Nova-Tech LMI Series G - SG Metering Pump - Manual (Page 15)

9
charging into a manifold having the slight-
est pressure difference between its several
discharge connections can diminish meter-
ing accuracy as the outlet with the lowest
pressure will receive more liquid than the
other outlets.
Back Pressure Valves
A Milton Roy Back Pressure Valve (Figure 4)
should be installed in the discharge line near the
pump to ensure sufficient discharge head pressure
for proper pump metering action. Back pressure
valves for large pumps with long and extremely
small discharge lines may have to be installed near
the point of discharge into the process (to minimize
siphoning tendencies).
Pulsation Dampeners
An accumulator, surge chamber, surge suppressor,
or pulsation dampener should be used with the
back pressure valve in the discharge line to absorb
the flow peaks between the pump and the back
pressure valve. Without the pulsation dampener
the valve mechanism will snap open and closed
with the surge from each pump stroke. The pulsa-
tion dampener will allow the back pressure valve to
oscillate about a partly-closed position, thus mini-
mizing wear on the valve. Discharge line pulsation
dampeners offer the further advantage of limiting
the flow and pressure variations characteristic of
this kind of pump. Installing a properly sized pulsa-
tion dampener will improve pump performance and
may reduce system costs dramatically by permit-
ting the substitution of smaller piping. Please con-
tact your LMI distributor for further information on
pulsation dampeners.
Safety Valves
Motor-driven positive displacement pumps can
develop excessive discharge pressures long
before thermal overload devices interrupt the motor
electrical circuit. To prevent a blocked discharge
line from causing damage to the pump, piping, or
process equipment, install a Milton Roy Safety
Valve in the pump discharge line. This valve is
designed and sized to handle system flow rates
and pressures safely while resisting corrosion by
the process liquid.
Install the safety valve in the discharge line
between the pump and the nearest shut-off valve.
(This will prevent pump damage from accidental
valve closure.) Pipe the safety valve outlet back to
the suction tank or to drain, but in either case
ensure that the pipe end is continuously visible so
safety valve leakage may be detected. Milton Roy
safety valves must be installed at top of supply tank
in order to function properly (see Figure 4).
Check Valves
A check valve should be installed at the point
where the discharge line enters a boiler or other
high-pressure vessel. This will prevent back flow
through the discharge piping and will isolate the
pump discharge from system pressures (a safety
consideration).
Shut-off Valves
Provide shut-off valves in both suction and dis-
charge lines next to the pump. Locate discharge
line shut-off valve downstream from the inlet con-
nection of the safety valve. Figure 4 shows recom-
mended valve locations.
2.6 LEAK DETECTION
The Series G Model G pumps are equipped with a
leak detection port. For ease of installation, each
pump has a plastic tubing connector installed in the
leak detection port (see item 448 in Figure 7, Sheet
2). In the event of a failure of the oil seal (70 in Fig-
ure 7, Sheet 1) or PTFE diaphragm assembly (260
in Figures 8 through 13), pump drive oil or process
fluid will escape from this leakage port. During
pump installation, actions should be taken to insure
that this leakage is safely collected by installing
tubing between the leak detection port and an
appropriate containment vessel.
2.7 ELECTRICAL CONNECTIONS
Ensure that the electrical supply matches the pump
motor nameplate characteristics.
OPERATION WITH THE WRONG
MOTOR ROTATION WILL DAMAGE THE
PUMP AND MOTOR AND VOID THE
WARRANTY.