Milton Roy Dosing Pump GB804

Ensure all shut-off valves are closed

Bleed all pressure from the liquid end

Disassembly (Refer to Figures 7 and 8)

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 is fully forward

Fit new O-Rings into position on the ball guide and seat

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

Sit the ball guide on a flat surface with the ball facing upwards

Position seat on the ball guide, trapping the ball inside

Press the seat into the ball guide with firm, even pressure

Position the union end onto the correct end of the ball guide

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

Ensure the following components are in place

Screw the correct end of the check valve assembly 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 (419, 423) between the coupling and the check valve assembly

Were new O-Rings used for each assembly?

Pre-Replacement Safety Measures

Ensure shut-off valves are closed

Inspection of Check Valve Components

Inspect ball check for chemical or physical damage

Inspect seat for sharp edge and damage

Replacement of Check Valve Components

Systematically change O-Rings and/or gaskets during valve replacement