9
Refer to paragraph 2-11 “Operation with Suction
Lift”, which outlines limiting conditions if suction lift
requirements are anticipated.
For more NPSH information, refer to Milton Roy
web site (www.miltonroy
.com) for aid in evaluating
applications for this liquid end.
The supply tank should incorporate a low-level
switch to cut off the pump motor circuit before the
suction intake is exposed to air. Otherwise, the
pump may occasionally run dry.
NOTE: Maximum safety and reliability may be
ensured by protecting liquid ends and piping
with an external relief valve installed in the sys-
tem discharge line.
Discharge Piping
The installation of an external Safety Valve is rec-
ommended, since the pump’s internal relief valve is
not in-tended to protect the piping system. Refer to
“Relief Valve Setting” in Section 3, for further relief
valve discussion. (Milton Roy offers a complete line
of back pressure and safety valves).
For satisfactory metering and capacity control, the
discharge pressure at the pump must be 50 PSIG
(3.5 Bar) Minimum. Therefore, when the pump is to
discharge into an open system, a back pressure
device must be installed in the pump discharge
cartridge or line. Installation of this spring will
assure repetitive metering accuracy.
A spring (XW, 1390) is attached to each XW pump
in a small cloth bag (1380) for installation in the dis-
charge cartridge to develop the required back pres-
sure on the pump if a separate back pressure valve
is not used. XT pump discharge check valves are
maufactured with a spring. The XW back pressure
spring should slip easily through the hole in the
seat. Do not disassemble the seat and/or ball to
insert spring. These check valves are precision
Figure 6. Typical Piping Syatem
Figure 5. Back Pressure Spring Installation
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