Nova-Tech LMI Series G - SD Metering Pump - Manual (Page 22)

Check Valve Replacement
General
Before beginning work on the valve assemblies, make
sure the suction and discharge shut-off valves are closed
and that pressure has been bled from the pump liquid
end. When replacing the valves, be sure to replace the
valve O-rings. Pay close attention to the proper assem-
bly and orientation of the check valves as shown in each
Liquid End figure. In the case of plastic check valves for
liquid end size SD7 and SD8, be certain that the ball is
placed on the sharp edge of the valve seat.
BE SURE TO FOLLOW INSTRUCTIONS
CAREFULLY AND REFER TO THE APPRO-
PRIATE FIGURE WHEN REASSEMBLING
CHECK VALVES. IF CHECK VALVE CAR-
TRIDGES ARE INSTALLED INCORRECTLY,
ONE OF THE FOLLOWING WILL OCCUR:
(A) IMMEDIATE AND SEVERE DAMAGE TO
PUMP MECHANISM.
(B) NO PUMPING OF FLUIDS.
(C) REVERSE PUMPING ACTION (FROM
DISCHARGE LINE INTO SUCTION LINE).
Preliminary Operations
1. Set the pump capacity knob to 0%. If stroke locking
screw (Item 320 in Figure 8) was previously tightened,
slightly loosen the locking screw.
2. Disconnect power to pump motor. Check that the
equipment cannot be accidentally started. Place a no-
tice at the location of the power switch indicating that
the pump is being serviced.
3. Disconnect the pump hydraulically by removing pipe
or tubing connections to suction and discharge check
valves.
4.5.1 CHECK VALVE ASSEMBLIES REPLACEMENT:
LIQUID ENDS SD2 AND SD4 - PVC, PVDF, AND
H
2
SO
4
(SEE FIGURE 9 OR 12)
IMPROPER BALL AND SEAT INSTALLATION
CAN CAUSE DAMAGE TO THE PUMP. SEE
FIGURE 9 OR 11 FOR PROPER BALL AND
SEAT ORIENTATION FOR BOTH THE SUC-
TION AND DISCHARGE VALVES
2 each, Seat: Item 420, Ball: Item 422 in Figure 13.
4 each, O-Ring: Item 419 in Figure 13.
Liquid End Kit for D7/D8 Polymer
RPM 211/210, Includes:
1 each, Diaphragm: Item 260 in Figure 13.
1 each, Oil Seal Bellows: Item 70 in Figure 13.
1 each, PTFE Seal Ring: Item 210 in Figure 13.
4.4.5 SIZE SD7 AND SD8 - STAINLESS STEEL
LIQUID ENDS
1 each, Diaphragm: Item 260 in Figure 6
1 each, Oil Seal Bellows: Item 70 in Figure 7
2 each, Check Valve Assembly: Item 425 in Figure
14.
Note: The check valves for the size SD7 and
SD8-PVC and PVDF liquid ends contain a re-
movable seat, which permits the replacement
of the seat, O-ring, and ball into a reusable
valve body. The liquid end size SD7 and SD8-
Stainless Steel check valve has an integral ball
seat, which necessitates replacement of the
entire check valve assembly.
4.5 CORRECTIVE MAINTENANCE
BEFORE CARRYING OUT ANY SERVICING
OPERATION ON THE PUMP OR PIPING, DIS-
CONNECT ELECTRICAL POWER FROM THE
PUMP, AND TAKE THE NECESSARY STEPS
TO ENSURE THAT ANY HARMFUL LIQUID
CANNOT COME INTO CONTACT WITH PER-
SONNEL. SUITABLE PROTECTIVE EQUIP-
MENT MUST BE PROVIDED. BE SURE THAT
THERE IS NO FLUID PRESSURE IN THE
PUMP LIQUID END AND PIPING.
Cleaning Fouled Check Valves
Check valve assemblies are designed to be self-clean-
ing and should seldom need servicing. Fouled check
valves can usually be cleaned by pumping a solution of
mild detergent and warm water (if compatible with liquid
being pumped) for 15 minutes, followed by flushing with
water.
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