CONTROL VALVES, PRESSURE

REGULATORS, SOLENOID VALVES

WHAT IS A CONTROL VALVE? A CONTROL VALVE IS A FINAL CONTROL

ELEMENT IN A PROCESS CONTROL LOOP TYPICALLY USED TO MANIPULATE FLOW OF MATERIAL WITH AN OBJECTIVE TO ATTAIN A DESIRED VALUE OF THE CONTROLLED PROCESS VARIABLE. THIS IS ACHIEVED BY THROTTLING FLOW OF MATERIAL BY OPERATING A CLOSURE MEMBER WHICH CLOSES THE VALVE’S PORT, PARTIALLY OR FULLY.

CONTROL VALVE SIZING CONTROL VALVE SIZING IS THE PROCESS

OF DETERMINATION OF REQUIRED FLOW CAPACITY OF A VALVE FOR A GIVEN SERVICE

TYPES OF CONTROL VALVES CONTROL VALVES MAY BE CLASSIFIED

INTO DIFFERENT TYPES BASED UPON : 1. TYPE OF CONTROL ACTION2. TYPE OF FLOW CHARACTERISICS3. TYPE OF CONSTRUCTION4. TYPE OF MOVEMENT

TYPES OF CONTROL VALVEBASED UPON CONTROL ACTION A CONTROL VALVE WHOSE CLOSURE

MEMBER CAN BE DRIVEN TO ANY POSITION BETWEEN FULL CLOSED AND FULL OPEN POSITION IN RESPONSE TO AN ANALOG SIGNAL AND USED FOR MODULATING CONTROL ACTION IS CALLED A MODULATING CONTROL VALVE.

A CONTROL VALVE WHICH IS USED IN EITHER FULL CLOSE OR FULL OPEN POSITION FOR ON/OFF CONTROL IS CALLED AN ON/OFF CONTROL VALVE.

TYPES OF CONTROL VALVEBASED UPON FLOW CHAR FLOW CHARACTERISTIC OF A VALVE

REFERS TO THE MANNER IN WHICH FLOW THROUGH A VALVE VARIES WITH OPENING OF THE VALVE FROM FULL CLOSE TO FULL OPEN POSITION. THE DIFFERENT CHARACTERISTICS ARE:

1. LINEAR2. MODIFIED LINEAR3. EQUAL PERCENTAGE4. QUICK OPENING

TYPES OF CONTROL VALVEBASED UPON FLOW CHAR THE INSTALLED CHARACTERISTIC OF A

VALVE IS DIFFERENT FROM ITS INHERENT FLOW CHARACTERISTIC.

THE FLOW CHARACTERISTIC OF A CONTROL VALVE IS DETERMINED BY ITS TRIM(SEAT AND PLUG OR EQUIVALENT PARTS).

SOMETIMES A DESIRED FLOW CHARACTERISTIC IS ALSO OBTAINED BY SUITABLY ADJUSTING/REPLACING POSITIONER PARTS, USUALLY A CAM.

TYPES OF CONTROL VALVEBASED UPON FLOW CHAR THE FLOW CHARACTERISTIC WHEN A

CONTROL VALVE IS SUBJECTED TO A FIXED PRESSURE DROP ACROSS IT IS CALLED ITS INHERENT FLOW CHACTERISTIC.

THE FLOW CHARACTERISTIC WHEN A CONTROL VALVE IS SUBJECTED TO A VARYING PRESSURE DROP IN ACTUAL PROCESS CONDITIONS WHEN INSTALLED IS CALLED ITS INSTALLED FLOW CHARACTERISTIC.

CONTROL VALVES - INHERENT FLOW CHARACTERISTICS

TYPES OF CONTROL VALVEBASED UPON CONSTRUCTION VALVES ARE CLASSIFIED BASED UPON CONSTRUCTION/DESIGN OF BODY/TRIM. THE COMMON TYPES ARE:1. GLOBE-TOP-GUIDED/BOTTOM GUIDED/TOP AND BOTTOM GUIDED2. CAGE/CAGE GUIDED3. BUTTERFLY4. ECCENTRIC DISC/TRIPLE OFFSET5. BALL6. PLUG7. GATE8. DIAPHRAGM/SAUNDERS/PINCH9. NEEDLE10. KNIFE-EDGE GATE11. SEGMENTED BALL VALVE(V-NOTCH BALL VALVE)12. DIVERTING VALVE13. MIXING VALVE14. 3/2-WAY PLUG VALVE15. DUAL PORTED VALVE16. DESUPERHEATER/ATTEMPERATOR17. PRESSURE REDUCING AND DESUPERHEATING (PRDS)18. LOW Cv

TYPE OF CONTROL VALVE DEPENDING UPON MOVEMENT CONTROL VALVES ARE ALSO CLASSIFIED

BASED UPON MOVEMENT OF CLOSURE MEMBER:

1. SLIDING STEM2. ROTARY

A TYPICAL CONTROL VALVE

CONTROL VALVE ACTUATORS CONTROL VALVES ARE USUALLY OPERATED IN

RESPONSE TO A CONTROL SIGNAL USING AN ACTUATOR.FOLLOWING ARE COMMONLY USED ACTUATORS:

1. SPRING-DIAPHRAGM/AIR OPERATED2. PISTON-CYLINDER/SINGLE OR DOUBLE

ACTING/AIR OPERATED3. ELECTRIC-SOLENOID OPERATED4. ELECTRIC-MOTOR OPERATED5. PNEUMATIC MOTOR OPERATED6. HYDRAULIC SOME CONTROL VALVES MAY ALSO BE

OPERATED MANUALLY.

CONTROL VALVESFAILSAFE POSITION CONTROL VALVES ARE ALWAYS DESIGNED TO

ATTAIN A SPECIFIED FAILSAFE POSITION IN CASE OF ACTUATING POWER ----(AIR/HYDRAULIC/ELECTRIC) FAILURE OR CONTROL SIGNAL FAILURE.

THE MOST COMMON FAILSAFE POSITIONS ARE FULL CLOSE/FULL OPEN/HOLD(LAST).

THIS IS USUALLY ACHIEVED BY USE OF SPRING-RETURN ACTUATORS OR SPECIALLY DESIGNED EMERGENCY BACKUP SYSTEM AND SUITABLE ACCESSORIES.

CONTROL VALVE ACCESSORIES IN ADDITION TO THE ACTUATOR, A CONTROL VALVE IS USUALLY

PROVIDED WITH ONE OR MORE OF FOLLOWING ACCESSORIES:1. POSITIONER-FOR POSITIONING A MODULATING CONTROL VALVE2. SOLENOID VALVE-FOR OPERATION OF AN ON/OFF VALVE OR

INTERLOCKING OPERATION OF A MODULATING VALVE.3. LIMIT SWITCHES-FOR DETECTING SPECIFIC POSITIONS OF VALVE4. AIR-FILTER REGULATOR-FOR FILTERED AND PRESSURE REGULATED AIR

SUPPLY5. POSITION TRANSMITTER – FOR REMOTE INDICATION OF VALVE POSITION6. VOLUME BOOSTER – FOR FAST VALVE OPERATION BY PROVIDING AIR IN

VOLUMES HIGHER THAN A NORMAL POSITIONER7. EMERGENCY BACKUP SYSTEM – THIS IS USUALLY PROVIDED FOR

ATTAINING FAILSAFE POSITION WITH SOME TYPE OF ACTUATORS. SOMETIMES IT MAY ALSO PROVIDE FOR EMERGENCY VALVE OPERATION.

8. I/P CONVERTER – FOR CONVERTING ELECTRIC CONTROL SIGNAL TO PNEUMATIC CONTROL SIGNAL IN CASE OF A MODULATING CONTROL VALVE.

CONTROL VALVE SELECTION AND SPECIFICATION EVERY CONTROL VALVE IS SPECIFICALLY SELECTED FOR A GIVEN APPLICATION.PROPER

SELECTION IS CRUCIAL FOR ACHIEVING DESIRED PERFORMANCE. SELECTION IS BASED UPON FOLLOWING CONSIDERATIONS:

1. SERVICE – FLUID,PHYSICAL AND CHEMICAL PROPERTIES OF FLUID AND OPERATING/NORMAL AND EXTREME PROCESS CONDITIONS.

2. CONTROL ACTION – MODULATING OR ON/OFF3. CONTROL OBJECTIVE – THE NATURE OF PROCESS PARAMETER TO BE CONTROLLED.4. MATERIAL OF CONSTRUCTION – TO BE SELECTED FOR COMPATIBILITY WITH FLUID AND SERVICE

CONDITIONS TO WITHSTAND EFFECTS OF CORROSION/EROSION/STRESS CRACKING/MATERIAL FAILURE.

5. END CONNECTIONS AND PHYSICAL DIMENSIONS.6. SUITABILITY OF GIVEN VALVE DESIGN/CONSTRUCTION.7. FLOW CAPACITY – CONTROL VALVE SIZING.8. FLOW CHARACTERISTIC.9. ALLOWABLE LEAKAGE IN FULL CLOSE POSITION.10. RESTRICTIONS ON FUGITIVE EMISSIONS.11. IDENTIFYING POTENTIAL FOR CAVITATION/CHOKED FLOW CONDITION/AERODYNAMIC NOISE AND

AVOIDING THE SAME.12. FAILSAFE POSITION.13. APPROPRIATE ACTUATOR TYPE AND SIZE.14. REQUIRED ACCESSORIES.15. APPLICABLE CODES,STANDARDS AND PRACTICES.16. PRIOR PERFORMANCE DATA IN SAME/SIMILAR APPLICATIONS.17. MANUFACTURER’S RECOMMENDATIONS.

CONTROL VALVE SIZING CONTROL VALVE SIZING IS A SYSTEMATIC PROCEDURE FOR DETERMINING REQUIRED

FLOW CAPACITY OF A VALVE FOR A GIVEN APPLICATION. FLOW CAPACITY OF A VALVE IS USUALLY EXPRESSED AS Cv (OR SOMETIMES Kv)

VALUE. Cv IS DEFINED AS THE AMOUNT OF WATER AT 60 DEG F IN USgpm FLOWING

THROUGH A FULL OPEN VALVE WHEN THE PRESSURE DROP ACROSS THE VALVE IS ONE psi.

APPROPRIATE VALVE IS SELECTED USING MANUFACTURER’S DATA WITH SELECTED Cv MATCHING OR NEXT HIGHER THAN CALCULATED Cv.

USUALLY VALVES ARE SIZED TO HAVE 75 TO 85% OPENING AT MAXIMUM FLOW RATE.

IT IS BEST TO SIZE A CONTROL VALVE WITH AN OBJECTIVE TO MEET DESIRED PROCESS GAIN SPECIFICATION.

USE OF APPROPRIATE SOFTWARE IS RECOMMENDED FOR VALVE SELECTION AND SIZING. IN SPECIAL APPLICATIONS, USE MANUFACTURER’S RECOMMENDED SIZING PROCEDURE.

CALCULATIONS ARE ALSO MADE TO CHECK FOR AND AVOID CAVITATION, CHOKED FLOW CONDITIONS AND AERODYNAMIC NOISE.

SUITABLE ACTUATOR IS ALSO DETERMINED USING ACTUATOR SIZING PROCEDURE.

CONTROL VALVE SIZING STANDARDS

CONTROL VALVE TESTING A CONTROL VALVE IS EXHAUSTIVELY TESTED AT

MANUFACTURING LOCATION WITH RESPECT TO MOC,PRESSURE RATING, MATERIAL / MANUFACTURING DEFECTS,ALLOWABLE LEAKAGE AND AS PER MODERN TREND MAY BE SUBJECTED TO STATIC AND DYNAMIC PERFORMANCE TESTS TO EVALUATE/PREDICT ITS LOOP PERFORMANCE WHEN INSTALLED.

THE APPLICABLE TEST PROCEDURES AND REQUIRED TEST CERTIFICATES ARE USUALLY SPECIFIED DURING PROCUREMENT.

IT IS RECOMMENDED TO TEST A CONTROL VALVE WHENEVER IT IS OVERHAULED OR REPAIRED.

PRESSURE REGULATING VALVES

PRESSURE REGULATING VALVES OR PRESSURE REGULATORS OR SELF-ACTUATED PRESSURE CONTROL VALVES ARE SPECIALLY DESIGNED VALVES WHICH USE THE ENERGY/PRESSURE OF PROCESS FLUID TO OPERATE THEIR CLOSURE MEMBER TO PARTIALLY OR FULLY CLOSE A PORT TO MAINTAIN A SET PRESSURE-DOWNSTREAM/UPSTREAM OR DIFFERENTIAL, USUALLY ADJUSTED BY ADJUSTING A SCREW USUALLY PROVIDED FOR THE PURPOSE.

PRESSURE REGULATING VALVES A PRESSURE REGULATING VALVE(PCV) MAY

CONTROL PRESSURE DOWNSTREAM OF IT,UPSTREAM OF IT OR DIFFERENTIAL ACROSS IT DEPENDING UPON APPLICATION.

PCVS ARE USUALLY CLASSIFIED BASED UPON:1. THE LOCATION OF PRESSURE IT CONTROLS IN

RELATION TO ITS INSTALLED LOCATION.2. CONSTRUCTION/DESIGN

PCV TYPE BASED UPON CONTROLLED PRESSURE DOWNSTREAM PCV UPSTREAM PCV OR BACKPRESSURE CV DIFFERENTIAL PCV

PCV TYPE BASED UPON CONSTRUCTION/DESIGN DIRECT OPERATED PCV – HERE THE CLOSURE MEMBER IS

DIRECTLY OPERATED BY ACTUATING DIAPHRAGM BY BALANCING FEEDBACK PRESSURE AGAINST SET PRESSURE SPRING FORCE. THE FORCE REQUIRED TO OPERATE THE CLOSURE MEMBER IS RELATIVELY LOW AND PCV SIZE/FLOW CAPACITIES ARE ALSO NOT LARGE.

PILOT OPERATED PCV – HERE THE CLOSURE MEMBER IS OPERATED BY PRESSURE DELIVERED TO ACTUATING DIAPHRAGM THROUGH A PILOT VALVE WHICH BALANCES FEEDBACK PRESSURE AGAINST SET PRESSURE SPRING FORCE. THIS CONSTRUCTION IS OFTEN USED WHERE SIZE/FLOW CAPACITY REQUIREMENTS ARE HIGH AND THE FORCE REQUIRED TO OPERATE THE CLOSURE MEMBER IS RELATIVELY HIGH.

DIRECT OPERATED PCV

PILOT OPERATED PCV

PILOT OPERATED PCV

VACUUM REGULATOR

COMPONENTS OF A STRAIGHT STEM DIRECT OPERATED PCV

COMPONENTS OF A LEVER STYLE DIRECT OPERATED PCV

COMPONENTS OF A LOADING STYLE PILOT OPERATED PCV

UNLOADING STYLE PILOT OPERATED PCV

SELECTION OF PCVA PCV IS SELECTED BASED UPON FOLLOWING CONSIDERATIONS: Service and application Maximum inlet and outlet pressures (operating and emergency) Adjustable pressure range Outlet pressure ranges Flow capacity End connection styles Regulator construction materials Accuracy Pressure registration (internal or external) Temperature capabilities After comparing the regulator capabilities of alternative models

SIZING OF PCV SIZING IS THE SYSTEMATIC PROCEDURE OF

DETERMINING FLOW CAPACITY OF A PCV FOR A GIVEN APPLICATION. IT IS USUALLY EXPRESSED AS Cv VALUE. REFER TO MANUFACTURER’S HANDBOOK.

IT IS IMPORTANT TO SIZE A PCV USING REGULATED FLOW CAPACITY RATHER THAN WIDE-OPEN FLOW CAPACITY;THE TWO ARE DIFFERENT. THE WIDE-OPEN FLOW CAPACITY IS GREATER THAN THE REGULATED FLOW CAPACITY AND TYPICALLY APPLIES WHEN A PCV FAILS OR IT IS USED WHEN SIZING VALVES FOR PRESSURE RELIEF APPLICATIONS.

SOLENOID OPERATED VALVES A SOLENOID OPERATED VALVE(SOV) USES AN

ELECTRIC SOLENOID TO OPERATE A PLUNGER TO SWITCH CONNECTIONS BETWEEN TWO OR MORE PORTS CARRYING A PRESSURISED FLUID.

PRIMARILY USED AS A CONTROL ACCESSORY TO OPERATE ON/OFF VALVES,PNEUMATIC ACTUATORS, HYDRAULIC ACTUATORS FOR ON/OFF SERVICE OR INTERLOCKING CONTROL VALVES TO FAIL SAFE POSITION.

IN SOME APPLICATIONS SOVS ARE USED TO DIRECTLY HANDLE PROCESS FLUID FOR ON/OFF SERVICE.

SOLENOID VALVES

TYPES OF SOVS SOVS ARE USUALLY CLASSIFIED BASED UPON

TOTAL NUMBER OF PORT CONNECTIONS,TOTAL NUMBER OF POSSIBLE SWITCHING STATES FOR SWITCHING PORT CONNECTIONS AND METHOD OF OPERATION-DIRECT OR PILOT OPERATED.

SOVS ARE AVAILABLE FOR VARIOUS OPERATING AC/DC VOLTAGES.

EX-PROOF AND INTRINSICALLY SAFE VERSIONS ARE AVAILABLE FOR USE IN HAZARDOUS AREAS.

TYPES OF SOVS PROPORTIONAL SOLENOID VALVES SOLENOID VALVES 2/2 PILOT OPERATED VALVES 2/2 PRESSURE OPERATED VALVES 3/2 PRESSURE OPERATED VALVES 4/2 AND 5/2 DIRECT / PILOT OPERATED EXPLOSIONPROOF SOLENOIDS SOLENOID VALVES 3/2 PILOT OPERATED SOLENOID VALVES 3/2 DIRECT OPERATED SOLENOID VALVES 2/2 DIRECT OPERATED SPECIAL SERVICE VALVES Dust collector systems : 9/01 Hot water and steam: 9/05 Medical +

analytical : 9/09 Engineering contractors : 9/02 Combustible gas (EN 161) and oil : 9/06

Magnetic latch : 9/10 NAMUR based valves : 9/03 Cryogenic: 9/07 Spool valve islands : 9/11 Fuel dispensing: 9/04 Vacuum service : 9/08

A TYPICAL SOV-3/2 WAY

A TYPICAL SOV-5/2WAY

SUGGESTED READING SELECTION AND SIZING OF CONTROL

VALVES – LES DRISKELL/ISA SELECTION OF CONTROL VALVES – ISA SIZING OF CONTROL VALVES – ISA CONTROL VALVE HANDBOOK – SKOUSEN CONTROL VALVE HANDBOOK – FISHER

CONTROLS REGULATOR HANDBOOK – FISHER

CONTROLS ASCO VALVE CATALOG

THANK YOU