Selection Guide | Air Motors | Ingersoll Rand

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Selection Guide

Ingersoll Rand offers two basic types of Air Motors:
Vane Motors
Are smaller, lighter and less expensive than piston motors or similar power. Simple in design and construction, they can be operated in most any position. Vane motors are available in a broad range of speeds, torques and power and are the most widely used type of air motor.
Radial Piston Motors

Operate at lower speeds than vane motors. Have excellent starting and speed control. Especially good for "lugging" heavy loads at slow speed. Standard operational position is horizontal.

Reversible / Non-Reversible Air Motors

Non-reversible air motors are rated at slightly higher speeds, torques, and horsepowers than reversible motors of the same family.

Air Pressure

When selecting air motors, remember that the specification listings show only one set of performance figures, at a particular pressure — 90 psig. Air motors are designed to produce optimum performance at this pressure.
Many other speeds, torques and power can be obtained from the same motor by regulating the pessure, air supply or exhaust. While they will operate at pessures below 40 psig, their performance may not be consistent. They can also be operated above 100 psig, but often at the expense of increased maintenance.
A good rule to follow is to size an air motor based on approximately 70% of the lowest available air pressure. This will allow additional power for starting and possible overloading.

Maximum Power

Ungoverned air motors develop maximum horsepower at approximately 50% of free (unloaded) speed while governed motors reach their peak horsepower at about 80% of free speed.

Desired Operating Speed

The desired operating speed, not the free and unloaded speed should be considered when selecting air motors.
Ungoverned air motors should not be run unloaded. The performance curves in this catalog indicate the maximum speeds at which the motor should be operated. The nameplate stamped speed is present for identification only.

Required Torque

Equally important as the speed at which an air motor is to be run is the required torque. The combination of the two factors—speed and torque—determine the power of the desired motor. Care should be taken to differentiate between stall (maximum) and running torques when selecting air motors.

Speed and Torque
Starting torques are approximately 75% of stall torques.
Operating or running torques at any speed can be approximated from motor performance curves—or calculated using the formula:
                        Horsepower x 5250
Torque (lb.ft.) = --------------------------------
                   speed (revolutions per minute)

                      Kilowatts x 9550
Torque (Nm) = --------------------------------
               speed (revolutions per minute)
Shaft Radial Loads
When an air motor is to be used with a pulley, sprocket, or gear on the shaft, the overhung load (perpendicular to the shaft), commonly called "shaft radial loading" must be considered. It is shown in the performance curves and is generally assumed to be applied at the mid-point of the keyway of the shaft.

Torque and Power Curves


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