CONTROL VALVE SELECTION AND SIZING ENGINEERING DESIGN GUIDELINE

TABLE OF CONTENT
INTRODUCTION
Scope 4
General Design Consideration 5
Control Valve Body 5
Control Valve Actuator 7
I) Diaphragm Actuators 9
II) Piston Actuators 9
III) Electro Hydraulic Actuators 10
IV) Manual Actuators 10
DEFINITIONS 11
NOMENCLATURE 14
THEORY OF THE DESIGN 16
A) Control Valve Flow Characteristic 16
I) Inherent Flow Characteristic 16
II) Linear Flow Characteristic 17
III) Equal Percentage Flow Characteristic 18
IV) Quick Opening Flow Characteristic 18
V) Installed Flow Characteristic 19
B) Control Valve Sizing 20
I) Sizing for Liquid Services 21
Flashing and Cavitation 25
Choked Flow 27
Computing ΔPcritical and Geometry Factors 28
Flow Correction Factor (FR) 31
II) Sizing for Vapor Services 32
Critical Pressure Drop 34
Calculating the Valve Flow Coefficient 34
APPLICATION
Example Case 1: Sizing a Control Valve in Liquid Hydrocarbon Application 36
Example Case 2: Sizing a Control Valve in Liquid Water Application 42
Example Case 3: Sizing a Control Valve in Vapor Hydrocarbon Application 46
Example Case 4: Sizing a Control Valve in Steam Application 51
REFEREENCES 56
SPECIFICATION DATA SHEET
Control Valve Data Sheet (Excel format) 57

CALCULATION SPREADSHEET
Excel Format (British & SI unit)
Sizing Spreadsheet for Liquid 58
Sizing Spreadsheet for Vapor 59
Example 1: Sizing a Control Valve in Liquid –Hydrocarbon 60
Example 2: Sizing a Control Valve in Liquid –Water 61
Example 3: Sizing a Control Valve in Vapor –Hydrocarbon 62
Example 4: Sizing a Control Valve in Vapor –Steam 63
LIST OF TABLE
Table 1: Equation Constants 24
LIST OF FIGURE
Figure 1: Single port control valve 5
Figure 2: Double port control valve 6
Figure 3: Direct acting diaphragm actuator 8
Figure 4: Reverse-acting diaphragm actuator 8
Figure 5: Flow characteristic curves 16
Figure 6: Installed flow characteristic for linear control valve installed in flow 20
systems having different values of α
Figure 7: Standard FCI Test Piping for Cv Measurement 22
Figure 8: Vena Contracta Illustration 25
Figure 9: Comparison of Pressure Profiles for High and Low Recovery Valves 26

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