developed head (TDH)
is the total resistance against which pump is
working. This resistance is comprised of three
general factors: Dynamic Head, Static Head and
Head Is the flow resistance (head) created
by friction in piping, valves, fittings and
To derive maximum
flow from a pump, avoid using piping smaller
than the pumps' discharge (increasing the size
of the outlet piping will decrease flow resistance).
Street "ells" and globe valves should
be avoided because they restrict flow. When
the size of the piping is smaller than the pumps'
discharge, or when long runs are required (over
20 feet), plumbing friction may easily comprise
50% or more of the TDH.
Head is the height (head) required to
which liquid must be raised. Note: When using
the flow charts in the pump selection, both
Dynamic Head and Static Head must be included
in estimating the TDH against which the pump
Head is the pressure (head) required
to accelerate the liquid to it's flow velocity.
This is usually a negligible factor of TDH and
can be disregarded unless piping is smaller
than the pump discharge and/or flow velocities
are greater than 15 feet per second.
higher the viscosity of a liquid, the more
resistance it has to flow. Pump viscosities
throughout this information given are stated
in SSU's (saybolt second universal). 70°
F water = 31 SSU. Light hydraulic oil = 350
SSU. #10 oil = 500 SSU. When choosing pumps,
be sure to note the designated fluid viscosity.