Dixon RZL-400, Operating And Maintenance Manual, Page: 58 / 78

58 Rotary Lobe Pumps - RZL-400 Series 800.789.1718
Troubleshooting
Problem Possible Cause Suggested Action
No Flow, Pump Rotors Are
Not Turning
Drive motor not running. Check resets, fuses, circuit breakers.
Key sheared or missing. Replace.
Drive belts, power transmission components
slipping or broken.
Replace or adjust.
Pump shaft, keys or gears sheared. Inspect and replace parts as necessary.
No Flow, Pump Rotors Are
Turning
Rotors turning in the wrong direction. Check motor hookup to reverse motor rotation.
Relief valve not properly adjusted or held open
by foreign material.
Adjust or clear valve.
Suction port is blocked, not allowing flow to the
pump.
Check all inlet valves, strainers and tank outlet
ports.
No Flow, Pump Not Priming Valve closed in inlet line. Open valve.
Inlet line clogged or restricted. Clear line, clean filters, etc.
Air leaks due to bad gaskets or pipe
connections.
Replace gaskets, check lines for leakage (can
be done by air pressure or by filing with liquid
and pressurizing with air.
Pump speed too slow. Increase pump speed.
Pump speed to fast for high viscosity liquid. Decrease pump speed.
Liquid drains or siphons from system during off
periods.
Use foot valve or check valves. Filling inlet
lines with material before startup may solve
startup priming problems due to no material in
system.
"Air" lock caused by fluids which "gas off" or
vaporize or allow gas to come out of material
during off periods.
Install and use a manual or automatic air bleed
from pump or lines near pump.
Extra clearance rotors, worn pump. Increase pump speed within limits, use foot
valve to improve priming.
Replace worn rotors.
NPSHA too low. Check net inlet pressure available against net
inlet pressure required. Change inlet system
as needed.
On "Vacuum" inlet system: On initial start-up,
atmospheric "blow back" prevents pump from
developing enough differential pressure to
start flow.
Install check valve in discharge line.
Insufficient Flow Speed too low or too high to obtain desired
flow.
Check curve and adjust as necessary.
Air leak due to bad seals, pipe connections or
other equipment.
Replace seals, check inlet fittings.
Insufficient Flow – Flow Being
Bypassed Somewhere
Flow diverted in branch line, open valve, etc. Check system and controls.
Relief valve not adjusted or jammed. Clear or adjust valve.
Insufficient Flow – High Slip Hot (HC) or extra clearance rotors being used
on "cold" fluid and/or low viscosity fluid.
Replace with standard clearance rotors.
Worn pump. Increase pump speed (within limits).
Replace rotors
High pressure. Reduce pressure by adjusting system settings
or hardware.