Cavitation

• Inadequate fluid supply because:

— Inlet line collapsed or clogged

— Clogged line strainer

— Inlet line too small or too long

— Air leak in inlet line

— Worn or damaged inlet hose

— Suction line too long

— Too many valves and elbows in inlet line

• Fluid too hot for inlet suction piping system.

• Air entrained in fluid piping system.

• Aeration and turbulence in supply tank.

• Inlet vacuum too high


Symptoms of Cavitation

• Excessive pump valve noise

• Premature failure of spring or retainer

• Volume or pressure drop

• Rough-running pump

• Premature failure of diaphragms

• Piston return spring failure (inside hydraulic end)

Drop in Volume or Pressure

A drop in volume or pressure can be caused by one or more

of the following:

• Air leak in suction piping

• Clogged suction line or suction strainer

• Suction line inlet above fluid level in tank

• Inadequate fluid supply

• Pump not operating at proper RPM

• Relief valve bypassing fluid

• Worn pump valve parts

• Foreign material in inlet or outlet valves

• Loss of oil prime in cells because of low oil level

• Ruptured diaphragm

• Cavitation

• Warped manifold from overpressurized system

O-Rings forced out of their grooves from overpressurization

• Air leak in suction line strainer or gasket

• Cracked suction hose.

• Empty supply tank

• Excessive aeration and turbulence in supply tank

• Worn and slipping drive belt(s)

• Worn spray nozzle(s)

• Cracked cylinder casting


Pump Runs Rough

• Worn pump valves

• Airlock in outlet system

• Oil level low

• Wrong weight of oil for cold operating temperatures (change

to lighter weight)

• Cavitation

• Air in suction line

• Restriction in inlet/suction line

• Hydraulic cells not primed after changing diaphragm

• Foreign material in inlet or outlet valve

• Damaged diaphragm

• Fatigued or broken valve spring

• Broken piston return spring (inside hydraulic end)


Premature Failure of Diaphragm

• Frozen pump

• Puncture by a foreign object

• Elastomer incompatible with fluid being pumped

• Pump running too fast

• Excess pressure

• Cavitation

• Broken piston return spring (50)


Water (or Process Fluid) in Oil

Reservoir

• Condensation

• Ruptured diaphragm

• Hydraulic cell not properly primed after diaphragm

replacement

• Frozen pump

• Diaphragm screw O-ring (18) missing or cracked

• Cracked cylinder casting


Strong Water (or Process Fluid)

Pulsations

NOTE: Small pulsations are normal in single-acting pumps

with multiple pumping chambers.

• Foreign object lodged in pump valve

• Loss of prime in hydraulic cell because of low oil level

• Air in suction line

• Valve spring (13) broken

• Cavitation

• Aeration or turbulence in supply tank


Valve Wear
• Normal wear from high-speed operation
• Cavitation
• Abrasives in the fluid
• Valve incompatible with corrosives in the fluid
• Pump running too fast


Loss of Oil
• External seepage
• Rupture of diaphragm
• Frozen pump
• Diaphragm screw O-ring (18) missing or cracked
• Worn shaft seal
• Oil drain piping or fill cap loose.
• Valve plate and manifold bolts loose


Premature Failure of Valve
Spring or Retainer

• Cavitation
• Foreign object in the pump
• Pump running too fast
• Spring/retainer material incompatible with fluid being
pumped
• Excessive inlet pressure.