Nova-Tech LMI Series G - SD Metering Pump - Manual (Page 25)

(C) REVERSE PUMPING ACTION (FROM
DISCHARGE LINE INTO SUCTION LINE)
1. Drop the ball (422) into the curved inner chamber end
of the body (424).
2. Set the body on a flat surface so that the end with the
ball faces upward. Position seat (420) on the body,
with the beveled edge of the seat facing outward. When
the seat is pressed into the body, the ball should be
sitting on the side with sharp corners as shown in Fig-
ure 13. The bevel should not face the inside of the
check valve. Use a flat surface such as a board to
press the seat into the body with firm, even pressure.
If the seat is improperly positioned, the ball will not cre-
ate a tight seal and poor pumping performance will re-
sult.
3. Fit new O-rings (419) into position on the body (424)
and seat (420).
DO NOT APPLY PTFE TAPE TO THREADS
OF CHECK VALVE BODY (424) AS THIS MAY
PREVENT ADEQUATE SQUEEZE FROM BE-
ING APPLIED TO THE VALVE O-RING WHICH
WOULD RESULT IN LEAKAGE.
Note: To assure a tight, leak free seal, new O-
rings should be used each time the check
valves are disassembled.
4. Position the union end (445) onto the correct end of
the body. Refer to Figure 12, as the correct end is
determined by whether the valve is intended for the suc-
tion or discharge port of the liquid end. Slip the union
nut (435) over the union end and screw tightly (hand
tight only) onto the body.
5. Screw the valve assembly into the pump head (hand
tight only). DO NOT OVERTIGHTEN.
4.5.6 CHECK VALVE REPLACEMENT: LIQUID END
SIZES D7 AND D8 - POLYMER (SEE FIGURE 13)
Suction
Follow the instruction for replacement of ball, seat, &
seal: liquid end D7 and D8 - PVC, PVDF, H
2
SO
4
and
polypropylene paragraph 4.5.5. The procedures are
the same.
Discharge
1. Unscrew the valve body (424) from the pump head
(280).
2. Remove the valve assembly: assembly includes two
O-rings (419), seat (420), ball (422), poppet (426), spring
(423) and check valve body (424).
3. Replace O-rings (419), seat (420), ball (422), poppet
(426), and spring (423).
4. Clean the valve body (424) and threaded port in the
head (280).
5. Install new check valve assembly in orientation shown.
On discharge side, drop cartridge assembly into threaded
port in head. Screw valve body into discharge side of
diaphragm head until valve is hand tight. DO NOT OVER-
TIGHTEN.
4.5.7 CHECK VALVE REPLACEMENT: LIQUID END
SIZES D7 AND D8 - SLURRY (SEE FIGURE 13)
1. Unscrew the valve body (424) from the pump head
(280).
2. Remove the valve assembly: assembly includes two
O-rings (419), slurry seal ring (420), ball (422), check
valve body (424), and dowel pin.
3. Clean the valve body (424) and threaded port in the
head (280).
5. Install new check valve assembly in orientation shown.
On discharge side, drop cartridge assembly into threaded
port in head. Screw valve body into discharge side of
diaphragm head until valve is hand tight. DO NOT OVER-
TIGHTEN.
On suction side, drop the cartridge assembly into check
valve body. Screw the suction valve body with cartridge
valve into suction side of head hand tight. DO NOT
OVERTIGHTEN.
4.5.8 CHECK VALVE REPLACEMENT: LIQUID END
SIZE SD7 AND SD8 - STAINLESS STEEL (SEE
FIGURE 14)
Disassembly
Stainless steel check valves differ from the plastic ver-
sions in that the ball seat is integral to the ball guide.
The seats cannot easily be inspected for damage or
wear. If you suspect that the check valve may be dam-
aged or worn, replace the entire check valve assembly
as per the instructions below.
1. Unscrew the coupling (445).
2. Unscrew the check valve assembly (425) from the
liquid end.
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