Q-Pumps QTS 203, Operation And Maintenance Manual, Page: 38 / 44

38
Operation and Maintenance Manual
QTS Series Twin Screw Positive Displacement Pump
QTS-M04
TR
O
U
B
L
E
SHO
O
TI
NG
Symptom Cause Solution
Drive motor is not running Check connection or VFD configuration.
Rotors are in contact
Check synchronization. Resynchronize if
necessary.
Inspect and replace if necessary.
If keys are sheared, inspect the entire pump for
rotor/rotor contact or rotorbody contact.
Rotors are turning in wrong direction Check connection or VFD configuration.
Discharge port is closed or blocked Open dicharge valves
Inlet port is closed or blocked Open inlet valves
Pump speed is to low Increase pump speed
Speed is to low or too high Check pump curve and adjust speed
Air leaks in inlet line
Check for bad seals, bad gaskets and piping
connections.
Net inlet pressure is too low
Check pump requirments and change system or
pump if necessary.
Product viscosity is greater than expected
Change system parameters, reduce inlet length
and/or increase inlet piping diameter.
Product viscosity is lower than expected Increase pump speed
Increase pump speed
Change rotors
Mechanical seals broken Inspect seal faces and replace if necessary.
Mechanical seals not installed properly Check mechanical seal assembly.
Missing o-rings or gaskets
Check mechanical seal and pump body
assembly.
Decrease pump speed
Change system parameters, reduce inlet length
and/or increase inlet piping diameter.
Reduce pump speed
Modify outlet line size
Viscosity is higher than expected Heat product or change system parameters
Mechanical componets in contact
Check pump assembly. Verify that all dowell pins
are in place.
Noise due to cavitation
Net inlet pressure is lower than required
Check system setup and change speeds and
temperature accordingly.
Rotors not synchronized properly
Check synchronization. Resynchronize if
necessary.
Rotors are in contact with body
Check pump assembly. Verify that all dowell pins
are in place.
Check system and change.
Reduce pump speed
Gears are worn Inspect and replace if necessary.
Bearings are worn Inspect and replace if necessary.
Coupling misalignment Check coupling alignment
Improper piping support
Support inlet and oulet piping correctly. Don’t let
the pump carry the load.
If rotors are standard, change to hardened rotors.
Change to a larger pump with lower speeds
Pump speed is higher than application rated Check system and modify to reduce pump speed.
System pressure is higher than application
rated
Check system and modify to reduce pump speed.
Improper bearing and gear lubrication
Inspect and replace if necessary. Keep correct oil
change intervals.
Water build up in bearing and gear case Check that all plugs are in place
Coupling misalignment Check coupling alignment
Pump is not running
Keys are sheared or missing
Rotors worn out due to pumping of abrasive
fluids
Viscosity losses higher than expected
Pressures higher than expected
Pressure is higher than pump rating
Product is abrasive
No flow delivered
Inadequate flow
Leaks
Excessice power is
required
Noise due to mechanical
contact
Short pump life
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