Milton Roy Dosing Pump GB402A

Refer to Figure 9 or 11 before starting disassembly

Unscrew the union nut (435) to separate the union end (445)

Unscrew the ball guide (424) from the liquid end

Screw the union nut part way onto the end of the ball guide with the seat

Place the ball guide/union nut onto a flat surface with the union nut down

Insert a thin, blunt instrument into the small center hole of the ball guide

Tap screwdriver gently with a hammer to release the ball and seat

Ensure all shut-off valves are closed and all pressure has been bled from liquid end.

Drain oil from the pump by unscrewing the drain plug (20) and O-Ring (19).

Set the stroke adjusting knob to 100%.

Disconnect the suction and discharge piping.

Unscrew the six diaphragm head bolts.

Remove the diaphragm head assembly from the pump body.

Turn the motor fan by hand until the end of the diaphragm assembly (261) is fully forward, and unscrew the diaphragm from the connecting rod (60).

Ensure the correct end of the check valve assembly is screwed into the liquid end

Trap a new O-Ring between the liquid end and the check valve assembly

Refer to Figure 10 for proper assembly order

Screw the coupling (445) onto the check valve assembly

Trap a new O-ring between the coupling and the check valve assembly

Unscrew the ball guide (424) from the liquid end

Remove and discard the O-Rings (419)

Carefully clean any parts to be reused

Do you suspect the check valve may be damaged or worn?

Replace the entire check valve assembly if damage or wear is suspected

Separate the following components

Remove and discard the three gaskets (419)

Were all parts cleaned for reuse?

List any chemicals used for cleaning and confirm compatibility with process liquid