PE Pipe and Fittings

Technical Informations / Pressure Impact

During opening/shutting the valve or pump, water-hammer may occur in the line. For this, theoretically, greater ps:

• a : Spread rate of pressure wave (m/h)
• v : Flow rate of fluid (m/h)
• p : Density of Fluid (kg/m3)

In practice ps value can be negative or positive:
Positive : During shutting armatures and opening pump.
Negative : Shutting off pump or instant change of hydraulic property (E.g.: a decrease in flow rate).

Spreading rate of pressure wave is calculated with below formulae:

• a : Spread rate of pressure wave (m/h)
• v : Flow rate of fluid (m/h)
• p : Density of Fluid (kg/m3)
• Em : Elasticity module of fluid (Esu)
• p : Density of Fluid (p=1000 kg/m3)
• Er : Elasticity module of material (of pipe) (N/m2)
• Dm : Pipe middle diameter (m)
• e : Pipe wall thickness (m)

In his formulae, short term elasticity module must be used. (Er= 800..1200N/mm2).

Short-term pressure changes and water-hammer effect do not cause damages on the HDPE pipes. In the sample table below, for various safety factors, to what extent new pressure value will appear with short term water-hammer at a temperature of 20 °C in proportion to nominal pressure. The pressure increases within these values do not damage the pipe.