Nova-Tech LMI Series G - SG Metering Pump User Manual

Page 21

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15

properly assemble the valve assemblies; the ball
must be placed on the sharp edge of the seats.

Check valves are supplied in four different configu-
rations: plastic, stainless steel, slurry, and polymer.
Be sure to refer to the appropriate instructional set
below.

BE SURE TO FOLLOW INSTRUCTIONS
CAREFULLY AND REFER TO THE
APPROPRIATE FIGURE WHEN REAS-
SEMBLING CHECK VALVES. IF CHECK
VALVE CARTRIDGES ARE INSTALLED
INCORRECTLY, ONE OF THE FOLLOW-
ING WILL OCCUR: (A) IMMEDIATE
SEVERE DAMAGE TO PUMP MECHA-
NISM, (B) NO PUMPING, (C) REVERSE
PUMPING ACTION (FROM DISCHARGE
LINE INTO SUCTION LINE).

4.4.1.1 Plastic Check Valves (PVC, PVDF,
Polypropylene, and Sulfuric Acid Service, Fig.
14A or 14C):

Disassembly

Check pump data plate for model number.

1. Unscrew the union nut (435). The union end
(445) is held in place by the union nut and will sep-
arate easily from the other liquid end parts.

2. Unscrew the ball guide (424) from the liquid
end.

3. Screw the union nut part way (one or two
turns) onto the end of the ball guide 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 onto a flat surface
with the union nut down. Looking into the top of
the ball guide, you will see four large holes sur-
rounding one small hole. Insert a thin, blunt instru-
ment such as a hex head screwdriver into the small
center hole until it rests on the top of the ball (422).

IF YOU ARE DISASSEMBLING UNIT
FOR INSPECTION 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 DISASSEMBLY,
THEY WILL HAVE TO BE REPLACED. IF
AVAILABLE, TO AVOID DAMAGE, IT IS
ADVISABLE TO USE GENTLE AIR
PRESSURE (APPLIED AT END OPPO-
SITE THE SEAT - 420) FOR BALL AND
SEAT REMOVAL.

5. Tap screwdriver gently with a hammer until the
ball and seat are released from the ball guide.

6. Carefully remove the two or three o-rings (de-
pending on model number) from the ball guide and
seat.

7. Carefully clean any parts to be reused. If any
chemicals are used in the cleaning process,
ensure that they are compatible with the process
liquid.

Reassembly

1. Fit new o-rings into position on the ball guide
and seat.

NOTE: To assure a tight, leak free seal, new
o-rings should be used each time the check
valves are disassembled.

2. Drop the ball into the curved inner chamber
end of the ball guide.

IF THE SEAT IS IMPROPERLY POSI-
TIONED, THE BALL WILL NOT CREATE
A TIGHT SEAL AND POOR PUMPING
PERFORMANCE WILL RESULT.

3. Set the ball guide on a flat surface so that the
side with the ball faces upwards. Position seat on
the ball guide, trapping the ball inside. When the
seat is pressed into the ball guide, the beveled
edge of the seat must be facing outward. The

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