Hydraulics and Pneumatics Lab1

8/6/2019 Hydraulics and Pneumatics Lab1

1/27

HYDRAULICS ANDPNEUMATICS LABDEPARTMENT OF MECHATRONICS ENGINEERING

AIR UNIVERSITY


2/27

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.


3/27

Components of a Pneumatic System


4/27

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.


5/27

Example: Pneumatic Punching Machine


6/27

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.


7/27

Components of a Hydraulic System


8/27

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.


9/27

Example: Hydraulic Brakes


10/27

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


11/27

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


12/27


13/27

BASIC HYDRAULIC SYSTEM

RESERVIOR

PUMP

CONTROL VALVES

ACTUATOR

RELIEF VALVE


14/27

HYDRAULIC RESERVIOR


15/27

PUMP TYPES

GEAR TYPE (150 bar, 90% efficiency)

VANE TYPE(95%)

PISTON(98%)


16/27

GEAR PUMPS (Lobe Pump)


17/27

HYDRAULIC POWER PACK

Hydraulic Power Pack


18/27

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


19/27

CONTROL VALVES

PRESSURE CONTROL VALVES

DIRECTIONAL CONTROL VALVES

FLOW CONTROL VALVES

NON-RETURN VALVES


20/27

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.


21/27

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.


22/27

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.


23/27

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


24/27

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


25/27

Types of actuation


26/27

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


27/27

Example

One way flow controlThrottle

Documents

Hydraulics and Pneumatics Lab1