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Title: Compressed%20Air%20Fundamentals%20


1
(No Transcript)
2
Fundamentos de Aire Comprimido
3
Life Cycle Cost of an air compressor
Compressed Air Fundamentals
Why are we here?
Energy consumption
Installation
Maintenance
Investment
4
Ciclo del costo de la vida de un compresor
Fundamentos del aíre comprimido
  • De las tres categorías del costo la energía puede
    ser arriba del 90 en dias años de trabajo de un
    equipo
  • de hecho dentro de los primeros 12 meses, el
    costo de inversion es exedido por el costo del
    uso de la máquina
  • Comprar un compresor representa el más bajo de
    los tres costos
  • El consumo de energía es por mucho el costo más
    significante en la operación de un equipo

Consumo de Energía
Instalacion
Mantenimiento
Inversión
5
Fundamentos del aíre comprimido
  • Que es el Aire Comprimido?

6
Fundamentos del aíre comprimido
  • Nosotros vivimos en el fondo de un mar llamado
    Atmosfera

7
Fundamentos del aíre comprimido
  • El aíre es como un sobre gaseoso que rodea la
    tierra ejerciendo una presión en cada cosa
  • La presión actual depende de la localización con
    respecto al mar.

8
Fundamentos del aíre comprimido
  • Al nivel del mar la presión atmosférica es de
    14.7 psiA
  • psiA Libras por pulgada cuadrada (Absolutas)

9
Fundamentos del aíre comprimido
  • a 500 pies bajo el nivel del mar, la presión del
    aire es 14.94 psiA

10
Fundamentos del aíre comprimido
  • En la cima de una montaña de 5000 pies, la
    presión del aíre es sólo de 12.2 psiA
  • La Montaña del Everest esta a 29,000 pies sobre
    el nivel del mar, la presión sólo es de 4.56 psiA

11
Fundamentos del aíre comprimido
  • Comprimir Forzar a que entre todo en un espacio
    más pequeño
  • Aire Es una mexcla incolora, inolora, e
    insipida, principalmente nitrogeno (78) y
    oxygeno (21)
  • Cuando se Controla, el aire comprimido puede ser
    usado para ejecutar un trabajo

12
Fundamentos del aíre comprimido
  • El aíre Comprimido guardado es energía...
  • La energía contenida dentro de un globo es igual
    a la energía que se requirió para inflarla.
  • Si el volume de una cantidad dada de aíre
    decrece, la presión se incrementará
  • Con un compresor de desplazamiento positivo, el
    aire comprimido se obtiene forzando a que este
    permanezca en un volume más pequeño.

13
Fundamentos del aíre comprimido
  • Porque la industria necesita aíre comprimido?
  • Por la energía El aíre comprimido es un
    excelente medio para guardar y transmitir
    energía para hacer cualquier trabajo.
  • Por requerimientos de Procesos El aíre
    comprimido es una parte activa de procesos
    (ejem. quimica, farmaceutica, fermentación, etc.)

14
Fundamentos del aíre comprimido
  • La energía del aíre
  • La energía del aíre comprimido es usda para
    impulsar equipos neumáticos en la producción
  • Ejemplos.--motores de aíre, actuadores,
    instrumentacion, herramientas, etc.
  • Para enfriar componentes o partes durante la
    fabricación
  • Para soplar basura
  • etc

15
Fundamentos del aíre comprimido
  • Aire de Proceso
  • El aíre comprimido es una parte integral de un
    proceso,
  • Quimicos
  • farmaceuticos
  • Comidas y Bebidas
  • Aeración y agitación
  • Semiconductores y Electronicos
  • Aire de respiración medica

16
Definiciones
  • Presión Absoluta
  • Es La Suma de la presión medidala presión
    atmosférica
  • (100 psig 14.2 psia 114.2 psia absolutos)

Relación de Compresión La relación de la presión
absoluta de salida entre la presión absoluta de
entrada (100 psiG 14.2 psiA) / 14.2 psiA 8.04
ratios), ó simplemente son las veces las cuales
se reduce el volume de un gas a determinada
presión a un volumen menor a una presión mayor
17
Definitions
  • Punto de Rocío
  • Es la temperatura de un gas a una presión dada, a
    la cual el vapor de agua comienza a condensarse

Capacidad Cantidad de un gas entregado,
típicamente se refiere a las condiciones de
entrada, que son humedad, presión y tempertura
ejemplos ACFM,ICFM, SCFM, Free air CFM, FAD
Aire Estandard (Ejemplo SCFM) Un volume dado de
aíre definido una especifica, o estandard
condicion. Los parametros comunmente aceptados
en la industria como estándar son 14.7 psiA, 60o
F, 0 RH
18
Definiciones
Desplazamiento Positivo Un volume de aíre es
atrapado dentro de un espacio cerrdo. El volume
es reducido causando un aumento de presión
(compresion)
  • Compresor Dinámico
  • El aumento de energía se obtiene convirtiendo la
    energía cinética en energía de presión,
    aumentando primero la velocidad de las partículas
    y después desacelarandolas

19
Definiciones
  • Interenfriamiento
  • El enfriamiento de un gas entre etapas de
    compresión
  • 1. Reduciendo la temperatura
  • 2. Reduciendo el volume para la siguiente etapa
  • 3. Licuando vapores condensables para reducir
    los HP
  • (Todo lo relacionado para reducir los HP)

20
Formulas
  • Cambio de Presión vs Cambio de BHP (potencia)
  • Para compresores de Desplazamiento positivo Un
    cambio de presión de 1 psig requiere un aumento
    de potencia del .5.
  • Ejemplo un compresor de 1000 CFM requiere 200
    BHP para 100 psiG. El mismo compresor, operando
    a la misma velocidad requerira (200 x 1.10) 220
    BHP para llegar a 120 psiG
  • Cálculo del costo de potencia--para un año de
    operación
  • BHP X .746 kW X X
    Oper. Hrs Oper.
  • Mtr. Eff. HP kWh Year
    Year

21
Formulas
Ejemplo - Para el compresor anterior el costo del
incremento de presión de 100 a 120 psiG. Es el
siguiente
  • 20 ?BHP X .746 kW X .09 X
    8700 Hrs. 12,560
  • .93 Eff. Mtr. HP kWh Year

Porque debo operar mi compresor a la más baja
presión posible? Sólo vea el ejemplo anterior!
22
Formulas
  • Para cálculos de aíre comprimido se requieren
    fórmulas termodinámicas.
  • En el sistema de mediciones Ingles, se utilizan
    las fórmulas siguientes para cálculos
    termodinámicos
  • La presión se expresa en Libras por pulgadas
    Cuadrada (psi, or lb/in2).
  • La temperatura se expresa en Fahrenheit (deg. F.)
  • El volume se expresa en pies cúbicos (Ft3)
  • Volume Flow Rate is expressed in cubic feet / min
    (Ft3/min)

23
Formulas
  • Relaciones de Presión
  • Todos los cálculos se basan en valores absolutos
    para Temp. Y Presión.
  • Presión Absoluta (psiA) Presión en medida
    (psiG) Presión barométrica(ambiente).
  • Ejemplo
  • 14.7 psiA Presión Barométrica
  • 100 psiG Presión de descarga
  • 14.7 100 114.7 psiA Presión absoluta de
    descarga.

24
Formulas
  • Relación de Compresión
  • Relación de Compresión Presión Absoluta de
    Descarga
  • Presión absoluta de entrada ó Medio
    Ambiente
  • Recuerdese Presión absoluta de descarga
    Presión de descarga medida (Presión barométrica
    ó ambiental (psiA)
  • Example
  • 14.7 psiA Presión de entrada
  • 125 psiG Presión de descarga
  • La Relación de Compresion es (14.7 125) /
    14.7 9.5

25
Ratings
  • Flujo de volume
  • Del Ejemplo anterior
  • Si un compresor de 100 CFM toma 100 CFM de aíre
    del medio ambiente y lo comprime a 125 psiG. El
    aíre a sido prensado 9.5 de su tamaño original, y
    ahora sólo ocupa 10.52 pies cubicos en su estado
    comprimido.

Relación de Compresión (14.7 125) / 14.7
9.5 100 pies Cúbicos / 9.5 10.52 pies cúbicos
Si la Relación de Compresión del compresor
9.5 este estará operando en el límite
26
Formulas
  • La presión barométrica decrece incrementando la
    altitud y viceversa.
  • Basandonos en una presión de descarga fija la
    relación de compresión se incrementa si se
    aumenta la altitud.
  • Ejemplo si el mismo compresor se operara ahora
    a
  • 3,000 Pies Sobre el nivel del mar 13.19 psiA
    Barometricos
  • Manteniendo la presión de descarga a 125 psiG
  • Relación de compresión (13.19 125) / 13.19
    10.5 Se incrementa
  • 100 Pies Cúbicos/10.5 9.52 pies cúbicos Se
    Reduce aún más la masa ó volume comparado con los
    10.52 anteriores

Si se sobrepasa la relación de compresión el
volume es más reducido, esto ocasionará mayor
fuerza para tenderse a liberar si el compresor no
está diseñado para esta fuerza se producirá
calentamiento ó aumento de temperatura
27
  • En la industria existen 4 diferentes capacidades
    para CFM.
  • Aíre Libre entregado (FAD CFM)
  • Actual Pies Cúbicos por minuto (ACFM)
  • Entrada Pies Cúbicos por Minuto (ICFM)
  • Standard Pies Cúbicos por Minuto (SCFM)

28
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29
The face of interaction
30
Fundamentos de Aire Comprimido
31
THE RIGHT CHOICE
  • COMPRESSOR TYPES
  • WORKING PRINCIPLES
  • CHARACTERISTICS
  • CONTROL SYSTEMS
  • STAGING
  • GENERAL INFORMATION

32
THE RIGHT CHOICE
  • COMPRESSOR TYPES
  • WORKING PRINCIPLES
  • CHARACTERISTICS
  • CONTROL SYSTEMS
  • STAGING
  • GENERAL INFORMATION

33
The basic principals of air or gas compression
34
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35
THE RIGHT CHOICE
  • COMPRESSOR TYPES
  • WORKING PRINCIPLES
  • CHARACTERISTICS
  • CONTROL SYSTEMS
  • STAGING
  • GENERAL INFORMATION

36
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37
Positive displacement principle
Reducing the volume of a gas increases its
pressure
38
Oil Free Rotary Screw Element Design
39
The Positive Displacement Principle As Applies To
Screw
The volume of the air or gas is progressively
reduced along the length of the screw,causing a
pressure increase.
40
  • THE AC ASSYMETRIC PROFILE
  • LOW ROTOR SPEEDS
  • -HIGH BEARING LIFE
  • -LESS WEAR AND TEAR
  • -LOW DYNAMIC AND MECHANICAL LOSS
  • BETTER SEALING
  • -LOW VOLUMETRIC LOSSES-HIGH VOLUMETRIC EFFECIENC
    Y
  • CONTACT POINT AT THE PITCH CIRCLE
  • -NO RELATIVE MOTION BETWEEN ROTORS

41
A SCREW IS A POSITIVE DISPLACEMENT MACHINE AND
HENCE CAPACITY SPEED
-The dynamic and mechanical losses
increase with the
rotor tip speeds -The volumetric losses
decrease -The total losses which are a sum of all
losses are minimum at 80 m/s for oil-free
elements and approximately 30m/s for lubricated
elements Since the total loss curve is almost
flat between 60-120 m/s this range can be
employed without much compromise on effeciency

42
Compressor Fundamentals
43
DYNAMIC COMPRESSOR
  • Dynamic Principle Velocity (Kinetic Energy)
    converted to pressure

44
CENTRIFUGAL COMPRESSORS WORKING PRINCIPLE
RADIAL DIFFUSERS
PRESSURE CUTS
FLOW CUTS
VANES
INDUCER
PRESSURE INCREASE FOLLOWS THE PRINCIPLE OF
BERNOULLI
45
A CENTRIFUGAL IMPELLER
46
TURBO WORKING PRINCIPLE
Blade
  • Wheel turns
  • Speed of the ball increases
  • Speed suddenly reduced to
  • create pressure increase

DIFFUSER
47
CENTRIFUGAL COMPRESSOR GENERAL ARRANGEMENT
48
THE RIGHT CHOICE
  • COMPRESSOR TYPES
  • WORKING PRINCIPLES
  • CHARACTERISTICS
  • CONTROL SYSTEMS
  • STAGING
  • GENERAL INFORMATION

49
GENESIS OF SCREW COMPRESSORS
  • IN THE 1930S COMPRESSED AIR AND GAS USERS HAD
    TWO MAIN OPTIONS RECIPS AND CENTRIFUGALS
  • RECIPS WERE POSITIVE DISPL. M/CS WHICH WERE
  • THERMODYNAMICALLY STABLE AND POWER SAVING BUT
  • REQUIRED EXPENSIVE INSTALLATION AND FOUNDATIONS
  • WERE MAINTENANCE INTENSIVE - EXPENSE/DOWNTIME
  • CAPACITY FELL WITH USE
  • LIMITED USE WITH DIRTY GASES
  • CENTRIFUGALS WERE LESS MAINTENANCE INTENSIVE BUT
  • REQUIRED EXPENSIVE INSTALLATION AND FOUNDATIONS
  • WERE THERMODYNAMICALLY UNSTABLE
  • OPERATING BAND WAS LIMITED
  • SENSITIVE TO DUST AND UNSUITABLE FOR DIRTY GASES
  • CAPACITY FELL EVEN WITH A FEW MICRON DUST
    BUILDUP

50
GENESIS OF SCREW COMPRESSORS II
  • PROFESSOR LYSHOLM OF THE ROYAL
    SWEDISH INSTITUTE OF SCIENCE
    DOING RESEARCH ON COMPRESSORS SET
    ABOUT FINDING AN IDEAL SYSTEM ON THE FOLLOWING
    HYPOTHESIS
  • TO OVERCOME WEAKNESSES OF THE
    RECIPS HIS DREAM MACHINE HAD TO BE A ROTARY
    WITH NO METAL CONTACT
  • TO OVERCOME DISADVANTAGES OF CENTRIFUGALS
    IT HAD TO BE A POSITIVE DISPLACEMENT MACHINE
  • THUS WAS BORN THE IDEA OF THE ROTARY
    SCREW WHICH COMBINED THERMODYNAMIC AND
    OPERATIONAL STABILITY AND LOW POWER CONSUMPTION
    WITH UNPARALLELED RELIABIITY

51
GENESIS OF SCREW COMPRESSORS III
  • ATLAS COPCO DREW ON THIS BASIC IDEA
    AND AFTER INTENSIVE RESEARCH COMMERCIALLY
    INTRODUCED THE U SERIES IN 1957. MANY OF
    THESE MACHINES ARE STILL OPERATING THE WORLD
    OVER
  • IN THE 1970S THE ATLAS COPCO RESEARCH
    CENTRE THE CERAC I NSTITUTE IN GENEVA
    DESIGNED AND PATENTED A REVOLUTIONARY
    ASSYMETRIC SCREW PROFILE WHICH IS CURRENTLY
    USED IN THE G AND Z SERIES MACHINES
  • IN THE WORLD TODAY 9 OUT OF 10 MACHINES
    PRODUCED AND SOLD IN THEIR RANGE ARE ROTARY SCREWS

52
COMPRESSOR CHARACTERISTICS
Performance curves
DYNAMIC COMPRESSOR
PRESSURE
POSITIVE DISPLACEMENT COMPRESSOR
CAPACITY
53
COMPRESSOR CHARACTERISTICS - DYNAMIC MACHINES
OIL FREE SCREW
SURGE LIMIT
SURGE CONTROL
PRESSURE
AT 25 DEG.C 1 BAR A
AT 40 DEG.C 0.97 BAR A
FLOW
60 85
100
POWER
OIL FREE SCREW
FLOW
54
Inlet throttle valve
55
DYNAMIC MACHINES- OPERATING BAND
Pressure
Surge
Stonewall
Flow
56
COMPRESSOR CHARACTERISTICS- DYNAMIC MACHINES
A DYNAMIC COMPRESSOR OPERATES IN A
BAND BETWEEN SURGE Breakdown of airflow due to
high back pressure (oscillation flow) AND STONE
WALL (choke) Maximum flow a compressor can handle
at a given speed
57
COMPRESSOR CHARACTERISTICS
Variables influencing compressor performance
  • Positive displacement compressors

P2 P1
n n-1
P P1 . V1 . ( ) -1
Inlet air temperature and weight flow (density)
have no effect on power
Where P Power P1 Inlet pressure V1
Inlet volume n Adiabatic factor P2/P1 Press
ure ratio
Variables influencing power P1 Inlet
pressure V1 Volume flow (not
mass!) P2/P1 Pressure ratio
58
COMPRESSOR CHARACTERISTICS
Variables influencing dynamic compressor
performance
POWER IS CALCULATED WITH FORMULA
There are three variables that affect the power
Where Hp Head pressure m Mass flow his
Isentropic efficiency
T Inlet temperature m Mass flow P2/P1
Pressure ratio
MASS FLOW IS HIGHER AT LOW TWMPERATURES AS WELL
AS HIGH AMBIENT PRESSURES HENCE HIGH POWER
CONSUMPTIONS AT THESE CONDITIONS
59
COMPRESSOR CHARACTERISTICS - DYNAMIC MACHINES
  • EFFECT OF SPEEDS
  • SINCE A DYNAMIC MACHINE DEVELOPS PRESSURES
    PROPORTIONAL TO THE
  • SQUARE OF THE VELOCITY REDUCTION
  • IT FOLLOWS THAT
  • IMPELLER SPEED REDUCTION CAUSES A PRESSURE
    REDUCTION ACCORDING TO
  • THE RELATIONSHIP
  • HENCE DUE TO FREQUENCY REDUCTION OF 3 THE OUTLET
    PRESSURE REDUCES BY 6

60
COMPRESSOR CHARACTERISTICS THERMODYNAMIC
INSTABILITY- DYNAMIC MACHINES
  • THERMODYNAMIC INSTABILITY CAN HENCE BE
    INTERPRETED AS
  • PRESSURE AND VOLUME ARE INVERSELY
    RELATED.PRESSURE INCREASE LEADS TO REDUCTION IN
    VOLUME CAPABILITY OF THE MACHINES.
  • LOWER AIR INLET TEMPERATURE RESULTS IN
  • - SAME VOLUME FLOW FOR HIGH POWER CONSUMPTION
  • - HIGHER MASS FLOW
  • - HIGHER PRESSURE CAPABILITY OF THE MACHINE
  • LOWER SPEEDS RESULT IN VERY LOW PRESSURES
  • THE MACHINE OPERATES WITHIN A NARROW BAND(BETWEEN
    SURGE AND STONEWALL)
  • THE SYSTEM IS PRONE TO SURGE DUE TO PRESSURE DROPS

61
BALANCED OPPOSED PISTONSFORCE BALANCE
F 1
F 1
1. HORIZONTAL FORCES F1 BALANCE OUT 2. UNBALANCED
VERTICAL FORCES F2 ACTING ALONG WITH THE WEIGHT
OF THE PISTON CAUSES CYLINDER
OVALITY 3. F2 FORCES ALSO CAUSE AN UNBALANCED
COUPLE, NECESSITATING HEAVY FOUNDATIONS.
62
WEAR ITEMS - A COMPARISON
SCREW
PISTON
VEE BELTS (6) CRANKSHAFTS MAIN BEARINGS (4) BIG
END BEARINGS (4) CONNECTING RODS (4) SMALL END
BEARINGS (4) CROSS HEADS (4) WIPER RINGS (4
SETS) PISTONS (4) PISTON RINGS (16) CYLINDERS
(4) 40 VALVES (SUCTION/DELIVERY) TOTAL 99 WEAR
ITEMS
2 GEARS 6 BEARINGS 2 ROTORS TOTAL 10 WEAR
ITEMS
WEAR ALONG WITH OVALITY CAUSES A CAPACITY
DERATION OF 5-6 PER YEAR,WITHOUT REDUCING
THE POWER CONSUMPTION A HIGH NUMBER OF WEAR
PARTS INCREASES DOWN TIME AND MANPOWER
OUTLAYS
63
P-V DIAGRAM - A COMPARISON
PISTON
SCREW
P
P
W
CV
DELIVERY
DELIVERY
V
V
CLEARANCE VOLUME CONTRIBUTES TO LOWER VOLUMETRIC
EFFECIENCIES AND HIGHER POWER CONSUMPTION
64
PISTON COMPRESSORSEFFECT OF VALVE FLUTTER ON P-V
DIAGRAM
EFFECT OF VALVE FLUTTER
  • .

P
w
V
VALVE FLUTTER CAUSES THE AREA OF THE P-V DIAGRAM
TO INCREASE WHICH RESULTS IN HIGHER THAN
INDICATED POWER CONSUMPTION. FLUTTER IS CAUSED
BY WEAR ON THE VALVE PLATES CAUSING AIR TO LEAK
IN SMALL CHANNELS.THE PLATES BEGIN TO
VIBRATE,SIMILAR TO A REED IN A FLUTE.FLUTTER
OCCURS AFTER A SHORT SPAN OF USAGE.
65
PISTON COMPRESSORS EFFECTS OF CYLINDER OVALITY
CYLINDER
PISTON
CYLINDER OVALITY PREVENTS RESUMPTION OF
CAPACITY TO ORIGINAL LEVEL EVEN WITH NEW RINGS
LEADING TO CONTINUED AIR LEAKAGE
66
SUITABILITY OF TURBO COMPRESSORS
  • CENTRIFUGAL COMPRESSORS ARE VERY SUITABLE FOR
  • HIGH VOLUME FLOWS ABOVE 6000 M3/HR
  • MASS RELATED PROCESSES LIKE AIR SEPARATION WHERE
    HIGH
  • POWER AT LOW TEMPERATURES IS COMPENSATED BY HIGH
    MASS FLOWS.
  • BASE LOAD OPERATION WHERE MACHINE RUNS AT FULL
    LOAD
  • PRESSURES UPTO 80 BAR

67
THE RIGHT CHOICE
  • COMPRESSOR TYPES
  • WORKING PRINCIPLES
  • CHARACTERISTICS
  • CONTROL SYSTEMS
  • STAGING
  • GENERAL INFORMATION

68
VERY FEW PROCESSES REQUIRE A CONTINOUS FLOW OF
AIR,ALTHOUGH THE DEGREE OF VARIATION CHANGES FROM
PROCESS TO PROCESS.THE AIR DEMANDS CAN CHANGE DUE
TO DIVERSE CAUSES SUCH AS THE EXTENT OF
UTILIZATION OF A FACTORY,ACCORDINDG TO THE DAY OF
THE WEEK OR THE TIME OF THE DAY.IT CAN CHANGE DUE
TO THE DEGREE OF MATURITY OF A PROCESS,SUCH AS IN
FERMENTATION OR OXIDATION PROCESSES.THE
MANUFACTURING SET-UP MAY EMPLOY VERY LARGE
CONSUMERS OF AIR SUCH AS FORGING HAMMERS,PAINTING
BOOTHS,PNEUMATIC PRESSES,ETC.,WHICH RUN OFF AND
ON.MASS DEPENDENT PROCESS MAY REQUIRE A FIXED
MASS OF AIR,BUT THE MASS FLOW THROUGH THE
COMPRESSORS CHANGE WITH THE AMBIENT
TEMPERATURES. OR SIMPLY BECAUSE THE AIR DEMAND IS
OVER ESTIMATED The compresor therefore requires a
control system to regulate the air generation of
the compressor in direct relation to the demand
69
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70
SCREW CONTROL SYSTEMS-MODULATION CONTROL
IN A MODULATION CONTROL A BUTTERFLY VALVE
REGULATES THE INTAKE
AT FULL LOAD THE BUTTERFLY VALVE IS OPEN AND
THERE IS FREE FLOW OF AIR.THE MACHINE OPERATES AT
THE BUILT-IN PRESSURE RATIO
AT PART LOAD THERE IS A RESTRICTION IN AIR FLOW
LEADING TO A VACUUM . HOWEVER OUTLET PRESSURE
REMAINS THE SAME SINCE THIS IS DETERMINED BY THE
AIR NET PRESSURE
VACUUM PREVAILS INTAKE 1/2 BAR A
INTAKE 1 BAR A
SCREW ELEMENT
OUTLET 8 BAR A
OUTLET 8 BAR A
PRESSURE RATIO IS 16 WHICH IS MUCH HIGHER THAN
THE BUILT IN PR.HENCE VERY INEEFECIENT AT PART
LOADS
PRESSURE RATIO8
FIGURES ARE USED FOR CONCEPT DEMONSTRATION ONLY
71
SCREW CONTROL SYSTEMSLOAD NO-LOAD REGULATION
  • IN A LOAD NO-LOAD CONTROL THE MACHINE RUNS AT
    EITHER AT FULL LOAD OR UNLOADED
  • IN THE LOADED CONDITION THE INLET VALVE IS
    COMPLETELY OPEN AND HENCE THE MACHINE
    MAINTAINS ITS BUILT-IN PRESSURE RATIO
  • IN THE UNLOADED CONDITION THE INLET VALVE IS
    COMPLETELY CLOSED AND THE OUTLET IS ISOLATED FROM
    THE AIR NET.
  • POWER CONSUMPTION DROPS ALMOST PROPORTIONATELY
    DUE TO THE MUCH REDUCED VOLUME FLOW AS WELL AS NO
    OPERATION ABOVE THE BUILT-IN PRESSURE RATIO

72
SCREW CONTROL SYSTEMSVARIABLE SPEED CONTROL
IN A VARIABLE SPEED CONTROL,THE SPEED OF THE
DRIVE MOTOR IS CONTINOUSLY VARIED TO MATCH THE
COMPRESSOR OUTPUT TO THE DEMAND. A SIMPLE SCHEME
IS SHOWN BELOW

THE P/I (PRESSURE TO CURRENT
CONVERTOR)GENERATES A 4-20
MA SIGNAL DEPENDING ON THE DOWNSTREAM
PRESSURE.PRESSURE INCREASE INDICATES A
DEMAND REDUCTION.THE VARIABLE SPEED CONTROL
(VSD) EMPLOYS THE CURRENT SIGNAL AS THE
INPUT,TO REDUCE THE FREQUENCY TO THE DRIVE
MOTOR(M). SINCE THE DRIVE MOTOR SPEED IS
PROPORTIONAL TO THE SUPPLY FREQUENCY.THE MOTOR
SLOWS DOWN.THE REDUCTION IN THE FLOW,AS A
RESULT,LEADS TO AN ALMOST PROPORTIONAL REDUCTION
IN POWER CONSUMPTION. VARIABLE SPEED CONTROLS
CONSTITUTE THE MOST EFFICIENT METHOD TO CONTROL
CAPACITY.
M
P/I
VSD
C
73
SCREW CONTROL SYSTEMSA COMPARISON
VARIABLE SPEED CONTROL
74
COMPRESSOR CONTROL - DYNAMIC MACHINES
SURGE LIMIT
SURGE CONTROL
PRESSURE
FLOW
60 85
100
DEMAND FALLS BELOW SURGE CONTROL
DEMAND IS ABOVE SURGE CONTROL
2 SCENARIOS CONTROL ABOVE SURGE CONTROL CONTROL
BELOW SURGE CONTROL
75
CONTROL SYSTEMS - DYNAMIC MACHINESCONTROL ABOVE
SURGE CONTROL
  • Inlet guide vanes
  • Energy savings with 100 - 65 capacity
    control
  • Constant pressure within control range

Inlet Throttle Valve
Inlet Guide Vane
76
CONTROL SYSTEMS-DYNAMIC MACHINES CONTROL ABOVE
SURGE CONTROL
V1
V1
V2
V2
VELOCITY CHANGE(V) V1-V2
VELOCITY CHANGE V1-V2 lt V
NORMAL
INLET GUIDE VANES
V1
V2
VELOCITY CHANGE V1-V2 lt V
DIFFUSER GUIDE VANES
ABOVE EXAMPLE IS FOR AXIAL FLOW MACHINES
77
ZH-series
Efficient centrifugal compressors
Adjustable inlet guide vanes provide a pre whirl
to the air or gas,smoothly controlling capacity
without any turbulence unlike the throttle valve
9energy savings at part
load
150
Pressure
100
Plant demand
Inlet throttle valve at 100 pressure
100
Inlet guide vanes at 100 pressure
90
80
Power
Energy savings
70
60
70
80
90
100
110
Capacity
78
CONTROL SYSTEMS-DYNAMIC MACHINES CONTROL BELOW
SURGE LIMIT AUTO DUAL AND MODULATED BLOW-OFF
CONTROLS
Pressure
Volume flow
RELOADING TIME IS LONG WITH CONVENTIONAL RADIAL
AND THRUST BEARINGS OFTEN CALLING FOR HUGE
STORED CAPACITY TO PROTECT PROCESS
ENTAILS BLOW-OFF AT PARTIAL LOADS THUS WASTING
POWER
79
BEARING CONFIGURATIONSDYNAMIC MACHINES
JOURNAL
SHAFT
SIMPLE TILTING PAD
TILTED PAD
DUE TO THE HIGH SPEEDS,DYNAMIC MACHINES EMPLOY
SLEEVE BEARINGS,WHICH EMPLOY AN OIL FILM TO
SUPPORT THE SHAFT.THIS BEARING SYSTEM INTRODUCES
RESTRICTIONS BECAUSE CHANGES IN LOAD PATTERNS
CAUSES THINNING OF THE FILM OR FILM
DISPERSION.SUDDEN OR FREQUENT CHANGES IN LOAD
CONDITIONS HAVE TO BE CONTROLLED.
80
THE FLEXIPAD BEARINGS
  • TILTING OR FLEXIPAD BEARINGS WITH THRUST PADS IN
    BOTH DIRECTIONS PROVIDE GOOD DAMPING
    CHARACTERISTICS WITH MANY BENEFITS
  • IMPROVED MECHANICAL SAFETY
  • IMPROVED STABILITY WHEN CROSSING
    CRITICAL SPEEDS
  • BETTER TOLERANCES TO IMPROVE EFFECIENCY
  • FASTER TURN AROUND FOR RELOADING
  • ABILITY TO RUN UNLOADED

81
THE RIGHT CHOICE
  • COMPRESSOR TYPES
  • WORKING PRINCIPLES
  • CHARACTERISTICS
  • CONTROL SYSTEMS
  • STAGING
  • GENERAL INFORMATION

82
STAGING OF COMPRESSORSA P-V DIAGRAM
REPRESENTATION
  • .

X X X X X
P
W
V
SINGLE STAGE
2 STAGE
X - ENERGY SAVING
MULTI-STAGING SAVES ENERGY AND LIMITS OUTLET
TEMPERATURES
83
STAGING - SCREW MACHINES
IF THE BUILT-IN PRESSURE RATIO IS 3 A 1-STAGE
MACHINE OPERATES BEST AT A PRESSURE RATIO OF
2.5-3.5 AND A 2-STAGE AT 6-10
X-EXCESS ENERGY
84
STAGING CRITERIA - TURBO MACHINESSAFETY
CONSIDERATIONS
  • THE NO.OF STAGES IS DEDUCED AS FOLLOWS
  • WITH 14 PH SS USED THE MAX. TIP SPEED IS 450
    M/S.
  • WHEN USING 45 DEG.IMPELLERS THIS IS ATTAINED WITH
    A PR OF 2.1 PER STAGE.
  • HENCE A 2 STAGE MACHINE CAN ACHIEVE A MAX.WORKING
    PRESSURE OF 2.1 EXP 2 4.41 - 1 3.41 KG/CM2
    (G).
  • AND A 3 STAGE MACHINE CAN ACHIEVE A MAX.WORKING
    PRESSURE OF 2.1 EXP 3 9.26 - 1 8.26 KG/CM2
    (G).

85

STAGING CRITERIA - TURBO MACHINESEFFECIENCY
CONSIDERATIONS
mechanical efficiency
aerodynamic efficiency
total efficiency
FACTORS DETERMINING AERODYNAMIC EFFECIENCY
ARE SPECIFIC SPEEDS MACH NUMBERS REYNOLDS NUMBERS
Efficiency versus number of stages 6-10.4 bar(e)
number of stages
CURVE CORRESPONDS TO 7-8 BAR OPERATION
86
STAGING CRITERIA -TURBO MACHINESEFFECIENCY
CONSIDERATIONS

  • 1/2
  • Specific Speed rpm x (flow)
  • -------------------
    3/4
  • (Adiabatic Head)

na
SPECIFIC SPEED
0.23 - 0.24
Operation above or below the optimum Specific
Speed compromises on Aerodynamic Effeciency(na).
Characteristically the optimum is achieved at
390-400m/s impeller tip speed with 45 deg.
impellers
87
STAGING CRITERIA-TURBO MACHINESEFFECIENCY
CONSIDERATIONS

Mach No. Velocity of Flow/ Velocity of Sound
na
MACH NO.
Mc 1.2
Operation above the Critical Mach Number
results in a rapid decrease in the Aerodynamic
Effeciency(na).The speed of sound being
332m/s,the critical Mach No.corresponds to about
400-410m/s
88
THE RIGHT CHOICE
  • FOR RECIPROCATING COMPRESSORS THE STAGING RULES
    (THEORETICALLY) ARE MAINLY DETERMINED BY THE
    OUTLET TEMPERATURE.THE LIMITING TEMPERATURE IS
    MUCH LOWER BECAUSE IN THESE MACHINES THERE ARE
    MANY MOVING PARTS IN FRICTIONAL CONTACT WITH EACH
    OTHER.HIGH TEMPERATURE CAUSES DRAMATIC INCREASES
    IN CONSUMPTION OF SPARE PARTS DUE TO LOWERED
    VISCOSITY AT THE PARTS INTERFACE.
  • DUE TO THIS REASON,THE STANDARD API 618 LIMITS
    THE OPERATING TEMPERATURE TO 140 DEG.C. IF THIS
    IS TO BE ACHIEVED,WORKING BACK FROM THE
    TEMPERATURE EQUATION,THE PRESSURE RATIO PER STAGE
    BECOMES
  • P2/P1(273140/27340)EXP (1.4/1.4-1)2.63 AT AN
    INLET TEMPERATURE OF 40 DEG C. THEREFORE, IDEALLY
    A 2 STAGE MACHINE SHOULD DELIVER 4.29 BAR(G)

89
THE RIGHT CHOICE
  • COMPRESSOR TYPES
  • WORKING PRINCIPLES
  • CHARACTERISTICS
  • CONTROL SYSTEMS
  • STAGING
  • GENERAL INFORMATION

90
TURBO COMPETITOR STRATEGY
  • UNLIKE THE ZH6 COMPETITORS GENERALLY FOLLOW A
    PREDICTABLE STRATEGY
  • CAPITAL COSTS ARE KEPT LOW
  • THEY PROVIDE INCOMPLETE PACKAGES WHICH REQUIRE
    HEAVY SITE EXPENSES.
  • CUSTOMERS ARE NEVER INFORMED IN ADVANCE . COST
    BEC 1M PER M/C
  • THEY PROVIDE LOW PROFILE MACHINES AND CHEAP
    COMPONENTS
  • 2 STAGE MACHINES INSTEAD OF 3 STAGE WITH HIGH
    SPEEDS
  • LOW VALUE HYDROSTATIC BEARINGS INSTEAD OF
    HYDRODYNAMIC BEARINGS
  • POOR QUALITY MICROPROCESSORS
  • THROTTLE VALVES INSTEAD OF INLET GUIDE VANES
  • LOW PROFILE CONTROL SYSTEMS
  • COPPER COOLERS INSTEAD OF CU-NI
  • MOTORS WITH HIGH SERVICE FACTORS
  • COST SAVINS OF BEC 1.5 M AT THE COST OF
    PERFORMANCE

91
TURBO COMPETITOR STRATEGY
  • STAINLESS STEEL INTAKE PIPING
    BEC 45,000
  • INTERCONNECTING AND INST. AIR PIPING AND VALVES
    BEC 80,000
  • MICRO INTAKE FILTER (2U)
    BEC 65,000
  • ISOLATED FOUNDATIONS (WITH CORK INLAY)
    BEC 350,000
  • INSTRUMENT AIR COMPRESSOR WITH DRYER
    BEC 75,000
  • EXPANSION JOINTS BEC 30,000
  • SILENCING CANOPY (OPTIONAL) BEC
    140,000
  • OTHER ITEMS (WATER MANIFOLD,ETC) BEC 100,000
  • TOTAL INSTALLATION COST BEC 885,000
  • TOTAL INSTALLATION TIME 30
    DAYS

92
ZH-series
Efficient centrifugal compressors
NO MANUFACTURER EXCEPT ATLAS COPCO PROVIDES READY
TO RUN TURBO MACHINES
  • Complete
  • and ready
  • to use
  • easy, low cost installation
  • no special foundation
  • no anchor bolts
  • minimal floor space

93
RADIAL MACHINESAPI 617 VS API 672
FLEXIBLE SHAFT
API 617
DUE TO DISPLACEMENT OF THE ENDS IN THE FLEXIBLE
SHAFT DESIGNS,A GENEROUS CLEARANCE IS TO BE
MAINTAINED BETWEEN THE IMPELLER AND THE
SHROUD,FOR SAFETY REASONS,CAUSING COMPROMISES ON
VOLUMETRIC EFFECIENCY. RIGID SHAFT DESIGNS CAN
MAINTAIN MUCH CLOSER TOLERANCES AS IN API 617
TURBOS OR IN SCREW COMPRESSORS
94
(No Transcript)
95
TURBO COMPETITOR STRATEGY
  • THEY UNDERSTATE RUNNING COSTS
  • CAPACITIES ARE STATED IN INTAKE VOLUME WHICH IS
    OFTEN MUCH LOWER THAN FAD DUE TO SYSTEM LOSSES
  • POWER IS ALWAYS SPECIFIED AT HIGHEST
    TEMPERATURES TO SHOW LOW POWER . FOR INSTANCE AT
    20 DEG C POWER IS 8.5HIGHER THAN AT 40 DEG C
  • SPARE PART CONSUMPTION IS HIDDEN ALTHOUGH THIS IS
    GENERALLY
  • HIGHER THAN SCREW. GUARANTEES ARE ALWAYS VAGUE.
  • HIGH SPEEDS AT TIMES RESULT IN IMPELLER RUBS
    ,BLADE RESONANCE, EROSION AND SALT DEPOSITIONS

96
TURBO COMPETITOR STRATEGY
  • RUNNING AND MAINTENANCE SOME FACTS TO CONSIDER
  • UNLIKE THE ZH6 ALL IMPELLERS ARE CUSTOM MADE
    .HENCE NO STOCK CAN BE KEPT.
  • - IMPELLER FAILURE MEANS THIS HAS TO BE
    MANUFACTURED.
  • IMPELLERS NEED TO BE PERIODICALLY CLEANED AND
    BALANCED. FEW HIGH SPEED BALANCING MACHINES ARE
    AVAILABLE.
  • OVERHAULS NEED TO BE DONE AT SITE MEANING
    PRODUCTION LOSS OR HIGH STANDBY CAPACITY
  • AFTER A POWER FAILURE,MACHINE SHOULD BE
    PRELUBRICATED BEFORE START- UP.
  • LOADING UNLOADING CYCLES SHOULD BE LIMITED TO 1
    IN 180 SECONDS.
  • PRESSURE DROPS IN FILTERS OR COOLERS CAN CAUSE
    SURGE IN THE MARGINAL DESIGNS OF COMPETITION

97
WE HAVE NO OPINION !
EACH COMPRESSOR TYPE HAS ITS OWN CHARACTERISTICS
AND IS BEST SUITED TO A PARTICULAR
APPLICATION.IT IS OUR RESPONSIBILITY TO LOOK INTO
THE APPLICATION AND SUGGEST THE TECHNOLOGY WHICH
SUITS HIM BEST. WE HAVE THEM ALL THE BEST
COMPRESSOR FOR A SPECIFIC APPLICATION
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