatible, that could be the problem. In the photo below the brass colored at the bottom right is the discharge coupler for this compressor. Can you tell what the make of that coupler is?

Ball check inside the couple

Compressed air coupler showing where the connector is inserted.
Compressed air coupler. Ball check is at the back of the aperture marked in red.

Inside the discharge coupler  is a check valve, usually a ball, that is pressed into the seals inside the coupler by an internal spring. That ball-on-seal is pressed into the seals by the spring and the air pressure behind it, preventing air from flowing out of the coupler.

Inserting the mating connector pushes open the ball inside the coupler, and allows air to flow.

Yet, since we do not know what the make of this discharge coupler, how do we know that we have the right connector?

If the connector you insert into the coupler is not the correct mating one, it still may insert, and it still may lock inside the coupler. It does not follow that it will unseat the ball check completely, and, if that is the case, only a small amount of compressed air would bleed into the air hose over time. Then, when you used the air tool, you would get only a short burst of air, and then just a dribble as the not-fully-open ball check slowly allowed more air out of the discharge coupler and into the air hose.

The same issue at the air line connection to the air tool

If the connector that you have inserted into your air tool is not a match for the air coupler at the end of the air line you are trying to connect to the air tool, you may be creating the same scenario. If the coupler and connector do not match, you may create an obstructed flow path of the compressed air to your air tool.

Only a short burst of air and the coupler

It is necessary to ensure that you have only one brand (or only compatible brands) of couplers and connectors in your workshop.

When you look on the shelf at your compressed air equipment store, make sure that the style of coupler (for example, it might show an “M” on the label) matches the connector. Ensure that you only get the right connectors for the coupler, and if you are not sure. it may be time to standardize in your workshop to ensure that your coupler / connector connection is not causing only a short burst of air to your air tool.

Air hose the problem?

The assumption we are making in this discussion is that your air hose hasn’t a Humm-vee or something sitting on it, blocking all but the littlest amounts of compressed air flow.

Do check to make sure that the air hose is not crimped or flattened in some way.

Now What?

OK. If the air path to the regulator is fine, and the couplers and connectors match, and there is nothing sitting on your blocking the air line to the air tool, and the air tool is functioning normally (except not enough air but a short burst to run) then we have to refocus on the regulator.

Dial the pressure setting on the regulator to zero. On some regulators this will effectively shut off the air flow. On others, it will reduce the air flow to a trickle.

Shut the compressor down, drain the air from the tank, remove the air line connector from the discharge coupler, and then remove the discharge coupler. That should leave you with an open line from the regulator out to atmosphere.

Start the compressor and let the tank fill with pressure until the compressor stops on high pressure cut out. Unplug the compressor or shut it off so it doesn’t start while you are… dialing the pressure regulator setting up as high as it will go. Monitor the air flow out the open pipe. If you turn the regulator knob quickly enough, you should get a large blast of air out of the open pipe as the tank pressure blasts out to atmosphere. You should, at least, if the regulator is allowing air flow.

If it doesn’t, then the problem is your air regulator. You can try to repair it, but since they are fairly low cost and locating spare parts for an air regulator is almost impossible, simply replace it.

Did this solve the problem of only a short burst of air?

If the preceding pages helped, please let us know via a comment. And, if the page is useful, let others know by clicking on the social buttons and updating your pages.

If there is still an issue with your air compressor relating to just a short burst of air coming out of the air line, please post details below.

By Ashley Pearce

As a passionate manufacturing and mechanical engineer, I've had my fair share of run ins with air compressors and compressed air systems. With over a decade of experience in the industry, I have both a fresh perspective and time-served hands and mind to help you with your compressor problems (along with our able community!)

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