A Control Valve is the most commonly used final control element used to regulate fluid flow in a process. In a process, normally it is the only controllable element residing in the loop. Ø This is a device used to modulate flow of process fluid in pipe lines by creating a variable area in the flow path. Ø The flow path is varied with respect to the control signal received from the controller towards the required flow modulation.

1. CONTROL
VALVES
Rejath Jacob Thomas

2. 2
CONTROL VALVE - An Introduction
Ø A Control Valve is the most commonly used
final control element used to regulate fluid flow in
a process. In a process, normally it is the only
controllable element residing in the loop.
Ø This is a device used to modulate flow of
process fluid in pipe lines by creating a variable
area in the flow path.
Ø The flow path is varied with respect to the
control signal received from the controller
towards the required flow modulation.

3. 3
CONTROL VALVE - ISA Definition
International Society of Automation -
ISA (previously known as Instrument
Society of America) defines the control
valve as a power operated device that
modulates the fluid flow rate in a
process control system

4. 4
CONTROL VALVE - In a process control loop
Representation of a typical process control loop

5. 5
CONTROL VALVE - PARTS

6. 6
PARTS OF CONTROL VALVE
ØValve body assembly
• Body
• Bonnet
• Bolting
• Seat ring
• Plug
• Stem
• Cage
• Packing
• Seal ring
• Gasket and shim
ØActuator assembly
Pressure Retaining Components
Trim Materials

7. 7
VALVE BODY
Main fluid boundary and pressure containing component
• End connections that allows installation in the pipeline
• Provision for attaching the bonnet
It Includes
• Provision for securing internal parts
BODY

8. 8
BONNET
• Also a major pressure containing component and
fluid boundary
• Bolted or threaded into valve body
• Bonnet locates and guides the valve stem and it
includes a bore for packing (packing box)
• Also includes yoke boss or some other means
mounting an actuator
BONNET

9. 9
TRIM
• Trim refers to all internal parts of a valve which
are in flowing contact with the controlled fluid
[also referred to as “Wetted” parts]
• It includes the valve plug, stem, cage, seat ring,
plug sealing rings, gaskets and packing parts
Trim Parts

10. 10
TRIM COMPONENTS
Ø Plug
Provides throttling control and shutoff in globe valves
Ø Seat ring
Seat rings in globe valves work with the valve plug to
arrest leakage.
ØCage
Provides plug guidance and flow characterization
ØStem
Connects the plug to the actuator

11. 11
PARTS OF CONTROL VALVE - Contd
Ø Stem Connector
A Clamp in two pieces to connect the actuator stem to
the valve plug stem.
ØYoke
The connecting structure / part between the Valve
Actuator and the bonnet assembly.
STEM
CONNECTOR
YOKE

12. 12
• Bonnet gasket :
Between Body and bonnet
• Seat ring gasket :
Between seat ring and body
Ø Gaskets
Provides sealing between mating surfaces.
Ø Packing
Prevents leakage of the fluid through the valve stem
• Packing is compressed to form a tight seal
between the packing box wall and the valve
plug stem
PARTS OF CONTROL VALVE - Contd

13. 13
ACTUATOR
It the part of the valve which generates the motive
power. It is the mechanism which operates the valve
plug, in correspondence to the control signal received
from the controller.
ØActuators Types:
• Pneumatic
Spring Diaphragm
Piston Cylinder
• Electrical
• Hydraulic

14. 14
VALVE ACCESSORIES
ØPOSITIONER
•Pneumatic
•Electro-pneumatic
•Conventional
•SMART – HART
•Foundation Field bus
ØPOSITION SWITCHES
•Inductive
•Mechanical Cam Operated

15. 15
VALVE ACCESSORIES – Cont . . .
ØSOLENOID VALVE
•Latching type
•Manual Reset
ØVOLUME BOOSTERS
ØAIR LOCK RELAY
ØAIR FILTER REFULATOR
ØAIR VOLUME TANK
ØHANDWHEEL

16. 16
ØCapacity : It is the ability of the valve to allow fluid flow through
it under stated condition.
ØCv –Valve Coefficient : It is the unit of measurement to define
the capacity of a valve. The number of US Gallons of water at 60
degrees F that will pass through a valve with a drop of one pound
per square inch in one minute.
ØVALVE Kv : Quantity of water in M3/Hr. at temperature
between 5 to 40 degrees C that will flow through the valve at a
specified travel with a pressure drop of 1 Bar.
•Kv = 0.856Cv
ØRated CV : Value of Cv at full open position.
VALVE TERMINOLOGIES

17. 17
Rangeability of a Control Valve is defined as the ratio of the
maximum controllable flow to the minimum controllable flow. The
Inherent rangeability of a valve is the ratio of the maximum and
minimum flow under constant pressure differential . Hence it is
expressed as Cv Max divided by Cv min.
TERMINOLOGIES Cont . .
ØLeakage:
ØRangeability:
Quantity of fluid passing through an assembled valve when the
valve is in the closed position under stated closure forces with
pressure differential and pressure specified. [ref to ANSI B-16 –
104-1976]

18. 18
Flow characteristics when constant pressure drop is maintained
across the valve.
TERMINOLOGIES Cont . .
Flow characteristics when pressure drop across the valve varies
as dictated by flow and related conditions in the system in which
the valve is installed.
•Inherent characteristics:
ØValve Characteristics:
•Installed Characteristics:
It is a relation between flow through the valve & percentage
rated travel as the latter is varied from 0-100%.

19. 19
Linear Rotary
Each type of valve has its special generic features, which
may, in a given situation, be either an advantage or a
disadvantage
ØDepending on the motion of the plug
CONTROL VALVE - CLASSIFICATION

20. 20
LINEAR VALVES ROTARY VALVES

21. 21
Control Valve
Rotary Motion
Linear Motion
Butterfly
Eccentric Plug
Ball
Swing Through
Lined
Eccentric
Segmented
Full
V-Notch
Globe
Diaphragm
Pinch or Clamp
Globe
Angle
3-Way
Single Seated
Double Seated
Split body
CONTROL VALVE - CLASSIFICATION
ØDepending on the motion of the plug

22. 22
SINGLE SEATED GLOBE VALVE
Sizes : 1/2" to 16" Higher sizes available on
request
To control large range of process parameters,
specially for oil and gas production, power
generation, chemical, petrochemical,
fertilizer, pharmaceutical, processed food
and other process industries.
Application :

23. 23
SINGLE SEATED GLOBE VALVE
Features :
Ø Leak proof packing are available on request
Ø Characteristics - Equal percentage, Linear and Quick open
Ø Can be supplied with wide range of interchangeable trim
sizes
Ø Large variety of trim design varying from contoured trims to
single stage ported and multiple stage low noise anti
cavitation trims
Ø High rangeability using low flow trims
Ø Tight shut off permissible
Ø Streamlined flow passage and excellent flow control
rangeability
Ø High powered actuator, field reversible
Ø High flow capacity and high gain

24. 24
DOUBLE SEATED GLOBE VALVE
Sizes : 11/2" to 18" (40 - 450 mm) Higher sizes
available on request
For high flow and high pressure services
Application :

25. 25
DOUBLE SEATED GLOBE VALVE
Features :
Ø High Flow Capacity Minimum differential plug areas to
reduce actuator force requirement
Ø Optional anti - cavitation / low noise trim option for high
pressure drop application
Ø Characteristics - Equal percentage, Linear, Quick open
Ø Leak proof packing are available on request
Ø Heavy duty top and bottom guided construction

26. 26
ANGLE VALVE
Sizes : 1/2" to 6"
Specially for very high pressure drop and also used where the
fluids contain solid particles.
Application :

27. 27
Features :
DOUBLE SEATED GLOBE VALVE
u High Flow Capacity
u Tight shut off
u High rangeability
u Body proportioned to withstand high pipe stresses without
distortion
u Wide range of interchangeable trim styles and sizes
available
u Adaptability to specialist duties i.e. venturi outlet, low noise
etc.

28. 28
THREE WAY VALVE
Sizes : 1/2" to 12“ Higher sizes available on request
Definition : is ideal for blending two separate flows, by having
two inlets and a common outlet, or dividing a flow into two
proportional parts by having one common inlet and two outlets.
For high temperature fluid and particularly for textile industries, to mix or divert fluids
Application :

29. 29
THREE WAY VALVE
Features :
u High Flow Capacity
uLeakage capability better than ANSI class IV & consistent
with normal single seat valve
u High rangeability
u Leak proof packing are available on request
u Valve is used for mixing or diverting services depending on
customers requirement

30. 30
THREE WAY VALVE
MIXING SERVICE DIVERTING SERVICE

31. 31
BELLOWS SEALED VALVE
Definition : Available as additional feature to give a leak
proof packing in the single seated, double seated and three
way valves.
For hazardous and corrosive fluids.
Application :
Features :
u Bellows are of stainless steel to withstand high
pressure & temperature.
uPTFE bellows available for low pressures on
request.

32. 32
BUTTERFLY VALVE
Sizes : 2" to 36"
Steel, Sugar and textile industries and specially for fluid
containing slurry particle. Used for on-off as well as
control applications.
Application :

33. 33
BUTTERFLY VALVE
Features :
u Water style connection Concentric design as
standard, offset design for special application
u Metal to metal or Sleeved type construction
u Choice of various rubber or PTFE sleeves
u Tight shut off with rubber sleeves
u Minimum obstruction for flowing media
u High Flow Capacity
u Simple & Light construction

34. 34
BALL VALVE
Sizes : 1/2" to 8" (15 - 200 mm)
Used in paper, Pulp and textile industries
Application :
Features :
u Tight shut off Minimum obstruction for the flowing
media
u High Flow Capacity
u 'O' Ball & 'V' Notch construction available

35. 35
DIAPHRAGM VALVE
Sizes : 1/2" to 14"
For water treatment plant, caustic soda plant, chemical
plants, fertilizers, specially for corrosive fluid.
Application :

36. 36
DIAPHRAGM VALVE
Features :
u Castings standardized to IS 210 FG grade cast Iron
u Better sealing and longer diaphragm life with the help of weir
design
u Stronger bonnet design to take care of higher thrust and
support to the diaphragm
u Diaphragm construction design with exclusively reinforced
fabric
u Fail safe assembly on auto valves totally protects process
operation in the event of electrical power or air supply failure
u Available in various linings to handle different fluids

37. 37
VALVE CLASSIFICATION - ACTUATOR TYPE

38. 38
Ø SCREWED
VALVE CLASSIFICATION – END CONNECTION
Ø WELDED END
Ø FLANGED END
Ø WAFER TYPE
Ø WELDED END
Ø WELDED END
• BUTT WELDED
• SOCKET WELDED
• RAISED FACE, RF
• FLAT FACE, FF
• RING TYPE JOINT, RTJ

39. 39
End connection – Screwed end
• Popular for small control valves because of their economy and
ease of installation
• Not available for bodies above 2 inch in size
• Aligning the threaded in valve with pipelines needs extreme care
and mismatch may lead to damage to thread in valve

40. 40
End connection – Welded end
• For high pressure and high temperature applications
• Valve body is directly welded into the pipeline
• Leak tight at all pressure and temperature
• Economical
• Socket weld ends are common for smaller valve sizes and butt
weld ends are standard for sizes 2-1/2 inch and larger valve bodies
• Precise alignment of valve body with pipe line is mandatory for
welded end connection
Butt Weld Socket Weld

41. 41
Butt welded end
Butt Weld end
Connection

42. 42
End connection – Raised Face (RF)
• Most common end connection
• Flange has circular, raised faces with concentric circular grooves
for good gasket sealing and resistance to gasket blowout
• Gasket only covers the raised face portion of the flange
• As line bolting is tightened, high stresses are produced at the
perimeter of each flange
• Not available for brittle/Soft material like Cast Iron, Bronze etc.

43. 43
End connection – Flat Face (FF)
• Allows full face contact with gasket clamped between the flanges
• Full face contact has the advantage of minimizing flange stresses
caused by forces of line bolting
• This type of flanges are common in cast iron bodies which are
brittle and would crack if raised face flanges were used. Flat face
flanges are also common in brass and aluminum bodies
• These materials are soft and would bend if raised face flanges
were used

44. 44
End connection – Ring type joint (RTJ)
• Well suited for extremely high pressure applications but generally
not used at high temperature
• Mating grooves in the body and pipe flanges retain a solid metal
seal ring
• As the line bolting is tightened the ring deforms and conforms to
the grooves
• Pressure assisted seal; since as the pressure increases, the ring
pushes against the grooves
• Soft iron or Monel is generally used as gasket material

45. 45
End connection – Separable flange
• Flanges are manufactured independently of the valve body
• Split rings are required to secure the flange to the body and to
transmit the bolting force to the gasket and mating connection
• If the body material is expensive separable flanges may result in
economy since flanges can be made of an economical material
like carbon steel

46. 46
End connection – Wafer style
• Generally called as Wafer style or flangeless
• Includes a raised-face contact surface in the body casting
• Long line bolting sandwiches the body and gasket between the
pipe flanges
• This is more economical body style since it requires less material
for construction
• Ball and butterfly valves are commonly available with this body
style

47. 47
Shutoff class
ØImportance of control valve shutoff
• To maintain proper operation of a process
– If a control valve leaks excessively in closed position the
leakage may affect the downstream processes & end
product quality
• To avoid potential damage to the valve in certain applications
– If a valve in boiler feed water application leaks, the high
velocity streams that leaks across the seat can erode
critical seating surfaces

48. 48
Shutoff class
ØThe ability of a control valve to prevent flow from the inlet side
to the outlet side of the valve in the fully closed condition.
ØANSI/FCI 70-2 came up with different shutoff classes to
standardize leakage across control valve
ØTo provide a range of shutoff options linear valves have
different type of plug and seat construction
ØRotary valves have various seal configuration and materials to
offer a range of shutoff

49. 49
Shutoff class
ANSI/FCI Leakage Classes
ANSI/FCI 70-2 Test Medium Pressure and temperature
Class II
Class III
Class IV
Class V Water Service DP at 10 to 52deg C
Port dia.
Bubbles per
Min.
mL per Min.
1 1 0.15
1 - 1/2 2 0.30
2 3 0.45
2 - 1/2 4 0.60
3 6 0.90
4 11 1.70
6 27 4.00
8 45 6.75
0.0005ml/min/psid/in. port dia
Class VI
Service DP or 50 PSID
whichever is lower at 10 to
52deg C
Water / Air
Service DP or 50 PSID
whichever is lower at 10 to
52deg C
Air
Maximum Leakage
0.5% valve capacity at full travel
0.1% valve capacity at full travel
0.01% valve capacity at full travel

50. 50
Flow Characteristic
Ø Relationship between flow through the valve and the
plug/disc travel.
Flow Characteristics
• Quick opening-Shut off & Fast flow
• Linear-Liquid level control
• Equal percentage-Pressure & Flow control

51. 51
Why Characterization?
ØTo compensate the process gain changes so that loop gain
remains independent of load.
ØTo provide uniform control loop stability over the expected range
of operations.
ØTo match the valve gain to the system gain for optimum
performance.
Characteristics methods:
• Trim shaping
• Positioner characterization
• Controller characterization

52. 52
Valve Characteristics

53. 53
Quick opening
• Inherent flow characteristic with high flow at initial % of travel.
• High and constant gain at initial half of its travel.
• Decreasing gain at travel above 70%

54. 54
Equal percentage
• Equal increments of change in valve travel produce equal
percentage changes in the existing flow coefficient
• Provides low valve gain at low percentage of valve travel, and
high valve gain at higher percentage of valve travel

55. 55
Linear Characteristics
• Flow is a linear function of travel
• Gain remains constant throughout the travel i.e 1

56. 56
Cage Shapes
Quick opening Linear Equal percentage

57. 57
Plug Shapes

58. 58
Plug Shapes

59. 59
Plug Shapes

60. 60
Inherent Characteristics
• Relationship between flow rate and valve travel, under
constant pressure drop conditions
• Inherent valve characteristics can be Quick opening,
Linear, Equal percentage

61. 61
Inherent Characteristics
uFlow at constant pressure drop

62. 62
Installed Characteristics
• Relationship between flow rate and valve travel, under actual
process conditions
• Installed flow characteristics is process dependent where
pressure drop changes with process variable

63. 63
Installed flow Characteristics
uFlow at varying pressure drops

64. 64
Valve Gain
Ratio of change in flow to change in stem travel
Valve Gain =

65. 65
Guidelines for selection of Valve
Characteristic

66. 66
Non Linear Process
• At Low flow, change in input signal will cause large change in
flow-rate.
• At high flows, the change in input signal will cause very small
change in flow-rate
• Impossible to tune controller for stability as the controllability
and the operating range sometimes is out of boundaries

67. 67
Compensation- for Non linear process
• To provide linear gain over entire system, in a non linear
process, equal percentage characteristic is chosen.
• The Equal Percent’s low gain compensates for high gain at
low flow
• Similarly, the Equal Percent’s high gain Compensates for
low gain at high flow

68. 68
Application guidelines
LinearConstant dPBack Pressure
Equal PercentMax dP>5X Min dP
LinearMax dP<5X Min dPLiquid Level
LinearSet point changes
Equal PercentLoad changesFlow
Equal PercentMostTemperature
Equal PercentGas , Large volume
Max dP > 5X Min dP
LinearGas , Large volume
Max dP < 5X Min dP
Equal PercentGas, Small volume
Equal PercentLiquid processPressure
GUIDELINESAPPLICATIONPROCESS

69. 69
Body/Bonnet material – carbon steel body
Ø Most commonly used carbon steel bodies are WCC and LCC
Ø WCC – Weldable Carbon steel Cast
• Preferable to killed carbon steel
• Above 427 deg C graphitization can occur
• Can be used between -29 to 427 deg

70. 70
Body/Bonnet material – carbon steel body
ØLCC – Low temperature carbon steel cast
• Quenched and tempered in order to meet impact requirement
• Same chemical composition as WCC
• Can be used between -46 to 343 deg C
• Impact tested for confirming suitability

71. 71
Body/Bonnet material – Alloy steels
ØAddition of Chromium and molybdenum enhances the resistance
to graphitization and tempering at elevated temperature
• WC6 : -29 to 593 deg C
• WC9 : -29 to 593 deg C

72. 72
Body/Bonnet material – Stainless steel
ØFor increased high temperature capability and for increased
pressure retaining capability, Alloys with still more chromium and
molybdenum are specified
ØTo avoid sensitization (formation of carbides) carbon content is
kept low in stainless steel
ØCF8M, CF3M, CG8M, CF8C

73. 73
P&ID symbols of various control valves per ISA S5.1

74. 74
Applicable codes and standards
Ø ASME B16.34 - valves - flanged, threaded and welding ends
Ø ASME B1.20.1 - Pipe threads
Ø ANSI FCI 70-2 - Control valve seat leakage
Ø ISA 71.01 - Environmental conditions for process measurement & control
systems: Temperature and Humidity
Ø ISA 75.01 - Flow equation for sizing control valves
Ø ISA 75.03 - Face to face dimensions for flanges globe-style control valve bodies
Ø ISA 75.04 - Face to face dimensions for flangeless control valves
Ø ISA 75.17 - Control valves aerodynamic noise prediction

75. 75
Applicable codes and standards
Ø NEMA ICS 6 - Enclosures for Industrial controls and systems
Ø IEC 529 - Specification for degree of protection provided by enclosure
Ø NFPA 70 - National electric code

76. 76
Major vendors
Valve Assembly
Ø Masoneilan Dresser
Ø Fisher
Ø Flowserve (Valtek)
Ø Tyco
Ø Instrumentation Limited
Ø Metso
Actuators
= EIM
= Bettis
= Keystone
= Automax
= Rotork
= Limitork

77. 77
Questions?
Thank You !