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🏭 Process Engineering References

Valves design standards, NPSH calculations, TEMA clearances, and piping schedules.

📚 Recommended Textbooks & Handbooks

CP

Crane Technical Paper No. 410 (Flow of Fluids)

Crane Co. Engineering Department

The bible of piping systems hydraulics. Provides the industry standard values for valve and fitting loss coefficients ($K$-factors), equivalent lengths, and flow formulas.

TM

Standards of the Tubular Exchanger Manufacturers Association

Tubular Exchanger Manufacturers Association (TEMA)

Establishes sizing tolerances, clearances, shell-pass arrangements, and heat transfer fouling resistance coefficients for industrial process condensers.

📋 Industry Standards & Codes

  • ANSI/ISA-75.01.01: Flow Equations for Sizing Control Valves. Incorporates specific gravity, critical pressure ratios, and Reynolds number correction loops. Used in our Control Valve Sizer.
  • ASME B36.10M / B36.19M: Specifies standard nominal dimensions, wall thicknesses, and weights for carbon and stainless steel piping lines. Used in our Pipe Dimensions lookup.
  • ISO 5167: Sets specifications for orifice plates, nozzles, and Venturi tubes used to measure differential pressure flow rates. Used in our Orifice Flow Calculator.

📊 Governing Process Equations

Control Valve Liquid Flow Coefficient ($C_v$)

Calculates the required valve capacity factor under non-cavitating conditions:

$$C_v = \frac{Q}{F_R} \cdot \sqrt{\frac{SG}{\Delta P}} \quad \left[\text{gpm/psi}^{1/2}\right]$$ $$K_v = 0.865 \cdot C_v \quad \left[\text{m}^3/\text{h/bar}^{1/2}\right]$$

Where $Q$ is flow rate in gpm, $SG$ is specific gravity, $\Delta P$ is pressure drop in psi, and $F_R$ is the viscosity correction factor (for high-viscosity oils).

Net Positive Suction Head Available ($NPSH_A$)

Determines the absolute pressure head margin at the pump impeller suction inlet to prevent vapor bubble collapse (cavitation):

$$NPSH_A = H_{surface} + z_s - h_{f,s} - H_{vapor} \quad \left[\text{m}\right]$$ $$NPSH_A = \frac{P_{surface}}{\rho g} + z_s - h_{f,s} - \frac{P_v}{\rho g} \quad \left[\text{m}\right]$$

Where $P_{surface}$ is surface tank pressure, $z_s$ is suction elevation height, $h_{f,s}$ is friction loss in suction pipe, and $P_v$ is liquid vapor pressure. Sized in NPSH Sizer.

Orifice Plate Mass Flow Rate ($\dot{m}$)

Derived from the Bernoulli equation, correcting for friction discharge $C_d$ and gas compressibility expansion factor $\epsilon$:

$$\dot{m} = C_d \cdot E \cdot \epsilon \cdot \frac{\pi d^2}{4} \cdot \sqrt{2 \rho \Delta P} \quad \left[\text{kg/s}\right]$$

Where $E = (1 - \beta^4)^{-1/2}$ is velocity of approach factor, and $\beta = d/D$ is the orifice bore diameter ratio.

🧠 Technical Application Guide

1. Liquid Cavitation vs. Flashing

If local static pressure at the control valve orifice vena contracta falls below the liquid's vapor pressure ($P_v$), the liquid vaporizes into bubbles. If downstream pressure recovers above $P_v$, these bubbles collapse violently (cavitation), causing noise and severe mechanical pitting. If downstream pressure remains below $P_v$, the flow remains two-phase (flashing), which limits fluid delivery.

2. Pipe Friction Factor Convergence

Our pipe network solver iteratively solves Hardy-Cross loops by balancing loop head losses. Because Colebrook's equation for friction factor $f$ is non-linear, we utilize derivative-based convergence loops inside our Fortran core. Sized in Hardy-Cross Solver.