Conveyor Bearings

Drive, tail, bend and take-up pulleys typically run in plummer-block housings (SN / SNH style and equivalents) with spherical roller bearings or similar, adapter sleeves, and labyrinth or taconite-type seals where dust and slurry are severe. Split housings matter on site because they allow bearing changes without a full shaft strip in some arrangements. Fits, clearance and whether the housing is located or floating are part of a correct replacement, not optional extras.

Idler bearings are usually smaller, built into the roller, and bought as rolls rather than loose bearings — unless you are a roller manufacturer or a workshop rebuilding shells. If your stores list says “idler bearings”, say whether you mean loose bearings for a rebuild line or replacement rollers. Mixing those two in one line item produces unusable quotes.

Lubrication, sealing and contamination dominate life on South African bulk plants. Transfer-house dust, wash-plant slurry and coastal moisture kill bearings that would last in a clean mill. Grease type, relubrication access and whether the housing is purged or sealed-for-life should be in the brief. Highveld temperature swing affects grease choice; it is a qualitative environment note, not a catalogue rating to invent.

Common applications

Bearing purchases are often emergency replacements after a hot pulley, or planned stores replenishment. Typical scopes:

• Pulley plummer blocks — Housed units at drive, tail, bend and take-up. Include housing size, shaft diameter, located versus floating side, and seal arrangement.
• Loose pulley bearings and sleeves — For workshops that keep housings and change internals. Adapter sleeves, locking elements and clearance class should match the existing build if it has been reliable.
• Idler bearing internals — Only when you rebuild rollers. Most plants should order complete idlers instead — say which you mean.
• Seal and grease upgrades — Labyrinths, end covers and grease systems on chronically contaminated pulley bearings. This is still a bearing-housing job, not a new drum.

Industries that use this equipment

Mines, coal plants and cement works run the largest pulley bearings in the harshest dust; contamination and sealing are the usual conversation.

Quarries and aggregate plants see shock and abrasive fines at short conveyors; repeated hot bearings often point to misalignment or failed seals rather than “weak” bearings.

Ports and coastal plants add corrosion in housings and fasteners; coating and stainless fasteners may belong in the same request.

Manufacturing and warehousing use lighter housed units on package conveyors — still bearings, but a different size class than a mine drive pulley.

Specifications buyers should consider

The list below is a briefing checklist, not a datasheet. Exact ratings, dimensions and standards must come from the duty, existing plant records and the supplier quotation — do not treat generic web copy as a specification.

• Application: pulley plummer block, loose bearing for a named pulley, or idler rebuild internals.
• Shaft diameter, housing designation if known, bearing reference from the existing unit.
• Located or floating housing, and bearing centres if replacing a pair.
• Seal type in service and whether slurry or dry dust is the contaminant.
• Grease type currently used, relubrication method, and any VSD or high-speed unusual duty.
• Whether housings, bolts and base alignment are included or bearing only.
• Photos of the plummer block, locking arrangement and any tagging.

Factors that affect selection

• Complete pulley versus bearing-only: if the shell is cracked or the shaft is fretted, you need Pulleys.
• Complete idler versus bearing-only: almost always order rollers unless you operate a rebuild shop.
• Seal design in wet slurry is not the same as a general-purpose cover.
• Drop-in interchange with the existing housing saves shutdown time; a “better” bearing that needs a different housing is a different project.
• Gearbox and motor bearings are not this category unless you clearly say so — those often sit with Gearboxes or Couplings alignment work.
• Do not invent a load rating. Give shaft size, duty (drive/tail/bend) and symptoms.

Common problems and failure considerations

• Repeat bearing failures from water ingress, over-greasing that blows seals, or under-greasing.
• Fretted adapter sleeves and spun inner rings after a seized bearing was left in service.
• Ordering idler bearings when the plant needed complete rollers — wrong lead time and wrong stores item.
• Misalignment from a soft or corroded plummer base blamed on the bearing brand.
• Hot drive bearings caused by belt mistracking or seized idlers, not by the bearing specification.

Maintenance considerations

• Listen and feel for noise and heat on pulley bearings during walkdowns; a hot plummer is an outage waiting to groove the belt.
• Grease to the housing design — more is not always better with labyrinths full of slurry.
• Keep housing bases tight and grout or packing sound so alignment is not lost.
• After a failure, inspect shaft seats and sleeves before fitting a new bearing on a damaged journal.
• Coordinate with pulley lagging and cleaner work; carryback packed into housings is a sealing problem.

Questions buyers should ask suppliers

• Are you quoting the bearing only, the complete plummer block, or a pulley workshop strip-and-rebuild?
• What seal arrangement do you recommend for our dust or slurry?
• Will this drop into our existing housing and shaft?
• What clearance and fit do you assume if we cannot provide the old reference?
• Is grease included, and which specification do you assume?
• If we actually need complete idlers or a new pulley, will you say so rather than forcing a bearing sale?

What to include when requesting a quote

Clear briefs produce comparable quotations. Include what you know, and mark estimates separately from measured values. Photos and drawings help more than extra adjectives.

• Photos of housing, shaft, nameplate or stamped bearing numbers.
• Pulley duty: drive, tail, bend, take-up.
• Shaft diameter and housing size if known.
• Located vs floating, quantity of units.
• Contamination: dry dust, wet slurry, wash-down.
• Supply only vs site change-out.
• Clear statement that this is not a complete idler or complete pulley unless you also tick those categories.

Related conveyor information

Related components: pulleys, idlers, gearboxes, couplings.

Guides: Conveyor Pulleys and Lagging, Conveyor Idlers and Rollers: Selection and Failures, Industrial Conveyor Maintenance Guide.

Resources: Conveyor maintenance guide, How to request a conveyor quote.

Frequently asked questions