Quarry Capacity Planning Annual Production Target

Why the annual target is not divided directly

Quarry capacity planning annual production target is the usual starting point, but reaching a machine size from it requires the right sequence. Dividing annual tonnes by calendar hours is the commonest error; it produces an hourly figure that is never achieved in practice and leads to an undersized plant. The correct route starts at the calendar and subtracts a loss at each step until effective operating hours remain.

The chain has four links. Calendar days reduce to days the quarry actually works, once public holidays, holiday shutdowns, blasting days and seasonal closures come out. Working days multiplied by shift hours give scheduled hours. Scheduled hours less breakdown and maintenance stoppages give available hours. Available hours less feed gaps, product changes, cleaning and waiting give effective hours. The nominal capacity requirement is the annual target divided by that last number.

Quarry capacity planning annual production target in numbers

Take a quarry targeting 300 thousand tonnes of saleable product a year. If it works 250 days and runs a single ten hour production shift, scheduled hours come to 2500. Assume availability of 85 percent and 2125 hours remain. Take utilisation at 85 percent as well and effective hours fall to roughly 1806. Dividing 300 thousand tonnes by 1806 hours gives a nominal capacity requirement of about 166 t/h.

The same arithmetic runs in reverse. Where a particular plant is already on the table, multiplying its nominal capacity by 1806 effective hours shows what that plant covers in a year under this shift pattern. The table below applies that conversion to the General 640, 800 and 950 mobile plants using the figures from their specifications.

The annual equivalents in the table are the result of a calculation, not a guarantee; change the number of shifts, the availability or the working days and every figure moves. The feed size and product fraction side of the model comparison is set out on the General 640 800 950 capacity selection page.

Seasonality creates a peak month

An annual total does not spread evenly across months. Asphalt and ready mix demand concentrates in the busy season, while rain and frost cut production in winter. If a significant share of a quarry's sales falls into three or four months, the plant has to be sized against the rate of those months. Otherwise a plant chosen on the annual average cannot keep up in season and stands idle in winter.

Two answers exist and they do not lead to the same place. The first is sizing the plant for the peak month: investment rises and winter utilisation falls. The second is building stock in the quiet season: investment stays flat, but stockyard area, handling cost and the risk of contaminating the product enter the picture. The decision follows from available land and from whether the product tolerates sitting in stock.

The weakest link in the chain

Crusher capacity on its own says nothing. The annual target materialises according to the weakest link in the line. If screen area is short the crusher waits; if belt speed or width is short the feed is interrupted; if the loading area has a single loader, trucks queue towards the end of the shift. Planning therefore keeps screen area, conveyor capacity, stock volume and haulage capacity in the same table as the crusher.

Water and power can bind too. In a washing circuit, water supply and settling pond capacity limit production rate directly. Where grid supply is short, generator capacity sets the ceiling. Leave those items outside the calculation and the annual target holds on paper but not on site.

A rate you have not measured cannot be assumed

Using guesses for availability and utilisation is the most fragile part of planning. Both ratios vary markedly from quarry to quarry and their only sound source is your own downtime record. Once the shift log carries the start time, duration and cause of each stoppage, real ratios appear at the end of a month. Sort the causes into five or six categories and it also becomes clear which loss is worth attacking.

A new quarry has no record. There the ratios of a plant working similar rock in a similar pattern serve as the opening assumption, replaced by real data at the end of the first quarter. Writing the assumption down matters, because when the target is missed the argument should be about the assumption rather than about the machine.

Updating the plan during the year

A capacity plan is not a document made once and shelved. A coarser muckpile slows the primary stage, a finer product mix loads the tertiary, a new customer specification adds a fraction. At each change the effective hours calculation is rerun and the required nominal capacity updated.

Reading this alongside the stage split, reduction ratio and feed size articles under mining engineering is worthwhile. Share your annual target, your shift pattern and your downtime records and the nominal capacity requirement can be worked out together.