How Should Buyers Specify a Ball Mill Trunnion Bearing?

Where Does a Trunnion Bearing Support the Mill?

The trunnion forms part of the mill end and rotates with the shell. Its journal is supported in a bearing assembly mounted to the foundation or bearing pedestal. Depending on the mill design, one end may locate the mill axially while the opposite end allows controlled movement. Buyers should therefore identify the feed or discharge end and confirm whether the support is fixed or floating before requesting a replacement.

A ball mill trunnion may be supported by a hydrostatic or hydrodynamic sleeve/pad bearing, while some mill designs use a rolling bearing arrangement. These constructions support the mill differently and have different lubrication, clearance, mounting, and inspection requirements. Metso, for example, lists hydrostatic and hydrodynamic sleeve/pad main bearings as well as roller-bearing options for some grinding mills, with fixed or floating arrangements depending on the design.

For oil-film bearings, the lubrication system is part of the bearing arrangement rather than a separate detail. Oil pressure, flow, temperature, filtration, and delivery paths should therefore be checked against the installed trunnion-bearing configuration.

The trunnion liner should not be confused with the bearing itself; it protects the internal mill flow path. Likewise, pinion bearings belong to the drive system rather than the trunnion main-bearing position. For an urgent inquiry, list the trunnion, bearing or bearing insert, housing, seals, lubrication components, and any drive-side parts separately so purchasing and the repair team can confirm the exact supply scope.

What Is Included in the Assembly and Oil Circuit?

The ball mill trunnion bearing assembly may comprise an insert or pads, a housing, seals, oil feeds and mounting components. Ask whether the quote includes an axial guide, temperature fittings, oil piping or only the bearing surface. A complete assembly needs more than an isolated bearing dimension.

The phrase ball mill trunnion bearing lubrication covers several working parts: reservoir, pump, filtration, cooling, supply lines and instruments. Depending on the mill’s existing design, its oil system may be hydrostatic or hydrodynamic. Metso trunnion lubrication retrofit systems monitor oil pressure, temperature and flow. These signals help the plant identify a supply problem before assuming the bearing alone failed.

On a hydrodynamic arrangement, oil film depends on the approved operating and start-up procedure. A hydrostatic arrangement relies on a specified pressure-fed support. Record the installed system and any lift-oil requirements rather than switching types based on a bearing quote. The mill engineer must approve changes to the oil circuit and operating sequence.

Trace a suspected oil issue from tank to bearing and back. Document dirty oil, low flow, heat exchanger performance, leaking seals and alarms. Replacing a pad while contaminated oil circulates can damage the new surface. Assign responsibility for cleaning and restarting the circuit before releasing the mill.

Which Loads and Alignment Checks Matter?

The trunnion support carries the loaded mill across start-up and steady operation. Check mill speed, operating load, journal size and any abnormal event such as an interrupted oil supply. If the mill has moved on its foundations or undergone a support repair, the bearing’s contact and load distribution may change.

Measure the journal and mating housing surfaces while the support is open. Record scoring, overheating, out-of-round wear, surface finish and any previous machining. A new bearing ordered from the worn journal diameter may not match the approved finished fit. The repair drawing should state the target geometry.

Also check axial location. A fixed and floating support do different work, even if their housings look similar. The buyer should confirm the feed or discharge position and whether a proposed replacement includes its axial restraint parts. A seal leak can expose the journal and lubricant to contaminants; therefore, inspect seals during the bearing repair window.

Oil temperature, pressure and flow trends provide context, but they cannot by themselves prove the bearing surface is reusable. Engineering should compare instrument readings with physical inspection and the approved operating limits. Avoid ordering a replacement solely because one alarm changed.

When Is Custom Supply or Assembly Repair Needed?

If the installed bearing has a complete rolling-bearing designation, the buyer can request a stock check after confirming the full suffix, mounting and housing. A sliding insert or pad is often drawing-specific; its purchase may require a measured sample, material callout and an approved journal repair plan. Neither path should be described as an automatic interchange.

For a damaged support, divide the work into bearing component, journal machining, housing repair, seals and oil-system service. Decide which contractor measures the final journal and which supplier manufactures to the approved dimensions. That boundary affects lead time and inspection responsibility more than a generic bearing name.

HSN Bearing Group can discuss stock bearings or a custom bearing component based on models, drawings, samples and working conditions. It can review agreed dimensional tolerance, hardness and clearance checks before shipment where applicable. A complete mill-end assembly, field machining or oil skid should be quoted as a separately verified scope, not presumed included with bearing supply.

For context, Metso’s trunnion bearing lubrication retrofit options differ according to the installed hydrostatic or hydrodynamic configuration. That illustrates the importance of site-specific approval. It does not mean another supplier’s loose bearing automatically fits a Metso system.

When the plant schedules a reline or shutdown, inspect bearing seals and journal surfaces during the same stop. Plan which parts can be released immediately and which await final measurements. A written hold point prevents custom production to an obsolete or worn dimension.

What Should Buyers Send for a Trunnion RFQ?

An RFQ should identify the mill end, bearing type and entire repair boundary. Photos alone can supplement, but should not replace, an approved assembly drawing for a custom support.

• Provide mill make, serial number, size and feed or discharge bearing position.
• Mark fixed or floating support, journal dimensions and full bearing designation if present.
• Send drawings and photos of insert, housing, seals and worn journal.
• State bearing material, load, oil-system type, pressure and flow history.
• List required components, quantity, agreed inspections, delivery destination and required arrival date.

Ask suppliers to return a line-by-line offer for the bearing, assembly pieces and optional repairs. If a drawing has been revised after journal machining, specify its revision in the order. Technical approval should precede any proposed material or lubrication change.

Finally, retain the old bearing identification and the as-installed measurements after the repair. These records shorten the next inquiry and help the site investigate any future oil or temperature anomaly.

FAQ

Is a mill trunnion liner the same as its bearing?

No. The liner protects the trunnion’s internal passage; the bearing supports its outer journal.

Can I quote a trunnion bearing without oil details?

A reliable quote needs the oil system, lubricant, pressure, flow, and temperature data.

Why ask HSN for a trunnion bearing quote?

HSN can review the bearing code or insert drawing, agree checks and quote the bearing separately from housing or oil-system work.

What should a U.S. buyer confirm for an assembly quote?

Send the mill ID, end position and drawings; define the bearing, housing and seal scope, quantity and deadline.

Remarks

For detailed ball mill trunnion bearing models not listed above, please contact HSN for model confirmation and supply discussion. When checking other bearing references, you can also send the complete model, photos, dimensions, quantity, application, and working conditions.

This article is based on independent analysis of publicly available technical information and industry understanding for knowledge sharing. All brand names and trademarks mentioned belong to their respective owners. HSN Bearing Group is an independent bearing supplier and technical service provider.

Tel: +86 156 6578 7336     Email: service@hsnindustrial.com    Website: www.rollingparts.com   www.hsnbearing.com