Water Hammer Calculation(b)

WATER HAMMER PRESSURE/ SURGE PRESSURE CAL Ratio of elastic modulus of water to 0.09 that of pipe material, Khs Gravitational constant, g (ft/s)

32.2

Fluid flow rate, (ft3/s) Specific Gravity of fluid Internal pipe diameter (in)

1.114 1 16

Actual flowing velocity, vw (ft/s) Pipe wall thickness (in) Ratio of internal pipe diameter (I.D) to pipe wall thickness, Br Length of pipe before valve, L (ft)

6.56 0.251968 63.5002 328

Velocity of propagation of elastic vibration in the discharge pipe, aw (ft) Maximum pressure developed by hydraulic shock, hwh (ft of liquid) Time interval required for the pressure wave to travel back & forth in the pipe, ts (sec)

You add the h wh to the existing pressure from the system to determine the Total Pressure on the pipe system Pipe distance before valve (ft)

aw (ft/s)

ts (sec)

hwh (ft of liquid)

hwh (psi)

0

1798.301

0

366.3618861

158.5982

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300

1798.301 1798.301 1798.301 1798.301 1798.301 1798.301 1798.301 1798.301 1798.301 1798.301 1798.301 1798.301 1798.301

0.111216 0.222432 0.333648 0.444864 0.556081 0.667297 0.778513 0.889729 1.000945 1.112161 1.223377 1.334593 1.445809

366.3618861 366.3618861 366.3618861 366.3618861 366.3618861 366.3618861 366.3618861 366.3618861 366.3618861 366.3618861 366.3618861 366.3618861 366.3618861

158.5982 158.5982 158.5982 158.5982 158.5982 158.5982 158.5982 158.5982 158.5982 158.5982 158.5982 158.5982 158.5982

1400 1500

1798.301 1798.301

1.557025 1.668242

366.3618861 366.3618861

158.5982 158.5982

1600 1700

1798.301 1798.301

1.779458 1.890674

366.3618861 366.3618861

158.5982 158.5982

1800 1900 2000

1798.301 1798.301 1798.301

2.00189 2.113106 2.224322

366.3618861 366.3618861 366.3618861

158.5982 158.5982 158.5982

URE/ SURGE PRESSURE CALCULATION (Developed by Engr. Abiodun Asade) Some typical Khs values for water/metal (Source: Pump Engineering data, Economy Pumps, Inc, 1951, Philadephia, Pa ) Khs

Metal Copper Steel Brass

0.017 0.01 0.017

Wrought Iron

0.012

Malleable cast iron

0.012

Aluminum

0.03

psi the pipe system

Normal pressure upstream of valve hwh Maximum shock pressure upstream of valve

133 158.5982 291.5982

Notes: 1. The pipe distance can be increased to suit your pipe length 2. When the time of abrupt closure of a device that stop the fluid flow is shorter than ts, then the maximum pressure hwh, will be exerted on the closed device and line. Reference: 1. Applied Process Design for Chemical and Petrolchemical Plants, Vol. 1, Third Edition by Ernest E. Ludwig

Equations: aw = {(4660)/√(1 + KhsBr)} ft/s hwh = (aw x vw)/ g ft of liquid(H2O) ts = (2L/aw) secs