Conveyor Clutches

A fluid coupling fills with oil and transmits torque with slip during start, cushioning shock and allowing the motor to approach running speed before the belt sees full pull. Scoop or drain-type couplings let operators or controls vary oil fill for longer start ramps or to disconnect. Mechanical disconnect clutches are used where a drive must be taken off without unbolting the whole train — less common on simple plant belts, more often on specialised machines.

Load sharing on dual drives is a reason some South African overland and decline systems still use fluid couplings even when VSDs exist elsewhere on the mine. The coupling does not replace gearbox ratio or motor kW; it changes how torque is applied in time. Overheating, wrong fill, and delayed start on a steep incline are practical risks when the coupling is mistimed or underspecified.

If you only need a spacer coupling after a bearing change, use Couplings. If you only need to ramp the motor electrically, use Belt Starters. Tick Clutches when the oil-filled or disconnect device is the item on the RFQ.

Common applications

Clutch and fluid-coupling work is usually a like-for-like replacement, a heat problem, or a start-up improvement. Typical scopes:

• Fluid coupling replacement — Like-for-like after seal leaks, fusible-plug events or bearing wear in the coupling. Provide size, oil fill practice and motor kW.
• Scoop or variable-fill couplings — When start time must be stretched or a drive disconnected under control. Describe the control interface — manual scoop, actuator, or none.
• Dual-drive load sharing — Two couplings that must behave together. State both drives and whether electrical load sharing already exists.
• Disconnect clutches — Mechanical separation of a drive. Rare on standard troughed belts; name the machine so suppliers do not quote a fluid coupling by habit.

Industries that use this equipment

Mining conveyors with high inertia or dual drives are the classic fluid-coupling users in South Africa.

Quarries and cement plants still run fluid couplings on feeders and plant belts that start loaded against crushers or bins.

Older plants may keep fluid couplings when electrical upgrades are staged; say if a VSD is planned so quotes are not fighting a future starter project.

Winches and tripper drives sometimes use different clutch types — name the application.

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.

• Device type: fluid coupling, scoop coupling, disconnect clutch — not “coupling” alone.
• Motor kW, speed, gearbox input shaft, existing coupling size and make if known.
• Oil type currently used, fusible plug practice, cooling (plain, delay chamber, external).
• Start duty: loaded, incline, dual drive.
• Whether an electrical soft starter or VSD is already fitted.
• Shaft sizes both sides, spacer needs, guards.
• Supply only versus align-and-commission.

Factors that affect selection

• Electrical soft start and fluid coupling can overlap; describe both so you do not buy two solutions to one shock problem without intending to.
• A shaft coupling (elastomer, grid, gear) does not provide start slip — wrong category.
• Heat dissipation and restart frequency matter more than copying a neighbour’s size code.
• Delay-fill chambers change start behaviour; they are not a generic spare for a standard fluid coupling without checking.
• Guarding and alignment are part of a safe change-out.

Common problems and failure considerations

• Overheating and plug melting because fill, delay chamber or start frequency is wrong.
• Belt slip at the pulley while the coupling still looks healthy — lagging or take-up, not always the clutch.
• Leaks that empty the coupling until there is no start.
• Quotes for elastomer shaft couplings because the RFQ said “coupling” not “fluid coupling”.
• A disconnect clutch quoted where a fluid coupling was meant, or the reverse.

Maintenance considerations

• Check oil level, leaks and plug condition on a defined interval; a dry fluid coupling will not start the belt.
• Listen for noise that suggests internal bearing wear.
• Keep alignment within the coupling maker’s practice; fluid couplings still need shaft alignment.
• After motor or gearbox change, confirm rotation and fill before loaded starts.
• Record start time and heat on steep belts after any fill change.

Questions buyers should ask suppliers

• Fluid, scoop or disconnect — which device are you quoting?
• What fill, delay and cooling do you assume for our start duty?
• Are shafts, tyres/elements, oil and fusible plugs included?
• Will this drop in on our existing distance between shaft ends?
• How does your proposal sit with our existing VSD or soft starter?
• Is alignment and guarding in scope?

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.

• Say “fluid coupling / scoop / disconnect clutch” in the notes.
• Motor and gearbox nameplates, photos both sides of the device.
• DBSE (distance between shaft ends) if known.
• Loaded start and incline notes.
• Existing electrical starting method.
• Oil and spare plug expectations.
• Site and outage for change-out.

Related conveyor information

Related components: couplings, drives, gearboxes, motors.

Guides: Types of Conveyor Systems, Industrial Conveyor Maintenance Guide.

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

Frequently asked questions