IMPORTANT information for owners of industrial gearboxes
PLANNED gearbox maintenance can help prevent costly breakdowns If you operate a system with a gearbox at its heart, you could be risking a costly breakdown if it has not been regularly inspected and maintained.
Listed below are some of the resulting causes of failure that can affect your older gear units that may not become apparent until the day the unit fails - usually with costly consequences.
Operating lives of rolling element bearings in auxiliary drives reduced due to oil contamination
Loss of auxiliary drive, damage to auxiliary components and possible secondary damage to main transmission gearing
High speed couplings become blocked
Accelerated wear due to lack of lubrication
Outer coupling system collects contaminant between the coupling teeth
Wear steps on gear teeth occur. If wear becomes greater than 0.020” or tooth surface deterioration results in loss of more than 50%, replacement components will be required.
Impurities gather inside planet spindles due to centrifugal forces
Sludge forms and prevents oil from reaching white metal bearing surfaces
Impurities which pass into the planet wheel
Surface scoring of planet wheel occurs and can cause breakdown of the white metal resulting in unit failure
Oil film breakdown due to water contamination
Breakdown of oil film between teeth of the running gear train giving rise to overstressing
Corrosion fatigue due to pitting condition
Possible corrosion attack and a reduction in endurance limit
Allen Gears’ experience has shown that failures due to solids in suspension and sludge formation inside the unit exceeded by far the failures due to corrosion-induced fatigue failure. Gear problems of the types outlined above can be minimised by regular planned maintenance where principally the objective is to clean the unit and NDT the component parts.
Recommended maintenance procedures Allen epicyclic gears - planned levels of maintenance
Noise & Vibration Survey
Survey taken with gearbox running under
normal operating conditions.
Inspect general appearance of components and any signs of rust
Inspect gear teeth using Borescope/ Videoscope
Check auxiliary drives
Remove gear internals from gearcase
Remove spindle end covers, inspect spindle bores,
remove sludge deposits and clean thoroughly
Dismantle gear completely, clean and inspect
Check all oilways are clear
Remove centrifuged sludge from high speed coupling sleeve, sunwheel and sunwheel coupling flange
Dismantle trunnion mounts, check, clean and lubricate
Check auxiliary drives
Check Helicoil inserts and renew all locking plates and
Check high and low speed alignments
These recommendations are based on continuous running for units with auxiliary drives.
For low-use plant the time period between examinations may be increased, but not more than 50%, even though nominated running hours may not have been completed