A ball mill can stop when its main bearing surface is damaged. Yet “ball mill bearing” can mean a trunnion bearing, pinion bearing, or drive component. Before requesting a replacement, identify the part and condition of its mating journal. This matters in mining and cement mills alike.
Which Parts Make Up a Ball Mill Trunnion Bearing?
The mill trunnion is the hollow end of a trunnion-supported mill. Its outside journal turns in a stationary main bearing, which may include a housing, replaceable insert, oil passages, and seals. The internal trunnion liner protects the material passage and is a different part. Some mills carry the shell on slide shoes instead.
Designs differ. A sleeve or segmented insert may have a bronze surface, a Babbitt (white-metal) lining on a backing, or another specified material. Other mills use roller bearings. “Hydrostatic” and “hydrodynamic” describe oil-film support, not insert material. Check the OEM drawing before proposing a substitute.
For replacement, identify which individual part needs making. JED lists custom Babbitt bearing shells and inserts and bronze components for mining machinery. A bronze bushing is relevant only when the original design or an approved change calls for one. Neither insert is the cast trunnion itself.
How Is a Trunnion Bearing Lubricated?
Oil must reach the loaded interface and stay clean. A circulation system may supply and return oil, with filtration, cooling, and seals to exclude dust, water, and slurry. Some arrangements use high-pressure lift at start-up, then operate on a hydrodynamic film. Follow the mill’s lubrication drawings and procedure.
Compare oil pressure, flow, temperature, and cleanliness with normal trends and OEM limits. Pump pressure alone does not prove oil reaches every bearing zone. Blocked passages, leaks, contamination, or cooling faults may change conditions before damage is visible.
If the replacement includes oil holes or grooves, verify their locations against the feed arrangement. Groove shape affects oil distribution and load area. See JED’s bronze bushing oil groove types for general geometry, but use the mill drawing for the actual pattern. Never copy oil grades, flow rates, or alarm settings from a generic article.
What Failure Signs Call for Inspection?
An unusual rise in bearing temperature, a change in oil pressure or flow, new vibration, persistent leakage, or visible debris in the oil should trigger inspection. During a planned shutdown, look for scoring, wiping or displacement of a soft lining, uneven contact, cracks, and damage to the journal or seal area. Record which bearing position changed and when; one reading without its operating context can mislead. Low oil supply can damage a sound bearing, while misalignment or contamination can ruin a new insert quickly.
These signs identify an investigation, not an automatic purchase order. Compare operating records with the OEM limits, examine the lubrication circuit, and have the journal and housing checked by the responsible maintenance or engineering team. If the trunnion journal is worn or scored, replacing only the bearing surface may leave the cause and the mating damage in place. Record photographs, measurement locations, and the observed wear pattern before dismantling or reworking the part.
What Data Is Needed for a Replacement Bearing Insert?
To quote a custom main-bearing insert or split shell, send a drawing or verified replacement specification that identifies:
- The mill make and model, component name and number, and feed or discharge end; note the locating or floating position if applicable.
- The original bearing material, lining and backing arrangement, split joint, and any specified bond or inspection requirements.
- The finished bore, outside fit, width, flange details, oil grooves and holes, and the tolerances that control installation.
- Measured journal and housing dimensions, with their measurement locations and condition; state whether the journal will be restored before final machining.
- The lubrication arrangement, mating parts, quantity, and required delivery date.
A worn sample can help identify geometry, but its bore may no longer represent the original running clearance. Specify which dimensions come from the OEM drawing and which were measured in service. The fit and final bore should be reviewed with the journal’s actual or planned restored size. JED’s cement-industry bearing page describes drawing-based Babbitt shells for ball mills and review of split joints, oil grooves, and mating dimensions.
If the drawing is incomplete, label unknown dimensions rather than guessing. Photos of the removed part, bearing location, split faces, and oil connections can help identify what still needs measurement before a quote is finalized.
Send Your Bearing Drawing for Review
If you need a replacement Babbitt-lined bearing shell or specified bronze insert, contact JED with your drawing and application details. We can review the manufacturable component, material callout, critical interfaces, and information still needed for a custom quote. Include the planned shutdown window so the discussion starts with your real delivery constraint.
Frequently Asked Questions
Can I replace a Babbitt-lined insert with bronze at the same dimensions?
Do not treat it as a dimension-only substitution. The bearing geometry, load, journal surface, clearance, and lubrication must be reviewed against the mill design before a different material is approved.
Are feed-end and discharge-end bearing inserts interchangeable?
Do not assume so. The ends may have different dimensions, oil features, or locating duties. Compare the OEM part numbers and drawings for the exact mill before ordering.
Can I order only one half of a split trunnion bearing?
Possibly, but the new half must match the retained half at the joint and form the specified bore when assembled. Send drawings and measurements of both halves for review before ordering one side alone.
