Mixer Drive Troubleshooting

Trouble What To InspectAction
Overheating1. Motor Overloada) Determine if the density and viscosity of the process liquid is the
same as originally specified

b) Is liquid level in tank above minimum operating levels, i.e. 2.5 times
the propeller diameter above the axis of the mixer shafts? If not,
cavitation may be taking place.

c) Are there any objects inside the tank impeding the propeller flow?

d) Check that shaft rotates freely by hand.

e) Check for mechanical or electrical problem. Correct supply/wiring.
Check motor nameplate details are correct.

f) Ensure no jet mixers or pump inlets are creating flow over the mixer
propeller. Ensure no large items impede the flow path of the propeller.
2. Belt slip/tensiona) Inspect belt for damage and replace if needed. Reinstall and tension
belt per Outline Installation Drawing (OID) in Section 14.
Noise1. Excess Turbulencea) See Overheating Reference 1b, 1c, 1f
2. Worn Bearingsa) On old units that have operated for long periods; check condition of

b) Check bearings for excessive grease loss; replace if required.
Unit not rotating1. Unit Jammeda) Lock out, tag out, and disconnect power and stop internal tank flow if
present. Inspect for damaged seal, worn/damaged bearings, belt
slip/tension. Verify free rotation by hand prior to reconnecting power.
2. Belt slip / tensiona) See Overheating Reference 2a
Vibration1. Check set screwsa) Check tightness of set screws on Bearing Sleeve. All set screws
should be held with Loc-tite #246 and a jam nut.
2. Excess Turbulencea) See Overheating Reference 1b, 1c, and 1f.
3. Belt slip/tensiona) Check belt tension chart on the Outline Installation Drawing (OID) in
Section 14.
4. Worn Bearingsa) See Noise reference 2.
5. Bolt Tightness a) Check the tightness of all fasteners (see torque value chart in the
Recommended Torque Values in Table 1).
6. Mixer Support
a) Is the tank nozzle/manhole and tank shell rigid enough to support

b) There could be a harmonic from the tank mounting exciting the Tank
7. Mixer Support Slinga) Is the mixer support sling correctly tensioned? (Reference
Common Parts drawing)
8. Damaged Shaft or
a) Has the shaft or propeller been damaged in transit, storage or
installation? Is it possible for the propeller to have been damaged on
any in-tank projectile? If propeller is site fitted, is it correctly fitted?
9. Swivel Locking
a) Swivel-Angle Units Only – Is the swivel locking mechanism locked
tight? Also check for wear on locking mechanism pins.
10. Autoswivel Brakea) Ensure brake is set snugly enough to prevent excess vibration but
does not strain the actuator system.
11. General
a) If vibration problem cannot be corrected take frequency readings on
displacement (in pk-pk) and velocity scale (in/sec peak) and report them
to Philadelphia Mixing Solutions.


TroubleWhat To InspectAction
Noise1. Coupling Weara) Check input coupling for wear. Replace if worn
2. Bearings and gears
properly lubricated
a) Shut off mixer and check the oil level.

b) Oil must be the grade specified in the lubrication
instructions. If it is not, flush mixer drive and refill with
the correct grade of oil
3. Mounting & coupling
a) Be certain that all mounting and coupling hardware is
tightened to the correct wrench torque.
4. Mixer support structurea) Does the mounting arrangement for the mixer provide
sufficient support to prevent wobbling or vibration of the
assembly? See Outline Installation Drawing for criteria.
Vibration1. Agitator shafta) Agitator shaft should not be bent.
2. Critical speeda) If the shaft and/or impellers are supplied by others,
check for a critical speed condition. Vibrations can
occur through a particular speed range.
3. Steady bearing (if
a) Has excessive wear occurred to the steady bearing?

b) Is the bearing securely bolted to the vessel and is it
properly aligned?
4. Inspect hardwarea) Is all blade hardware (and extension arm hardware, if
applicable) properly torqued? Including agitator shaft
couplings and mounting hardware?
Oil Leakage1. Plug at drain and
standard pipe fittings
a) Apply pipe joint sealant, or equal, and tighten fittings.
2. Housing and caps a) Tighten cap screws or bolts to proper torque. If not
entirely effective, remove housing cover and caps.

b) Clean mating surfaces and apply new sealing

c) Ensure mounting surface is level and is not distorting
mixer housing.
3. Mixer output shafta) Has the recommended oil level been exceeded?

b) Check oil level. Drain oil to the correct level.
4. Breathera) Breather must be open and clean
Cannot read oil level1. Oil Level Window Glassa) Drain gear oil, remove sight glass, clean glass surfaces
using solvent. Replace sight glass and refill mixer oil to
correct level.