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.

This yields two
relationships that are useful.

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.

Example:

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?

Solution:

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

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.