Malfunction Possible cause Remedy
Pump does not convey me- dium
Pump not sufficiently immersed in the medium,
formation of vapour lock at the inlet of the impeller
Repeat pre-filling of the system, increase height of NPSHSystem
Differential pressure between inlet pressure and steam pressure of the medium too low
Increase NPSHSystem
Suction bellmouth or impeller is blocked
Check the suction chamber and the entire pump for blockage
Speed too low Check the speed conditions
Flow resistance of the pipe is greater than the delivery head of the pump
Checking the pipe resistances Pressure-side valve closed Open valve
Pressure line blocked Flush pressure line High power consumption or
power loss
Speed too high Check motor speed
Incorrect direction of rotation Check the direction of rotation of the motor
Flow resistance in the pipe is greater than the delivery head of the pump
Check the pipe resistance, check and/or correct the valve setting Unexpectedly high density and/or vis-
cosity of the medium being conveyed
Contact ANDRITZ for further in- structions
Deformed or eccentric pump shaft Replace pump shaft and bearing assembly
Rotating objects or pump components rubbing in the pump
Dismantle the pump and check the interior of the pump
Pump components are worn, damaged or blocked
Check pump; replace worn or damaged parts as necessary Vortex formation at the suction bell-
mouth inlet
Check minimum requirements for the suction chamber.
Pump does not reach the specified values for delivery head and flow rate regularly or not at all
Pump not sufficiently immersed in the medium,
formation of vapour lock at the inlet of the impeller
Repeat pre-filling of the system, increase height of NPSHSystem
Differential pressure between inlet pressure and steam pressure of the medium too low
Increase NPSHSystem
Incorrect direction of rotation Check the direction of rotation of the motor
Incorrect speed Check the speed of the motor
Suction bellmouth or impeller is blocked
Check the suction chamber and the entire pump for blockage Flow resistance of the pipe is greater
than the delivery head of the pump
Checking the pipe resistances Pressure-side valve throttled Open valve
Unexpected air/gas proportion in the medium being conveyed
Contact ANDRITZ for further in- structions
Malfunction Possible cause Remedy Unexpectedly high viscosity of the me-
dium being conveyed
Contact ANDRITZ for further in- structions
Pump components are worn, damaged or blocked
Check pump; replace worn or damaged parts as necessary
Damaged bearings Dismantle pump and replace
bearings Vortex formation at the suction bell-
mouth inlet
Check minimum requirements for the suction chamber.
Excess noises and/or vibra- tions
Differential pressure between inlet pressure and steam pressure of the medium too low
Check the suction line, increase height of the NPSHSystem
Unexpected air/gas proportion in the medium being conveyed
Contact ANDRITZ for further in- structions
Air ingress into suction line or shaft seal
Check the suction line and shaft seal
Suction line, suction valve or impeller are blocked
Check the suction line and the en- tire pump for blockage
Speed too high Check motor speed
Speed too low Check motor speed
Flow resistance of the pipe is greater than the delivery head of the pump
Check the pipe resistances and valve settings
The output of the pump is below the permitted minimum flow rate
The requirements of the pump system must be checked The foundation is unsuitable Lay a new foundation
Insufficient support of the pipe Check the support of the pipe, re- inforce as necessary
Pump and motor not sufficiently aligned Check the alignment of pump and motor or realign them
Broken or eccentric shaft Replace the shafts and bearings Rotating objects or pump components
rubbing in the pump
Dismantle the pump and check the interior of the pump
Pump components are worn, damaged or blocked
Check pump; replace worn or damaged parts as necessary Bearings worn or loose Dismantle the pump and replace
the bearings if necessary Insufficient or excess lubrication Check the pump for appropriate
lubrication
Impeller damaged or unbalanced Dismantle the pump and replace the impeller if necessary
Excess bearing wear Pump and motor not sufficiently aligned Check the alignment of pump and
Malfunction Possible cause Remedy
Poorly installed or soiled bearings Replace the bearings if necessary and check the lubrication for con- tamination
Incorrect bearings or bearings that are not original parts installed in the pump
Install original bearings Overheating or blocking of
the pump
Pressure-side valve closed Open valve
Pump insufficiently pre-filled Repeat pre-filling of the system The output of the pump is below the
permitted minimum flow rate
The requirements of the pump system must be checked Pump and motor not flush with each
other
Check the alignment of pump and motor or realign them
Bearings worn or loose Dismantle the pump and replace the bearings if necessary Broken or eccentric pump shaft Replace pump shaft and bearing
assembly
Impeller damaged or unbalanced Dismantle the pump and replace the impeller if necessary
Rotating objects or pump components rubbing in the pump
Dismantle the pump and check the interior of the pump
Flow resistance of the pipe is greater than the delivery head of the pump
Check and minimise the pipe res- istances
Tab. 17: Malfunction table