Equivalent Piping Length Head Loss Equation Fluids

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 Fluid Power Equipment

Equivalent Piping Length Head Loss Equation Fluids

Minor losses may be expressed in terms of the equivalent length (Leq) of pipe that would have the same head loss for the same discharge flow rate. This relationship can be found by setting the two forms of Darcys equation equal to each other.

Head Loss

This yields two relationships that are useful.

Head Loss

Typical values of Leq/D for common piping system components are listed in Table 1. The equivalent length of piping that will cause the same head loss as a particular component can be determined by multiplying the value of Leq/D for that component by the diameter of the pipe. The higher the value of Leq/D, the longer the equivalent length of pipe.

Head Loss


A fully-open gate valve is in a pipe with a diameter of 10 inches. What equivalent length of pipe would cause the same head loss as the gate valve?


From Table 1, we find that the value of Leq/D for a fully-open gate valve is 10.

Head Loss

By adding the equivalent lengths of all components to the actual length of pipe in a system we can obtain the Leq value for the entire piping system.

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