Hydraulics Pumps & Valves by Hindustan Hydraulics & Pneumatics Chennai
Hydraulics and Pneumatics Lab1
Transcript of Hydraulics and Pneumatics Lab1
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HYDRAULICS ANDPNEUMATICS LABDEPARTMENT OF MECHATRONICS ENGINEERING
AIR UNIVERSITY
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Pneumatic Systems
Pneumatic systems are designed to move loads bycontrolling pressurized air in distribution lines andpistons with mechanical or electronic valves.
Air under pressure possesses energy which can bereleased to do useful work.
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Components of a Pneumatic System
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Components of a Pneumatic System
Compressor is the power source of a pneumaticsystem. It is usually driven by a motor or an internalcombustion engine. The compressed air is first stored
in a strong metal tank called reservoir. Before entering the cylinders and valves
, thecompressed air has to pass through the air
treatment devices, including air filter to remove dustand moisture, pressure regulator to adjust pressure.
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Example: Pneumatic Punching Machine
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Hydraulic Systems
Pneumatic systems are open systems, alwaysprocessing new air, and air is simply exhausted tothe atmosphere. Hydraulic systems are closed
systems, always recirculating the same oil.
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Components of a Hydraulic System
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Example: Hydraulic Jack
Only a small force isrequired by theoperator to raise theheavy load. The largepiston can be stopped
at any point becausethe oil cannot becompressed.
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Example: Hydraulic Brakes
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Comparison B/W Hydraulic and
Pneumatic System (Advantages)
Pneumatic Hydraulic
Air is easily available High output force
Fast response Accurate hydraulic pressure
Air is non-flammable No corrosionContinuous variable transmission Continuous variable transmission
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Comparison B/W Hydraulic and
Pneumatic System (Disadvantages)
Pneumatic Hydraulic
Output force is limited Fluid might leak out
Compressibility of air Fluid may degrade due to heat
Corrosion may occur Fluid flow speed is limitedPipe length is limited Pipes are complicated
Working fluid is often flammable
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BASIC HYDRAULIC SYSTEM
RESERVIOR
PUMP
CONTROL VALVES
ACTUATOR
RELIEF VALVE
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HYDRAULIC RESERVIOR
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PUMP TYPES
GEAR TYPE (150 bar, 90% efficiency)
VANE TYPE(95%)
PISTON(98%)
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GEAR PUMPS (Lobe Pump)
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HYDRAULIC POWER PACK
Hydraulic Power Pack
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PUMP SELECTION CRITERIA
WORKING PRESSURE REQUIRED
FLOW RATE REQUIRED
TYPE OF FLUID TO BE PUMPED
SIZE AND WEIGHT
LIFE REQUIRED NOISE
EFFECT/TOLERENCE OF DIRT
EFFICIENCY
EASE OF MAINTENANCE AVIALABILITY OF SPARE PARTS
COST
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CONTROL VALVES
PRESSURE CONTROL VALVES
DIRECTIONAL CONTROL VALVES
FLOW CONTROL VALVES
NON-RETURN VALVES
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PRESSURE CONTROL VALVES
RELIEF VALVES
The pressure in a system is set and restricted by
these valves. The control pressure is sensed at the
input (P) of the valve.
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Directional Control Valves
The following rules apply to the representation of directionalcontrol valves:
Every switched position is represented by one square.
Therefore the number of squares drawn indicates the
number of possible positions it can be switched in. The pressure and return lines are drawn attached to the
square that represents its normal (non-operated) position.
By shifting the corresponding square we get the differentpossible positions.
Lines in the squares indicate the ways of flow within thevalve. Arrows represent the direction of the flow.
The way of operation is drawn using symbols as well.
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Example
The picture on the right is the basesymbol of a valve. Only the lines andthe arrows indicating flow-paths anddirections have to be applied.
What information can be derived from this symbol now?
We are dealing with a valve having 2 positions.
This valve has 5 connection points.
5 connections and 2 positions ==> a 5/2-valve
The square on the right is its normal position.
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Example
Each individual position is shown in a square
Flow paths are indicated by means of arrows within a square
Closed square
Two flow paths
Two ports are connected and two are closed
Three ports are connected and one is closed
All ports are connected
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Representation of a Direction Control
Valve
Port Designations
P
TA
B
Pressure port
Return port
}Power ports
2/2-way valve
3/2-way valve
4/2-way valve
4/3-way valve
Number of ports
Number of switching positions
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Types of actuation
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Flow control valves
Flow control valves have the task of controlling thespeed of hydraulic actuator. This is achieved byvarying the open cross section of the restrictor,
therefore changing the volumetric flowrate throughthe actuator.
Restrictor One way flow controlThrottle
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Example
One way flow controlThrottle