Quick Exhaust;
speed up your air cylinder.

Quick Exhaust: a nifty little device that can speed up the cycle speed on an air cylinder where necessary.

On some equipment, the power valve is sometimes located quite a distance from the cylinder it’s powering. This has negative ramifications for the speed of the air cylinder.

Whether the air cylinder is single or double acting, if the power valve that feeds the air to that cylinder is some distance away, even though the compressed air moves very quickly (I’m told at the speed of sound) it still takes time for the air to flow from the valve to the cylinder when the valve is shifted.

If it’s a double acting cylinder, not only has the new air got to travel from the valve to the cylinder, but the air presently in the air cylinder has to travel back down the exhaust air line to the valve exhaust. Since the exhaust air is being driven from the double acting air cylinder by the inrushing air pushing the cylinder piston to the opposite end, the out flowing air may not move as quickly as the incoming air, and this slows the piston movement and the cylinder cycle.

Installing a quick exhaust at the cylinder ports will allow the exhausting air to exit the cylinder and the air line right at the cylinder port, rather than having it travel back down the air line to the valve exhaust.

In a single acting cylinder, it’s the internal spring that’s pushing the piston back to home position when the valve shifts and air starts to bleed from the cylinder. Same story as the D.A cylinder. The moving piston has to force the air out of the cylinder and back down the air line to the exhaust on the valve.

Installing a quick exhaust at the air port of the S.A. cylinder will allow the air in the cylinder to escape right at the cylinder port.

How It Works

The quick exhaust is nothing more than a vented check valve. When air is flowing into the air cylinder through the Q.E. the ball or flap inside seats on the exhaust port, and compressed air has full flow access to the cylinder.

When the air pressure in the supply line through the Q.E. to the cylinder loses pressure, that when the power valve supplying that line has shifted, the ball or flap inside the Q.E. moves with the now higher pressure inside the cylinder, and this allows the air in the cylinder to flow out to atmosphere right there rather than all the way back down the line to the valve exhaust.

Your cylinder will cycle much faster as a result.

The downside of a Q.E. is that, if you are using in-line or valve-exhaust flow controls to control the entire stroke of the air cylinder, using the quick exhaust negates their usefulness.







With a functioning quick exhaust in place, the cylinder will stroke very quickly and the cylinder piston will likely impact the inside of the cylinder end caps during cycling. This might cause damage, unless the load / piston is stopped externally by the tooling or an external shock absorber.

Here’s the generally accepted schematic for a Quick Exhaust.

Quick exhausts come in a variety of plumbing options.

Some come with instant fittings on the supply port. Some come with integral mufflers, others with a FNPT thread to screw in your own muffler.

Quick exhausts are sold by a huge number of manufacturers, some making theirs out of cast metal, others from composites, or a blend of both.

Your fluid power distributor will likely stock one or two brands.







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