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HANDBOOK FOR CONTROL VALVE SIZING

CONTROL VALVE SIZING AND SELECTION

The proper sizing and selection of a control valve must be based on a thorough understanding of the operation.

1 - DATA PROCESSING

At the very least, the following information should be known:

a - Fluid type and its chemical-physical and thermodynamic properties, such as pressure "p," temperature "T," vapour pressure "pv," thermodynamic critical pressure "pc," specific mass "r," kinematic viscosity "n" or dynamic viscosity "m," specific heat at constant pressure "Cp," specific heat at constant volume "Cv," specific heat ratio "g," molecular mass "M," compressibility factor "Z," presence of solid particles, inflammability

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b - Maximum operational range of flow rate in relation to fluid pressure and temperature at valve inlet, as well as Dp across the valve.

c - Operating circumstances (normal, maximum, minimum, and so on).

d - The ratio of the available pressure differential across the valve to the total head loss throughout the process line at various operating circumstances.

e - Operational data such as: - maximum differential pressure with valve closed

- stroking time - plug position in the event of a power outage

- maximum permissible valve leakage in closed position - fire resistance - maximum outward leakage

- Noise restrictions

f - Interface information, such as: - downstream safety valve sizing - valve accessibility

- pipe connection materials and types

- total dimensions, including space for disassembly and maintenance

- Create a pressure and temperature design

- the types of goods that are accessible and their characteristics

2- VALVE DESCRIPTION

On the basis of the aforementioned information, it is feasible to finalise the precise specification of the valve (data sheet), i.e. to select:

- valve rating - valve body and type

- body size, after determining the maximum flow coefficient Cv using the proper sizing equations

- trim style

- trim materials of various trim sections

- leaking class - intrinsic flow property

- kind of packaging

- actuator type and size - accessories

CONTENTS IN HANDBOOK FOR CONTROL VALVE SIZING

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NOMENCLATURE

VALVE SIZING AND SELECTION

1 PROCESS DATA

2 VALVE SPECIFICATION

3 FLOW COEFFICIENT

4 SIZING EQUATIONS

5 PARAMETERS OF SIZING EQUATIONS

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