L.S.Aluthge
Content
• Introduction
• Compressed Air Production and Distribution
• Compressed Air Preparation
• Pneumatic Actuators
• Pneumatic Valves
• Signal Sources
• Pneumatic Control System Structure
• Maintenance of Pneumatic Systems
Introduction
• When the air pressure is reached more than atmosphere(1 bar), it’s
called compressed air.
• When air is compressed it can be used to perform work. This is known
as pneumatic.
• Advantages
Compressed air is fast
Compressed air is clean
Exhaust air can be discharge directly into atmosphere
Compressed air is safe. It’s not burn or explode under wide range of
operating temperature.
Pressure
• Pressure is defined as force acting per unit area.
• Atmospheric pressure ( regarded being a constant at sea level) is 100kPa( 1
bar).
• For measuring lower pressure millibar is used. (1000 mbar=1bar)
• There are many units of pressure measurement. Some of these and their
equivalents are listed below.
1 bar = 100000 N/m2
1 bar = 100 kPa
1 bar = 14.50 psi( pound per square inch)
1 mm Hg = 1.334 mbar approx.
1 mm H2O = 0.0979 mbar approx.
Flow units
•
•
Flow is measured as a volume of free air per unit of time
Popular units are :
• Litres or cubic decimetres per second
l/s or dm3/s
• Cubic metres per minute
m3/m
• Standard cubic feet per minute (same as cubic feet of free air) scfm
•
1 m3/m = 35.31 scfm
•
1 dm3/s = 2.1 scfm
•
•
1 scfm = 0.472 l/s
1 scfm = 0.0283 m3/min
Compressed air production and distribution
COMPRESSORS
POSITIVE
DISPLACEMENT
RECIPROCATING
SCREW
TWIN LOBE
DYNAMIC
ROTARY
CENTRIFUGAL
AXIAL
Air Compressors
• In many types as the air is compressed in the form of heat is
concentrated in a smaller space.
• So, most compressors include cooling unit to reduce the temperature
of the compressed air.
• Compressed and cooed air then stored a tank called reservoir.
• Also, dryer is used to dry air (remove moisture in air) to reduce
corrosion in distribution pipes and components.
Compressed air production System
Compressed Air Preparation/ FLR unit
• Service unit is used to prepare the air when it enters the machine circuit.
• An FRL unit comprises a filter (F), regulator (R), and lubricator (L).
• Filters: Filters remove water, dirt, and other harmful debris from an air
system, which is often the first step in improving air quality.
• Regulators: The second step in an FRL system is a regulator. Regulators adjust
and control the air pressure of a system to ensure that down-line components
do not exceed their maximum operating pressures.
• Lubricators: Lubricators reduce the internal friction in air tools by releasing a
controlled oil mist into the compressed air. This is often done last and/or right
before the component that needs lubrication.
FLR unit
LOUVER
4
2
P2
6
40
80
120
lbf/in2
bar
8
10
P1
FILTER
WATER PARTICLES
P1
P2
P2
P1
DRAIN PLUG
FLR unit
Pneumatic Actuators
• Actuator is an output device for the conversion of supply energy into
a useful work.
Other Types of Cylinders
• Adjustable end position
cushioning cylinders
PNEUMATIC ACTUATORS
LINEAR
MOTION
Single Acting
Cylinder
Double Acting
Cylinder
ROTORY
MOTION
Other
Cylinders
Rotary
Module
Air Motor
• Double acting cylinder
with double ended
piston rod
• Hollow piston rod
• Rod-less cylinders
Single Acting Cylinder
• Produce work in only one direction
• The piston is returned to initial position by a spring
• Applications such as clamping, stamping, ejecting, lifting,
feeding
Normally out
Normally in
Double Acting Cylinder
• Produce work in two directions
• The major difference being that the return spring is not used
• A second inlet port is required on the piston rod side
Double Acting Cylinder Without Cushion
Double Acting Cylinder With Cushion
Double Acting Cylinder With Adjustable Cushion
progressively slows the piston rod down over the last part of stroke
Double Acting Cylinder With double ended piston rod
Rod-less cylinders
Linear motion is converted into rotary motion through a gear train
Rotary module/ Rotating vein cylinder
Air motor/ Rotary vein motors
Pneumatic Valves
Function of valve;
• Open and close flow paths
• Regulate pressure
• Adjust flow volume
• Direct flow through various path
Types of valves;
• Directional control valves
• Non-return valves
• Pressure valves
• Flow control valves
• Combination valves
Directional Control Valves
• Directional control valves, control the path of the air flow in pneumatic or
electro-pneumatic control systems
• The directional control valve redirects/blocks, supply air to specific air supply
lines, and/or exhaust air to the surroundings via the exhaust opening
Symbols of directional control valves
Identification of ports
Valve actuation types-Manual
Valve actuation types-Pneumatic
Valve actuation types-Mechanical
Valve actuation types-Electrical
Symbols of directional control valves
3/2 way directional control valve
Symbols of directional control valves
5/2 way directional control valve
5/3 way directional control valve
Non-return Valves
AND valve/ Two pressure valve
OR valve/ Shuttle valve
Quick Exhaust valve
Maintenance of pneumatic systems
1.Drain the water from filter.
2.Check the air pressure in pressure gauge. It should be in setting pressure.
3.Ensure the oil level in lubricator unit.
4.Ensure any air leakage in ,Air gun’s, FRL unit, Valves, hoses, pipelines, fittings etc.
5. Ensure the oil dropping ,whether it is normal or ant disturbances.
6.Check any oil leakage in lubricator unit.
7.Ensure any crack or damage in air hoses.
8.Clean the filter unit.
9.Remove any dirt in lubricator unit
Drain the
water
Check the
pressure
Clean the silencer twice
in a month
Check the oil level
in lubricator
No oil in lubricator
NEVER ALLOW AIR LEAKAGE ANYWHERE
Power loss due to Compressed Air leakage
Motor power (kW)
Flow Rate (m^3/min)
Precentage of leakage(%)
Plant Annual operation time (hours)
Sri Lanka electricity prices for Business (Rs./kWh)
Flow Rate (CFM)
Leakage rate (CFM)
Specific Power Consumption (kW/CFM)
Specific Power Consumptionfor leakage (kW/CFM)
Annual Energy Requirement for leagkages
Additional cost for leakages (Rs.)
75
13
1
7200
42.00
459.0906672
4.590906672
0.163366423
0.75
5400
226800
Thank you..