Head loss is an important aspect in pipe design. The loss in pipe flow energy may lead to insufficient head to reach the highest supply level in downstream. To calculate head loss, we can use either Darcy-Weisbach equation or Hazen-Williams head loss gradient equation.
Pipe flow velocity can be estimated by using Hazen-Williams equation. Pipe velocity is usually limited by authority to control the effect of water hammer that occur when a pipe is shut by valve. This effect can be estimated by using Joukowsky’s equation. Pressure increases in the event of water hammer, and this must be taken into account when designing the pipe section. The pressure resistance of pipe can be calculated using Barlow’s formula.
The following introduces five useful pipe design formulas. Watch the video above for full details.
Formulas overview
Overview of five useful formulas introduced in this section.
Pipe overview
Overview of the MSCL pipe and design flow in our example.
Moody Diagram (For Darcy-Weisbach equation)
Determining friction factor for Darcy-Weisbach equation by using Moody Diagram.
Darcy-Weisbach equation
Solve for the head loss in pipe.
Hazen-Williams head loss gradient equation
Solve for the head loss gradient over the flow length.
Hazen-Williams equation
Solve for the flow velocity under fully pressurized flow.
Barlow's Formula
Solve for maximum allowable pressure a pipe section can sustain.
Joukowsky's Formula
Estimate the change in pressure due to water hammer.
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