This document discusses air motors, which are power producing devices that use compressed air to provide high rotational speeds up to 25,000 rpm. There are two main types of air motors: reciprocating (piston type) and rotary (vane type). Reciprocating air motors use a piston-cylinder arrangement where compressed air admitted into the cylinder causes the piston to move linearly, producing rotational shaft work. Rotary air motors consist of a rotor with radial slots holding vanes, where compressed air enters and causes the rotor to rotate. Common applications of air motors include powering hand tools, mining equipment, woodworking machines, and for tasks like hammering, drilling and riveting.

1. Unit No:02
Energy Conversion Devices
Prof. Yash B. Parikh
M.Tech (Computer Integrated Manufacturing)
B.E.(Mechanical Engineering)
Assistant Professor
Department of Mechanical Engineering

2. Air Motor
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3. Air Motor
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• Air motors are power producing device.
• They provide very high rotary speed, as high as
25,000 rpm.
• It uses compressed air, received from a compressor.
• Used where the I.C.Engines or electric motors can’t
be used due to fire hazards.
e.g. mining applications
• It’s also used for running the pneumatic tools like
drills, rammers, etc.
• Air motors work on the cycle.
• There are two types :
i) Reciprocating type air motor (Piston type)
ii) Rotary type air motor (Vane type)

4. Reciprocating or Piston Type Air Motor
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• Reciprocating air motor is also known as piston type
air motor.
• It uses piston-cylinder arrangement.
• The high pressure air is admitted into the cylinder
through inlet valve for a limited period during suction
stroke.
• This cause the piston to move.
• Now, inlet valve is closed and piston moves further
expanding air upto atmospheric pressure.
• Thus producing shaft work.
• Now piston reverses its motion.
• The discharge valve opens and air is discharged to
the atmosphere, completing a cycle.

5. Reciprocating or Piston Type Air Motor
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• They are used in applications where high power,
starting torque and accurate speed control at low
speeds are needed.
• They have either two, three, four, five or six cylinders
arranged either axially or radially within housing.
• Output torque is developed due to the pressure
acting on pistons that reciprocates inside cylinders.
• Power developed by these motors depends on the
inlet pressure of air, no of pistons, piston area, and
stroke.

6. Rotary or Vane Type Air Motor
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• Normally used in applications requiring low to
medium power outputs.
• It consists of a rotor which has radial slots.
• Rotor is placed symmetrically about the axis of the
output shaft.
• A vane is inserted in each slot, which are generally 3
to 10 in no’s.
• These vanes moves in and out from the slot with the
help of spring force.

7. Rotary or Vane Type Air Motor
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8. Rotary or Vane Type Air Motor
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• The air enters at high pressure from one end on
these vanes.
• It causes the rotary motion of the rotor which is
coupled to the shaft.
• Thus it produces the torque on the shaft.
• A pneumatic tool like drill can be attached to perform
the required work.
• Vane type motors run at 100 to 25,000 rpm.

9. Advantages of Air Motor
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• These are light in construction and simple in
operation.
• They are inexpensive.
• There are no fire risks, hence used for mining
applications.
• No cooling arrangements are needed.
• Directions of rotary air motors can be reversed easily.
• Explosion proof.

10. Limitations of Air Motor
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• These are noisy in operation.
• Efficiency is low.
• It has a variable speed, varies according to load.

11. Applications of Air Motor
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• Used in Hand Tools.
• Mining Engineering Applications.
• Wood working fields.
• Construction engineering.
• Mechanical applications like hammering, riveting,
drilling, etc.
• Indoor Manufacturing plants.