Capacity Selection for a Block Factory in Iraq: Sizing From Orders, Not Machines

Capacity selection for a block factory in Iraq starts at the order book, not at a catalogue. A buyer who begins with the machine compares cycle times and pallet sizes and still cannot say whether the plant will deliver on time. Work backwards: blocks ordered, days available, hours in a shift, cycles the host must complete inside them. The figure that survives is the only capacity worth quoting.

The arithmetic fits on one page, and it does not change in Baghdad, Basra or Erbil. What changes is the order pattern, the working calendar and the mix of hollow block, kerb and paver. Get the four inputs wrong and every later decision inherits the error: host size, yard, forklifts, loading gang.

Which four inputs does the calculation need?

All four belong to the buyer, not the supplier: blocks per order, the delivery window in days, the working days inside that window, and the shift hours the plant will really run. An order of 60,000 hollow blocks at 390 x 190 x 190 mm, delivered over 20 working days on one 8-hour shift, is 3,000 blocks a shift. Every machine must beat it.

A quoted 120,960 standard bricks per 8-hour shift means nothing until you place it against your own 3,000.

• Blocks per order: count each size separately, because a hollow block and a paver do not fill a pallet alike.
• Delivery window and working days: the calendar you will actually run, holidays included.
• Shift hours: 8 hours is the reference behind every quoted output, so deduct your losses from it.

From cycle time to pallets per hour

Cycle time is the whole calculation. A 20 second cycle is three a minute, 180 an hour, 1,440 pallets in an 8-hour shift. Multiply by cavities: six hollow blocks of 390 x 190 x 190 mm per mould gives 1,080 blocks an hour, 8,640 a shift. At 25 seconds the same host makes 144 pallets an hour, 1,152 a shift. One machine on a 15 to 25 s band spans 1,152 to 1,920 pallets, so any single quoted figure guesses the end you run at.

Published outputs sit at the fast end. A QST6-15 is listed at 8,640 to 11,520 hollow blocks a shift with 6 per mould, which works back to 1,080 to 1,440 cycles a shift, a cycle of 20 down to 15 seconds, against its own 15 to 23 s band. The figure is honest: it describes the machine on a good mix with a crew that changes nothing.

Why is nameplate output not sellable output?

Four losses eat a shift. Mould change, an hour or two when the product changes. Breakdown, the jam under the mould or the sensor that drops its signal. Curing space, the quiet one: a full yard leaves green blocks nowhere to go and stops the press with nothing broken. Truck loading, where a late flatbed fills the yard and stops it again.

Deduct hours, not percentages. Take 1,440 pallets from a 20 second cycle, remove an hour for a mould change and an hour for stoppages, and 6 running hours remain: 1,080 pallets, or 6,480 hollow blocks at 6 per mould. The 3,000-block order clears. Raise it to 6,000 and the plant fails while the catalogue still promises 8,640.

Should you size the plant for the peak month?

Almost never. Orders rarely arrive flat. A plant may average 3,000 blocks a day and run at three times that for two months when a housing contract lands. Sizing the host for that peak buys a machine, a yard, a loading gang and a power connection for eight weeks of demand, then idles it part loaded all year.

The peak is better met with hours than with iron. The same host on a second shift doubles the shift count without adding floor area at the press. At 6,480 sellable hollow blocks a shift, two shifts make 12,960, and labour goes to 3 to 6 persons per shift on a complete line. What must grow is the yard and the pallet count.

When a smaller host on a second shift beats a bigger one

Compare on the same product. A QST6-15 on standard brick is listed at 46,080 to 61,440 bricks a shift; at 6 running hours it makes 34,560 to 46,080, and on a second shift 69,120 to 92,160. A QST1800 is listed at 220,000 in one shift. The big machine wins on paper and loses in a month where you can sell 70,000.

It also asks less of the site. A QST1200 needs 57.6 kW and a 1,350 x 880 x 25 mm pallet; the QST1800 needs 104 kW and a 1,400 x 1,400 x 30 mm pallet, so every pallet, rack and forklift in the yard changes with it. The bigger host wins when windows are tight and 24 hours is the hard limit.

Where a full line earns its place, and where one machine does

A QSGW line is configured from 30,000 to 250,000 pcs per 8-hour shift, so below 30,000 a line is the wrong purchase: batching, transfer cars and cuber run at a fraction of their cycle while you pay for idle automation. Up to about 120,000 standard bricks a shift, a single QST-class host with a cuber, a pallet magazine and a yard does the same work with 3 to 6 people.

The line earns its place when pallet handling, not pressing, is the bottleneck. A cuber rated 3,800 pallets a shift does not make the plant faster; it clears what the host makes, so size it from the host's pallet count. Above 120,000 bricks, or where the crew lifts by hand, the line is the cheaper way to add output.

Which two checks come before you sign?

The first is the curing yard, measured in a week. Two shifts at 1,080 sellable pallets each is 2,160 pallets a day, so five days is 10,800 pallets standing there before one is sold. Each takes a 1,350 x 880 mm footprint, and a stack built to 1,400 mm holds a countable number. A yard that holds three days stops the press on day four.

The second is loading. A clamp takes 500 to 800 standard bricks or 40 hollow blocks a bite, no more than 10 layers of standard brick or 5 of hollow. At 6,480 hollow blocks a shift that is 162 bites, and the trucks you load a day set the forklift count. If loading is manual the yard is the buffer, and a buffer that fills in three days is no buffer.

Fill this in before comparing quotations. A morning with the order file, the plot plan and a tape measure turns a catalogue into a decision.

• Order quantity: ____ blocks at ____ mm, ____ blocks at ____ mm.
• Delivery window ____ working days, ____ hours a shift, ____ shifts a day.
• Required a shift: order divided by days and shifts = ____ blocks.
• Cycle ____ seconds, cavities ____, so pallets an hour ____.
• Nominal pallets a shift ____, then running hours after mould change ____ of 8.
• Sellable output a shift ____ blocks, against the requirement, not the catalogue.
• Pallets a week ____, stacks the plot holds ____. If the second is smaller, fix the yard.
• Bites a shift ____, forklifts at the ramp ____, trucks a day ____.