Valves and actuators

1. CONTROL VALVES
SUBMITTED TO
AMANDEEP SHARMA
Submitted by
Dhruv Upadhaya

2. CONTENTS
• ACTUATORS
PNEUMATIC, HYDRAULIC AND ELECTRICAL.
• CONTROL VALVE
INTRODUCTION, TYPE SIZING AND SPECIFICATIONS

3. WHAT IS CONTROL VALVE???
• CONTROL VALVES ARE THE VALVES USED TO CONTROL CONDITIONS SUCH AS
FLOW, PRESSURE, TEMPERATURE AND LIQUID LEVEL BY FULLY OR PARTIALLY
OPENING AND CLOSING IN RESPONSE TO THE SIGNALS RECEIVED FROM THE
CONTROLLERS THAT COMPARE A “SETPOINT” TO A “PROCESS VARIABLE” WHOSE
VALUE IS PROVIDED BY SENSORS THAT MONITOR CHANGES IN THAT CONDITION.
• IT IS ALSO CALLED FINAL CONTROL ELEMENT
• THE OPENING AND CLOSING OF CONTROL VALVES IS DONE BY PNEUMATIC,
ELECTRICAL OR HYDRAULIC ACTUATORS

4. AN AUTOMATIC LEVEL
CONTROL SYSTEM
REPLACES A HUMAN
WITH A CONTROLLER
AND USES A SENSOR TO
MEASURE THE LEVEL.
Figure 1

5. PARTS OF CONTROL VALVE
THERE ARE THREE PARTS OF CONTROL VALVES
• VALVE’S ACTUATOR
• VALVE’S POSITIONER
• VALVE’S BODY

6. ACTUATORS
• MEANS OF OPERATING THE VALVE
• IT REQUIRES A CONTROL SIGNAL AND A SOURCE OF ENERGY
• SUPPLIED MAIN ENERGY
SOURCE
(MAY BE ELECTRIC CURRENT,
HYDRAULIC PRESSURE OR
PNEUMATIC PRESSURE)
• CONTROL SIGNAL :
LOW ENERGY
CAN BE ELECTRICAL VOLTAGE
OR CURRENT , PNEUMATIC
PRESSURE OR HYDRAULIC
FLUID PRESSURE

7. PNEUMATIC ACTUATORS
• A PNEUMATIC ACTUATOR CONVERTS ENERGY ( IN THE FORM OF COMPRESSED
AIR ) INTO MECHANICAL MOTION.
• THE MOTION CAN BE ROTARY OR LINEAR DEPENDING UPON THE TYPE OF
ACTUATORS USED.

8. PNEUMATIC ACTUATORS
THEY ARE BASICALLY OF TWO TYPES
• PISTON ACTUATOR
• DIAPHRAGM ACTUATOR
THESE ACTUATORS ARE DESIGNED SO THAT WITH A SPECIFIC CHANGE OF AIR
PRESSURE, THE SPINDLE WILL MOVE SUFFICIENTLY TO MOVE THE VALVE
THROUGH ITS COMPLETE STROKE FROM FULLY-CLOSED TO FULLY-OPEN.

9. DIAPHRAGM ACTUATOR
• THEY HAVE COMPRESSED AIR
APPLIED TO A FLEXIBLE MEMBRANE
CALLED THE DIAPHRAGM
• THEY ARE SINGLE ACTING I.E. AIR IS
SUPPLIED FROM SINGLE SIDE OF THE
DIAPHRAGM
FAIL
OPEN
FAIL
CLOSESINGLE ACTING
DAIPHRAGM
ACTUATOR

10. PISTON ACTUATOR
• THEY CAN WITHSTAND HIGHER INPUT
PRESSURES.
• CAN OFFER SMALL CYLINDER VOLUMES.
• THEY ARE GENERALLY USED WHERE
THERE IS LONG STEM TRAVEL OR LARGE
AMOUNT OF FORCE TO BE POSITIONED.
SINGLE
ACTING
DOUBLE
ACTING

11. HYDRAULIC ACTUATORS
• PNEUMATIC ACTUATORS THAT USE HYDRAULIC FLUIDS ARE CALLED HYDRAULIC
ACTUATORS BUT THEY ARE MORE POWERFUL FOR THE SAME DIMENSIONS

12. PRINCIPLE OF HYDRAULIC
ACTUATOR
• AS THE FLUID/ GAS IS HEATED IT
EXPANDS AND A PRESSURE IS
EXERTED BY THE GAS/FLUID IN THE
CYLINDER TO THE PISTON. THIS
PISTON MOVES UPWARDS THUS
CONVERTING PRESSURE TO LINEAR
MOTION

13. ELECTRICAL ACTUATORS
• ELECTRICAL ACTUATORS USE ELECTRICAL SIGNAL TO PRODUCE THE MOTION
• THEY ARE OF TWO TYPES SOLENOID ACTUATORS AND MOTOR DRIVEN
ACTUATORS.

14. SOLENOIDAL ACTUATORS

15. MOTOR DRIVEN ACTUATORS

16. CONTROL VALVE
• A CONTROL VALVE IS A POWER-OPERATED DEVICE USED TO MODIFY THE FLUID
FLOW RATE IN A PROCESS SYSTEM.
• THERE ARE TWO BASIC TYPES OF CONTROL VALVES
A) ROTARY MOTION VALVES HAVING BALL, BUTTERFLY OR PLUG TYPE
CLOSURES.
B) LINEAR MOTION VALVES HAVING GLOBE , DIAPHRAGM OR PINCH TYPE
CLOSURES.

17. CONTROL VALVE CLASSIFICATION
Control
Valve
Linear
Motion
Globe
Globe
Single
Seated
Double
Seated
Angle
3 wayDiaphragm
Pinch
Rotary
Motion
Ball
Butterfly
Plug

18. The area where
disc/wedge closes on
the valve body to
stop or reduce flow.
Directs flow, and
attachment component
to system
Provides a seal between the stem
and bonnet. Keeps pressure off
packing when valve is open.
Body to bonnet seal.
Upper part of valve.
Support for, yoke
actuator, handwheel,
etc..
Seal between the stuffing
box and stem.
The location for
packing to be placed.
Compresses
packing..
Gland Flange is a one
piece unit used to
compress packing.
Follower consists of
two separate pieces.
Bolted or threaded.
Support element
connection between
bonnet and
handwheel.
Transfer motion of Handwheel to
the disc.
Attached to disc by: Split Joint
Threaded
One piece
Pins/cotter
keys.
Backseat
Stem
Gasket
Stuffing Box
Gland
Handwheel
Yoke bushing
or stem nut
Yoke
Bonnet
Body
Wedge/Disc
Seat
Gland Flange/
Follower
Packing
Controls the movements
of the disc.
Component part of the valve that opens
or closes against the seat to start or stop
flow.

19. LINEAR MOTION

20. SINGLE SEATED GLOBE VALVE
• FEATURES
• LARGE AMOUNT OF FORCE
REQUIRED TO DRIVE THE STEM
• TIGHT SHUT OFF
• USED IN SMALL DIAMETER
APPLICATIONS
• APPLICATIONS
• USED FOR CONTROLLING LARGE
RANGE OF PROCESS PARAMETERS
HENCE USED IN OILAND GAS
PRODUCTION, POWER GENERATION

21. DOUBLE SEATED GLOBE VALVE
• FEATURES
• STEM CAN BE DRIVEN WITH SMALL AMOUNT OF
FORCE
• CAN NOT ACHIEVE PERFECT CLOSURE
RESULTING IN LEAKAGE
• USED IN LARGER DIAMETER APPLICATIONS
• BODY PARTS WEAR OUT DUE TO EROSION AND
CAVITATION WHICH RESULTS IN ANNOYING
NOISES
• APPLICATIONS
• USED FOR HIGH FLOW AND HIGH PRESSURE
SERVICES

22. DAIPHRAGM VALVES
• FEATURES
• CONSISTS OF A SADDLE OR SEAT
UPON WHICH THE DIAPHRAGM
CLOSES THE VALVES.
• CAN HANDLE CORROSIVE FLUIDS.
• APPLICATIONS
• USED AS SHUT OFF VALVES IN FOOD
AND BEVERAGE , PHARMACEUTICAL
AND BIOTECH INDUSTRIES.

23. PINCH VALVE
• FEATURES
• TIGHT SHUT OFF
• THE FLEXIBLE SLEEVE ALLOWS THE
VALVE TO CLOSE DROP TIGHT AROUND
SOLIDS , SOLIDS THAT WOULD TYPICALLY
BE TRAPPED BY THE SEAT OR STUCK IN
CREVICES IN GLOBE, DIAPHRAGM,
BUTTERFLY, GATE OR BALL VALVES.
• APPLICATIONS
•BEST USED IN CONTROLLING CORROSIVE
FLUIDS, STEAM AND THERMIC FLUIDS.

24. ROTARY
MOTION

25. BALL VALVE
• FEATURES
• TIGHT SHUT OFF
• MINIMUM OBSTRUCTION FOR THE FLOWING MEDIA.
• HIGH FLOW CAPACITY
• CAN WITHSTAND HIGH PRESSURE AND
TEMPERATURES
• APPLICATIONS
• USED FOR HAZARDOUS AND CORROSIVE FLUIDS

26. BUTTERFLY VALVE
• FEATURES
• HIGH FLOW CAPACITY
• UNLIKE BALL VALVE THE DISC IS PRESENT
IN THE FLOW OF THE LIQUID AND HENCE A
PRESSURE DROP IS ALWAYS INDUCED IN
THE FLOW.
• TIGHT SHUT OFF
• APPLICATIONS
• USED IN STEEL , SUGAR AND TEXTILE
INDUSTRIES

27. VALVE SIZING
• IT IS A PROCEDURE BY WHICH THE DYNAMICS OF A PROCESS SYSTEM ARE
MATCHED TO THE PERFORMANCE CHARACTERISTICS OF A VALVE.
• THIS IS TO PROVIDE A CONTROL VALVE THAT WILL BEST MEET THE NEEDS OF
MANAGING FLOW WITHIN THAT PROCESS SYSTEM.

28. FLOW COEFFICIENTS
• THE VALVE FLOW COEFFICIENT, CV IS THE NUMBER OF GALLONS PER MINUTE OF
WATER AT 60 DEGREES F WHICH WILL PASS THROUGH A GIVEN FLOW
RESTRICTION WITH A PRESSURE DROP OF 1 PSI.
• FOR EXAMPLE, A CONTROL VALVE WHICH HAS A FLOW COEFFICIENT, OR CV, OF 12
HAS AN EFFECTIVE PORT AREA THAT IT PASSES 12 GALLONS PER MINUTE OF
WATER WITH 1 PSI PRESSURE DROP.

29. BASIC INFORMATION REQUIREMENTS
FOR EFFECTIVE VALVE SIZING
• FOR THE SYSTEM:
• PRESSURE BEFORE AND AFTER THE CONTROL VALVE, ΔP
• FLOW RATE, QUANTITY AND UNITS, Q
• PROCESS TEMPERATURE WITH UNITS, T
• PROPERTIES OF THE MEDIA, (VISCOUS, FIBER SUSPENSION, GASEOUS ITS VAPOR
PRESSURE, SOMETIMES MOLECULAR WEIGHT)
• FOR THE CONTROL VALVE:
• FLOW CAPACITY (CV), INHERENT THROTTLING CURVE, KC (CAVITATION
INDEX), FL² (CRITICAL FLOW FACTOR)

30. DELTA P (P)
• P SIZING IS THE PRESSURE DROP ACROSS THE VALVE USED FOR CONTROL
VALVE SIZING AT A SPECIFIC FLOW RATE
• MOST APPLICATIONS HAVE MULTIPLE FLOWS FOR SIZING WITH DIFFERENT ΔP
FOR EACH
• IN A GIVEN SYSTEM, HIGHER FLOW RATES GENERALLY RESULT IN LOWER
PRESSURE DROP ACROSS THE VALVE.

31. FLOW CHARACTERISTICS
• CONTROL VALVE FLOW CHARACTERISTICS ARE DETERMINED PRINCIPALLY BY
THE DESIGN OF THE VALVE TRIM.
• THE THREE BASIC FLOW CHARACTERISTICS AVAILABLE ARE:
• QUICK OPENING
• LINEAR
• EQUAL PERCENTAGE (=%)
• A MODIFIED CHARACTERISTIC (SOMETIMES CALLED MODIFIED PERCENTAGE)
GENERALLY FALLING BETWEEN THE LINEAR AND EQUAL PERCENTAGE
CHARACTERISTICS MAY ALSO BE AVAILABLE.

32. VALVE PLUGS

33. CHARACTERISTIC

34. WHY USE EQUAL PERCENTAGE
•PROVIDES EQUAL PERCENTAGE
INCREASES IN RATE OF FLOW FOR
EQUAL INCREMENTS OF PLUG
MOVEMENT.
•PROVIDES THE BEST CHOICE OF
FLOW CHARACTERISTIC FOR MOST
SYSTEMS.

35. DeZurik Operation
October 2005
0
20
40
60
80
100
0 20 40 60 80 100
% Open
%Cv
Equal Percent
Modified Parabolic
Linear
Quick Opening
WHAT IS DESIRED ?
- AFTER INSTALLATION, GENERALLY IT
SHOULD
BE NEAR LINEAR.
WHY?
TO PROVIDE A MORE PREDICTABLE
FLOW
CHANGE IN RESPONSE TO EACH
INCREMENTAL VALVE POSITION CHANGE

36. OTHER CONSIDERATIONS

37. CONTROL VALVE SEAT LEAKAGE
• IT IS BECOMING MORE COMMON TO EXPECT A CONTROL VALVE TO PROVIDE
ISOLATION DUTY, THUS ALLOWABLE LEAKAGE BECOMES MORE IMPORTANT.
• LEAKAGE CLASSES ARE CLASS I-VI.
• CLASSES I-V ARE MEASURED USING WATER, CLASS VI IS MEASURED USING AIR.
• THE MOST COMMON CLASS FOR METAL SEATED CONTROL VALVES IS CLASS IV.
(0.01% OF RATED CV)
• CLASS VI GENERALLY APPLIES TO RESILIENT SEATED VALVES ONLY.

38. FLUID VELOCITY
• EXCESSIVE FLUID VELOCITY CAN CREATE EROSION, AND
ACCELERATE CORROSION DAMAGE. IT ALSO CONTRIBUTES TO NOISE
LEVEL AND VIBRATION.
• VALVE USERS WILL GENERALLY DEFINE ACCEPTABLE VELOCITY IN
VALVES AND PIPES FOR THE ABOVE REASONS. LIQUID VELOCITY OF
UP TO 15 FT/SEC. IS COMMON; FOR GAS OR STEAM 400 FT/SEC. OR
HIGHER, DEPENDING UPON SIZE, IS PERFECTLY ACCEPTABLE.

39. NOISE AND VIBRATION
NOISE RESULTS FROM THE CONVERSION OF THE MECHANICAL ENERGY
OF THE FLOW INTO ACOUSTIC ENERGY AS THE FLUID PASSES THROUGH
THE VALVE RESTRICTION.
VIBRATION IS A DIRECT RESULT OF NOISE AND CAN CREATE ISSUES WITH
VALVE LIFE.
NOISE CAN BE REDUCED THROUGH TWO MEANS, INTERNAL AT THE
VALVE TRIM, AND EXTERNAL SUCH AS PIPE INSULATION OR
DOWNSTREAM SILENCERS.

40. FLOWDIRECTION
•MANY VALVE TYPES HAVE A PREFERRED FLOW DIRECTION TO
MINIMIZE THE EFFECTS OF VELOCITY, TO CREATE THE TIGHTEST
SHUT-OFF, AND TO OPTIMIZE THE RESPONSE TO INPUT SIGNAL.