FRICTION LOSS
The friction loss in hydraulic can be evaluated through the use Of various flow coefficients. one such coefficient is the HazenWilliams C factor. This factor for PVC & CPVC plastic piping system has been set at at C=150. The following formulae express the friction loss in feet of water and the water velocities in feel per second.
Friction loss is based on HazenWilliams formula
where,
F= friction head loss in feet of water per 100 feet of pipe C= constant for inside pipe roughness (c=150 for extruded smooth wall thermoplastic pipe) Q= flow in us gallons per minute di= inside diameter of pipe in inches
The value of c 150 for thermoplastic pipe is based on engineering measurements made with new and used thermoplastic pipe in several laboratories. Thus the value of c = 150 has a conservative bias. Using c = 150 the equation reduces to
Water velocities in feet per second v may be calculated as follows
Typical values of the Hazen Williams coefficient
Water Hammer_Pressure surge
Maximum pressure caused by water hammer May be calculated with the following formulae.
Where,
P = pressure surge (psi) A = wave velocity (ftsec) V = maximum velocity change (ftsec) G = acceleration of gravity (32.2 ft sec^{2}) K= fluid bulk modulus (300 000 psi for water) Di = pipe inside diameter (inches) E = modulus of elasticity of the pipe (420 000 psi for PVC 360 000 psi for CPVC) t = wall thickness (inches)
