Pressure Surge Analysis

Preliminary water hammer screening for liquid-filled pipe using Joukowsky surge pressure, Korteweg wave speed, slow-closure reduction, and pressure-limit checks.

Input Parameters

Use SI engineering units. Results recompute when you press Calculate.

Process Conditions

Operating Pressure — (barg)

Design Pressure — (barg)

Liquid Flowrate — (m3/h)

Valve Closure Time — (s)

Fluid Properties

Liquid Name

Select a preset to fill density, vapor pressure, and bulk modulus.

Custom Liquid Name

Optional label only.

Operating Temperature — (°C)

Liquid Density — (kg/m3)

Vapor Pressure — (barg)

Liquid Bulk Modulus — (GPa)

Pipe Specifications

NPS

Select NPS and schedule to fill pipe ID and wall thickness.

Schedule

Manual ID and wall thickness are enabled.

Pipe Internal Diameter — (mm)

Pipe Wall Thickness — (mm)

Pipe Length — (m)

Young's Modulus — (GPa)

Allowable Stress Factor

Operating Pressure Build-Up

Poperating should be built from static head at maximum suction inventory level, maximum normal suction pressure, and the applicable pump discharge pressure. Do not use suction-vessel design pressure or PSV set pressure.

Ready to calculate

Enter values and press Calculate to see results.

Engineering Tips

This is a first-pass screening aid for single-phase liquid in a single pipe segment. Gas, two-phase, pump-trip, branched-network, and mitigation-device cases require detailed transient analysis.

Basic Surge Equations:
c = √[1 / (ρ × (1/K + D/(e×E)))]
Rapid: Psurge = c × ρ × V
Slow: Psurge = (2 × L × ρ × V) / ts

Valve Closure Time: Effective closure time is usually the final flow-controlling travel: about 5% for gate, 15% for butterfly, 25% for ball, and 30% for plug valves.

Occasional-Load Factor: ASME B31.3 allows an occasional-load factor of 1.33 for transients lasting < 10 hrs/yr. Use 1.10 for stricter limits.

Cavitation Risk: If down-surge pressure falls below the fluid's vapor pressure, liquid column separation occurs, which can cause severe damage when the column rejoins.

Method & References: Rapid closure uses the Joukowsky equation. Slow closure uses the Michaud / Allievi reduction when the valve closure time is longer than the wave return period. Wave speed uses the Korteweg elastic-pipe model, and the allowable over-pressure limit is screened using an ASME B31.3 occasional-load factor selected by the user.

Recommended values

Wave speed: a ≈ 1 000–1 400 m/s for water in steel; entrained air or flexible pipe lowers it sharply.
Rapid closure: If closure time tc < 2L/a the full Joukowsky surge ΔP = ρ·a·Δv develops.
Slow closure: Surge falls roughly in proportion to (2L/a)/tc — slowing the valve is the first mitigation.
Mitigation: Add surge vessel / air chamber / relief for long lines or fast trip valves.

Limitations

Joukowsky basis: Rigid-column / single-pipe estimate — no method-of-characteristics network solve.
Not included: Column separation, vapour cavitation, and pump-trip transients need a full transient package.

About the standards

Joukowsky: Water hammer / surge pressure.
Korteweg: Wave celerity in elastic pipes.
Michaud-Allievi: Effective surge pressure.