Wear Part Life Tracking Method

Why tonnes rather than the calendar

The first decision in any wear part life tracking method is the unit you count life in. Records kept in days or running hours mislead, because a plant that crushes limestone on Monday and basalt on Thursday performs very different amounts of work per hour. The meaningful unit is tonnes passed. Once life is stated in tonnes it can be compared across two quarries, across two shift patterns and across two feed sizes.

Tonnage comes from a belt scale or from truck counts. Where no scale exists, trucks per shift multiplied by average payload produces a workable figure; approximate as it is, it beats the calendar decisively. What matters is applying one method unchanged for the whole life of the part, because comparisons are ruined by a change of method far more often than by measurement error.

Fixing the measuring points

A thickness reading only means something if it is taken at the same place every time. When a new part is fitted, three to five marked points are chosen: the heaviest wearing central zone, the inlet edge and the discharge edge. Their positions are sketched, and a copy of the sketch lives in the crusher cabin. A different technician on a different shift then reads the same points.

The instrument depends on geometry. A depth gauge or vernier caliper is enough on flat plates. On curved profiles a template is cut from the profile of a new part, and the gap between template and worn surface is measured. On complex chamber surfaces a laser profile scan gives a faster and more repeatable result.

Wear part life tracking method: the limit of ultrasonic gauging on manganese steel

On cast manganese steel parts, readings from ultrasonic thickness gauges are often unreliable. The coarse grained austenitic structure of these alloys scatters the sound wave, the back wall echo weakens and readings become noisy. The work hardened surface layer changes sound velocity locally and widens the scatter further. The effective depth of that hardening is known to be limited to a thin surface layer, yet its effect on the signal cannot be ignored.

The practical consequence is direct. On manganese parts the primary data is mechanical measurement and ultrasonic readings serve only as support. Hard numbers come from the scale: weigh the part before fitting and again at removal, and mass loss is known exactly. Divided by tonnes passed, that loss gives wear per tonne.

Wear rate and remaining allowance

The arithmetic has two steps. Rate first: loss between two readings divided by tonnes passed in the same interval, expressed in millimetres per thousand tonnes for thickness data or grams per tonne for mass data. Remaining life second: the allowance left down to the minimum permitted thickness divided by that rate, which yields remaining tonnes. Dividing remaining tonnes by average daily output converts the answer into a dated change window.

The intervals above are a starting discipline. If the rate comes out similar over two consecutive intervals, the interval can be stretched. If it jumps, then feed size, setting or rock type has changed, and the interval tightens instead.

Site conditions that corrupt the reading

The commonest obstacle to a thickness reading is packed material on the surface. Damp fines plaster themselves onto chamber faces and the gauge rests on that crust, making the part look thicker than it is. Scraping the face with a spatula or wire brush before measuring removes the error. Temperature is the second obstacle: on a crusher just stopped the part is still hot, and cooling has to be waited out for the sake of both instrument and personnel.

Lighting is the third. A reading taken inside a chamber by torchlight does not reveal whether the gauge is seated flat. Stopping the machine, applying isolation and lockout and then rigging fixed lighting improves repeatability visibly.

What the log sheet contains

One page is enough: date, cumulative tonnage, point number, reading, and who took it. Underneath, the rock type crushed in that interval and the discharge setting are noted. Without those two entries rate figures cannot be compared, because the same part erodes markedly faster in hard abrasive rock. As records accumulate per part, real life figures for your own quarry emerge and purchasing plans against them.

Life data also feeds the cost side. Part cost per tonne is the price divided by life tonnage, which puts it on the same footing as the line items in the operating cost TCO calculator. Whether an expensive long lasting alloy is genuinely cheaper then stops being an argument and becomes a calculation.

Three recurring mistakes

The first is changing parts purely by eye, which produces both premature changes and unplanned stoppages. The second is measuring only just before removal: a single point yields no rate, and at least two readings are required. The third is failing to track parts fitted as a set individually, since asymmetric wear signals a feed distribution problem and that signal is otherwise lost.

Once the measuring routine stands, revisiting part selection is the logical next move, and the articles under maintenance and wear deal with alloy and profile decisions. Share the life records you already hold and the part and setting recommendation can be worked out from your measured rates.