COMPRESSED AIR SYSTEM OPTIMIZATIONieeegypt.org/wp-content/uploads/2017/04/CASO-Expert-Training.pdfCompressed Air System Efficiency Fact: Compressed air is an inefficient source of

COMPRESSED AIR SYSTEM

OPTIMIZATION

EXPERT TRAINING

1

Introduction toIntroduction to Compressed Air

1

1. Introduction to Compressed Air Systems1. Introduction to Compressed Air Systems

• Compressed air has 3 primary uses– Power

• As an energy source to perform work

– Process

2

Process• Air becomes part of a process

– Control • To stop, start or regulate the

operation of a machine

2


• A compressed air system includes both the supply side components and the demand

3

side components.


• Old Management Technique– Plant production is #1

priority

• New Management Technique– Plant productivity is the #1

prioritypriority– Plant compressed air

system must always be maintained

– Over supply of compressed air is acceptable, under supply is not acceptableMi i t

priority– The plant air demand must

always be supplied– The compressed air system

must be in balance with demand. Both over supply and under supply are unacceptable

– Compressed air pressure t b t bl P

4

– Minimum pressure must be maintained. Higher pressure is acceptable

must be stable. Pressures higher than required are unacceptable as are pressures lower than required.

3

Com

pres

sed

Air

Sys

tem

Opt

imis

atio

nD

efin

ed

Ther

e ar

e th

ree

basi

c w

ays

to o

ptim

ise

the

cons

umpt

ion

of a

co

mpr

esse

d ai

r sys

tem

:

1.P

rodu

ce c

ompr

esse

d ai

r mor

e ef

ficie

ntly

2.C

onsu

me

less

com

pres

sed

air

3.U

tilis

eth

e he

at o

f com

pres

sion

Sou

rce:

AS

ME

EA

-4

5

Com

pres

sed

Air

Sys

tem

Effi

cien

cy

Fact

:Com

pres

sed

air i

s an

inef

ficie

ntso

urce

of

ener

gy

and

shou

ld b

e us

ed w

isel

y.

Con

side

r thi

s:

•An

air

mot

or w

ith 0

,68

kW s

haft

outp

ut c

onsu

mes

50

m3 /h

r

6

•An

air

com

pres

sor c

onsu

mes

abo

ut 5

.6 k

W to

pro

duce

50

m3 /h

r at 7

bar

, or 8

tim

es a

s m

uch!

4

8

Compressed Air System Efficiency

2

4

6

hp

PowerLosses onSupply and

DemandSides

(includingheat of

compression

0

losses)

Input Powerto Electric

Motor

Shaft PowerRequired byCompressor

PowerLosses andUseful Work

Useful Work

Source: Compressed Air Challenge

Compressed Air System Cost

Compressed air power is costly

• The 0,68 kW compressed air motor shaft output costs RM 16 000 per year at 8 760 hours operation.

• An electric motor with a similar shaft output would consume about 0,85 kW and cost RM 2 430 per year to operate.

8

5

Compressed Air System Costs

System losses further increase the costs:

Typically 35 to 45% of compressed air is wasted to leakage andTypically 35 to 45% of compressed air is wasted to leakage and artificial demand before it gets to the user. And 10%+ may be wasted through inappropriate uses.

Artificial Demand – 10-15%

Inappropriate Uses – 5-10%

9

Production – 50%

pp pLeaks – 25-30%



Pressure differentials typically reduce end use pressure by 1Pressure differentials typically reduce end use pressure by 1 or 2 bar forcing discharge pressures higher. Compressor power increases 6 to 7% per unit output for every bar increase.

10

6



Air compressors often do not run at full efficiency due to poor control and lack of storage receiver capacity

60

80

100

120nt

kW

Inpu

t

11

0

20

40

0 20 40 60 80 100 120

Per cent Capacity

Per c

en

The Systems Approach

Application of a systems approach to a compressed air system assessment and resulting energy measures directs the focus towardsassessment and resulting energy measures directs the focus towards total system performance rather than individual component efficiency

• Understand compressed air point of use as it supports critical plant production functions

• Correct existing poor performing applications and those that upset system operationEli i t t f l ti l k tifi i l d d d

12

• Eliminate wasteful practices, leaks, artificial demand, and inappropriate use

• Create and maintain an energy balance between supply and demand• Optimize compressed air energy storage and air compressor control

Source: ASME EA-4

7

Life Cycle Costs

Typically over 75% of the lifetime costs of compressed air are energy relatedenergy related


13


Based on 30 cen per kWh blended rate 55 kW fully loaded compressor at 4200 hours over ten years.

Typical Compressor Operating Cost

Item: Typical 160 kW air cooled screw compressorDuty: Full load at 7 5 bar 4 200 hours per yearDuty: Full load at 7.5 bar, 4 200 hours per yearRate: 30 cen per kWh blended

Power at full load: 182.5 kWFlow: 505 l/sec Specific Power: 36.1 kW/ 100l/s

Energy Cost = kW x hours x rate

Energy Cost = RM 229 950 per yearPurchase Price = RM 189 540

14

8

Comparing Energy Usage and Efficiency

15

Three 160 kW compressed air systems are being evaluated in

Compressed Air System Comparisons

an existing plant :

1. Existing fixed speed air cooled load/unload compressor, standard refrigerated dryer, standard filter and small receiver

2 A new fixed speed load/unload compressor new refrigerated2. A new fixed speed load/unload compressor, new refrigerated dryer, oversized filter and large receiver

3. A VSD compressor, cycling refrigerated dryer, oversized filter and medium receiver

16

9

Compressed Air System Comparisons

Air cooled compressor, 8 bar 8 760 hour operation, peak flow 330 l/s average flow 175 l/s cost 0 3 cen per kWh330 l/s, average flow 175 l/s , cost 0,3 cen per kWh

Option 1 – Existing unit – Base Case

Ave Compressor Power = 134,5 kW

Dryer Power = 6,0 kW

17

Total Energy = 1 230 780 kWh

Specific Power = 80,3 kW/100 l/s

Electrical Cost = RM 369 200

Compressed Air System ComparisonsAir cooled compressor, 7 bar 8 760 hour operation, peak flow 268 l/s, average flow 133 l /s, cost 0,3 cen per kWhg p

Option 2 – New more efficient load/unload , larger storage, lower pressure, cycling refrigerated dryer, leak reduction

Ave Compressor Power = 85,1 kWDryer Power = 1,7 kW

18

Total Energy = 760 400Specific Power = 65,3 kW/100 l/sElectrical Cost = RM 228 100Saved = RM 141 100 or 38%Project Cost = RM 400 000

10

Compressed Air System ComparisonsAir cooled compressor, 7 bar 8 760 hour operation, peak flow 268 l/s, average flow 133 l /s, cost 0,3 cen per kWhg p

Option 3 – New VSD unit, medium storage, lower pressure, cycling refrigerated dryer, leak reduction

Ave Compressor Power = 46,0 kWDryer Power = 1,7 kW

19

Total Energy = 417 850 kWhSpecific Power = 35.9 kW/100 l/sCost = RM 125 400Saved = RM 243 800 or 66%Project Cost = RM 485 000

Compressed Air System Payback

Option Project Savings PaybackOption Project Cost

Savings Payback

O1 - Base 0 0 0

O2 - New load/unload RM 400 000 RM 141 100 2.8

O3 - New VSD RM 485 000 RM 243 800 2.0

20

11

Compressed Air System Incremental Payback

Option Project Savings PaybackOption Project Incremental Cost

Savings Payback Years

O1 - Base RM 235 000 0 0

O2 - New load/unload RM 165 000 RM 141 100 1.2

O3 - New VSD RM 250 000 RM 243 800 1.0

21

Artificial Demand• If the required• If the required

pressure is 5.5 bar • Operating at 7 bar

creates 2.8 m3/min of artificial demand

• 20% of the air that is• 20% of the air that is supplied to the system is wasted.

22

12


Finding leaks• soap connections• locate source of noise• ultra-sound device

Example:hole diameter: 3 mm air loss: 0.5 m3/min (6 bar gauge)0 5 m3/min x 60 min/h = 30 m3/h

23

0.5 m /min x 60 min/h = 30 m /h 30 m3/h x 8000 h/year = 240,000 m3/year

240,000 m3/year x cost/m3 = ????


Leakage losses

At RM 0.30/kWh, a 6 mm leak costs over RM 35,478 /year in power plus additional service on the compressed i i t

Hole diameter

1 mm2 mm4 mm6 mm

Air consumptionat 6 bar (g)

m3/min0.050.210.832 12

Loss kW

0.31.35.2

13 5

24

air equipment.

Class exercise: Calculate the cost over 4,000 hours.

6 mm 2.12 13.5

13


Leakage losses

Hole diameter

1 mm2 mm4 mm6 mm


m3/min0.050.210.832 12

Loss kW

0.31.35.2

13 5


25

6 mm 2.12 13.5 air equipment.

Class exercise: Calculate the cost over 4,000 hours.13.5 kW x 4,000 x 0.30 = RM 16,200Question: How much if at 7 bar?


Leakage losses

Hole diameter

1 mm2 mm4 mm6 mm


m3/min0.050.210.832 12

Loss kW

0.31.35.2

13 5


26

6 mm 2.12 13.5 air equipment.

Class exercise: Calculate the cost over 4,000 hours.13.5 kW x 1.06 x 4,000 x 0.30 = RM 17,170Question: If this leak was repaired how much would be saved?

14

1. Introduction to Compressed Air Systems1. Introduction to Compressed Air SystemsMeasuring leakage lossesby exhausting an air receiver

Leakage volume

Feed pipeshut offVR x ( pI - pF )

VL = T

VL = Leakage volumeV = Receiver volume

g(tools not in use!)

x 1.25

27

VR = Receiver volumePI = Initial receiver

pressurePF = Final receiver

pressureT = Measuring period

Example:VR = 500 litrespI = 9 bargpF = 4.5 bargT = 30 sec

VL =500 l x ( 9 – 4.5 )

30 sec= 75 x 1.25 = 94 l/s

Leakage losses in the compressed air system: 94 l/s

28

15


Measuring leak lossesby measuring loaded time of the compressor with end users shut off

Pressure gauge reading(bar(g))

T

VL = Leakage volume in m3/minVC = Compressor volumetric flow rate in m3/mint = Time units during which the compressor

ran on loadT = Total time of the measurement procedure

Example:Volumetric compressor flow rate V = 3 m3/minCompressor time on load t =t1+t2+t3+t4+t5 = 120 sec3

4

5

6

7

8

29

Time

Compressor time on load t t1+t2+t3+t4+t5 120 secTotal measurement time T = 600 sec

3 x 120600

= 0.6 m3/min = 20%1

2

3

c

1. Introduction to Compressed Air Systems1. Introduction to Compressed Air SystemsLeak measurement of the consumers

In factories where a large number of air tools, machines and

Using the two methods described previously, two measurements are carried out:

In factories where a large number of air tools, machines andequipment are used, hose connectors and valves often causeconsiderable leak losses.

A B

30

The difference between A and B represents the losses in the pneumatic tools, etc. and their fittings.

Tools, machines and equipmentare connected for normal operation(total leakage)

The shut-off valves upstream of the connectors of the consumers are closed (air distribution leakage)

16

Key Learning Points• Compressed air is a necessary utility for industrial p y y

plants.• For some production uses compressed is a process

variable.• Many systems waste 50% of more of the compressed

air that is consumed.• System management must focus on productivity rather

than traditional goalsthan traditional goals.• The Systems Approach is an integrated approach, not

component efficiency.• Generating compressed air is an inefficient energy

conversion.

31

Key Learning Points• Using air only when other alternatives are not Us g a o y e ot e a te at es a e ot

available.• Eliminating inappropriate uses of compressed air.• Reducing delivered pressure to the system

eliminates Artificial Demand.• Reducing the amount of leakage loss in the system.• Minimize Irrecoverable Pressure Loss.Minimize Irrecoverable Pressure Loss.• Operating compressed air systems at the lowest

practical pressure.• Optimize compressor control with a properly

implemented control strategy.

32

17

For more information:Wayne PerryTechnical DirectorKaeser CompressorsP O Box 946

Tom TarantoPresidentData Power Services8417 Oswego Road PMB 236

33

P.O Box 946Fredericksburg, VA 22404USA540 898 [email protected]

8417 Oswego Road PMB-236Baldwinsville, NY 13027USA315 635 [email protected]

1

2. Understanding 2. Understanding ggCompressed AirCompressed Air

1

2. Understanding Compressed Air2. Understanding Compressed Air

Power stationgrid system

transformeruser

What is compressed air?Compressed air is ...

... compressed atmospheric air

... a mixture of gases

... compressible

... an energy carrier

userair main

air treatmentAir center

air?

2

Proportional relationship between pressure, temperature and volume: still valid:

userair treatment

2


Basic units m = Meter

s Second

kg = Kilogram

A = Amperes = Second

K = Kelvin

A = Ampere

mol = Molar mass

Derived units N = Newton Pa = Pascal

3

N = Newton

bar = Bar

J = Joule

C = Celsius

Pa = Pascal

= Ohm

W = Watt

Hz = Hertz


Physical laws

COMPRESSED AIR is atmospheric air under pressureCOMPRESSED AIR is atmospheric air under pressure. That means energy is stored in the air. When the compressed air expands againthis energy is released as WORK.

pressure (energy)

4

EXPANSION

WORK

3


Components of air

oxygen21%

other gasses1%

5

nitrogen78%


Atmospheric pressure...

...is generated by the weightof the atmosphere. It is dependent on the DENSITYof the air and the height:

The normal atmospheric pressure at sea level is 1.013 bar (760 mmHg (Torr))

6

( g ( ))

4


Absolute pressure ...... is the pressure measured

from absolute zero

Gauge pressure ...

... is the practical reference pressure

atmospheric pressurepamb

from absolute zero.It is used for all theoreticalcalculations and is required invacuum and blower applications.

and is based on atmospheric pressure.

absolute pressure

7

vacuum100%

0%

absolute pressure

gauge pressurevacuum

(g) (g) (g) (g)Pg


Generally:Equivalents

105 Pa = 1 bar

1 MP 10 bF (F)

Definition of pressures

1 MPa = 10 bar

Gauge pressure1 bar = 14.5 psi(g)

1 hPa = 0.001 bar

1 bar = 10197 mmWC

1 bar = 750.062 Torr

Dimensions:

1 Pascal (Pa) =1 Newton (N)

1 m² (A)

Pressure (p) = Force (F)Area (A)

8

A = 1 m2

5


ambient air pressure1 bar (a)

Volume

7 m³ atmospheric

air volume

working pressure7 bar (a) = 6 bar (g)

9

1 working m³


Expansion:Volume

Ambient air pressure p0, V0

Working pressure7 bar (a)= 6 bar (g)Working

pressurep1, V1

10

The volume of atmospheric air decreases at an inverse ratio to the respective absolute pressures (at constant temperature,without taking humidity into account) 1

0

0

1

pp

VV

6


Temperature DensityRelativehumidityPressure

Definition of volumes

Volume accordingto DIN 1343(normal physical state)

Volume accordingto DIN/ISO 2533

Volume related

humidity

0°C =273.15K

1.01325bar 0%

1.294kg/m³

15°C =288.15K

1.01325bar 0%

1.225kg/m³

atmospheric atmospheric atmospheric

11

Volume related to atmosphere (normal state)

Volume related to operating state

atmospherictemperature

atmosphericpressure

atmospherichumidity variable

working temperature

workingpressure

variablevariable


Conversion of normal volume to volume according to DIN 1343

VN = Normal volume to DIN 1343VI = Volume at inlet conditionsTN = Temperature to DIN 1343, TN = 273.15KT = Maximum temperature at the installation in K

VI x TN x (pI - (Hrel x pD))pN x TI

VN =

12

TI = Maximum temperature at the installation in KpN = Air pressure to DIN 1343, pN = 1.01325 barpI = Lowest air pressure at the installation in barHrel = Maximum relative humidity in the air at the installationpD = Saturation pressure of the water vapor contained in the air

in bar, dependent on the temperature of the air

7


Extract from the table for the saturation pressure of water vapour at saturation

-10 0.00260-9 0.00280-8 0.00310-7 0.00340-6 0.00370-5 0.00400-4 0.00440-3 0.00480-2 0.00520-1 0.005600 0 00610

10 0.012311 0.013112 0.014013 0.015014 0.016015 0.017016 0.018217 0.018418 0.020619 0.022020 0 0234

30 0.042431 0.044932 0.047333 0.050334 0.053235 0.056236 0.059437 0.062738 0.066239 0.069940 0.0738

Saturation pressurepD (bar) at airtemperature t (° C)

13

0 0.006101 0.006402 0.007103 0.007404 0.008105 0.008706 0.009407 0.010008 0.010709 0.01150

20 0.023421 0.024522 0.026423 0.028124 0.029825 0.031726 0.033627 0.035628 0.037829 0.0400

41 0.077842 0.082043 0.086444 0.091045 0.096846 0.100947 0.106148 0.111649 0.117450 0.1234


Gas laws – Boyle’s Law

If the volume is reduced under constant temperature, the pressure increases.

Gas laws Boyle s LawIsotherms (constant temperature)

14

Heat dissipation

1100 VPVP

8


Isotherms (constant temperature)

Heat dissipation

p

p1T0 = T1

1

15

V

p0

V1 V0dV

0


Gas laws – Charles’ LawIsobars ( constant pressure )If heat is applied under constant pressure,The air volume behaves directly proportionalto its absolute temperature.

Isobars ( constant pressure )

00 TV

16

Application of heat11 TV

9


Isobars (constant pressure)

p

p0= p10 1

T

p0 = p1Application of heat

17

VV1V0 dV

T1

T0


A li ti f h t

Gas laws – Amonton’s LawIsochors (constant volume)

If heat is applied with constant volume, the pressure behaves directly proportional to the absolute temperature.

Application of heatIsochors (constant volume)

00 TP

18

11 TP

10


Isochors (constant volume)

p

p1

V0=V1

1

19

p0

V

T0

T1

0

Application of heatV0=V1


If th l i d d d h t t b di i t dHeat insulation

Adiabatic or Isentropic(no heat transfer)

If the volume is reduced and heat cannot be dissipated,temperature increases with the pressure

p

p1 1

p p

20

Vp0

V1 V0

T1T0

dV

0

11


Gas law relating to a closed system:Gas equation

p0 x V0 p1 x V1T0 T1

= = R = constant

p = pressure (bar (absolute))V = volume (m3)

21

T = temperature (K)R = special gas constants

e.g. R = 28.96 = 289.6

for dry air

bar·m³K

Jkg·K


Flow velocity in air lines

• A1 v2

A1

v1

A2v2

valid is:

22

V = flow volumev = velocityA = pipe sectional area

V = A1 x v1 = A2 x v2 A1A2

v2v1=

•

12


Flow profilepipe wall

border layer

23

flow velocity


Flow typesWe differentiate between:laminar (even) and turbulent (swirling) flow

24

13


Straight-line graphfor determining inside

Pipe length in m

Free air deliverym³/h m³/min

Insidepipe dia. (mm)

Pressure lossesbar

for determining insidepipe diameter (steps 1 to 8)

1

2

3

4

5

678

m³/h - m³/min

System-pressurebar (g)

25


Compressed air in motion

bar)

Pressure lossis dependent on:

sectional areavelocitypipe length

Pre

ssur

e (b

26

internal surface area of the pipelength (m)

14


PerformancePressure drop ...

... is caused by: Working press.bar (g) % kW

6.0 100 3.0

5.5 86 2.6

5.0 74 2.2

•high flow velocities •turbulence•internal friction (molecules)•friction on the pipe walls

Pressure drop lowers the performanceof the consumers, increasesthe cost of compressed air generation

27

4.5 62 1.9

4.0 52 1.6

Performance loss caused by pressure drop

the cost of compressed air generationand thus production too!


Minimum diameters of pipes

FADm3/min

working pressure 7.5 bar (g)

length of pipelineup to 50 m up to 100 m up to 200 m over 200 m

see straight-line graph

up to 12.5up to 15,0up to 17.5up to 20.0

2 1/2"2 1/2"2 1/2"

3"

2 1/2"2 1/2"

3"3"

3"3"

DN100DN100

28

pup to 25.0up to 30.0

3"3"

DN100DN100

DN100DN100

up to 40.0 DN100 DN100 DN 125

15


Flow resistance of fittingsexpressed in equivalent pipe lengths

fitting example

6 10 15 25 30 50 60

equivalent pipe length in m

pipe inside diameter in mm25 40 50 80 100 125 150

3 5 7 10 15 20 25

29

0,3 0,5 0,6 1 1,3 1,6 1,9

Total pipe length: Loverall = Lstraight + Lequivalent

or roughly: Loverall = 1,6 x Lstraight


Pressure dropIf the normal working pressure of a pneumatic tool is 6 bar (g),If the normal working pressure of a pneumatic tool is 6 bar (g), any increase above that pressure costs money.

Example:V = 30 m3/min demand at 7 bar (g) 160 kWAt 8 bar (g) approximately 6% more power is required, i.e. around 9.4 kW more

Costs:9.4 kW x 0.05 $/kWh x 4000 h/year = 1880 $/year (13,160 ZAR) !

30

Air main:On a well designed air piping system a pressure drop of 0.1 bar is normally expected.

The maximum pressure drop in the air piping systemshould be no more than 1.5 % of the working pressure

16


1. Main piping 0.03 bar2. Loop main (distribution) 0.03 bar

Pressure dropp ( )

3. Connecting lines 0.04 bar4. Refrigeration dryer 0.2 bar5. FRL unit and hose 0.5 bar

max. 0.8 bar

Overall pressure drop 0.8 bar1

2

3 5

31

Max. pressure at compressor 7.0 bar (g)Pressure at consumer 6.0 bar (g)Difference 1.0 bar 4


GThe right fittings

C E

32

AB

F

A. Valve (we recommend ball valves)B. Filter (separation of water and rust)C. Regulator (constant working pressure)D. Lubricator (mostly oil mist lubricators)E. Quick release couplings (flexibility at the workplace)F. Hose (length: 3-5 m)G. Tool balancer (reduction of work effort)

17


Points to be observed when sizing and gchoosing air system piping:

Cross-section of the pipe• Air consumption• Length of the piping

33

g p p g• Working pressure• Pressure drop• Flow resistance


Points to be observed when sizing and o ts to be obse ed e s g a dchoosing air system piping:

Pipe layout• Loop/spur main• Connecting lines

34

Connecting lines• Dead-end lines• Pipe connections• Fittings

18


Points to be observed when sizing and

Fittings andconnections• Types of outlets• Shut-off valves

• Lubricators• Particulate filters• Oil filters

choosing air system piping:

35

• Stopcocks• Condensate separators

O e s• Regulators• Hoses • Couplings


Points to be observed when sizing and choosing airPoints to be observed when sizing and choosing air system piping:

Choice of materials• Environmental conditions (humidity, temperature, chemical pollution of the air)• Quality of the air (moisture content oil content

36

• Quality of the air (moisture content, oil content,temperature)

• Costs• Expected working life

19


Uncontrolled Storage:With t P Diff ti l

Air OutWithout Pressure Differential

Quiet zone

Moisture separator

Protects downstream equipment from oil slugs

Air In

9.5 bar

9.5 bar

37

equipment from oil slugs

Prevents compressor from excessive cycling No “ Real” StorageNo “ Real” Storage


4,000 140

Uncontrolled pressure and flow

500

1,000

1,500

2,000

2,500

3,000

3,500

Pressure (psig)

Flow

(scf

m)

120

100

80

60

40

20

38

0

04:2

6:25

.00

05:0

1:25

.00

05

:36:

25.0

0

06:1

1:25

.00

06

:46:

25.0

0

07:2

1:25

.00

07

:56:

25.0

0

08:3

1:25

.00

09

:06:

25.0

0

09:4

1:25

.00

10:1

9:31

.00

10

:54:

31.0

0

11:2

9:31

.00

12

:04:

31.0

0

12:3

9:31

.00

13

:14:

31.0

0

13:4

9:31

.00

14

:24:

31.0

0

14:5

9:31

.00

15

:34:

31.0

0

16:0

9:31

.00

16

:44:

31.0

0

17:1

9:31

.00

17

:54:

31.0

0

18:2

9:31

.00

19:0

4:31

.00

19

:39:

31.0

0

20:1

4:31

.00

20

:49:

31.0

0

21:2

4:31

.00

21

:59:

31.0

0

22:3

4:31

.00

23

:09:

31.0

0

23:4

4:31

.00

Time

0

PressureFlowAverage Flow

20


Controlled Storage:With Pressure Differential

Air Out

7 5 b

Flow Controller

With Pressure Differential

Quiet zone

Moisture separator

Protects downstream equipment from oil slugs

Prevents compressor from excessive cycling

Air In

9.5 bar

7.5 bar

3 m3

6 m3 Useable Storage!

39

y g

PLUS 6 m3 of useable air in storage!

Pressure DifferentialCreates Stored Energy!

2. Understanding Compressed Air2. Understanding Compressed Air Flow

Pressure (Before controller)

Average Flow (Before controller)

Pressure (w/ controller)

Average Flow (w/ controller)Controlled pressure and flow

1,500

2,000

2,500

3,000

3,500

4,000

Pressure (psig)F

low

(scf

m)

120

100

80

60

40

140

40

0

500

1,000

04:2

6:25

.00

05:0

1:25

.00

05:3

6:25

.00

06:1

1:25

.00

06

:46:

25.0

0

07:2

1:25

.00

07:5

6:25

.00

08:3

1:25

.00

09

:06:

25.0

0

09:4

1:25

.00

10:1

9:31

.00

10:5

4:31

.00

11

:29:

31.0

0

12:0

4:31

.00

12:3

9:31

.00

13:1

4:31

.00

13

:49:

31.0

0

14:2

4:31

.00

14:5

9:31

.00

15

:34:

31.0

0

16:0

9:31

.00

16:4

4:31

.00

17:1

9:31

.00

17

:54:

31.0

0

18:2

9:31

.00

19:0

4:31

.00

19:3

9:31

.00

20

:14:

31.0

0

20:4

9:31

.00

21:2

4:31

.00

21:5

9:31

.00

22

:34:

31.0

0

23:0

9:31

.00

23:4

4:31

.00

Time

)

0

20

21


41

1

3. 3. Understanding Compressors & Their Application

1

3. Understanding Compressors & Their Application

Types of Compressors

2

2


Compressor types

ejector centrifugal-turbo

axial-turbo

rotary reciprocating

displacementcompressor

dynamic compressor

3

vane liquidring

screw rotaryblower

labyrinth diaphragm

y p g

piston crosshead free-piston

single-rotor double-rotor

helical


Reciprocating compressorsi l / t tsingle / two stage

Note thedifference:

- single / two stage- single acting / double acting

Installation: - portable

4

- stationary

Application: (single stage)

- common 10 bar- boosters 35 bar

3


Double-actingwith crosshead

Application:High pressure, up to 1000 barin combination with screw compressors.Compression of gas

5


Reciprocating compressorClearances that affect efficiency

upper piston clearance(dead space)

Clearances that affect efficiency

6

machining tolerances clearances in

valves andvalve recesses

constructionalpeculiarities

4


Effective air delivery with reciprocating compressors

Inlet pressure drop leakage losses heating ofinlet air detrimental

clearancesdisplacement volume

losses

7

Effective air delivery


1 bar absolute8 bar

top deadcentre

stroke

Upper piston clearance(dead space)

8

bottom dead centre

5


1 bar absolute8 barupper clearance

back expansion

stroke

top deadcentre

bottom dead centre

9

dead centreV is lost from

the displacement


Compression

air escapes pastthe piston rings

Compression

10

losses

the piston ringsinto the crankcase

6


inlet filter

losses caused by throttlingand filter contamination

Suction

11


Reciprocating compressors

Volumetric efficiency of singleand two stage compressors 2-stage

1-stage

ffici

ency

12

Volumetric efficiency =theoretical displacement

free air delivery

pressure

Volu

met

ric e

f

7


Rotary Screw compressors

13

• Single Stage Rotary • Two Stage Rotary


• Single Stage Rotary Screw

• Two Stage Rotary Screw

14

8


Rotary Screw compressorscompressedair

fluid-air mixture

cooled fluid

Construction:

2nd stage, Separator elementa) coarse filter

layer

Fluid separation:

15

fluid with heat of compression

thermostaticvalve

fluid filter

hot fluid

1st stage,centrifugal

b) fine filter layer


Efficiency - comparison of specific power consumption

Pspec =P* * depending on reference point:- compressor shaft power

Specific power consumption* = power* in kW

Effective FAD in m3 / min

16

Pspec V

p p- motor output power- electric power input

9


Function of the fluid in a lubricated rotary screw

First task:

Second task:Third task:

Fourth task

heat transfer, discharge temperatureapproximately 75 - 80 oC

lubrication of bearings

sealing the gap between rotors andcasing, prevention of metallic contactabsorbing dust,sulphur etc

17

sulphur, etc.


compressed air inletFluid and aftercooler:

compressed air inlet80 °C

cooling air inlet20 °C

cooling air outlet

18

compressed air outlet26 °C

g40 °C

Delta-t = 6 K

10


98-99%

2nd stage, fluidFluid separationseparator element

a) coarse filter layerb) fine filter layer

19

1st stage,centrifugal


Rotary tooth compressors

quieter running thanreciprocating compressors Inlet channel

Advantages:

Disadvantages:

compressors

20

high power consumptionmore expensive8 bar max. gauge pressure

Air discharge

11


Rotary tooth compressor

21


Rotary sliding vane compressors• single shaft rotary compressor• single shaft rotary compressor

• poor efficiency at high pressures

• high remaining oil content with clean oil injection and oil mist separator

• high maintenance costs to maintain constant efficiency

22

Main applications:2 - 5 barVacuum down to 1 x 10-3 bar

12


Rotary Blowers

Characteristics:capacity: up to 1200 m3/minair flow: 2 or 3 pulsations per working cyclepressure range: - 0.5 to +1 bar (g)speed: 300 to 11000 min-1

Rotary Blowers

23

p


Scroll compressors

air delivery: up to 0.5 m3/minair flow: constant, no pulsationpressure range: up to 10 bar (g)speed range: up to 3100 min-1

24

1 Gas chamber 4 Oscillating spiral 6 Suction 6 Suction2 Inlet 5 Fixed spiral 7 Discharge3 Discharge 8 Compression

13


Scroll compressorSuction chamberInlet

21

Rotating spiral

Discharge

Pressure chamber

Fixed spiral

25


ROTARY SCREW COMPRESSOR CONTROLS

26

14

Load / Unload Control

27

Load / Unload ControlAverage kW vs Average Capacity w ith Load/Unload Capacity Control

120

40

60

80

100

Per c

ent k

W In

put

28

0

20

0 20 40 60 80 100 120

Per cent Capacity

1 gal/cfm 3 gal/cfm 5 gal/cfm 10 gal/cfm

15

Inlet Valve Modulation Control

Rotary Compressor Performance with Inlet Valve Modulation

40.0

60.0

80.0

100.0

120.0

nt k

W In

put P

ower

Rotary Compressor Performance with Inlet Valve Modulation

29

0.0

20.0

0 20 40 60 80 100 120

Per c

en

Per cent Capacity

Inlet modulation - No Blowdown

Variable Displacement Control120.0

Rotary Compressor Performance with Variable Displacement

40.0

60.0

80.0

100.0

Per e

cnt k

W In

put P

ower

30

0.0

20.0

40.0

0 20 40 60 80 100 120Per cent Capacity

Rotary Compressor Performance with Variable Displacement

16

Variable Speed ControlVariable Speed Lubricant Injected Rotary Screw Compressor Package

120.0

40.0

60.0

80.0

100.0

Per c

ent k

W In

put P

ower

31

0.0

20.0

0 20 40 60 80 100 120

Per cent Capacity

%kW input vs % capacity With unloading With stopping

©1998 Compressed Air Challenge

Variable Speed Control“Control Gap”

eman

d (m

3 )

Max VFD Output

Base + Max VFD Output

Base +Min VFD Output

Fixed Speed Compressor10.0

12.5

20.0

CONTROLGAP

32

32

12:00a 8:00 a 5:00 p 12:00a

De

Min VFD OutputFixed Speed Compressor

Base Load 10 m3/min2.5

17

Variable Speed ControlEliminating “Control Gap”

2 x Base +Min VFD Output16.5CONTROLOVERLAP

man

d (m

3 )

Max VFD Output10.0

Base + Max VFD Output17.0

Base +Min VFD Output9 5CONTROLOVERLAP

2 x Base + Max VFD Output24.0

33

33

12:00a 8:00 a 5:00 p 12:00a

Dem

Min VFD OutputFixed Speed #1 Compressor

Base Load 7 m3/min2.5

9.5 OVERLAP

3. Understanding Compressors

DYNAMIC AIR COMPRESSORS

34

18


Turbo compressors

Centrifugal turbo compressorCentrifugal turbo compressor

35

Characteristics:Capacity: 35 - 1200 m3/minStages: 1 - 6Pressure range: 3 - 40 bar (g)Speed range: 3000 - 80000 min-1


Characteristics:Capacity: 600 - 30000 m3/minStages: 10 - 25Pressure range: 0 - 6 bar (g)Speed range: 6000 - 20000 min-1

Axial compressor

36

19


Centrifugal turbo compressor

centrifugal impeller

37

Air Flow

Drive axis

Air Flow


Axial compressor

Axial impeller

38

Drive axisAir Flow Air Flow

20

Centrifugal Compressors

• Most Common Dynamic CompressorMost Common Dynamic Compressor– Relatively easy to install

– Attractive first cost esp. larger capacities

– 500 Hp (2000 cfm) -> 15,000.. 20,000 cfmp ( ) , ,

– Efficient operation• Low Specific Power while operating in turndown range• Very inefficient when operating in blow-off

Centrifugal Compressors• Smaller size centrifugals now availableg

– Over lap in performance with large positive displacement compressors

– More combined systems with a mix of positive displacement and centrifugal machines.

• Dynamic Control -> Constant Pressure

• Displacement Control -> Pressure Band

• Special Considerations when Controlling Mixed Systems

21

Centrifugal Compressors• Centrifugal Compressor Driversg p

– Range 200 Hp through 3,500+ Hp

– Electric motors are common• 208, 230/460, & 575 volt / 3 phase / 60 Hz• 220, 380-400 volt / 3 phase / 50 Hz• Synchronous 1.0 or 0.85 leading optional > 500 Hp• Large compressor motors medium voltage

– 2,300 or 4,160 volt / 60 Hz; 3600 volt / 50 HzMedium Voltage (1kV 35 kV) * Medium Voltage ANSI/IEEE 1585 2002– Medium Voltage (1kV - 35 kV) Medium Voltage - ANSI/IEEE 1585-2002 [It is assumed that this is ac.]

– Other air compressor drivers• Engine drive, natural gas and diesel• Steam Turbine drive• Gas turbine drive in larger sizes


Construction of a Centrifugal compression stage

Impeller blades

Air Flow

g p g

42

Impeller

casing

22


Centrifugal impeller velocities

At inletC1 = velocity of the air to be compressedU1 = peripheral speed of the compressor

impeller W1= relative velocity between air and

compressor impeller

At outletC2 = velocity of the air to be compressed

43

U2 = peripheral speed of the compressor impeller

W2 = relative velocity between air and compressor impeller


centrifugal impeller, singlesided

di ti fImpeller profile direction of rotation

Impeller profilebackward-bent impeller vanes

44

air flow

23


Turbo compressor: Throttle controlTurbo compressor: Throttle control

45

Partial load


Turbo compressor: Throttle controlu bo co p esso ott e co t o

46

Full load

24


Turbo compressor: Volume controlInlet guide vanes - Full load

47


T b V l t lTurbo compressor: Volume controlInlet Guide Vanes – Closed

48

Partial load

25

Centrifugal Compressor Performance• Dynamic Compression

– Air enters the eye of the impeller

– Velocity increases to the impeller tip

– Air enters the diffuser and volute

– Velocity decreases energy converts to pressure

– Air exits to the inter-stage

– The process repeats

Centrifugal Compressor Performance

rge

e • Dynamic Compression

Headpsig

Surg

Line

DesignPoint

Chokeor

StonewallRegion

• Dynamic Compression– Flow –vs – Pressure –

Power Curve

Flow (cfm)

PowerbHp

26


rge

e of m • Dynamic Compression

Headpsig

Surg

Line

DesignPoint

Chokeor

StonewallRegion

Locu

s o

Max

imum

Effic

ienc

y

Dynamic Compression– Flow –vs– Pressure – & Power Curve – with Locus of Maximum

Efficiency

Flow (cfm)

PowerbHp

Centrifugal CompressorPerformance

Surg

eLi

ne

• Dynamic Compression

Headpsig

DesignPoint

Chokeor

StonewallRegion

Throttling

Blow-offExcess Flow

100 %

100 %

Dynamic Compression– Throttling Range – Blow-off

Flow (cfm)

PowerbHp

MinimumSafe Flow

80% (Typical)

Constant PowerDuring Blow-off

100 %

100 %

80 %

27

Centrifugal CompressorPerformance


Headpsig

Surg

eLi

ne

DesignPoint

Chokeor

Stonewall

Throttling

Blow-offExcess Flow

110 psig

100 psig

90 psig

120 psig Positive

DisplacementCompressor

Artificial Demand

Flow (cfm)

StonewallRegion

PowerbHp

MinimumSafe Flow

80% (Typical)


100 %

100 %

80 %

80 psigSystem Target

Pressure

28



29


Head

Surg

eLi

ne

Headpsig

DesignPoint

Chokeor

StonewallRegion

Throttling

Blow-offExcess Flow

100 %

110 psig

100 psig

90 psig

80 psig

120 psig Positive

DisplacementCompressor

System Target

Pressure

Storage Delta-P

Flow (cfm)

PowerbHp

MinimumSafe Flow

80% (Typical)


100 %

100 %

80 %


• Major HVAC Equipment Manufacturer• Major HVAC Equipment Manufacturer– Multi-building site 3.5 million sq. ft.

– Power House multiple mixed compressors

– 3 additional centrifugals in 3 locations

– Operating with multiple machines in blow-off

30


• Project Goals• Project Goals

– Cost effective reduction in energy use

– Improve system reliability

– Consistent pressure to support production

– Eliminate compressed air related downtime

Centrifugal Compressor Performance• Project Implementationj p

– $ 23,000 Assessment– $ 68,000 (1) Flow & (3) backpressure controls– $ 8,000 reuse (2) 30,000 gal LP Tanks– $ 47,400 (14) Thermal mass flow transducers– $ 39,900 (4) microprocessors, BMS– $ 10,300 (10) Digital power kW / kWh meters

$ 96 800 E i i I t ll ti T i i– $ 96,800 Engineering, Installation, Training

– $ 293,600 Total Project Cost– 36% Reduction in Energy Use– 3.7 Mwh Annual Energy Savings

31


• Project Life Cycle Cost• Project Life Cycle Cost– $ 293,600 Total Project Cost– $ 280,000 Annual Energy Savings– Simple Payback 1.05 years

– 3.7 Megawatts Annual Energy Savings– 15 year project life $4.2 million total savings


• Centrifugal Compressor MaintenanceCentrifugal Compressor Maintenance– Routine operational checks and maintenance items are

critical.

– Minor maintenance items that are not repaired can result in major failures.

– Check capacity and surge controls, along with safety shutdowns

– Other checks per the manufacturer’s recommendations

32


• Centrifugal Compressor MaintenanceCentrifugal Compressor Maintenance– Centrifugal compressors are less forgiving than other

designs.

– Routing checks and maintenance are important epically in harsh environments.

If there is a history of marginally effective routine– If there is a history of marginally effective routine maintenance, consider alternatives.

– Run to failure maintenance of centrifugal compressors is very expensive.


• Key Points– There are two broad categories of industrial air compressors, positive

displacement and dynamic.

– Reciprocating compressors are positive displacement compressors.

– Rotary screw compressors are also positive displacement compressors.

– Rotary screw compressors are the most common type of industrial air compressor.

64

compressor.

– There are many different types of part load capacity control for rotary screw compressors.

– Different types of part load capacity control have different part load power characteristics.

33


• Key Pointsy

– Centrifugal air compressors are the most common type of dynamic compressor used by industry.

– Aerodynamic design determines the head -vs- flow performance curve for centrifugal air compressors.

65

– Operating centrifugal compressors with blow-off control can be extremely inefficient.

– Operating in the stonewall (or choke) region of a centrifugal compressor's performance range is in efficient.


• Key Pointsy

– When operating multiple centrifugal air compressors in a system it is preferable to throttle multiple compressor as opposed to operating in blow-off.

– When operating a system using a combination of positive displacement and centrifugal compressors requires special

tt ti t t l t t d th t '

66

attention to control strategy and the system's pressure profile.

– Performing poor routine maintenance for centrifugal air compressors can lead to expensive failures of major air compressor components.

1

4. 4. Understanding Air gTreatment

1

4. Understanding Air Treatment

Impurities in the air

2

Regardless of which type of construction, all compressorsdraw in the impurities in the air and concentrate them many times

2


Solid particles in the air%

3

Size in micron5-10µm 10-20µm 20-40µm 40-80µm0-5µm


Overall hydro carbon concentrationMean daily value (mg/m3)

10

12

14

16mg/m3

Mean daily value (mg/m )Location: a small German town

Period: July 1992

4

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 310

2

4

6

8

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

3


Sulphur-dioxide (SO2) concentrationPeriod: July 1991 - June 1992

0·08

0·10

0·12

0·14

ppm

Period: July 1991 June 1992Location: a small German town

5

0

0·02

0·04

0·06

0 08

Jul-91 Aug-91 Sep-91 Oct-91 Nov-91 Dec-91 Jan-92 Feb-92 Mar-92 Apr-92 May-92 Jun-92Jul-91 Aug-91 Sep-91 Oct-91 Nov-91 Dec-91 Jan-92 Feb-92 Mar-92 Apr-92 May-92 Jun-92


mg/m3

Concentration in mg of mineral oil / m3 airTime period 8:00 - 17:00

Gear grinding workshop

Drilling workshop

Turning shop

Other

mg/m Time period 8:00 17:00

6

4

4. Understanding Air TreatmentQuality classification of compressed airto ISO 8573-1: 2001 (E)

ISO

8573-1

Class

Solid particle content Moisture contentOil

contentmax. number of particles per m³ sized d [μm]

µm mg/m³

PDP / (x=liquid water content g/m³ ) mg/m³ 0,1 0,1< d 0,5 0,5< d 1,0 1,0< d 5,0

0 as specified by the equipment user or supplier and more stringent than class 11 - 100 1 0 - - -70 °C 0,012 - 100.000 1.000 10 - - -40 °C 0,13 - - 10.000 500 - - -20 °C 1,0

7

4 - - - 1.000 - - +3 °C 5,05 - - - 20.000 - - +7 °C -6 - - - - 5 5 +10 °C -7 - - - - 40 10 x 0,5 -8 - - - - - - 0,5 x 5,0 -9 - - - - - - 5,0 x 10,0 -


Air quality downstream of the compressor

8

5


CONDENSATE:

9

This compressor with an air delivery of 5 m3/min (referred to +20° C, 70 % moisture carry-over

and 1 bar absolute) transports around 30 litres ofwater into the air main during an 8 hour day


CONDENSATE:around 20 litres of this water

accumulates in the aftercoolerin the form of condensate (at

7 bar gauge working pressureand an outlet temperature of

+30° C at the aftercooler)

10

6


CONDENSATE:As the air cools down further the remaining 10 litres

accumulate at convenient points in the air main

the results are expensivemaintenance, repairs and d f t i

11

defects in production


Water Content of Ambient AirDewpoint g/m3

+100+90+80+70+60

588.208417.935290.017196.213129.020

Dewpoint g/m3

+6+4

+0-10

7.2466.3595.5704.8682.156

+2

12

+50+40+30+20+10+8

82.25750.67230.07817.148

8.3429.356

-20-30-40-50-60-70

0.880.330.1170.038

0.00330.011

7


P d i

pressuredewpoint in degrees °C.

Pressure dewpoint -atmospheric dewpoint

Example:Pressure dewpoint: 2-3 °C.Working pressure: 7 bar

13

Working pressure: 7 barAtmospheric dewpoint: - 25 °C.

atmospheric dewpoint in °C.

4. Understanding Air TreatmentCompressed air drying methodsDiffusion

Solid drying

Adsorption (desicc.)

Liquid drying method

Absorption

SorptionCondensation

Mechanism Cooling

RefrigerationCoolingOverpressurisation

14

Regeneration

Warm airregeneration

HeatedHeatless

Solid drying Deliquescentdrying

8


Why Dry Compressed Air?Untreated air

dirt

oil aerosols

moisture

Problems in the air main

corrosion

pressure loss

contamination

Problems with equipment

contamination

tool wear

scrap

Why Dry Compressed Air?

15

freezing

maintenance

p

downtime

COSTSCOSTS

4. Understanding Air Treatmentair outlet

air inletCondensate separation

cyclonicair movement

deflectorTo ensure sufficient separation,liquids and heavy particles are

subjected to centrifugal forces athigh rates of flow.

The degree of separation is around 95% t 6 b 20 °C d th i l

16

condensate collection

air movement95% at 6 bar, 20 °C and the nominalvolumetric flow rate. The pressure

drop is approximately 0.05 bar .

9


Condensate separation

The compressed air discharged from the aftercooler of a compressor is normally 100% saturated with water vapor. If the temperature of the compressed air falls, the water vapor condenses.

A coarse separation of the condensate

17

compressedair outlet

condensatecollector

condensatedrain

A coarse separation of the condensate can be achieved if the pipework and the compressed air outlets are installed as shown in the illustration.


Condensate separation

• used directly at the takeoff point• mechanical filter • rotating movement• deflection plate• condensate drain (important!)

Fine filter

18

condensate drain (important!)

10


Simplest methodDisadvantage: high energy requirement

Over-compressing

Suction of atmospheric air,

high compression e.g. 300 bar (g),

Example:

High-voltage safety switchWorking pressure 15 bar (g)Preliminary compression to 300 bar (g)

Manufacture of high pressure cableWorking pressure 0.5 bar (g)Preliminary compression to 30 bar (g)

19

cooling the airand separationof condensate,

decompression to15 bar (g).

high humiditylow humidity


Refrigeration drying

1. Air inlet2. Air to air heat exchanger3. Refrigerant to air heat exchanger4. Refrigerant compressor5. Condensate separation,

automatic condensate drain

20

6. Compressed air outlet

11

4. Understanding Air TreatmentHigh Inlet Temperature Refrigerated Dryer

Description:

Air inlet temperatures up to 82 °C Centriflex separator system Automatic, float-controlled

condensate drain

Ideal for reciprocating compressors

Description:

Advantages:

21

Pressure dew point +10 °C : selected to suit the practical requirements of reciprocating compressor operation

Hot gas-bypass valve for constant PDP


The hot-gas bypass controller allows high-pressure refrigerant gas to flow g yp g p g gto the inlet of the refigerant compressor under fluctuating load.

This ensures constant temperature cooling of the compressed air.

> no pressure dew point fluctuations> no danger of freezing

22

12

4. Understanding Air TreatmentAir inlet

Separator systems

First stage of separation:A special stainless steel insert separates all particles larger than 10 micron, using the basic principle of centrifugal force and deflection. The re-usable separator is fabricated as a

for refrigeration dryersCentriflex

Displaced holes

23

The re usable separator is fabricated as a cartridge and is easy to remove for cleaning.

Air outlet


Separator systems for compressed air dryersType: Zentri-Dry

mesh of stainless steel

air inlet

air outletwaterseparatorsystem

Type: Zentri Dry

24

condensate

air inlet

stainless steel housing

13


Water Vapor Outlet Water Vapor at Atmospheric Pressure

Air Inlet Air Outlet

Water Vapor Outlet

25

Membrane Dryer


filler neck for toppingup the drying medium

Absorption dryingmedium

dry airdrying

medium

Chemical processSolid soluble drying mediumDeliquescent drying medium

Periodic renewal of the drying mediumDewpoint: + 15 ° Celsius

Low compressed air inlet temperatures

26

predrying

condensate

humid air

14


Application:Desiccant drying - heatless

Application:Systems subjected to freezing.High ambient temperatures.Extreme requirements of air quality.

1 microfilter (0.01 µm, 0.01 ppm)2 changeover valve

27

g3 flow diffuser4 desiccant bed: moisture adsorption5 outlet collector6 particulate filter 1 µm7 purge (regeneration ) air valve8 desiccant bed: regeneration9 purge air exhaust silencer

Design of the heatless regenerating desiccant dryers 100 % desiccant volume100 % air flow35 °C inlet temperature

Standard Cycle

10

time (min)

4 min regenerating

0.5 min pressurising0.5 min standby

35 C inlet temperature7 bar (g)pressure dew point - 40 °C

Regenerating air requirement:average 14 %

+ chamber filling 1 %

total average 15 %

28

0

5

5 min drying

g g

Regenerating air (max.)

15 % x 5 min

4.5 min 17 %

15

Conventional dryers80 % desiccant volume

100 % air flow35 °C inlet temperature

Standard Cycle

10

time (min)

4 min regenerating

0.5 min pressurising0.5 min standby

p7 bar (g)pressure dew point - 40 °C



total average 18 %

29

Regenerating air (max.)

18 % x 5 min

4.5 min0

5

5 min drying

4 min regenerating

20 %

Economy Dryer

60 % desiccant volume100 % air flow35 °C inlet temperature

Economy Cycle

10

time (min)

35 C inlet temperature7 bar (g)pressure dew point - 40 °C



total average 24 %

30

0

5

2.5 min drying

2 min regenerating0.25 min pressurising0.25 min standby Regenerating air (max.)

24% x 2.5 min

2.25 min 27 %

16


Desiccant drying -i t ll h t d

- integrated heating rods(desiccant not heated evenly duringregeneration)

- low purge air requirement (cooling,pressure build-up)

internally heated

31

- constant dry, oil-free and cleancompressed air

4. Understanding Air TreatmentDesiccant drying - externally heated

1 microfilter (0.01 µm, 0.01ppm)2 changeover valve3 flow diffuser4 desiccant bed: adsorption 5 outlet collector6 regeneration (purge) valve7 particulate filter

32

8 desiccant bed: regeneration 9 purge air inlet

10 purge air blower11 purge air heating12 purge air outlet

17


1 microfilter (0 01 µm 0 01ppm)

Desiccant drying, externally heat regeneratedPrinciple of no compressed air loss: 1 microfilter (0.01 µm, 0.01ppm)

2 changeover valve3 flow diffuser4 desiccant bed: adsorption5 outlet collector6 particulate filter7 purge air blower

Principle of no compressed air loss:

11

33

8 desiccant bed: regeneration 9 purge air heating

10 changeover valve11 purge air inlet12 purge air outlet

12

7 microfilter 0.01µm8 changeover valve9 flow diffuser

10 desiccant bed11 outlet collector12 particulate filter13 blower14 purging (regeneration) of drying

1 compressed air inlet2 air/air heat exchanger3 refrigerant/air heat

exchanger4 refrigerant compressor5 automatic condensate drain 14 purging (regeneration) of drying

medium15 purge air heating16 changeover valve17 purge air recovery18 cooling/purge air outlet

5 automatic condensate drain6 compressed air outlet

12

15

171311

34

5 18

14

16

18


100 %Absolute

Refrigerationdryers

Adsorptiondryers

Absolutehumidity Ranges of

dryer application

35

020400 %

-40-20

After-cooler

Pressure dewpointt


Pressure dewpoints for some areas of application

Area of application Required pressure dewpoint in °C

Workshop air - indoor pipework

Paint spraying

Instrument air

Air motors

10 to - 10

10 to - 25

10 to - 40

10 to - 40

36

Sand blasters

Pneumatic tools

Packaging

Plastics industry

5 to 0

5 to - 25

5 to - 25

5 to - 40

19

4. Understanding Air TreatmentHow large are the impurities in the air?

Description: vapour / mist / smoke dust fog: spray rain

Perception: Description: microscopic visualPerception: Description: microscopic visual

Falling time at 1 m heightSec.

Min.

foundry sandheavy industrial smogwater mist

carbon dusttraffic dust

cement dustpollen

plant sporesbacteria

metallurgical dust

oil mistoil vapoursVirusestobacco smoke

paint spray mist

Influence of the Brownian Molecular movement

37

tobacco smokegas molecules

pore dia, activ. carbon, silica-gel, etc.

centrifugalnormal

heavybag-typeair filter

separation and filtration performance

Particle size in microns


Permissible particle sizes

Compressed airusage

Permissible particlesize in micron

rotary vane air motorspercussion tools

cylindercontrollers

40 - 20

20 - 5

p

38

control systems. instru-ments, spray guns

fluidic elements, phar-maceutics. electronics

pure breathingair

5 - 1

< 1

0.01

20


Current hydro carbon carry-over limits

Application Max. hydro carbon carry-overin compressed air in mg/m3

Working airNormal breathing air

< 5

for various applications

39

Testing air

Pure breathing air

Oil-free air

< 1

< 0.5

< 0.003


Prefilter

Streamed from the inside to the outside.Used as a liquid filter

Principle the same as all deep bed filters

used as a coarse filter for 100% saturated compressed air (or for water vapor components in the liquid phase)

40

Principle the same as all deep-bed filters

21


Particulate filter

Streamed from the outside

used as dust filterfor dried air (e.g.downstream of adesiccant dryer)

41

Streamed from the outside to the inside. Used as surface filter


MicrofilterMicrofilter

0.01 to 0.001 micronfor liquids(aerosols) and particles

42

Streamed from the inside to the outside. Used as a deep-bed filter

22

4. Understanding Air TreatmentHow does the microfilter work?

contaminated air filter medium (deep-bed filter) technically oil-free clean air

43

Direct interception

Impact

Diffusion /Coalescence


Coalescing filter behaviour in the partial load range

0 010

0.015

0.020

0.025

Rem

aini

ng o

il m

g/m

³

Filter (old)

44

10 20 30 40 50 60 70 80 90 100 110 120 130

0.005

0.010

Loading (flow in %)

Filter (old)Filter (new)

23


Quality of inlet air:Activated carbon adsorberQuality of inlet air:

hydro carbon content 0.01 m

• long contact time of the air and activated carbon bed

• long and reliable life

Particulate

filter 1 µm

(recommended)

45

g

• hydro carbon indicator for continuous quality control

Quality of outlet air:

hydro carbon content 0.003 mg/m3


Condensate drainage

46

Reliable drainage must be ensured at all condensate collectingpoints of the air main

24


Condensate drains: float type

Drainage occurs only when sufficient condensate has collected

condensate inlet

air back flow line connection

47

No compressed air blowoff

Regular maintenance required

manual valvecondensate

outlet


Condensate drains: solenoid valve,

1

3

2

1 ball valve2 dirt trap3 solenoid valve with

integrated or externaltimer

,timer controlled

48

• automatic and regular drainage• interval 1.5 to 30 min• opening period 0.4 to 10 sec• condensate can be directed into a disposal canister

25


Condensate drains: Electronic level-sensing typeCapacitive level sensingAutomatic pressure matchingSelf-monitoringVolt-free alarm contact

49

2 collection chamber 9 discharge pipe6 level sensor8 valve seat

1 condensate inlet 4 solenoid valve2 collection chamber 5 valve diaphragm

3 pressure balance line


What’s the reason for treating condensate?

50

Regardless of which type of construction, all compressorsdraw in the impurities in the air and contentrate them many times

26


Condensate: Oil-Water separator

1 condensate inlet2 expansion chamber3 separating tank: gravitational separation4 oil overflow drain5 oil collector tank6 prefilter: retention of solids 7 adsorption filter: retention of oil particles8 water drain (clean water)

51

Used to separate condensate dispersions

( )


Pollutants in the condensate of oil-freed il l d it

Sample

oil-free

fluid-injected

oil-free

fluid injected

HC mg/l

4.2

7.1

7

0 1

Ph Cu mg/l

7 1

6.6

5.5

Zn mg/l

0.75

1

0.22

0 04

Cl mg/l

1.3

1

2.4

1

Pb mg/l

0.2

0.2

0.2

0 2

Fe mg/l

0.2

0.2

0.2

0 2

Na mg/l

1.6

0.12

0.45

0 64

2.5

1.7

1.1

0 11

4.7

and oil-cooled compressor units

52

fluid-injected

oil-free

oil-free

0.1

5.3

16

7.1

4.2

6.2

0.04

2

2.2

1

6.4

1

0.2

2.1

0.2

0.2

4

0.2

0.64

1.5

0.76

0.11

0.11

HC .... Hydro carbon contentPh .... ph value

27


53

1

5. 5. Understanding Systems

The Demand Side

1

5. Understanding Systems

Pneumatic PowerPneumatic PowerAir Flow > Mass or Weight of AirPressure > Potential Energy

Increasing – or – DecreasingFl P

2

Flow – or – PressureIncrease – or – Decrease

Power Delivered & Power Consumed

2


5 TON CLAMP CYLINDER12” Bore x 10” Stroke5.6 Tons @ 100 psig

5 Ton Clamping Cylinder1.5 seconds4 cycles per minute320mm Bore (45,000 Newtons @ 6.9 bar)250mm Stroke Length

Time Required to Clampand Unclamp is 1.5 Seconds

Machine Operates at4 Cycles / Minute

MainlineCompressed Air

Header

3

Filter Regulator Lubircator


Cylinder Volume CalculationCylinder Volume Calculation

Cylinder Air Use

meterscubiclrV 02.0

1000250)160(

1000 32

3

2

4

3


Cylinder Average Air Demand (1 i t )Cylinder Average Air Demand (1 minute)

What Size Components?Air Line Size

5

Air Line Size _______________________Filter, Regulator, Lubricator ___________Valve Size _________________________


Cylinder Peak Dynamic Flow RateCylinder Peak Dynamic Flow Rate

What Size Components Now?Air Line Size

6

Air Line Size _______________________Filter, Regulator, Lubricator ___________Valve Size _________________________

4


•When does the Peak Air Flow Occur?•When does the Peak Air Flow Occur?

•When is the High Pressure Required?

•What Size Components Now?

7

•What Size Components Now?


•Flow Static Demand•Flow Static DemandPeak air flow and minimum pressure required do not occur simultaneously.

•Flow Dynamic Demand

8

Peak airflow rate and minimum pressure required must occur simultaneously.

5

•Perceived High Pressure Demands


Perceived High Pressure DemandsOften Dictate the System Pressure

Validate Pressure Requirements

Rule Out Excessive Pressure Drop

Measure Flow & Pressure (Data Logging)

Evaluate • Connection Practice – Modify Equipment – Storage – Pressure Boosters

9


Validate Perceived High PressurePressure Gauges – Mechanical DampingPressure Gauges Mechanical Damping

Air System AuditPoint of Use (P5) Pressure @ Test Machine

5.8

6

6.2

6.4

6.6

6.8

7

Pres

sure

(bar

)

10

5

5.2

5.4

5.6

11:05 11:10 11:15 11:20 11:25 11:30

Time of Day 11/13/92System Supply Pressure (bar) Header Pressure (bar)Average Point of Use Pressure (bar) Minimum Point of Use Pressure (bar)

© 1992 Tom Taranto

6


Test Machine Flow Dynamic DemandWhat’s Wrong With This Picture?What s Wrong With This Picture?

11

•High Volume Intermittent Demand


•High Volume Intermittent DemandConsume Large Airflow for Short Periods

High Peak Airflow Rate and Low Average Demand

Affects the System Pressure ProfileControl Signals Supply PressureDistribution Gradient Use Point Pressure

12

7

High Volume Intermittent Demand


High Volume Intermittent Demand•Wastes Energy

Initiates Compressor Start-upOperational Remedy – Increased PressureAdds to Artificial Demand

•Data Logging Airflow & Pressuregg gPeak Airflow RateDuration of Event & Total Air ConsumedDwell Time Between Events – Storage RefillEvaluate Control Response & Excess Supply Pressure

13


High Volume Intermittent DemandHigh Volume Intermittent Demand Event - Dynamic Profile

5.6

5.8

6

6.2

6.4

6.6

6.8

7

7.2

Pres

sure

(bar

)

8

10

12

14

16

18

20

22

24

Flow

to S

yste

m (m

3/m

)

Dense Phase Transport System (Tanks 1 & 2) - Test 2

14

4.8

5

5.2

5.4

11:25 11:26 11:27 11:28 11:29 11:30 11:31 11:32 11:33 11:34 11:35 11:36 11:37

Time of Day on Tuesday 03/20/2001

0

2

4

6

System Pressure (bar) Event Flow @ Tanks 1&2 (m3/m)

Page 2

© 2001 Tom Taranto

8

•Pipe Layouts – Point of Use Piping


Pipe Layouts Point of Use Piping Delivers Air From Header to – Demand Energy = Airflow & Pressure

•1 to 2 bar Loss in Point of Use Piping is Common Poor Unreliable, Inconsistent Applications Performance Don’t Increase Pressure Don t Increase Pressure Decrease Piping Resistance

15


16

• Which Piping Configuration Performs Best?

9

Key Points


Key Points• Identify dynamic airflow conditions of average

–vs- peak airflow.

• Classify air demands as Flow Static and Flow Dynamic.

• Point of use connection practice has a significant affect on applications performance.

17

– Key Points


– Key Points• Review perceived high pressure air

demands to validate their pressure requirements.

P h l t• Pressure gauges have slow response to pressure changes. It may be necessary to use pressure transducers and high-speedsampling to capture pressure dynamics.

18

10

Key Points


Key Points• Minimize the use of hose for connections.

Hose has much smaller ID size (higher pressure drop) than pipe.

• Where hose must be used select the hose size based on the inside diameter and peaksize based on the inside diameter and peak airflow rate. Avoid the use of hose barbs and pipe clamps, they are dangerous, very restrictive and frequently develop leaks.

19

Key Points


Key Points • Do not use redundant point of use dryers, filters, etc.

as each component represents additional pressure drop.

• Avoid over filtration, maintain an appropriate compressed air cleanliness class for the application requirements.

• Size all connection equipment to the actual dynamic conditions associated with the application.

• Account for to peak airflow rate that must be supported, do not size equipment based on average airflow rate.

20

11


BALANCING THE SUPPLY TO DEMAND

21


• Supply > Demand ~ Pressure

Demand > Supply Pressure• Demand > Supply ~ Pressure

22

12


• Air System Minimum Pressure• Air System Minimum PressureWhat is the correct pressure?What is the Cost?

• Increased Air Pressure = Waste

23

Artificial Demand Increasing Pressure Increases Airflow

• Artificial Demand


– Increasing pressure applied to a hole in the air system, increases the airflow through the air system.

– Leaks and unregulated air demands all have a potential component of artificial demand.

– Leak repair without pressure control is not fully effective.

24

13


Discharge of Air Through an OrificeIn cubic meters of free air per minute at standard atmospheric pressure 1.013 bar absolute and 21° C

Gauge pressure

before orifice, bar

Diameter of Orifice, mm

1 2 3 4 5 6 7 8 9 10 15 20

4 0.03 0.11 0.25 0.45 0.70 1.01 1.38 1.80 2.28 2.82 6.34 11.284.5 0.03 0.12 0.28 0.50 0.78 1.12 1.52 1.98 2.51 3.10 6.98 12.40

5 0.03 0.14 0.30 0.54 0.85 1.22 1.66 2.16 2.74 3.38 7.61 13.535.5 0.04 0.15 0.33 0.59 0.92 1.32 1.79 2.34 2.97 3.66 8.24 14.65

6 0.04 0.16 0.35 0.63 0.99 1.42 1.93 2.52 3.19 3.94 8.87 15.786.5 0.04 0.17 0.38 0.68 1.06 1.52 2.07 2.70 3.42 4.23 9.51 16.90

7 0 05 0 18 0 41 0 72 1 13 1 62 2 21 2 88 3 65 4 51 10 14 18 03

25

7 0.05 0.18 0.41 0.72 1.13 1.62 2.21 2.88 3.65 4.51 10.14 18.037.5 0.05 0.19 0.43 0.77 1.20 1.72 2.35 3.06 3.88 4.79 10.77 19.15

8 0.05 0.20 0.46 0.81 1.27 1.82 2.48 3.24 4.11 5.07 11.40 20.278.5 0.05 0.21 0.48 0.86 1.34 1.93 2.62 3.42 4.33 5.35 12.04 21.40

9 0.06 0.23 0.51 0.90 1.41 2.03 2.76 3.60 4.56 5.63 12.67 22.529.5 0.06 0.24 0.53 0.95 1.48 2.13 2.90 3.78 4.79 5.91 13.30 23.6510 0.06 0.25 0.56 0.99 1.55 2.23 3.03 3.96 5.02 6.19 13.94 24.77Table is based on 0.61 coefficient of flow.


Engineer Appropriate StorageAir System Audit - Artificial Demand Reductiony

Test #21 Throttled System Response

6.9

7

7.1

7.2

7.3

7.4

7.5

7.6

7.7

7.8

7.9

8

Pres

sure

(bar

)

34

36

38

40

42

44

46

48

50

52

54

56

yste

m F

low

(m3/

m)

26

6.3

6.4

6.5

6.6

6.7

6.8

13:07 13:08 13:09 13:10 13:11 13:12 13:13 13:14 13:15 13:16 13:17 13:18 13:19 13:20

Time of Day 11/14/92

22

24

26

28

30

32 Sty

System Pressure (bar) C#1 225 kW Discharge Pressure (bar)

C#2 262 kW Discharge Pressure (bar) Stystem Flow (m3/m)

© 1992 Tom Taranto

14


Storage; A Lake – vs – A Reservoir

LAKE

AIR RECEIVER

RESERVOIR

AIR STORAGE

27

8.2 barWorking Pressure

6.2 barWorking Pressure

8.2 barStorage Pressure

IntermediateControl

• Stabilize System Operation


Stabilize System Operation– Minimize the cost of generating compressed air.– Control air demand and reduce artificial demand.– Create controlled air storage to supply peak

demand

• Evaluating Controlled Storage• Evaluating Controlled Storage– Meet surge demands– Satisfy events as defined in the demand profile– Improve compressor control response

28

15

5. Understanding SystemsCompressed Air Storage - for Stable System Operation

603 0 bar

Useable air in storage based on receiver size and pressure differential

20

30

40

50ab

le A

ir St

orag

e (m

3 )3.0 bar

2.5 bar

2.0 bar

1.5 bar

1.0 bar

Receiver = 10 m3

Useable Air Storage@ 3.0 bar 30 m3

@ 2.5 bar 25 m3

@ 2.5 bar 25 m3

@ 1.5 bar 15 m3

@ 1.0 bar 10 m3

@ 0.5 bar 5 m3

@ 0.2 bar 2 m3

29

0

10

20

0 2 4 6 8 10 12 14 16 18 20Receiver Size (m3)

Usea

0.5 bar

0.2 bar


Tuning Compressor & System ControlsAi S t P f T t C iAir System Performance Test Comparison

Properly Tuned System Performance w/ Intermediate Control

5.65.8

66.26.46.66.8

77.27.47.67.8

Pres

sure

(bar

)

40

45

50

55

60

65

70

75

80

85

90

95

Syst

em F

low

(m3 /m

)kW

x 1

0

30

4.44.64.8

55.25.4

19:00

19:10

19:20

19:30

19:40

19:50

20:00

20:10

20:20

20:30

20:40

20:50

21:00

Time of Day on Thursday 5/26/94

10

15

20

25

30

35

S

Storage Pressure (bar) System Pressure (bar )Flow (m3/m) kW x 10 (source)

© 1994 Tom Taranto

16


Tuning Compressor & System ControlsAir System Performance Test ComparisonAir System Performance Test Comparison

Improperly Tuned System Performance w/ Compressor Source Control

5.4

5.6

5.8

6

6.2

6.4

6.6

6.8

7

7.2

7.4

7.6

7.8Pr

essu

re (b

ar)

35

40

45

50

55

60

65

70

75

80

85

90

95

Syst

em F

low

(m3 /m

)kW

x 1

0

31

4.4

4.6

4.8

5

5.2

19:00

19:10

19:20

19:30

19:40

19:50

20:00

20:10

20:20

20:30

20:40

20:50

21:00

Time of Day on Wednesday 5/25/94

10

15

20

25

30

Storage Pressure (bar) System Pressure (bar )

Flow (m3/m) kW x 10 (source)

© 1994 Tom Taranto


Key Points• Stabilize system operating pressure.• Increased air pressure increases

compressed air demand at leaks and unregulated air demands.

• Leakage can be reduced by controlling

32

to a lower system pressure.• Artificial demand is a component of any

unregulated leak or air demand.

17


Key PointsTarget pressure should be the lowest optimal• Target pressure should be the lowest optimal pressure to supply productive air demands.

• Air storage should be designed to supply surge demands, satisfy events defined in the demand profile, and improve compressor control response.Th t f i t d d

33

• The amount of energy in storage depends on storage volume and controlled pressure differential.


UNIDO Industrial Systems Optimization Module 4 Compressed Air Systems -Instructor Notes

© 2005 US Department of Energy and Lawrence Berkeley National Laboratory – Tom Taranto and Wayne Perry 1

6. Pressure Profile

Graphical description of d icompressed air pressure as

measured throughout the system.

1

Typical pressure measurement locations

• Compressor maximum working pressure (MWP)• Compressor control range• Treatment equipment pressure drop• Pressure differential reserved for primary storage• Supply header pressure to the system• Distribution header pressure in one or more

demand side locations• Point of use connection pressure• End use pressure

2

UNIDO Industrial Systems Optimization Module 4 Compressed Air Systems -Instructor Notes

© 2005 US Department of Energy and Lawrence Berkeley National Laboratory – Tom Taranto and Wayne Perry 2

Compressor 001-5040Atlas Copco GA250-100

300 Hp 480 Volt254 kW FL - 56 kW NL

1,448 acfm 107 psig

TA1TP1

Plant Air Compressors

Compressor 001-5130Gardener Denver EAUSAV

300 Hp 416

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