Hydro Jetting Pressure & Flow Rate Calculator
Calculate the required pressure, flow rate, nozzle velocity, hydraulic horsepower, and impact force for hydro jetting operations based on nozzle specifications and system parameters.
Formulas Used
1. Nozzle Exit Velocity (Torricelli / Orifice Equation):
v = Cd × √(2 × gc × ΔP / ρ)
Where: Cd = discharge coefficient, gc = 32.174 lbm·ft/(lbf·s²), ΔP = pressure differential (lb/ft²), ρ = fluid density (lb/ft³)
2. Flow Rate per Orifice:
Qsingle = Aorifice × v
Where: Aorifice = π/4 × d² (orifice cross-sectional area)
3. Total Flow Rate:
Qtotal = Qsingle × Norifices
4. Hydraulic Horsepower (HHP):
HHP = (P [PSI] × Q [GPM]) / 1714
The constant 1714 = 33,000 ft·lbf/min ÷ (231 in³/gal × 1/144 ft²/in²)
5. Nozzle Impact Force (Momentum Flux):
F = (ρ × Qtotal × v) / gc
Derived from Newton's 2nd Law: force equals the rate of momentum change of the fluid jet.
6. Supply Pipe Velocity:
vpipe = Qtotal / Apipe
Assumptions & References
- Fluid is assumed incompressible and Newtonian (water-based).
- Pressure drop across the nozzle equals the full operating pressure (negligible upstream losses assumed for nozzle sizing).
- Discharge coefficient (Cd) of 0.95–0.98 is typical for sharp-edged orifices per Crane Technical Paper 410.
- The HHP formula (P × Q / 1714) is the standard industry formula per WJTA-IMCA Recommended Practices for the Use of High Pressure Waterjetting Equipment.
- Impact force calculation assumes a free jet impinging on a flat surface (full momentum transfer); actual force may vary with standoff distance and surface geometry.
- Supply pipe velocity should remain below 20 ft/s to limit friction losses; see Hydraulic Institute Standards.
- Water density at 60°F ≈ 62.4 lb/ft³ (8.34 lb/gal). Adjust for temperature or additives.
- References: WJTA-IMCA (2012); Crane Co. TP-410; Munson, Young & Okiishi, Fundamentals of Fluid Mechanics, 8th ed.