Sludge Pressure
Pressure wave velocity 'a' is the function of pipe material, pipe wall thickness, specific gravity and bulk modules of the liquid being transported. The pressure wave velocity can be calculated using following equation:
a=√ 1/w/g[1/k+D.c1/E.e]
a = Pressure Wave Velocity
g = Acceleretion due to gravity
D = Diameter of pipe
e = Tickness of pipe
E = Elastic modulus of the pipe material
k = Volume modulus of water
C1 = Depend up on poisson's ratio of the pipe material is equal to
C1 = [5/4-µ] for a pipe anchored at upper end and wihout expensions joints
C1 = [1-µ2] for a pipe anchored at against longitudinal movement thoughrout its length
C1 = [1-µ/2] for a pipe with expensions joints
Piosssion,s Ratio 'µ'
Steel - 0.33
PVC - 0.40
Cast Iron - 0.33
HDPE - 0.50
Modulus of Elasticity of some pipe material
Steel - 2.0x106kg/cm2
CI - 1.12x106kg/cm2
PVC - 30000kg/cm2
HDPE - 9000kg/cm2
Preesure wave velocity in water has value ranging 900-1200 m/sec steel concerte for pipe which reduces 175-400 m/sec for HDPE pipes. This low wave velocity in PE helps in limiting pressure rating of pipe and prevents the damege to pipe,values,fittings etc. due to higher wave velocityies