Wilden Pump & Engineering Co. - Manufacturer of air-operated double-diaphragm pumps.

Pump will not run or runs slowly

Ensure that the air inlet pressure is at least 5 psig (9.35 Bar) above startup pressure and that the differential pressure (the difference between air inlet and liquid discharge pressures) is not less than 10psig (.7 Bar).
Check air inlet filter for debris (see recommended installation).
Check for extreme air leakage (blow by) which would indicate worn seals/bores in the air valve, pilot spool and main shaft.
Disassemble pump and check for obstructions in the air passageways or objects which would obstruct the movement of internal parts.
Check for sticking ball check valves. If material being pump is not compatible with pump elastomers, swelling may occur. Replace ball check valves and seals with proper elastomers. Also, as the check valve balls wear out, they become smaller and can become stuck in the seats. In this case, replace balls and seats.
Check for broken inner piston which will cause the air valve spool to be unable to shift.
Remove plug from pilot spool exhaust.
Ensure that air supply is attached to pump center section (air inlet) and NOT to pump air valve body.

Pump runs but little or no product flows

Check for pump cavitation; slow pump speed down to allow thick material to flow into the liquid chambers.
Verify that vacuum required to lift liquid is not greater than the vapor pressure of the material being pumped (cavitation).
Check for sticking ball check valves. If material being pump is not compatible with pump elastomers, swelling may occur. Replace ball check valves and seals with proper elastomers. Also, as the check valve balls wear out, they become smaller and can become stuck in the seats. In this case, replace balls and seats.

Pump air valve freezes

Check for excessive moisture in compressed air. Either install a dryer or hot air generator for compressed air. Alternatively, a coalescing filter may be used to remove the water from the compressed air in some applications.

Air bubbles in pump discharge

Check for ruptured diaphragm.
Check tightness of outer pistons. Check tightness of clamp bands and integrity of O-rings and seals , especially at intake manifold.
Ensure pipe connections are airtight. Product comes out air exhaust.
Check for diaphragm rupture.
Check tightness of outer pistons to shaft

Product comes out air exhaust

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