CHAPTER 11
PNEUMATICS TRANSMISION
Objectives:
The purpose of this chapter is to describe:
1. Advantages and disadvantages of pneumatic transmission
2. Operation and performance of various pneumatic elements.
3. Operation and performance of some usually used circuits.
Upon completing this chapter, you should be able to:
Be familiar with the main pneumatic components and
standardized symbols used for their representation on circuit
diagrams.
Explain the operation principle and performance
characteristics of some usually used circuits.
Describe the function of each basic component in a practical
pneumatic circuit
Design a circuit to perform a desired function.
CHAPTER 11
PNEUMATICS TRANSMISION
11.1 Pneumatics Overview
11.1.1 Pneumatic System Structure & Its Operation Principle
In pneumatic system, compressors are used to compress
and supply the necessary quantities of air that comes from the
atmosphere.
To operate and control these actuators, other pneumatic
components are required i.e. air service units to prepare the
compressed air and valves to control the pressure, flow and
direction of movement of the actuators.
Fig.11.1 A Basic Pneumatic System
In production section: ①compressor, ②electric motor, ③pressure
switch, ④check valve, ⑤tank, ⑥pressure gauge, ⑦auto drain, ⑧
safety valve, ⑨refrigerated air dryer, ⑩line filter
In consumption section: ①air take-off, ②auto drain, ③air service
unit, ④directional valve, ⑤actuator, ⑥speed controllers
11.1.2 Pneumatics Properties
Table 11.1.Advantages of Pneumatics
Availability
Transport
Storage
Temperature
Explosion
proof
Air is available practically everywhere in unlimited
quantities.
Air can be easily transported in pipelines, even over long
distances.
Compressed air can be stored in a reservoir and removed as
required.
Compressed air is relatively insensitive to temperature
fluctuations.
Compressed air offers no risk of explosion of fire.
Components
Unlubricated exhaust air is clean. Any unlubricated air that
escapes through leaking pipes or components does not cause
contamination.
The operating components are of simple construction and
therefore relatively inexpensive.
Speed
Compressed air is a very fast working medium. This enables
high working speeds to be attained.
Overload safe
Pneumatic tools and operating components can be loaded to
the point of stopping and are therefore overload safe.
Cleanliness
CHAPTER 11
PNEUMATICS TRANSMISION
Table 11.2.Disdvantages of Pneumatics
Preparation
Compressed air requires good preparation.
Dirt and condensate should not be present.
Compression
It is not always possible to achieve uniform and
constant piston speeds with compressed air.
Force
requirement
Compressed air is economical only up to a
certain force requirement. Under the normal
working pressure of 600 to 700 kPa (6 to 7 bar)
and dependent on the travel and speed, the
output limit is between 40000 and 50000 N.
Noise level
The exhaust air is loud. This problem has now,
however been largely solved due to the
development of sound absorption material and
silencers.
11.2 Air Generation and Treatment
Fig.11.2 Structure of Air Preparation System
11.2.1.2 Air generation equipments and preparation
Fig.11.4 Two Stage Piston Compressor
11.2.1.2 Air generation equipments and preparation
Fig.11.5 Rotary sliding vane compressor
11.2.1.2 Air generation equipments and preparation
Fig.11.6 Screw Compressor
11.3 Actuators
11.3.1. Linear Cylinder
Fig.11.15 Construction of a Cylinder
11.3.2 Rotary Actuators
11.3.3. Air Motors
Air motors are similar in construction and function to
hydraulic motors, and are most commonly of the rotary vane,
gear, radial piston, or axial piston type.
They can operate at speeds in excess of 10,000rpm.
Air motors have several advantages that are important in
some applications. One advantage is that air motors can stall
under full load for indefinite periods of time, another is that they
can be used in applications where electric motors would
constitute a fire hazard.
11.4 Pneumatic Control Valves
11.4.1 Pressure Control Valves
Fig.11.20 Safety Valve
11.4.3 Directional Control Valves
Fig.11.38 Solenoid Valves
11.5 Basic Pneumatic Circuits
Fig.11.50 Automatic Reciprocate