ReliefValveSizing is a static screening utility for preliminary pressure-relief calculations. It does not hold a thermodynamic system or relief-valve state: the constructor is private, and callers supply the required relieving properties directly to each static method.

The calculations support transparent comparisons and early design studies. They do not establish scenario completeness, certified valve capacity, installation acceptability, conformity with a purchased standard edition, or approval for design or construction. Confirm the governing edition, certified coefficients, applicable correction factors, inlet and outlet hydraulics, reaction forces, disposal-system back pressure, and independent review before using a result for an engineered relief system.

Class: neqsim.process.util.fire.ReliefValveSizing

Unit contract

The public methods do not accept unit strings. Convert all inputs before calling them.

Quantity Required unit or basis
Mass flow kg/s
Volumetric flow m³/s at relieving conditions
Set and back pressure Pa absolute
Temperature K
Molecular weight kg/mol
Density kg/m³ at relieving conditions
Dynamic viscosity Pa·s
Latent heat J/kg
Heat capacity J/(kg·K)
Orifice and wetted area m²
Gas fraction, overpressure, $Z$, and $C_p/C_v$ dimensionless

Current API

Screening task Static method Result
Gas or vapour required area calculateRequiredArea(...) PSVSizingResult, including required and selected areas
Gas or vapour capacity calculateMassFlowCapacity(...) Capacity in kg/s
Liquid required area calculateLiquidReliefArea(...) LiquidPSVSizingResult
Two-phase required area calculateTwoPhaseReliefArea(...) Area in m²
Wetted-surface fire heat input calculateAPI521FireHeatInput(...) Heat input in W
Reseat pressure screening calculateBlowdownPressure(...) Pressure in Pa
Approximate valve coefficient calculateCv(...) Approximate $C_v$

Complete Java 8 example

The following program exercises the gas, liquid, two-phase, and fire helpers with explicit SI conversions.

import java.util.Locale;
import java.util.logging.Logger;
import neqsim.process.util.fire.ReliefValveSizing;

public final class ReliefValveSizingExample {
  private static final Logger LOGGER =
      Logger.getLogger(ReliefValveSizingExample.class.getName());

  private ReliefValveSizingExample() {
  }

  public static void main(String[] args) {
    ReliefValveSizing.PSVSizingResult gasResult =
        ReliefValveSizing.calculateRequiredArea(
            5000.0 / 3600.0,
            110.0e5,
            0.10,
            1.013e5,
            333.15,
            0.018,
            0.95,
            1.30,
            false,
            false);

    ReliefValveSizing.LiquidPSVSizingResult liquidResult =
        ReliefValveSizing.calculateLiquidReliefArea(
            50.0 / 3600.0,
            850.0,
            25.0e5,
            0.10,
            1.013e5,
            0.004,
            false);

    double twoPhaseArea =
        ReliefValveSizing.calculateTwoPhaseReliefArea(
            30000.0 / 3600.0,
            80.0e5,
            0.10,
            5.0e5,
            373.15,
            0.30,
            50.0,
            700.0,
            250000.0,
            2500.0);

    double fireHeatInput =
        ReliefValveSizing.calculateAPI521FireHeatInput(80.0, true, true);

    if (gasResult.getRequiredArea() <= 0.0
        || liquidResult.getRequiredAreaM2() <= 0.0
        || twoPhaseArea <= 0.0
        || fireHeatInput <= 0.0) {
      throw new IllegalStateException("Relief screening produced a non-positive result");
    }

    LOGGER.info(
        String.format(
            Locale.ROOT,
            "gas=%.6g m2 (%s), liquid=%.6g m2 (%s), two-phase=%.6g m2, fire=%.1f kW",
            gasResult.getRequiredArea(),
            gasResult.getRecommendedOrifice(),
            liquidResult.getRequiredAreaM2(),
            liquidResult.getRecommendedOrifice(),
            twoPhaseArea,
            fireHeatInput / 1000.0));
  }
}

The current implementation gives approximately:

Result Screening value
Gas required area and selected standard orifice $6.74\times10^{-5}$ m²; D
Liquid required area and selected standard orifice $2.71\times10^{-4}$ m²; G
Two-phase required area $5.88\times10^{-5}$ m²
Fire heat input for 80 m² with drainage 1570 kW

These values are regression examples for the stated inputs, not recommended design cases.

Gas and vapour screening

calculateRequiredArea(...) uses the source implementation’s gas/vapour screening equation and returns both the required area and the first standard D-through-T area that is not smaller. The method uses $K_d=0.975$, $K_c=0.9$ when an upstream rupture disk is declared and $K_c=1.0$ otherwise, plus the implemented simplified back-pressure correction. It does not obtain molecular weight, compressibility, or heat-capacity ratio from a NeqSim fluid; the caller must supply properties that are consistent at the relieving state.

Use these explicit result getters:

Liquid screening

calculateLiquidReliefArea(...) requires volumetric flow at relieving conditions, density, absolute pressures, viscosity, and the balanced-bellows selection. The current implementation applies its simplified $K_d$, $K_w$, $K_v$, and overpressure correction before selecting a standard orifice.

LiquidPSVSizingResult exposes getRequiredAreaM2(), getRequiredAreaIn2(), getMassFlowRate(), getVolumeFlowRate(), getRecommendedOrifice(), getSelectedAreaIn2(), getDischargeCoefficient(), getBackPressureCorrectionFactor(), and getViscosityCorrectionFactor(). It does not contain a $K_c$ field.

Two-phase omega-method screening

The source defines the inlet mixture specific volume as

\[v_{\mathrm{mix}}=xv_g+(1-x)v_l\]

and evaluates

\[\omega=\frac{xv_g}{v_{\mathrm{mix}}}+\frac{c_{p,l}TP_0(v_g-v_l)^2}{h_{fg}^2v_{\mathrm{mix}}}\]

where $x$ is inlet gas mass fraction, $v_g$ and $v_l$ are gas and liquid specific volumes, $c_{p,l}$ is liquid heat capacity, $T$ is inlet temperature, $P_0$ is relieving pressure, and $h_{fg}$ is latent heat. The method then applies the implemented critical-ratio expression, back-pressure floor, mass-flux expression, and $K_d=0.85$.

The method returns only required area. It does not select an orifice, calculate fluid properties, establish the applicable two-phase scenario, or qualify homogeneous-equilibrium assumptions.

Wetted-surface fire heat input

Call calculateAPI521FireHeatInput(wettedAreaM2, hasDrainage, hasFireFighting) with all three arguments. The current implementation uses a fixed environmental factor of 1.0 and branches on hasDrainage, giving approximately

\[Q=43192A_w^{0.82}\ \mathrm{W}\]

with drainage, and

\[Q=70959A_w^{0.82}\ \mathrm{W}\]

without drainage, for $A_w$ in m². The hasFireFighting argument is currently retained in the public signature but does not change the numerical factor. Do not infer a firefighting credit from that boolean.

Engineering limits