Controlling pressure buildup in air motors

Problem: Air motors operate a variety of industrial equipment, including hoists, elevators, positioners, and tensioners. Airflow to the motor is controlled by a manual or remotely actuated valve.
By Staff January 1, 2000

Problem: Air motors operate a variety of industrial equipment, including hoists, elevators, positioners, and tensioners. Airflow to the motor is controlled by a manual or remotely actuated valve. Valves occasionally do not shut off tightly and let air leak by, which allows pressure to build up within the motor and it will “inch over” or rotate a slight amount. The process repeats and eventually the motor rotates enough to put excessive stresses on whatever it is connected to, which might lead to disastrous results. It is very possible that this movement might not be noticed by an operator because of ambient noise or the remote location of the air motor. The process might takes days, or even weeks, before stresses develop to the point of failure. Can this problem be headed off?

Solution: Drill a 1/8-in. hole in the air line between the valve and air motor. This hole prevents air pressure from building up in the air motor when sitting idle and keeps the air motor from rotating. The air motor can be operated normally when needed, and the amount of air wasted through the drilled hole during an intentional operation is negligible.

Contributor: C.R. Barr, Everett, WA