Nova-Tech LMI Series G - SD Metering Pump - Manual (Page 24)

2. Unscrew the check valve assembly (425) from the
pump head (280).
3. Screw the union nut part way (one or two turns) onto
the end of the ball guide (424) that has the seat in it. Be
sure the union nut is on loosely. This will allow a gap for
the seat (420) to fall into as it is removed from the ball
guide.
4. Set the ball guide/union nut on a flat surface with the
union nut down. Looking into the top of the ball guide,
you will see four large holes surrounding one small hole.
Insert a thin, blunt instrument such as a hex head screw-
driver into the small center hole until it rests on the top
of the ball (422).
5. Tap screwdriver gently with a hammer until the ball
and seat are released from the ball guide.
IF THE UNIT IS DISASSEMBLED FOR IN-
SPECTION ONLY, BE SURE TO USE A BLUNT
INSTRUMENT AND TAP GENTLY TO AVOID
DAMAGING THE BALL. IF THE BALL AND/
OR SEAT ARE DAMAGED DURING DISAS-
SEMBLY, THEY WILL HAVE TO BE RE-
PLACED. IF AVAILABLE, TO AVOID DAM-
AGE, IT IS ADVISABLE TO USE GENTLE AIR
PRESSURE (APPLIED AT END OPPOSITE
THE SEAT (420) FOR BALL AND SEAT RE-
MOVAL.
6. Carefully remove the two O-rings (419) from the ball
guide and seat.
7. Carefully clean any parts to be reused. If any chemi-
cals are used in the cleaning process, ensure that they
are compatible with the process liquid.
Reassembly
THE ORDER OF ASSEMBLY AND ORIENTA-
TION OF THE SUCTION AND DISCHARGE
CHECK VALVES IS DIFFERENT. REFER TO
FIGURE 13 FOR PROPER ASSEMBLY OR-
DER AND ORIENTATION. IF CHECK VALVE
CARTRIDGES ARE INSTALLED INCOR-
RECTLY, ONE OF THE FOLLOWING WILL
OCCUR:
(A) IMMEDIATE SEVERE DAMAGE TO PUMP
MECHANISM
(B) NO PUMPING
18
Disassembly
Remove the check valves by unscrewing them from the
pump head.
Reassembly
Apply a small amount of thread sealing compound and
PTFE pipe tape to check valve threads and install check
valves by screwing them into the pump head with the
flow arrows pointing up. DO NOT OVERTIGHTEN
CHECK VALVES.
4.5.4 CHECK VALVE REPLACEMENT: LIQUID END
SIZE D4 - SLURRY (SEE FIGURE 11)
1. Unscrew the valve body (424) from the pump head
(280).
2. Remove the valve assembly: assembly includes ball
(422), check valve body (424), and retainer sleeve (428).
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.
THE CHECK VALVES WILL NOT OPERATE
IF THEY ARE INSTALLED UPSIDE DOWN.
INSTALL CHECK VALVES WITH THE FLOW
ARROW POINTING IN THE DIRECTION OF
PROCESS FLOW (UP). TURN CHECK VALVE
ASSEMBLIES INTO LIQUID END BY HAND
AND TIGHTEN. DO NOT OVERTIGHTEN,
DAMAGE TO THE CHECK VALVES MAY OC-
CUR.
4.5.5 REPLACEMENT OF BALL, SEAT, & SEAL:
LIQUID END SD7 AND SD8 - PVC, PVDF, AND
H
2
SO
4
(SEE FIGURE 13)
Disassembly
1. Unscrew the union nut (435). The union end (445) is
held in place by the union nut and will separate easily
from the other liquid end parts.