Carryback Conveyor Mining: Costs You Can Defend in a Budget

Carryback Control · Lifecycle Cost

Carryback conveyor mining costs get quoted at you constantly, and almost none of the figures survive contact with a finance team. The numbers in circulation are vendor estimates built on assumed tonnages, assumed product values and assumed labour rates, which is why they collapse the moment someone asks where the inputs came from. Your own maintenance system already holds most of what you need. This sets out which parts you can source, which part you cannot, and how to put a figure in front of a budget holder without borrowing anyone else's arithmetic.

01Why the published figures cannot be used

Search for what carryback costs and you will find per tonne figures, annual loss figures and payback periods. Read the method behind them and the pattern is consistent: a tonnage captured on one belt at one site, multiplied by a product value the author chose, against a cleaner price the author also chose.

Those studies are not dishonest. They are written to show a product in a setting the author controlled, and most of them say so. The problem is structural. A carryback figure is the product of your tonnage, your product value, your labour rate and your belt replacement cost, and none of those four travel between sites. A figure derived at a sand plant in Texas tells you nothing usable about a coal overland in the Bowen Basin.

FM8 will not publish a number for your site either, and that is deliberate. What follows is the method, which does travel.

Answer Published carryback costs are site-specific arithmetic presented as industry figures. The method transfers between sites. The number does not.

02The four places carryback shows up in your cost base

Carryback is usually argued as a cleaning problem, which is why it gets funded out of a cleaning budget and loses. It appears in four separate cost lines, and only the first is normally attributed to it.

• Spillage clean up labour. Crew hours, vac truck hire, and the access and isolation each clean up needs. This is the line everyone already counts.
• Idler and pulley replacement. Material packing on return idlers makes them seize, and a seized idler abrades the belt cover until someone catches it. Your replacement rate on the return run is a carryback signal.
• Belt cover life. The largest of the four by a wide margin, and the one carried in a capital line rather than a maintenance line, which is how it escapes attribution.
• Conveyor downtime cost mining operations carry on the production side. Unplanned stops to clear a build up, plus the planned stops to clean what should not be there. Your production system records these, usually under a reason code that says nothing about carryback.

Splitting them matters because three of the four sit outside the budget that buys blades. A cleaner that pays for itself twice over in belt cover life will still be refused by a maintenance budget that only sees line one.

Answer Carryback costs land in four budgets and is normally charged to one. The case fails on attribution before it fails on arithmetic.

03What your own records already hold

Three of the four lines are already in systems your site runs. None of this needs new instrumentation.

• Clean up labour comes from work orders. Count the carryback related clean ups over a full year, not a quarter, because wet season and dry season behave differently.
• Idler and pulley replacement comes from your consumption records. Compare the replacement rate on the return run against the carry run on the same conveyor. The gap is the part of your idler spend that carryback is driving.
• Downtime comes from the production system. Pull the stops on the conveyors you suspect and read the comment field rather than the reason code, because the reason code will say blocked chute or housekeeping.

The fourth line, belt cover life, is the one your records will not give you, and it is dealt with in section 04.

Two cautions on the labour number, both of which have sunk otherwise sound cases. Count the isolation and the access time, not only the time spent with a shovel, because on most sites those exceed the cleaning itself. And resist annualising a bad month. A single wet fortnight will carry the whole year if you let it.

Tying blade condition to those records is what turns the figures into a trend rather than a tally. A service tech photographs the blade in place on their phone and the FM8 Conveyor Cleaner Health app estimates percent wear from the image for the tech to confirm, with the date, the work order reference and the blade position recorded against it. That removes the variation an eyeball call produces, which matters here: two techs, same blade, same shift, two different numbers is not a basis for a cost case.

Answer Work orders give you clean up labour, consumption records give you idler spend, and the production system gives you downtime. Pull a full year of each, and count isolation and access time in the labour line.

04The number you cannot source, and what to do about it

Belt cover life is the largest cost carryback drives and the one you cannot pull from a report. A belt that should have run twelve years and goes at nine has lost three years of asset life, and nothing in your maintenance system attributes those three years to anything.

There is no honest way to calculate it after the fact. What you can do is bound it. Take the belt's installed cost, divide by its design life to get an annual cost of ownership, and then put the question to your reliability group as a range rather than a figure: how many years of this belt's life do we believe the cleaning line is taking? Two engineers who know the conveyor will give you a range within a year or so of each other, and a bounded range sourced from your own people beats a precise number sourced from a brochure.

Carry it into the business case as a range, label it as an estimate, and state who gave it. A finance team will accept a labelled estimate alongside three sourced figures. What it will not accept is four figures of unexplained provenance, which is what a vendor calculator produces.

Answer Belt cover life cannot be sourced from records. Bound it from installed cost over design life, get the years lost as a range from your own reliability group, and label it as an estimate in the case.

Carryback conveyor mining and the evidence a supplier claim needs

Once the four lines are built, a supplier's claim becomes testable. Before you buy, you have a baseline. After you fit, you have the same four lines over the same period, which is the only comparison that settles whether anything changed.

It also changes which claims you are willing to listen to. A blade life figure quoted without your belt speed, your product, your splice type and your tensioner is a figure from someone else's conveyor, and the same is true of a carryback reduction percentage. Ask for the method rather than the result, and ask what the baseline was measured against.

Where the cleaner itself is concerned, FM8's engineering stance is that the useful question is what happens to blade-to-belt pressure as the blade wears. A tensioner that advances continuously holds the force it was set to; holding the pressure takes that tensioner together with a blade profiled so its contact area grows as the tip force rises, which is what the FM8 Constant Pressure Tensioning System is built around. The reason that matters to a cost case is that a pressure which climbs across blade life drives three of the four lines above at once, and it does so without appearing on any gauge. We see this weekly in the field: sites with a rising idler replacement rate on the return run, a belt cover going early, and a cleaning budget that looks under control.

If you want the root cause work that sits upstream of the costing, the conveyor carryback diagnostic covers finding it before another blade goes on.

Build the case with FM8

Send the four lines once you have them, with your belt speed, product, splice type and the tensioner fitted. FM8 will tell you which part of the cost base a cleaner change would move, and say so plainly where the constraint sits somewhere other than the blade.

Australian operations are supported through your FM8 Distributor. International enquiries are handled by FM8 Engineering directly.

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FM8 · Engineered to Exceed · Proprietary Engineering Content

This article is published by FM8 for the technical information of maintenance, reliability, engineering and procurement personnel. It describes a costing method and FM8 design intent, and does not constitute a design specification, a financial model or advice on any particular conveyor installation. No cost, saving or payback figure is stated or implied for any site; the ranges a reader derives are their own and depend on inputs FM8 has not seen. The blade condition workflow described uses photographic assessment with app assisted wear estimation and is not a measurement to an instrument standard. Blade selection, tensioner settings and mounting positions should be confirmed against your own site conditions, risk assessment and applicable standards. The FM8 Constant Pressure Tensioning System described is specified for surface conveyor installations; hazardous area requirements are assessed per site. The FM8 constant pressure tensioner and constant pressure blade profile are the subject of international patent applications. All FM8 product designs, blade geometries, material formulations and the FM8 Conveyor Cleaner Health application remain the intellectual property of FM8. Reproduction, adaptation or reverse engineering of FM8 designs or content is not permitted without written consent.