What Is a Crushing and Screening Plant and How Is It Set Up? Flowsheet Guide

A crushing and screening plant is a chain of machines that turns raw rock from the quarry into saleable fractions for concrete, asphalt, road sub-base, ballast or industrial raw materials. A plant’s success comes less from the quality of a single machine than from how well the machines work together: if the primary crusher cannot feed the secondary, if the screen area is insufficient or if the bins are wrongly sized, even the most expensive equipment runs below its capacity.

This guide summarises the steps to follow when building a plant from scratch or expanding an existing one, together with practical checkpoints distilled from field experience.

1. Material and Market Analysis

Plant design starts not with machines but with the material and the product to be sold.

• Rock properties: Compressive strength, crushability (work index), abrasiveness index (e.g. LCPC/Ai), silica content, density.
• Contamination: Clay, soil and moisture content; determine the need for washing and the type of feeder.
• Quarry feed size: The largest block size, which depends on the blast design.
• Product specifications: Which fractions will be sold in what proportions (e.g. 0–5 sand, 5–12, 12–19, 19–25 chippings)? Particle shape (flakiness index), fines (filler) and cleanliness limits (standards such as EN 12620 and EN 13043).
• Market balance: The demand ratio of the fractions should be reflected in the circuit design to avoid “unwanted” products piling up in stock.

2. Capacity Calculation

When moving from an annual sales target to an hourly design capacity, realistic operating time must be used:

• Annual target ÷ working days ÷ daily shift hours = gross hourly requirement,
• This value is divided by plant availability (maintenance, breakdowns, weather; usually 75–85%) to give the design capacity.
• In closed circuits, the recirculating load must be taken into account; the total load entering the secondary/tertiary crusher is greater than the product capacity.

3. Flowsheet (Process Design)

A typical hard-rock aggregate plant consists of the following stages:

1. Primary crushing: Truck dump bin → vibrating grizzly feeder → jaw crusher. If dirty, the grizzly undersize is separated as “soil” on a separate scalping screen.
2. Surge stockpile: Increases availability by letting the primary and secondary circuits run independently.
3. Secondary crushing and screening: Cone crusher (hard rock) or impact crusher (limestone) + vibrating screen; the screen oversize returns to the crusher in closed circuit.
4. Tertiary crushing and sand production: Cone crusher or vertical shaft impactor (VSI); fine, well-shaped product.
5. Washing/classification (if needed): Screw sand washer, dewatering screen, water recovery.
6. Stockpiling and loading: Belt conveyors, stockpile conveyors, loading bins and weighbridge.

For low-abrasion materials such as limestone, two-stage plants with lower investment, consisting of a primary impact crusher + secondary impact crusher, are possible. For hard, abrasive rock, a jaw + cone + cone/VSI combination is usually the most economical solution in terms of cost per tonne.

4. Critical Rules in Equipment Selection

• The maximum feed size of each crusher must match the top size of the product of the previous stage.
• Crushers must be able to be choke fed; for this they need a level-controlled bin and feeder in front of them.
• After crusher capacity, screen area is where mistakes are most often made; screen area should be calculated with the actual size distribution and closed-circuit load.
• Conveyor widths and speeds should be chosen according to the largest particle size and peak capacity; chutes at transfer points should be designed to prevent wear and blockage.
• Spare parts standardisation: using the same types of bearings, idlers, belts and motor sizes as far as possible within a plant reduces stock costs.

5. Stationary, Mobile or Modular?

6. Layout and Civil Works

• Use the topography: On sloping ground, placing the primary crusher at a high level reduces conveyor lengths and energy consumption.
• Maintenance access: Crane access for every crusher and screen, enough space for liner and screen media changes, walkways and stairs should be planned.
• Foundations: Crusher foundations should be calculated for dynamic loads; a ground investigation should be carried out.
• Stockpile areas: Stockpile capacity per fraction should be set according to sales fluctuations; the need for drainage and reclaim tunnels should be assessed.
• Traffic: Quarry trucks and customer trucks should be kept on separate roads as far as possible.

7. Electrics, Automation and Energy

• On large motors, a soft starter or frequency inverter allows starting without loading the grid.
• Sequential starting and interlocks (when one conveyor stops, the ones before it stop) via central control (PLC/SCADA) are essential.
• Automatic feed control based on crusher power and level measurement considerably increases capacity and liner life.
• Power factor correction, energy monitoring and kWh/ton tracking are necessary to control operating costs.

8. Environment, Permits and Safety

• Dust control: Enclosed chutes at transfer points, water spray (atomising) systems and, where necessary, dust collection systems with pulse-jet filters.
• Noise: Distance from residential areas, rubber screen panels, enclosed crusher buildings.
• Permits: Legal processes such as the mining licence, environmental impact assessment, emission and environmental permits and building permits should be included in the project schedule from the start.
• Safety: Guards at all nip points, emergency stop systems, LOTO procedures, safe maintenance platforms.

9. Commissioning

1. Mechanical checks: alignment, bolt torques, oil and grease fills, directions of rotation.
2. Idle running: each machine individually, then sequential starting and interlock tests.
3. Loaded commissioning: gradually increasing capacity, fine-tuning crusher settings and screen apertures.
4. Performance test: capacity, product distribution (sieve analysis), energy consumption and particle shape measurements.
5. Training for operators and the maintenance team; drawing up the maintenance plan and critical spare parts list.

10. Items That Determine Operating Cost

The largest items in a crushing and screening plant’s cost per tonne are usually energy, wear parts, staff and maintenance. The most effective ways to reduce wear part consumption are the right crushing chamber, choke feeding and removing fines beforehand; to reduce energy, running crushers at full load and avoiding unnecessary recirculating load. A regular preventive maintenance schedule greatly reduces stoppages caused by breakdowns.

Frequently Asked Questions

How long does it take to set up a crushing and screening plant?

Modular and mobile plants can be commissioned within a few weeks, while for large stationary plants the time is measured in months, including design, manufacturing, construction and permitting.

Which crusher combination should I choose?

The choice depends on the hardness and abrasiveness of the rock, the required products and capacity. Impact crushers stand out for limestone; jaw + cone combinations for hard rock such as granite and basalt.

Can I increase the capacity of my existing plant?

In most plants, the bottleneck comes from causes that can be fixed, such as insufficient screen area, a starved crusher or the wrong crushing chamber. Low-cost improvements can be found through a flowsheet analysis and sieve analyses.

Example Flowsheet: A 300 t/h Basalt Aggregate Plant

To make the concepts concrete, let us look at the simplified flow of a 300 t/h plant producing concrete and asphalt aggregate from a hard rock:

1. Primary stage: Truck dump bin → vibrating grizzly feeder (grizzly opening ~100 mm) → jaw crusher (CSS ~120 mm). If dirty, the grizzly undersize is separated on a soil screen.
2. Surge stockpile: The primary product (0–200 mm) goes to a surge stockpile; the secondary circuit is fed by feeders in the reclaim tunnel.
3. Secondary stage: Cone crusher (medium-coarse profile) + 3-deck screen. Material above 32 mm returns to the crusher (closed circuit).
4. Tertiary stage: Fine-profile cone crusher or VSI; a second screen group for 0–5, 5–12, 12–19 and 19–25 mm products.
5. Sand processing: 0–5 mm is sent to an air classifier or washing line depending on its filler content.
6. Stockpiling: A stockpile conveyor and loading arrangement for each fraction.

In this type of plant, total installed power can reach several megawatts depending on the choice of crushers and screens; the energy infrastructure (transformer capacity) must be decided at the start of the project. For energy savings, see our energy efficiency guide.

Project Schedule: Typical Phases

Long-lead equipment (large crushers, transformers, special screens) and permit processes usually determine the critical path.

Common Design Mistakes

• Choosing too small a screen area: The most common plant bottleneck; products mix and the recirculating load increases.
• No surge stockpile or bin: Every stoppage in the primary circuit also stops the secondary circuit; availability falls.
• Forgetting maintenance access: In plants without crane access for liner and screen changes, every maintenance job takes hours longer.
• Poor chute design at transfer points: Becomes a source of blockage, spillage, wear and dust.
• Ignoring market balance: Fractions that cannot be sold pile up in stock; the circuit should have the flexibility to recrush these fractions.
• Planning too small an electrical infrastructure: Transformer and panel capacity is insufficient for a crusher or washing line to be added later.
• Leaving dust and noise for later: Measures added later are much more expensive than those included in the design. See dust and noise control.

Critical Spare Parts and Maintenance Organisation

Before the plant is commissioned, a critical spare parts list and minimum stock levels should be set for each piece of equipment. The workshop, lifting equipment, oil store and spare parts store should be included in the layout. Training the maintenance team with the equipment supplier during installation and commissioning considerably reduces the failure rate in the first years. In the long term, condition monitoring and predictive maintenance practices increase availability further.

An Example from the Field: A New Crusher for More Capacity?

A plant wanting to increase its capacity was planning to replace its secondary cone crusher with a larger model. A flowsheet analysis showed that the crusher was already running only at partial load; the real bottleneck was the insufficient area of the screen after the crusher and worn screen media. Screen area was increased with an additional screen and level-controlled feeding was added in front of the crusher. Capacity increased markedly without replacing the crusher. In plant expansion decisions, measuring the performance of the existing circuit first prevents unnecessary investment.

More Questions

What tests should be carried out when setting up a plant?

The rock’s compressive strength, Los Angeles abrasion resistance, abrasiveness index, crushability (work index), density and water absorption, clay and fines content, and the standard tests required for the target products should be carried out.

How many people are needed to run a plant?

It depends on the level of automation, plant size and number of shifts. Plants with central control and automatic feed control need fewer operators; the competence of the maintenance team remains critical in every case.

Does it make sense to build a plant with second-hand equipment?

Equipment in good condition and overhauled can reduce investment costs; however, spare parts availability, remaining life and compatibility with the plant’s flowsheet must be assessed carefully.

What Is a Crushing and Screening Plant and How Does It Work?

A crushing and screening plant is the set of equipment that reduces run-of-mine rock from the quarry with crushers, separates it by size with screens and conveys it to the stockyard. Its working principle is staged reduction and classification: after each crushing stage, screens separate material of the required size and oversize returns to the crusher (closed circuit).

Example Flowsheet

The flow of a typical three-stage plant producing chippings and manufactured sand is as follows:

For the differences between crusher types see our what is a crusher guide, for investment and operating cost items our crusher and plant prices guide, and for conveyor sizing our belt conveyor calculation guide.

What does a crushing and screening plant do?

It produces aggregate of defined size and quality for concrete, asphalt, road sub-base, ballast and industrial raw materials; in mining operations it prepares ore for grinding.

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