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

`ValveMechanicalDesign` Class

Method	Return	Description
`calcDesign()`	void	Performs all mechanical design calculations
`getAnsiPressureClass()`	int	Returns ANSI class (150, 300, 600, 900, 1500, 2500)
`getNominalSizeInches()`	double	Returns nominal valve size in inches
`getFaceToFace()`	double	Returns face-to-face dimension in mm
`getBodyWallThickness()`	double	Returns body wall thickness in mm
`getRequiredActuatorThrust()`	double	Returns required actuator thrust in N
`getActuatorWeight()`	double	Returns estimated actuator weight in kg
`getDesignPressure()`	double	Returns design pressure in bara
`getDesignTemperature()`	double	Returns design temperature in °C
`getWeightTotal()`	double	Returns total valve weight in kg

Valve Sizing Standards

NeqSim supports multiple valve sizing standards that can be selected via setValveSizingStandard():

Single-Phase Standards (Control Valves)

Standard	Description	Best For
`default`	IEC 60534-based calculation	General control valves
`IEC 60534`	Full IEC 60534-2-1 implementation	Engineering calculations
`IEC 60534 full`	Extended IEC 60534 with all factors	Detailed sizing studies
`prod choke`	Production choke sizing with Cd	Wellhead chokes

Multiphase Standards (Production Chokes)

Standard	Description	Best For
`Sachdeva`	Mechanistic two-phase model (SPE 15657)	When fluid composition is known
`Gilbert`	Empirical correlation (1954)	Quick estimates, field matching
`Baxendell`	Empirical correlation (1958)	Higher flow rates
`Ros`	Empirical correlation (1960)	Low GLR systems
`Achong`	Empirical correlation (1961)	High GLR systems

Example: Setting Sizing Standard

ValveMechanicalDesign mechDesign = (ValveMechanicalDesign) valve.getMechanicalDesign();

// For control valves (single-phase)
mechDesign.setValveSizingStandard("IEC 60534");

// For production chokes (two-phase)
mechDesign.setValveSizingStandard("Sachdeva");
mechDesign.setChokeDiameter(0.5, "in");
mechDesign.setChokeDischargeCoefficient(0.84);

Multiphase Choke Helper Methods

For production choke sizing, additional methods are available:

Method	Description
`setChokeDiameter(value, unit)`	Set choke diameter (units: “m”, “mm”, “in”, “64ths”)
`getChokeDiameter()`	Get choke diameter in meters
`setChokeDischargeCoefficient(Cd)`	Set discharge coefficient (0.75-0.90 typical)

See Multiphase Choke Flow Models for detailed two-phase choke documentation.

Valve Characteristics

Available valve characteristics for flow control:

Characteristic	Formula	Application
Linear	`Cv/Cv₁₀₀ = opening/100`	Constant ΔP systems
Equal Percentage	`Cv/Cv₁₀₀ = R^((opening/100)-1)`	Variable ΔP, process control
Quick Opening	`Cv/Cv₁₀₀ = sqrt(opening/100)`	On/off, safety applications
Modified Parabolic	`Cv/Cv₁₀₀ = opening²/10000`	Compromise between linear/EQ%

Example: Setting Valve Characteristic

ValveMechanicalDesign mechDesign = (ValveMechanicalDesign) valve.getMechanicalDesign();
mechDesign.setValveCharacterization("equal percentage");

IEC 60534 Gas Sizing Formula

For compressible fluids, the Kv (or Cv) is calculated using:

\[K_v = \frac{Q}{N_9 \cdot P_1 \cdot Y} \sqrt{\frac{M \cdot T \cdot Z}{x}}\]

Where:

$Q$ = volumetric flow rate at inlet conditions (m³/h)
$N_9$ = 24.6 (numerical constant for SI units)
$P_1$ = inlet pressure (kPa abs)
$Y$ = expansion factor = $1 - \frac{x}{3 \cdot F_\gamma \cdot x_T}$
$M$ = molecular weight (g/mol)
$T$ = temperature (K)
$Z$ = compressibility factor
$x$ = pressure drop ratio = $\Delta P / P_1$
$F_\gamma$ = specific heat ratio factor = $\gamma / 1.40$
$x_T$ = pressure drop ratio factor at choked flow

Choked Flow

When $x \geq F_\gamma \cdot x_T$, flow becomes choked and:

$Y = \frac{2}{3}$ $x_{effective} = F_\gamma \cdot x_T$

Valve Equipment - Valve simulation overview
Compressor Mechanical Design - Compressor mechanical design
Process Package - Package overview
Safety Systems - Safety valve sizing

Acoustic-Induced Vibration (AIV) Analysis

Throttling valves are primary sources of Acoustic-Induced Vibration (AIV) due to the turbulent flow and acoustic energy generated during pressure reduction. AIV can cause fatigue failures in downstream piping.

AIV Calculation

The ThrottlingValve class includes AIV analysis per Energy Institute Guidelines:

\[W_{acoustic} = 3.2 \times 10^{-9} \cdot \dot{m} \cdot P_1 \cdot \left(\frac{\Delta P}{P_1}\right)^{3.6} \cdot \left(\frac{T}{273.15}\right)^{0.8}\]

Where:

$W_{acoustic}$ = Acoustic power (kW)
$\dot{m}$ = Mass flow rate (kg/s)
$P_1$ = Upstream pressure (Pa)
$\Delta P$ = Pressure drop across valve (Pa)
$T$ = Temperature (K)

AIV Risk Levels

Acoustic Power (kW)	Risk Level	Action Required
< 1	LOW	No action required
1 - 10	MEDIUM	Review piping layout
10 - 25	HIGH	Detailed analysis required
> 25	VERY HIGH	Mitigation required

Using AIV Analysis

// Create valve with significant pressure drop
ThrottlingValve valve = new ThrottlingValve("PCV-100", feed);
valve.setOutletPressure(30.0, "bara");  // Large ΔP from ~80 bara inlet
valve.run();

// Calculate AIV power
double aivPower = valve.calculateAIV();  // Returns kW
System.out.printf("AIV Power: %.2f kW%n", aivPower);

// Calculate AIV likelihood of failure (requires downstream pipe geometry)
double downstreamDiameter = 0.2032;  // 8 inch
double downstreamThickness = 0.008;  // 8mm wall
double aivLOF = valve.calculateAIVLikelihoodOfFailure(
    downstreamDiameter, downstreamThickness);
System.out.printf("AIV LOF: %.3f%n", aivLOF);

// Set AIV design limit as capacity constraint
valve.setMaxDesignAIV(10.0);  // kW (default is 10 kW for valves)

// Access AIV constraint
CapacityConstraint aivConstraint = valve.getCapacityConstraints().get("AIV");
double utilization = aivConstraint.getUtilization();  // Current/Design ratio

AIV Mitigation Strategies

When AIV is identified as a concern:

Increase downstream pipe wall thickness - Reduces LOF
Use acoustic/vibration analysis software - Detailed assessment
Install acoustic dampeners - Reduces transmitted energy
Multi-stage pressure reduction - Reduces ΔP per stage
Increase pipe diameter - Reduces velocity and acoustic intensity

Valve Mechanical Design

Overview

Design Standards Reference

Design Calculations

1. ANSI Pressure Class Selection

2. Nominal Valve Size

3. Face-to-Face Dimensions

4. Body Wall Thickness

5. Actuator Sizing

6. Weight Estimation

Body Weight

Trim and Bonnet

Actuator Weight

Total Weight

Usage Example

API Reference

ValveMechanicalDesign Class

Valve Sizing Standards

Single-Phase Standards (Control Valves)

Multiphase Standards (Production Chokes)

Example: Setting Sizing Standard

Multiphase Choke Helper Methods

Valve Characteristics

Example: Setting Valve Characteristic

IEC 60534 Gas Sizing Formula

Choked Flow

Related Documentation

Acoustic-Induced Vibration (AIV) Analysis

AIV Calculation

AIV Risk Levels

Using AIV Analysis

AIV Mitigation Strategies

`ValveMechanicalDesign` Class