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1. Basic of Control
Valve

2. Process Block Diagram

3. Control Valve ????
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4. 4
Valve Actuator
Valve Body
Control Valve
• A Control Valve is one which Controls the
flow rate.
• It is a Final control element through which
a fluid passes, that adjusts the flow
passage as directed by a signal from a
controller to modify the flow.
• Main parts of Control valve are:-
1. Actuator
2. Valve Body
3. Bonnet
Bonnet

5. Types of Control Valve

6. Types of Actuator
Diaphragm Type Piston Type
Rack & Pinion
Type

7. Types of Diaphragm Actuator & Its Parts
FC ( Fail to Close)
Air to Open
FO ( Fail to Open)
Air to Close

8. Types of Piston Actuator & Its Parts
Single Acting Actuator Double Acting Actuator Single Acting Actuator Double Acting Actuator

9. Rack & Pinion Actuator & Its Parts
Anti- clockwise
Air is supplied forcing the
Pistons away from each
other (towards the end),
rotating the Drive Pinion
anticlockwise
Clockwise
Air failure (loss of pressure)
allows the compressed
springs to force piston
towards each other (towards
centre) , rotating the Drive
Pinion clockwise &
exhausting the air.

10. Actuators @ Plants
10
Diaphragm Type
Double Acting
Piston Type
Diaphragm Type
Single Acting
Piston Type

11. Types of Globe valve Body & Its Parts
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13. Valve Body Flow Direction

14. Valve Travel %
Valve Characteristics
CV
%
CAM 1 - Linear
CAM 2 - Equal Percentage
CAM 3- Quick Opening

15. Valve Characteristics
Balance Type Plug
Seat & Cage

16. Seat Leakage Class
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ANSI FCI 70-2 supercedes ANSI B16.104 and specifies six different seat leakage
classifications; class I to class VI.
Leakage Class I is also known as dust tight and can refer to metal or resilient seated valves.
Leakage Class II establishes the maximum permissible leakage generally associated with
commercial double-seat control valves or balanced single-seat control valves with a piston ring
seal and metal-to-metal seats.
Leakage Class III establishes the maximum permissible leakage generally associated with
Class II, but with a higher degree of seat and seal tightness.
Leakage Class IV is also known as metal to metal. It is the kind of leakage rate you can
expect from a valve with a metal shut-off disc and metal seat.
Leakage Class V is usually specified for critical applications where the control valve may be
required to be closed, without a blocking valve, for long periods of time with high differential
pressure across the seating surfaces. It requires special manufacturing, assembly and testing
techniques. This class is generally associated with metal seat, unbalanced single-seat control
valves or balanced single-seat designs with exceptional seat and seal tightness.
Leakage Class VI is known as a soft seat classification. Soft Seat Valves are those where the
seat or shut-off disc or both are made from some kind of resilient material such as Teflon.

18. CV Accessories – I2P Convertor
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19. CV Accessories – I2P Convertor
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In the Current to Pressure converter, we usually give input current signal as 4 – 20
mA . We also give a continuous supply of 20 P.S.I to the Flapper Nozzle assembly. As
we give input current signal, Electromagnet gets activated.If the current is more, then
the power of magnet will get increased. The Flapper of the Flapper-
Nozzle instrument is connected to Pivot so that it can move up and down and a
magnetic material was attached to other end of flapper and it is kept near the
electromagnet. As the magnet gets activated. the flapper moves towards the
electromagnet and the nozzle gets closed to some extent. So the some part of 20
P.S.I supplied will escape through nozzle and remaining pressure will come as output.
If the current signal is high, then power of the magnet will increase, then flapper will
move closer to the nozzle, so less pressure will escape through nozzle and output
pressure increases. In this way the output pressure will be proportional to the input
current. For the input current of 4 – 20 mA we can get the output pressure of 3 – 15
P.S.I

20. CV Accessories - Positioner
• A Positioner is a pneumatic Controller to control the
control Valve Position.
• In other words, Positioner is a device used to increase
or decrease the air load pressure driving the actuator of
a control valve until the valve’s stem reaches a position
balanced to the output signal from the process variable
instrument controller.
• Positioner is used with control valve because:
• It works as a amplifier
• It Minimize valve stem packing friction effects and
the resulting hysteresis, particularly for high
temperature packing materials.
• It Increases the speed of response to a change in
process.
• Allow for split ranging i.e. one controller for two
valves.
• Positioners generally work on :
• Force Balance Principle
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21. CV Accessories - Positioner
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IL positioners are further classified according to their
action:
Single acting
Double acting
Single acting Positioners:
These positioners are used with single acting IL valves.
It has one air inlet port, one pneumatic signal (3-15 psig)
port and one output port.
It is a force-balance type .
Positioners are also available of both type direct acting and
reverse acting.
Direct acting positioner can be changed to reverse acting
positioner (or vice- versa) by just rotating pilot assembly by
1800.
Basic parts of a positioner can be seen in the picture.

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