Surge Pressure & Water Hammer Calculator for Pipelines
Surge Analysis Calculator
System Setup
Fluid Properties
Pipe Properties
Operating Conditions
Intermediate Calculations
Inner Diameter (D):
-
Wall Thickness (t):
-
Fluid Velocity (Vβ):
-
Surge Analysis Results
Wave Velocity (a):
-
Critical Time (Tr):
-
Estimated Actual Surge (ΞP):
-
Peak System Pressure (Pmax):
-
Technical Notes
Variable Definitions
- Ο = Fluid density.
- K = Fluid bulk modulus (compressibility).
- E = Pipe material Youngβs modulus.
- Ξ½ = Poissonβs ratio of pipe material.
- L = Pipe length between disturbance point and reflection boundary (valve, pump, tank, etc.).
- D = Pipe internal diameter; t = wall thickness.
- Q = Flow rate; Vβ = initial average fluid velocity.
- a = pressure-wave (acoustic) velocity in the pipe-fluid system.
- Tc = valve closure time (or equivalent transient time).
- Tr = critical (round-trip) time = 2L/a.
- ΞP = surge (transient) pressure rise estimate; Pmax = Pop + ΞP.
- MAOP = Design pressure / Maximum Allowable Operating Pressure for comparison.
Formulas / Logic Used
- Area: A = Ο(D/2)Β²
- Velocity: Vβ = Q / A
- Wave speed (water-hammer theory): 1/aΒ² = Ο/K + (ΟΒ·D)/(EΒ·t)
- Joukowsky (instantaneous closure) surge: ΞPmax = ΟΒ·aΒ·ΞV (ΞVβVβ)
- Critical time: Tr = 2L/a
- Slow closure (simple linear reduction): if Tc > Tr, ΞP β ΞPmaxΒ·(Tr/Tc)
- Peak pressure: Pmax = Pop + ΞP
- Safety utilization: Utilization = Pmax / MAOP
Assumptions / Notes
- This tool provides a screening-level surge estimate using classical water-hammer equations (elastic pipe + compressible fluid).
- It assumes a single, uniform pipe reach and does not model multi-branch networks, pump trip dynamics, vapor cavities/column separation, or detailed valve closure laws.
- Restraint factor Ο approximates effect of axial restraint; fully flexible (expansion joints) trends to fluid acoustic velocity (pipe wall flexibility neglected).
- For non-steel materials (ductile iron / PVC / HDPE), wall thickness is estimated using a conservative Barlow-type relation from MAOP with a practical minimum thickness floor; verify against your piping specification.
- Units: internally computed in SI (m, s, Pa). Display converts to bar/psi and mm/in/ft as selected.
- Recommended references: classic water-hammer texts (e.g., Wylie & Streeter) and water-industry guidance (e.g., AWWA manual practices) for detailed transient analysis and mitigation design.
Input Guidance (Typical Ranges)
- Water: Οβ1000 kg/mΒ³; Kβ2.0β2.4 GPa (temperature dependent).
- Steel pipe: Eβ190β210 GPa; Ξ½β0.28β0.30.
- PVC/HDPE: much lower E β significantly lower wave speed and different surge behavior.
- Ensure MAOP β₯ operating pressure. If Pmax approaches MAOP, consider detailed transient study and mitigation (surge relief, slow-closing valves, accumulators, flywheels, etc.).