Water Hammer in Pipe | Online Calculator

Fluid Dynamic Calculators

Water Hammer in Pipeline

Water hammer is an unsteady fluid motion with pressure fluctuations that can be hazardous to the pipeline strength. Water hammer occurs in a pipeline when the elastic fluid flow rate changes sharply as a result of rapid valve opening or closing, pump stopping, or some other reasons.

After closing the valve, a thin layer of fluid adjacent to the valve stops immediately its motion first, while the rest of the fluid mass continues to move by inertia for some time. As a result, the pressure increases near the valve and after a while, the fluid starts to flow in the opposite direction under the influence of this pressure. The process occurs cyclically and has a damping nature. The theoretical pressure rise ΔP of a fluid with density ρ in case of a sharp change in the velocity ΔW is calculated using the following equation:

ΔP = ρ*Wc*Δw

Wc - shock wave velocity, depending on pipe diameter D, elastic modulus of pipe material Ep, elastic modulus of fluid Ef and pipe thickness t.

INITIAL DATA

Ef - Young's modulus of the fluid;

Ep - Young's modulus of the pipe material;

ρ - Fluid density;

D - Mean pipe diameter;

t - Pipe wall thickness;

ΔW - Change in fluid velocity in the pipeline.

RESULTS DATA

Wc - Shock wave velocity;

ΔP - Maximum pressure increment due the hydraulic hammer.

Fluid Young's modulus (Ef)

Pipe Young's modulus (Ep)

Fluid density (ρ)

Pipe diameter (D)

Pipe wall thickness (t)

Change in fluid velocity (ΔW)

Shock wave velocity (Wc)

Pressure increment (ΔP)

BASIC FORMULAS

Shock wave velocity:

Wc = [Ef / ρ]1/2 / [1 + (D/t)*(Ef / Ep)]1/2;

Pressure increment:

ΔP = ρ*Wc*ΔW

INITIAL DATA

Ef - Young's modulus of the fluid;

Ep - Young's modulus of the pipe material;

ρ - Fluid density;

D - Mean pipe diameter;

t - Pipe wall thickness;

ΔW - Change in fluid velocity in the pipeline.

RESULTS DATA

Wc - Shock wave velocity;

ΔP - Maximum pressure increment due the hydraulic hammer.

FLUID PROPERTIES

Fluid

Dynamic viscosity

Pa*s

(lb*s/ft2)

Density

Kg/m3

(lb/ft3)

Water

0.001

(0.0000208)

1005

(62.8)

Freon-11

0.00048

(0.00001)

1494

(93.4)

Freon-12

0.00028

(0.00000586)

1330

(83.1)

Freon-22

0.00025

(0.00000522)

1202

(75.1)

Freon-113

0.00074

(0.0000155)

1573

(98.3)

Kerosene

0.00256

(0.0000535)

804

(50.25)

Benzene

0.00069

(0.0000144)

879

(54.9)

Glycerol

1.393

(0.029)

1261

(78.8)

Ethanol

0.00122

(0.0000255)

789

(49.3)

Mercury

0.00159

(0.0000332)

13545

(846)

Linseed oil

0.044

(0.000919)

924

(57.75)

FLUID YOUNG'S MODULUS

Fluid

Young’s modulus

Water

2*109

Gasoline

1.3*109

Kerosene

1.28*109

Motor oil

1.3÷1.7*109

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