Pneumatic & hydraulic hight tech SPKT

Pneumatic & hydraulic hight tech SPKT

Chapter 1

Overview

Pneumatic & Hydraulic Technology

Ho Chi Minh City University of Technical Education

Overview

Instructor: Phan Thi Thu Thuy

H igher E ngineering E ducation A lliance P rogram

Chapter 2:

Air Generation

Chapter 2:

Air Generation

Pneumatic & Hydraulic Technology

Ho Chi Minh City University of Technical Education

Air Generation and Distribution

Air Generation and Distribution

Instructor: Phan Thi Thu Thuy

1 Piston compressor

2 Two stage piston compressor V -type

3 Two stage piston compressor double acting

4 Piston – diaphragm compressor

Air compressor

1

4 Piston – diaphragm compressor

5 Sliding vane rotary compressor

6 Screw compressor

7 Roots compressor

8 Turbine compressor

9 Turbine compressor – four stages – radial compressor

10 Axial turbine compressor

describe the working principle of certain positive

describe the working principle of certain positive

3 After attending a lecture, be able to explain

the differences between intercooler and

Compressor types

Types of compressor

Reciprocating piston compressor

Piston Diaphragm

Rotaty piston compressor

Flow compressure

Radial - flow Axial – flow

 Reciprocating compressor are very common and provide

a wide range of pressure and delivery rates

 For higher pressures multistage compression is used

with intercooling between each stage of compression

Piston compressor

Diaphragm compressure

Sliding vane rotary compressor

Roots compressor

Radial - flow compressure

Axial – flow compressure

Two – axial screw compressor

Compressor types based on

working principle

The major classifications of compressors are positive displacement and dynamic type

 Positive displacement can be further divided into

(a) Reciprocating (b) Rotary

In case of positive displacement compressors increase the pressure of air/gas by reducing the volume

 Dynamic compressors divided into

(a) Radial (b)Axial

Dynamic compressors increase the air or gas velocity, which is then converted to increase the pressure

Compressor types

The optimum range of pressure for reciprocating

compressors are approximately:

 Up to 400kPa (4 bar/58 psi) Single stage

 Up to 1500kPa (15bar/217.5 psi) Double stage

 Over 1500kPa Treble or

multi-stage

1 Piston Compressor

port.

1 Piston Compressor

and sucks air from the

atmosphere.

not mechanically.

1 Piston Compressor

port closes and exit port

opens The air is being

pushed against the

pushed against the

prevaling pressure.

depends on valve

design.

2 Two stage piston compressor

V-type

 Two pistons are driven by

one crank shaft

 The air, compressed to

certain degree passes

from the left cylinder

through the intermediate

Intermediate Cooler

through the intermediate

cooler before given it’s

final rate of compression in

the right cylinder

the first stage is

determined by the degree

of cooling obtained

2 Two stage piston compressor

V-type

The three main types of air coolers are:

 Precoolers: heat exchangers that cool the air before it

is compressed

 Intercoolers: heat exchangers that cool the air between the compressive stages of a multi-staged compressor.

 Aftercoolers heat exchangers that cool the air after it

 Aftercoolers heat exchangers that cool the air after it has been compressed.

 Precoolers and aftercoolers commonly employ water as a medium for heat dissipation, whereas intercoolers

commonly use air as the cooling medium

 A typical intercooler is composed of three different parts:

a fan, fins, and core tube

3 Two stage piston compressor

double acting

during the upward and

downward stroke.

move the piston downwards

piston rod side and the inlet

port on the piston side have

opened so that compression

and suction takes place

simultaneously.

3 Two stage piston compressor

double acting

 The same principle is also

employed in the second

stage

 The cylinder of the second

stage is smaller than the

cylinder of the first stage

cylinder of the first stage

because the volume of

compressed air is less

 This compressor is equipped

with a cross piston drive

 The positive advantage of this

more precise bearing is a long

service life

4 Piston – diaphragm compressor

 The working principle of this

compressor is the same as that

of a piston compressor, but

sealing is provided by a

diaphragm

 The diaphragm usually permits

 The diaphragm usually permits

a shorter piston stroke only

 The advantage of this type is

air, free of oil contamination

 Compared with other

compressors designs the

sealing of compression volume

is simplified

5 Sliding vane rotary compressor

 Drive and compressor shaft are

identical and are placed

excentrically in a round cylinder

volume

 A rotor is fitted on the shaft with

slots and sealing vanes The

slots and sealing vanes The

vanes are pressed against the

cylinder wall due to rotational

forces and spring action

 When rotating, the vanes move in

and out of their slots resulting in a

large number of chambers with

differing volumes

5 Sliding vane rotary compressor

on the suction side ,

the smallest on the

6 Screw compressor

of two screw type profiles to

rotate against each other

6 Screw compressor

to rotate in opposite

directions

continously between the

continously between the

screws and the side

walls of the housing.

7 Roots compressor

shafts which rotate one

against the other.

in the chambers

between the profiled

shafts and the housing

is pushed against the

pressure at the exit side.

8 Turbine compressor

high revolutions

Turbine sections on

the shaft accelerate

the air to a high

the air to a high

speed

required, each stage

will increase the

pressure at a ration of

9 Turbine compressor - four

stages-radial compressor

this type with

distribution of the

driving force via gears

are designed for very

are designed for very

10 Axial turbine compressor

the vanes and is

D = Cylinder bore (metre)

L = Cylinder stroke (metre)

S = Compressor speed (rpm)

χ = 1 for single acting and

2 for double acting cylinders

n = No of cylinders

Test question

 Question 1: Which of the following parameters are NOT

required for evaluating volumetric efficiency of the

compressor?

a Power b Cylinder bore diameter

c Stroke length d None of them

 Question 2: Which of the following is not a positive displacement compressor?

a Centrifugal b Screw

c Vane d Piston

e Diaphragm

b intercoolers use water.

c the intercooler has less cooling capacity

c the intercooler has less cooling capacity

d intercoolers are installed between the compression stages

e aftercoolers are smaller

Test question

Question 4: What will become of dirt which is allowed

to enter the intercooler tubes while they are being

cleaned? It will:

a stay there

b vent to atmosphere

c be drawn into the first stage

c be drawn into the first stage

d be drawn into the second stage

e go directly into the receiver

Question 5: The discharge temperature of two stage compressor compared to single stage one is

a) Lesser b) Same c) Higher d) None

1 Water in compressed air

Air dryers

2

Water in compressed air

Water in compressed air

 When large quantities of air are compressed,

noticeable amounts of water are formed

 The natural moisture vapour contained in the

fully

vapour contained in the atmosphere is squeezed out like wringing out a damp sponge

 The air will still be fully saturated (100% RH) within the receiver

Drain

saturated air

Condensate

Water in compressed air

 The amount of water vapour contained in a sample of theatmosphere is measured as relative humidity %RH Thispercentage is the proportion of the maximum amount thatcan be held at the prevailing temperature

Grams of water vapour / cubic metre of air g/m 3

Water in compressed air

 The illustration shows four cubes each representing 1

cubic metre of atmospheric air at 20oC Each of these

volumes are at a relative humidity of 50% (50%RH) This means that they actually contain 8.7 grams of water

vapour, half of the maximum possible 17.4 grams

Water in compressed air

 When the compressor squashes these four cubic metres to form one cubic metre there will be 4 times 8.7 grams, but only two of them can be held as a vapour in the new 1

cubic metre space The other two have to condense out as water droplets

L

Water in compressed air

 4 cubic metres at 50%RH and 1000 mbar

atmospheric pressure contained in the

space of 1 cubic metre produce a

pressure of 3 bar gauge

 17.4 grams of water remain as a vapour

producing 100% RH (relative humidity)

producing 100% RH (relative humidity)

and 17.4 grams condense to liquid water

 This is a continuous process, so once the

gauge pressure is over 1 bar, every time

a cubic metre of air is compressed, and

added to the contained 1 cubic metre, a

further 8.7 grams of water are condensed

Air dryer – Absorber

Adsorber – Cooldryer

 There are several ways to

remove humidity from

compressed air

 Top picture: Absorber

Air flows from below

against through a stack of

against through a stack of

humidity absorbing

material to the exit on top

The material dissolves in

water and must be

replaced from time to

time

Air dryer – Absorber

Adsorber – Cooldryer

 Lower picture: Adsorber

Two chambers are filled with

a humidity binding material

Compressed air will pass

through one chamber while

the other is being

the other is being

regenerated with hot air The

material can be used for a

long time Regular switchover

necessary

Air dryer – Absorber

Adsorber – Cooldryer

 Center picture: Cool drying

The humidity diagram shows

that the water can be

condensed at low temperature

Compressed air therefore is

Compressed air therefore is

passed through cooling coils

Low temperature drier

 Humid air enters the first

heat exchanger where it is

cooled by the dry air going

out

 The air enters the second

heat exchanger where it is Dry air out

Humid air in

heat exchanger where it is

refrigerated

 The condensate is collected

and drained away

 As the dry refrigerated air

leaves it is warmed by the

incoming humid air

M Drain

Refrigeration

plant

 If 1 cubic metre of fully saturated compressed air (100%RH) is cooled to just above freezing point, approximately 75% of the vapour content will

be condensed out When it is warmed back to 20 O C it will be dried to nearly 25% RH

Low temperature drying

Low temperature drying

 If 1 cubic metre of fully saturated compressed air ( 100 % RH ) is cooled

to just above freezing point, approximately 75% of the vapour content will be condensed out When it is warmed back to 20 O C it will be dried to nearly 25% RH

Low temperature drying

 If 1 cubic metre of fully saturated compressed air ( 100 % RH )

is cooled to just above freezing point, approximately 75% of the

vapour content will be condensed out When it is warmed back

to 20 O C it will be dried to nearly 25% RH

Cooling unit

Air inlet Air outlet

Refrigeration dryer

 Using refrigeration methods, it is possible to achieve

dew points of between +2 and +5 °C

Refrigeration dryer

 The most common type of dryer today is the refrigeration dryer

 With refrigerated drying, the compressed air is passed through a

heatexchanger system through which a refrigerant flows

 The aim is to reduce the temperature of the air to a dew point which ensures that the water in the air condenses and drops out in the

quantity required.

 The air entering into the refrigeration dryer is pre-cooled in a heat

 The air entering into the refrigeration dryer is pre-cooled in a heat

exchanger by the escaping cold air It is then cooled in the cooling unit

to temperatures between + 2 and + 5 °C The dried compressed air is filtered.

 Before the compressed air is output into the network, the air is heated

to bring the air back to ambient conditions.

 Using refrigeration methods, it is possible to achieve dew points of

between + 2 and + 5 °C.

Adsorption dryers

 Adsorption: water is deposited on the surface of

solids The drying agent is a granular material (gel)

consisting almost entirely of silicon dioxide

 Usually two tanks are used When the gel in one tank

is saturated, the air flow is switched to the dry,

second tank and the first tank is regenerated by air drying

hot- The lowest equivalent dew points (down to – 90 °C) can be achieved by means of adsorption drying

Absorption dryers

Absorption dryers

 Absorption: A solid or liquid substance bonds a gaseous

substance Absorption drying is a purely chemical process Absorption drying is not of major significance in present-day practice, since the operating costs are too high and the

efficiency too low for most applications

 Oil vapour and oil particles are also separated in the

 Oil vapour and oil particles are also separated in the

absorption dryer The moisture in the compressed air forms

a compound with the drying agent in the tank This causes the drying agent to break down; it is then discharged in the form of a fluid at the base of the tank

 The mixture must be regularly drained and the fluxing agent must be regularly replaced

Fitting of water seperators

 From the compressor air

should flow to an

aftercooler (with large

compressors, this is

required by regulations)

 From here the air flows to

 From here the air flows to

an receiver after which the

cool dryer, adsorber or

absorber is installed It is

recommended to install

condensed water

collectors before and after

the water seperator

Test question

Question 1:

The basic function of air dryer in a compressor is:

a prevent dust from entering compressor

b storage and smoothening pulsating air output

c reduce the temperature of the air before it enters the

c reduce the temperature of the air before it enters the next state to increase efficiency

d to remove remaining traces of moisture after cooler

after-Test question

Question 2:

Which method of removing the moisture from

compressed air has the lowest operating cost?

a Adsorption

b Absorption

b Absorption

c Refrigeration

d Silica gel attachment

e Water separation sieves

Air receiver Air receiver

Air receiver

 The main purpose for the air

receiver is to store

pressurized air for future use

The air receiver ensures that

a steady supply of pressurized

air is available

air is available

 It also dampens piston

compressor pulsations caused

by the pumping action of

compressor pistons

Air receiver

 These are always installed to act as

an reservoir, to maintain an even

pressure and allow switch – on and

off periods for compressor control

Also required are:

Also required are:

- Pressure gause,

- Drain cock for condensed water,

- Shut – off valve

- Thermometer is recommended

Test question

Question 1: What components might be found at an air receiver?

a Draincock, safety valve, and lubricator

b Draincock, safety valve, and pressure guage

c Regulator, safety valve, and pressure switch

c Regulator, safety valve, and pressure switch

d Regulator, lubricator, and check valve

e Compressor, filter, and lubricator