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

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It is recommended that the oil seal and diaphragm
be replaced at the same time. The instructions
given under “Replacing the Oil Seal” are complete
instructions for replacing both the oil seal and dia-
phragm. If you plan to replace both, refer to the
“Replacing the Oil Seal” instructions, and disregard
the instructions below. These instructions are
intended for use only if the diaphragm is being
replaced independent of the oil seal.
4.4.2.1 Diaphragm Removal (All types; Refer to
Figures 6-13)
1. Set the stroke adjusting knob to 100%.
2. Disconnect the suction and discharge piping.
3. Unscrew the six diaphragm head bolts (290).
4. Remove the pump head (280) from the pump
body.
5. Turn the motor fan by hand (remove the motor
shroud if necessary) until the end of the diaphragm
(240) is fully forward, and unscrew the diaphragm
assembly from the connecting rod (60).
Figure 6. Diaphragm Assembly
4.4.2.2 Disassembly (Only Those Units With a
“Hex Head “ Diaphragm Cap Design, Figure 6)
1. Secure the hex cap (240) in a vise, and loosen
the support nut (270) using a 30mm hex socket.
2. After complete disassembly inspect the sup-
port nut (270). It should be free of corrosion and
clean. The angled surface must be smooth to pro-
tect the diaphragm from damage. If the support
nut does not meet these requirements, replace it.
4.4.2.3 Reassembly
1. Mount the hex cap (240) in a vise (do not over-
tighten), and with surfaces cleaned place a new
diaphragm (260) onto the cap as shown Figure 6
through Figure 13 (convolution pointing toward the
support nut).
2. The set screw (250) hand tight in the cap (240)
with the hex socket end visible.
3. Screw the support nut (270) onto the set screw
until hand tight
4. DO NOT OVERTIGHTEN the support nut.
Use a 30mm hex socket and torque wrench to
tighten the support nut. The torque depends on
pump model number.
• For model numbers SG5 & SG6: Torque is
20 foot pounds.
• For model number SG7: Torque is 30 foot
pounds.
4.4.2.4 Reinstallation of Assembly (Refer to
Figures 6 Through 13)
1. With the stroke adjusting knob at 100% and
the diaphragm fully forward as in steps 1 and 5 of
paragraph 4.4.2.1, screw the diaphragm assembly
into the connecting rod until it reaches its natural
mechanical stop.
2. Turn the motor fan by hand until the diaphragm
rests properly on the diaphragm support (230).
Reinstall the motor shroud if previously removed.
3. Fit the diaphragm head back into place on the
pump body.