Piping Control Valve Sizing

Calculate liquid control valve sizing and maximum flowrate from delta pressure and flowrate.

The control valve sizing is calculated in two steps using the ISA-75.01.01 iteration method for Kv flow coefficient. The other flow factors (Av, Cv-uk, Cv-us, Cv-met, Cv*, K, and Cd) are calculated from Kv.

Step 1 : Calculate the required valve flow coefficient (Av, Cv-uk, Cv-us, Cv-met and Kv) assuming that the valve ID is equal to the pipe ID. Use the required flow coefficient to select a suitable valve.

Step 2 : Select a suitable valve size, type and flow coefficient based on manufacturers data. If a full bore valve is too large, a smaller valve should be selected, with assumed concentric reducers. Calculate the required flow coefficient for the selected valve. The required flow coefficient should be less than or equal to the valve flow coefficient. A trial and error process may be required to determine the appropriate valve. It is recommended that the valve diameter is not less than half the pipe diameter. The calculation is not valid if the valve diameter is greater than the pipe diameter. The calculation might not converge if the valve size is too small.

For viscous fluids or very low flow velocity flow, with low Reynolds number (Rev < 10,000) use the Reynolds number factor option. For most flow cases the Reynolds number can be ignored (Fr = 1).

Check for choked conditions. If the outlet pressure for step 1 or step 2 is greater than the minimum (choked) outlet pressure, set the outlet pressure equal to the choked outlet pressure. The maximum (choked) flowrate, maximum (choked) delta pressure and minimum (choked) outlet pressure are calculated from the fluid vapour pressure, and the fluid critical point pressure. Specially designed valves are required to operate at choked conditions.

The K factors should include fittings located with 2D upstream and 6D downstream. The fluid velocity is calculated from the valve ID. The piping is assumed to be constant diameter upstream and downstream of the valve. The liquid pressure recovery factor Fl, and the valve design factor Fd depend on the valve type and geometry. Typical values are included in the data tables. Manufacturers data should be used if it is available. Check that the convergence is close to or equal to one. Convergence problems can indicate that the selected valve size is too small.

The dimensionless flow coefficient Cv* equals Cv-us / IDin^2, where IDin is the valve inside diameter in inches. For control valves, a maximum Cv* value of 30 is recommended, equivalent to a minimum K factor of 1.

Reference : ISA-75.01.01 Industrial Process Control Valves Part 2-1 Flow Capacity Sizing Equations For Fluid Flow Under Installed Conditions

Tool Input

• schdtypea : Pipe Pipe Schedule Type
• diamtypea : Pipe Diameter Type
  • ODau : User Defined Pipe Outside Diameter
  • IDau : User Defined Pipe Inside Diameter
• wtntypea : Pipe Wall Thickness Type
  • tnau : User Defined Pipe Wall Thickness
• schdtypeb : Valve Pipe Schedule Type
• diamtypeb : Valve Diameter Type
  • ODbu : User Defined Valve Outside Diameter
  • IDbu : User Defined Valve Inside Diameter
• wtntypeb : Valve Wall Thickness Type
  • tnbu : User Defined Valve Wall Thickness
• kfactype : Fitting K Factor Type
  • Kiu : User Defined Inlet Fitting K Factor (Within 2D Upstream)
  • Kou : User Defined Outlet Fitting K Factor (Within 6D Downstream)
• qptype : Fluid Flowrate Type
  • Qu : User Defined Volume Flowrate
  • Mu : User Defined Mass Flowrate
• frtype : Reynolds Number Factor Type
  • νu : User Defined Kinematic Viscosity
  • Fdu : User Defined Valve Design Factor
• ddtype : Valve Diameter Type
• Pi : Fluid Inlet Pressure
• Po : Outlet Fluid Pressure
• Pv : Fluid Vapour Pressure
• Pc : Fluid Critical Pressure
• ρ : Fluid Density
• Fl : Liquid Pressure Recovery Factor

Tool Output

• ΔP : Delta Pressure
• ΔPx : Maximum Delta Pressure (Choked)
• ΣKi : Sum Of Inlet K Factors
• ΣKo : Sum Of Outlet K Factors
• Av : SI Flow Coefficient
• Cd : Discharge Coefficient
• Cv* : Dimensionless US Flow Coefficient (Cv-us / IDin^2)
• Cv-met : Metric Flow Coefficient
• Cv-uk : UK Flow Coefficient
• Cv-us : US Flow Coefficient
• Fr : Reynolds Number Factor
• IDin : Valve Inside Diameter (inches)
• IDp : Pipe Inside Diameter
• IDv : Valve Inside Diameter
• IDv/IDp : Valve Diameter Over Pipe Diameter Ratio (0 ≤ IDv/IDp ≤ 1)
• K : Friction Factor Or Resistance Factor
• Kv : EU Flow Coefficient
• Pox : Minimum Outlet Pressure (Choked)
• Q : Volume Flowrate
• Qx : Maximum Volume Flowrate (Choked)
• Rev : Valve Reynolds Number
• V : Valve Velocity
• cvg : Convergenve Check (== 1)
• m : Mass Flowrate

Calculate pipe fitting inside diameter and inside cross section area from pipe diameter and wall thickness.

Use the Result Table option to display a table of the inside diameter and cross section area versus either outside diameter or wall thickness.

Tool Input

• schdtype : Schedule Type
• diamtype : Diameter Type
  • ODu : User Defined Outside Diameter
  • IDu : User Defined Inside Diameter
• wtntype : Wall Thickness Type
  • tnu : User Defined Wall Thickness

Tool Output

• AX : Pipe Inside Cross Section Area
• ID : Nominal Inside Diameter
• OD : Nominal Outside Diameter
• OD/tn : Diameter Over Wall Thickness Ratio
• tn : Nominal Wall Thickness

Calculate pipe fitting gas velocity and flow rate.

The gas specific gravity is the ratio of gas density over the density of dry air at base temperature and pressure. The compressibility factor is assumed to equal 1 at the base conditions. The gas specific gravity is proportional to the gas molar mass.

Tool Input

• schdtype : Pipe Schedule Type
• diamtype : Pipe Diameter Type
  • ODu : User Defined Outside Diameter
  • IDu : User Defined Inside Diameter
• wtntype : Wall Thickness Type
  • tnu : User Defined Wall Thickness
• fluidtype : Gas Type
  • SGu : User Defined Gas Specific Gravity
• voltype : Gas Flowrate Type
  • Qfu : User Defined Gas Volume Flow Rate
  • Mfu : User Defined Gas Mass Flow Rate
  • Ngu : User Defined Gas Mole Flow Rate
  • Vfu : User Defined Gas Velocity
• P : Gas Pressure
• T : Gas Temperature
• Z : Gas Compressibility Factor

Tool Output

• ρ : Gas Density
• ID : Inside Diameter
• M : Gas Molar Mass
• Mf : Gas Mass Flowrate
• Ng : Gas Mole Flowrate
• Qf : Gas Volume Flowrate (At T P)
• R : Gas Constant
• SG : Gas Specific Gravity
• Vf : Gas Velocity
• vg : Gas Mole Volume (At T P)

Calculate pipe fitting steam table properties from temperature and pressure.

Steam table values can be calculated for water and steam, saturated water, saturated steam, saturated water and steam, metastable water, and metastable steam. The calculations for water and steam are valid between 273.15 K and 1073.15 K (0 to 100 MPa), and between 1073.15 K and 2273.15 K (0 to 50 MPa).

The saturated water and steam calculations are valid between 273.15 K and 647.096 K.

The metastable calculation is valid between 273.15 K and 647.096 K, and for pressure from the saturated vapour line to the 5% equilibium moisture line (user defined). Use the Result Plot option to plot the steam properties versus temperature and pressure.

Note : There is an anomaly in the steam calculation for region 3 between the saturated vapour line, the regions 2/3 boundary, and the critical pressure. Refer to the region 3 anomaly help page for more details (click the utility button on the data bar). IAPWS R7-97 is intended for industrial use, and is a simplified version of IAPWS R6-95 for scientific use. IAPWS R7-97 was developed as an improvement of the IFC-67 model.

Reference : IAPWS R7-97 Industrial Formulation for thermodynamic Properties of Water and Steam

Tool Input

• anomtype : Region 2/3 Anomaly Type
• proptype : Steam Phase
  • Pu : User Defined Pressure
  • Tu : User Defined Temperature
  • Xu : User Defined Saturated Steam Quality

Tool Output

• ρ : Density
• Cp : Specific Heat Constant Pressure
• Cp-Cv : Delta Specific Heat (Cp - Cv)
• Cp/Cv : Specific Heat Ratio
• Cv : Specific Heat Constant Volume
• P : Pressure
• T : Temperature
• Vc : Speed Of Sound
• Z : Compressibility Factor
• cvg : Convergence Check
• h : Enthalpy
• s : Entropy
• u : Internal Energy
• vg : Mole Specific Volume
• vm : Specific Volume
• wv : Specific Weight

Calculate pipe fitting gas dynamic and kinematic viscosity for: methane CH4, ethane C2H6, propane C3H8, iso-butane C4H10, n-butane C4H10, iso-pentane C5H12, n-pentane C5H12, n-hexane C6H14, n-heptane C7H16, n-octane C8H18, n-nonane C9H20, n-decane C10H22, air N2 + O2, ammonia NH3, argon Ar, carbon dioxide CO2, carbon monoxide CO, chlorine Cl2, helium He, hydrogen H2, hydrogen chloride HCl, hydrogen sulphide H2S, nitrogen N2, oxygen O2, steam H2O.

Calculate kinematic viscosity from dynamic viscosity, or dynamic viscosity from kinematic viscosity. The kinematic viscosity is equal to the dynamic viscosity divided by the density. Change viscosity units on the setup page. The gas compressibility factor is calculated from the critical point temperature, critical point temperature, and the accentric factor using either the Peng Robinson, Soave, Redlich Kwong or Van Der Waals equations of state (EOS). The viscosity calculation is valid for gas phase only.

Tool Input

• fluidtype : Fluid Type
  • Pcu : User Defined Critical Point Pressure
  • Tcu : User Defined Critical Point Temperature
  • ωu : User Defined Accentric Factor
  • SGu : User Defined Gas Specific Gravity
• eostype : Equation Of State Type
  • Zu : User Defined Gas Compressibility Factor
• visctype : Viscosity Type
  • μu : User Defined Dynamic Viscosity
  • νu : User Defined Kinematic Viscosity
• P : Fluid Pressure
• T : Fluid Temperature

Tool Output

• μ : Fluid Dynamic Viscosity
• ν : Fluid Kinematic Viscosity
• ρ : Fluid Density
• ω : Accentric Factor
• Pc : Critical Point Pressure
• Rg : Specific Gas Constant
• SG : Gas Specific Gravity
• Tc : Critical Point Temperature
• Vm : Molar Volume
• Z : Compressibility Factor
• cvg : Convergence Check
• mmg : Gas Molar Mass

Calculate typical liquid control valve recovery factor and flow factors for various valve types.

Use the result table option to display a table of liquid recovery factor and flow factors versus valve type.

Note : The calculated values are typical. Manufacturers data should be used if it is available.

Tool Input

• schdtype : Pipe Schedule Type
• diamtype : Pipe Diameter Type
  • ODu : User Defined Outside Diameter
  • IDu : User Defined Inside Diameter
• wtntype : Wall Thickness Type
  • tnu : User Defined Wall Thickness
• vktype : Valve Type (Fully Open Valve)

Tool Output

• Av : SI Flow Coefficient
• Cd : Discharge Coefficient
• Cv* : Dimensionless US Flow Coefficient (Cv-us / IDin^2)
• Cv-met : Metric Flow Coefficient
• Cv-uk : UK Flow Coefficient
• Cv-us : US Flow Coefficient
• Fl : Liquid Recovery Factor
• ID : Pipe Inside Diameter (meter)
• K : Friction Factor Or Resistance Factor
• Kv : EU Flow Coefficient