Crane EPRO Series, Operation & Maintenance Manual

Page: 27 / 57

Pump Throttle Valve
(pointer 15 on Fig. 4)
This valve is installed as a standard
feature on all EPRO – 1500 through
EPRO – 8000 reverse osmosis
systems. It provides an adjustment
for pump flow, which will vary as the
required system pressure changes.
To understand this concept, please
refer to the pump curves in figure 10.
Note that with a centrifugal pump,
the pump flow decreases as the
operating pressure increases.
Example:
PRESSURE 1 HP 1.5 HP
120 psi 10.5 gpm 12 gpm
150 psi 8 gpm 10.5 gpm
180 psi 4 gpm 8 gpm
Figure 10: Pump Curves
As the feed water temperature
decreases, and/or the feed water
TDS increases, the system will
require a higher operating pressure
to produce the specified permeate
flow. An EPRO-1500 installed in
Florida may provide the specified
permeate flow of 1 gpm at 130 psi;
however, the same EPRO-1500
installed in Maine – much colder
feed water – may require 190psi to
produce this same amount of
permeate. The Florida system would
have higher concentrate flow to
drain because of the lower operating
pressure, which would result in poor
system recovery.
The pump throttle valve can be
adjusted to the desired system
recovery for applications that fit the
system specifications.
EPRO 150-8000 O&M MANUAL Rev.04/03 Page 25 of 55