En_LO2-UD2 Classifications and Construction Characteristics of Valves

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UNIVERSIT DEGLI STUDI DI SALERNOFACOLT DI INGEGNERIA

Bachelor Degree in Chemical Engineering

Course:Instrumentation and Control of Chemical Processes

VALVE TECHNOLOGY

CLASSIFICATIONS AND CONSTRUCTION

CHARACTERISTICS OF VALVES

Rev. 3.51 June 8, 2012

INTRODUCTION

The requirement to regulate and control the flow rate of fluids inhydraulic circuits is very common in industrial process.

It recurs in energy and steam production, control of level and

pressure in tanks containing liquid and gas, control of temperaturein rooms and pipes, control of chemical composition of a specifiedproduct.

The final control elements used to regulate the flow rate of fluidsare valves and pumps.

The selection of the valve type, its characteristics and the properdesign can significantly affect the performance of a control system.

15.06.2012 2Instrumentation and Control of Chemical Processes - Prof. M. Miccio


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INTRODUCTION


VALVE DEFINITION

A mechanical device that is used in a fluid power system, which is

used to provide some change of state of the fluid.from http://www.engnetglobal.com/tips/glossary.aspx?search=valve

GENERIC VALVE SYMBOL

CONTROL VALVE DEFINITION

A valve that modulates the flow of fluid in a conduit in response to asignal from a process measurement control system.

From http://www.answers.com/topic/control-valve

VALVES: COMPONENTS

Body

Closure member

Actuator (device that supplies force and motion to a

valve closure member)

Joints



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VALVES(schematic drawing)

CLOSURE MEMBER

ACTUATOR

JOINTS

taken from:Magnani, Ferretti e Rocco (2007)

BODY

COMPRESSED AIR

SEAT

MEMBRANE

INGOINGFLUID

OUTGOINGFLUID

SPRINGSTEM


1st CLASSIFICATION OF VALVES(based on FUNCTION)

Valves have the function of:

ON/OFF: valves having two positions:

In the one position the passage of a fluid is stopped (with a leak-tight seal).

In the other position flow is allowed with a low pressure drop

DIVERT SERVICE: valves having two positions, which never block flow:

In the one position flow is allowed from the common port to port A.

In the other position flow is allowed form the common port to port B

THROTTLING: in order to regulate the fluid flow rate by changing the

position of the closure member

PRESSUREREGULATING: in order to regulate pressure of gas and

steam

SAFETY/PRESSURE RELEASE: in order to prevent the overcoming of ahazardous pressure for structural resistance of piping and equipment

CHECK VALVE: to allow the one way flow of a fluid only



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VALVE FUNCTIONS:EXAMPLES

ON/OFF valve Check valve Safety valve


scheme Divert valve section drawing

2nd CLASSIFICATION OF VALVES(based on SIZE and/or EXTERNAL SHAPE )

BIB COCK (NPS


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2nd CLASSIFICATION OF VALVES(based on size and/or external shape )

BIB COCK (NPS


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SIDE VIEW TOP VIEW

The ball valve is themost common devicefor ON/OFF switch ofa flow in pipes.

It operates by meansof the 90rotation of

a spherical closuremember in acylindrical cavity,coaxial to the flow.

This valve allows thefull closure/openingand, to some extent,the pressure-regulation of theflow.

BALL VALVE/COCK (for ON/OFF)


SCHEMATIC DRAWING

CUTAWAY DRAWING

MODULATING BALL VALVE

(for THROTTLING)


SCHEMATIC DRAWING

CUTAWAY PICTURE


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EXAMPLE OF MODULATING BALL VALVE


CUTAWAY PICTURE

PLUG VALVES/COCKS(conically-tapered, cylindrical)

NPS 1

SIDE VIEW TOP VIEW

SCHEMATIC DRAWING


TWO-PORT CONICALLY-TAPERED PLUG COCK


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MULTI-PORT COCKS(spherical, cylindrical, conically-tapered)

NPS 1

THREE-PORT

PLUG COCK

FOUR-PORT

PLUG COCK

TOP VIEW

SCHEMATIC DRAWING


BUTTERFLY COCK

SCHEMATIC DRAWING ANIMATED DRAWING


SIDE VIEW FRONTAL VIEW TOP VIEW


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BUTTERFLY VALVE


BUTTERFLY VALVE(DN 32-1200)

Construction details:

1. Body and flanges; stem extension for theinsulation.

2. Stem with position indicator.

3. Disk.

4. Interchangeable hose.

5. Plain bearing.

6. Lap-jointed disk.

7. External gasket.8. Anti-ejection gasket.


CUTAWAY DRAWINGS


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BIB COCK (NPS


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EXAMPLES OF GATE VALVES(for ON/OFF)

Constructiondraw

ing

Picture



BIB COCK (NPS


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GLOBE VALVES and COCKS

NOTE:

They operate for THROTTLING.They are known as globe because their body was formerly spherical.

GENERAL EXAMPLE of GLOBE VALVE


Construction drawing Animated drawing

GLOBE VALVES (NPS>1)

Automatic globe valve with float

Guided-flow valveor

Z-body globe valve


Free-flow valveor

Y-body globe valve


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3rd CLASSIFICATION OF VALVES(based on the position/coupling with the piping

in the process)

ANGLE VALVE

BOTTOM VALVE

STRAIGTH-FLOW VALVE

NOTE:The bodies of valves have an

arrow indicating the directionof the flow.For bidirectional valves, suchas butterfly, globe and gatevalves, no indication isreported.


ANGLE GLOBE VALVE

1. Body

2. Bonnet

3. Closure member

4. Seat

5. Stem

6. Handwheel

7. Gland nut



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BOTTOM GLOBE VALVE


DIAPHRAGM VALVE(OR MEMBRANE OR PINCH VALVE)

Schematic drawing Animated drawing Section drawing

WEIRVALVE

HOSE

VALVE

Guided-flow Free-flow

NOTE:The throttling and the

hermetic are directlyperformed by thecompression of an elasticor plastic membrane onthe body of the valve



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Picture

DIAPHRAGM VALVE(OR MEMBRANE OR PINCH VALVE)


4th CLASSIFICATION OF VALVES(based on the shape of the CLOSURE MEMBER)

DISK VALVE

CAP VALVE

PISTON VALVE

NEEDLE VALVE

CAGE VALVE

V-PORT

GATE VALVE

BUTTERFLY VALVE

PLUG VALVE (spherical, cylindrical, conically-tapered)

G

lobevalve



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CLOSURE MEMBERS

DISK CLOSURE MEMBERThe increase of the flowrate occurs almost exclusively in the first part of the opening , afterwhich further increase of flowrate are almost negligible.

For this reason, the disk closure member is also formerly known as quick opening.It is commonly used for on/off function.

LINEAR CLOSURE MEMBERIn this case a linear relation between the opening of the valve and the flowrate.The shape of the closure member is usually parabolic.Closure members with a linear characteristic are used when the operating pressure drop orflowrate do not change significantly with the time during the process.

EQUAL PERCENTAGE CLOSURE MEMBERIn this case for a constant increase of the trim travel we have an equal percentage increaseof the flowrate, for the same pressure drop. Considering and increase of 10% of the opening,the flowrate increases about 50% of the initial flowrate. It follows that the most increase offlowrate of the valve occurs in the last part of the travel of the closure member.

The equal percentage closure members are used when most of the pressure drop islocalized in the plant and only the lower part occurs crossing the valve. They are alsosuggested when the flowrate and the operating pressure drop are subjected to significantchanges during the process.

see also: 13.5 - Stephanopoulos, Chemical process control: an

Introduction to theory and practice, Prentice Hall, 1984


CLOSURE MEMBERSIN THROTTLING GLOBE VALVES

taken from Magnani, Ferretti e Rocco (2007)



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NEEDLE VALVE

Picture


CAGE VALVE


Picture


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V-PORT GLOBE VALVE


5th CLASSIFICATION OF VALVES(based on the MOVEMENT of the closure member)

LINEAR VALVES

ROTARY VALVES



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BIB COCK (NPS


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RUPTURE DISK


CHECK VALVES

Fig. 32.67 - Valvola diritegno a "clapet".

Fig. 32.69 - Valvola di ritegno a flusso libero.

Fig. 32.68 - Valvola diritegno orizzontale aflusso avviato

Fig. 32.70 - Valvola diritegno verticale

Clapet checkvalve

Guided-flowcheck valve

Vertical check valve

Free-flowcheck valve



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ROTARY VALVES for bulk solids


Exploded view drawing

ROTARY VALVES for bulk solids

Animated drawing

Documents

En_LO2-UD2 Classifications and Construction Characteristics of Valves