Valve Mechanical Design

This document describes the mechanical design calculations for control valves in NeqSim, implemented in the ValveMechanicalDesign class.

Overview

The valve mechanical design module provides sizing and design calculations for control valves based on IEC 60534, ANSI/ISA-75, and ASME B16.34 standards. The calculations enable:

Valve body sizing and pressure rating selection
Body wall thickness estimation
Weight estimation for procurement and installation planning
Actuator sizing for control applications
Module dimension calculation for layout planning

Design Standards Reference

Standard	Description
IEC 60534	Industrial-process control valves
ANSI/ISA-75.01	Flow Equations for Sizing Control Valves
ANSI/ISA-75.08	Face-to-Face Dimensions for Flanged Globe-Style Control Valve Bodies
ASME B16.34	Valves - Flanged, Threaded, and Welding End
API 6D	Pipeline and Piping Valves

Design Calculations

1. ANSI Pressure Class Selection

The pressure class is automatically selected based on the design pressure:

Design Pressure	ANSI Class
≤ 19.6 bara	Class 150
≤ 51.1 bara	Class 300
≤ 102.1 bara	Class 600
≤ 153.2 bara	Class 900
≤ 255.3 bara	Class 1500
≤ 425.5 bara	Class 2500

// Design pressure with 10% margin
designPressure = operatingPressure × 1.10

2. Nominal Valve Size

The nominal valve size is calculated from the Cv coefficient using the ISA correlation for globe valves:

Cv ≈ 10 × d²

Where d is the nominal pipe size in inches. Rearranging:

d = sqrt(Cv / 10)

The calculated size is then rounded to the nearest standard pipe size:

0.5”, 0.75”, 1”, 1.5”, 2”, 3”, 4”, 6”, 8”, 10”, 12”, 14”, 16”, 18”, 20”, 24”

3. Face-to-Face Dimensions

Face-to-face dimensions are per ANSI/ISA-75.08 for globe-style control valves:

Nominal Size (in)	Face-to-Face (mm)
≤ 1.0	108
1.5	117
2.0	152
3.0	203
4.0	241
6.0	292
8.0	356
10.0	432
12.0	495
> 12.0	508 + (size - 12) × 30

Adjustment for Pressure Class:

Class 600+: multiply by 1.05
Class 900+: multiply by 1.15

4. Body Wall Thickness

Wall thickness is calculated using the ASME B16.34 pressure vessel formula:

t = (P × R) / (S × E - 0.6 × P) + CA

Where:

P = design pressure (MPa)
R = inner radius (mm)
S = allowable stress = 138 MPa (carbon steel at ambient)
E = joint efficiency = 1.0 (forged body)
CA = corrosion allowance

Minimum: 3.0 mm wall thickness

5. Actuator Sizing

The required actuator thrust is calculated from:

Fluid Force: Force to overcome pressure across the seat
```
F_fluid = P_design × A_seat
```
Packing Friction: Typically 15% of fluid force
```
F_packing = 0.15 × F_fluid
```
Seat Load: For tight shutoff (Class IV/V)
```
F_seat = π × d_seat × 7 N/mm
```

Total Thrust:

F_total = (F_fluid + F_packing + F_seat) × 1.25

6. Weight Estimation

Valve weight is estimated using empirical correlations:

Body Weight

W_body = 2.5 × (size_inches)^2.5 × (class / 150)^0.5

Trim and Bonnet

W_trim = 0.3 × W_body

Actuator Weight

W_actuator = 0.015 × F_thrust + 5.0 kg (minimum 10 kg)

Total Weight

W_total = W_body + W_trim + W_actuator

Usage Example

import neqsim.process.equipment.valve.ThrottlingValve;
import neqsim.process.mechanicaldesign.valve.ValveMechanicalDesign;

// Create and run valve
ThrottlingValve valve = new ThrottlingValve("PCV-101", inletStream);
valve.setOutletPressure(60.0, "bara");
valve.run();

// Get mechanical design
ValveMechanicalDesign mechDesign = (ValveMechanicalDesign) valve.getMechanicalDesign();
mechDesign.calcDesign();

// Access results
System.out.println("ANSI Class: " + mechDesign.getAnsiPressureClass());
System.out.println("Nominal Size: " + mechDesign.getNominalSizeInches() + " inches");
System.out.println("Face-to-Face: " + mechDesign.getFaceToFace() + " mm");
System.out.println("Body Wall: " + mechDesign.getBodyWallThickness() + " mm");
System.out.println("Actuator Thrust: " + mechDesign.getRequiredActuatorThrust() + " N");
System.out.println("Total Weight: " + mechDesign.getWeightTotal() + " kg");

API Reference