Crushing Power
POWER & RENEWABLE ENERGY

Crushing Power

As the construction industry matures, Charu Bahri finds that contractors are paying greater attention to the correct selection, installation and optimal use of crushing and screening equipment.

The Indian market for crushing and screening equipment is one of the most promising in the world. Its rapid growth in recent years has mainly been driven by the construction sector; and within this, infrastructure projects like national highways, expressways, bridges, rural roads, urban infrastructure, airports, railway ballast and dams.

“The kicking off of many infrastructure projects has widened the market for crushers and screening equipment to include major construction companies,” says Satya Raju, Regional Product Line Manager – Mine Crushers, West Asia, Sandvik Mining and Construction. “As long as the construction sector was predominantly unorganised, larger companies tended to sublet their contracts to small and medium-sized contracting firms. Now, however, they are focusing on setting up higher capacity plants for infrastructure projects as well as commercial quarrying purposes.”

Market size

Industry voices speak in unison about the scope of this sector. “We estimate the Indian market for crushing and screening equipment to be worth at least $300 million,” shares Leo Lu, Marketing Director, Shanghai Longzhen Heavy Industry Co Ltd. “We’re targeting monthly sales of $1.5 million, which would make our share at least 6 per cent of the market pie.”

“The Indian infrastructure sector offers the most potential and is the most stable, economically, with rapid but controlled growth and Rockster will definitely play a role in the country’s development,” says Wolfgang Kormann, Managing Director, Kormann Rockster Recycler GmbH (Austria). “The worldwide demand for construction aggregates is growing at the rate of 2.9 per cent. But demand in the Asia-Pacific region, home to China and India, is clocking the highest growth rates, which hints at better times to come for manufacturers of aggregate-making machines,” adds Subhash Niyogi, Managing Director, Rockster Recycler India Pvt Ltd.

“Ensuing five year plans till the year 2019 propose total investments of US$ 1 trillion in the infrastructure sector. This outlay has been endorsed by CII & Goldman Sachs. Further, international norms peg the construction equipment market at about 20 to 23 per cent of these total investments. Around 12.5 per cent of the construction equipment share is estimated to be spent on crushing, screening and aggregate plants,” says GN Raju, Managing Director, NAWA Engineers & Consultants (P) Ltd.

Select smart

Intense competition is nowadays compelling contractors to review their choice of crushing and screening equipment. “The right equipment can help achieve desired performance levels, productivity, profitability, and keep investments in line with what the company can afford,” says Raju. Lu recommends that crushing and screening equipment be chosen after considering
the features of the proposed equipment in terms of its ability to deliver the desired quality and quantity of aggregate. Also,
you must get a feedback on the quality of after-sales services offered by the vendor from existing customers.

Ideally, a contractor would like the crushing process to be achieved by a single machine. As this entails a reduction ratio of about 50, when a piece of 1 cu m is crushed into 20 mm pieces, which is practically not feasible, it becomes necessary to use an appropriate number of crushing stages and equipments to reach the required product size.

“Primary crushers are chosen after considering the size of the intended feed and the transport services or conveyor belt facility that is available or can be created between the primary and secondary crusher,” explains Satya Raju. “Usually, a jaw or gyratory crusher capable of reduction ratios of 2-3 and 3-4 respectively is used as the primary crusher. But as many plants are expected to accept large intakes, we often find ourselves recommending a primary crusher of higher capacity than the rest of the installation.” This helps customers with substantial indirect savings in mining costs. But he observes that most of the time customers do not go for bigger size jaws because of the initial investments involved; they fail to realise the potential savings at the end of their projects. Some Sandvik customers like Rock-N-Rock of Hyderabad, Ravi Hitech Stone Crusher near Nalgonda (Andhra Pradesh), and other customers in Kerala, procured bigger jaw crushers (CJ411) to handle bigger lumps, even though their secondary (CH430)/tertiary crushers are somewhat smaller than the primary - they were driven to take this decision by virtue of being fully aware of the benefits of this arrangement.

Secondary crushing generally employs a secondary type cone crusher, so chosen that it can handle the top size and capacity of the jaw crusher. After scalping the product from the cone crusher through a screen, the required product is sent to the tertiary stage and the oversize is re-circulated. A fine cone crusher is generally employed in the tertiary stage. Where a superior product shape is required, such as aggregates for concrete, sand, road surfacing, etc., a vertical shaft impactor (VSI) is used. The final products are screened to ensure their suitability using a product screen.

Locate right

It’s not enough only to select the right equipment. Installing crushing and screening equipment at the right spot is vital to improve its performance, productivity and profitability. “The aim is to locate the equipment so as to lower the cost per tonne of finished products; this requires a thorough knowledge of the whole quarrying process,” explains Raju. “Of course, these objectives also call for support to reduce downtime, optimise uptime, and sufficient trained operators.”

For his part, Rajbir Singh, Director, C & C Constructions, observes, “In choosing a spot for a static crusher, you first need to comply with state government regulations. These differ from state to state. Some typical norms are that the plant has to be 500 m away from the passing main road, 2 km away from the nearest inhabitation, which is applicable in Rajasthan, and so on.”

As the location of crushing and screening equipment plays such an important role in maximising yield, manufacturers like LZ Crushers and Sandvik offer assistance in selecting the right spot. According to Lu, “Crushing and screening equipment should be installed in a dry environment, both near the source of raw material and to a road to facilitate deliveries, and where there is regular power supply.”

Optimise performance

“Crushers must be used within the prescribed design limits and be maintained as per the recommended regimen to maximise uptime and minimise the operating costs and, thus, the cost per tonne of the yield,” opines BV Raisinghani, President, Jaiprakash Associates Ltd. “By and large, jaw crushers have the lowest operating costs, followed by cone crushers. VSIs are most expensive to run.” As crushers have a long life, say 20 to 35 years, some contractors may still be using machines driven by old technologies. They would benefit more from using the latest range of crushers based on advanced technology as these also improve productivity. “Such machines cut down on power costs and consumables, and use improved parts such as gearboxes, drives and fluid couplings (vis-à-vis mechanical couplings) that safeguard systems against mechanical overload,” he adds. “Proper feeding is another important aspect. It enhances productivity, reduces maintenance costs, and helps correlate power draws, crushing force and volumetric capacity (for a desired reduction ratio) to have them peak simultaneously.”

The key to getting the most returns out of a crusher is to control the rate of feed by using a variable speed belt, variable frequency vibrating feeder and variable gate opening, irrespective of whether the crusher is fed by direct discharge from a belt, a feed bin, vibrating feeder, rock box, chute or combination of the above. Also, the crusher should be fed with a homogenous mix of rocks that is evenly distributed all around the feed chamber. This helps prevent fines accumulating in one area. Else, as fines can’t be crushed as much as solid streams, they end up causing fluctuation in the crushing forces generated around the cavity and reducing the efficiency of the process. Fines in a jaw crusher also cause breakage of the swing-stock. Use of a mechanised rotating feed distributor helps avoid problems caused by segregated feed. “If the feed gradation permits a cone crusher to be used as the primary crusher, you benefit from consistent choke feeding, more consistent power draw and larger crushing surface area,” says Raisinghani. “If a jaw crusher is used as the primary crusher, a grizzly feeder helps improve throughput by providing constant feed and separating the fines.”

‘Green’ aggregates

Crushed stone, sand and gravel are vital for the economic development of the country. “Still, environmental concerns also need to be looked into; the construction industry must bear the responsibility for depleting natural aggregates and adopt recycling methods in a bigger way,” observes Niyogi. “Recycled asphalt from worn-out roads can be mixed with additives to ensure that its strength is comparable with natural aggregates. This protects the environment because the oil in dumped worn-out asphalt otherwise it seeps into the ground and enters underground water streams. Other raw material sources for recycled aggregates are concrete from demolished buildings and construction and demolition debris. Secondary construction aggregate like blast-furnace slag is also environment-friendly.”

What do contractors make of the concept of eco-friendly aggregates? “It makes sense to use Mitsubishi or Rockster machines to produce recycled aggregates, especially if the raw materials comes from worn-out city roads as you can’t keep raising the level of inter-city roads [unlike highways],” responds Singh. Still, the reuse must be worthwhile - the material must pass appropriate tests.” While there were no tests available to verify the quality of materials for recycling until a few decades ago, now there is a range of tests to evaluate whether this material is fit for use. “The MORST also prescribes the use of laboratory tests to ensure the quality of infrastructure constructed that makes use of recycled aggregates. It’s a safety hazard to recycle unworthy raw material as well as a waste of public funds.”

Recycling advantages

Recycling is faster and less expensive than the traditional method of producing aggregates as it does away with preliminary operations like drilling and blasting. The process typically uses mobile machines that are far more compact than conventional crushers. Such machines are also less cumbersome to operate; Niyogi points out that the Rockster Recycler track-mounted mobile crusher and screener, which is imported as is and needs no reassembly in India, may be operated by remote control. “One operator can handle both the recycler and excavator, thus saving on manpower costs and also enhancing safety,” he explains. “Its performance is also not hampered by the snapping of the belt used for the conveyor feeder systems; its belt is barely 2-3 m long and integrated within the recycler with the screening box mounted on the discharge conveyor. As the machine is based on the patented ‘duplex’ system, it produces both recycled and natural aggregate and can thus supplement recycled aggregate produced at site with natural aggregates.”

Rockstar model R-900’s ‘duplex’ system is what attracted Girish Bhatkhande, Director, Popular Construction, to the brand. A division of Popular Infra Resources, Belgaum, the company currently crushes 1.3 million tonne per annum in four different locations. It is targeting 2.0 million tonne by year-end, after expanding its activities to eight locations. Rapidly expanding operations called for an innovative, cost-effective, compact, high-performing, engineered track-mounted mobile crusher. “We’ve used more than 15 mobile crushers and screens, global brands, too, but saw benefit in Rockstar’s machine because it supports switching over from impactor to jaw crushing and vice-versa in two-and-a-half hours flat at site,” he says. “The machine’s versatility is well supported by readily available spares and technical expertise made available at site.”

Indeed, smart choices are helping Indian contractors crush more, faster. If the present rate of expansion is anything to do by, crushing is set to grow more powerful in the near future.

Mobile vs static crushers

“Although the yield of stationary crushers is superior to mobile machines, the latter offer significant savings when they are used near ground excavations,” says Rajbir Singh, Director, C&C Constructions Ltd. “You can crush excavated rocks as you excavate. Static machines that take six to nine months to set up can’t serve the same purpose.” Nevertheless, he points out that the scope for mobile crushers and screeners will increase if state governments change their approach towards issuing licenses for their use. “At present, they only issue licenses for one particular place, as in the case of stationary crushers,” he adds. “But that defeats the very purpose of the mobile machine.

The commercial angle

According to BV Raisinghani, President, Jaiprakash Associates Ltd, “Contractors executing long-term projects, that is, of three to five years duration, would benefit from buying their own crusher and screener. Usually, you break even by the third year, which means you save on costs during the remaining duration of the project. Plants may be relocated to a new project site thereafter. Besides the commercial aspects, using company-owned crushing and screening plants helps ensure quality aggregates, uniform costs and savings on transportation costs. Market prices of aggregates fluctuate a lot.”

Role of conveyors

In the wake of improved construction standard specifications and larger projects, using two to three-stage crushing plants has become the norm. In such scenarios, Rajbir Singh, Director, C & C Constructions Ltd opines that conveyors play a huge role in ensuring the right flow of feed at the intermediary stages. Fortunately, conveyors of larger modern machines now available are far superior and safer to the rubber belts in vogue in past decades. Conveyors or belts used to transport the intermediate products affect plant performance. "Such transport mediums must transport the output of one machine continuously and evenly to the next in the process," says Leo Lu, Marketing Director, Shanghai Longzhen Heavy Industry Co Ltd.

As the construction industry matures, Charu Bahri finds that contractors are paying greater attention to the correct selection, installation and optimal use of crushing and screening equipment. The Indian market for crushing and screening equipment is one of the most promising in the world. Its rapid growth in recent years has mainly been driven by the construction sector; and within this, infrastructure projects like national highways, expressways, bridges, rural roads, urban infrastructure, airports, railway ballast and dams. “The kicking off of many infrastructure projects has widened the market for crushers and screening equipment to include major construction companies,” says Satya Raju, Regional Product Line Manager – Mine Crushers, West Asia, Sandvik Mining and Construction. “As long as the construction sector was predominantly unorganised, larger companies tended to sublet their contracts to small and medium-sized contracting firms. Now, however, they are focusing on setting up higher capacity plants for infrastructure projects as well as commercial quarrying purposes.” Market size Industry voices speak in unison about the scope of this sector. “We estimate the Indian market for crushing and screening equipment to be worth at least $300 million,” shares Leo Lu, Marketing Director, Shanghai Longzhen Heavy Industry Co Ltd. “We’re targeting monthly sales of $1.5 million, which would make our share at least 6 per cent of the market pie.” “The Indian infrastructure sector offers the most potential and is the most stable, economically, with rapid but controlled growth and Rockster will definitely play a role in the country’s development,” says Wolfgang Kormann, Managing Director, Kormann Rockster Recycler GmbH (Austria). “The worldwide demand for construction aggregates is growing at the rate of 2.9 per cent. But demand in the Asia-Pacific region, home to China and India, is clocking the highest growth rates, which hints at better times to come for manufacturers of aggregate-making machines,” adds Subhash Niyogi, Managing Director, Rockster Recycler India Pvt Ltd. “Ensuing five year plans till the year 2019 propose total investments of US$ 1 trillion in the infrastructure sector. This outlay has been endorsed by CII & Goldman Sachs. Further, international norms peg the construction equipment market at about 20 to 23 per cent of these total investments. Around 12.5 per cent of the construction equipment share is estimated to be spent on crushing, screening and aggregate plants,” says GN Raju, Managing Director, NAWA Engineers & Consultants (P) Ltd. Select smart Intense competition is nowadays compelling contractors to review their choice of crushing and screening equipment. “The right equipment can help achieve desired performance levels, productivity, profitability, and keep investments in line with what the company can afford,” says Raju. Lu recommends that crushing and screening equipment be chosen after considering the features of the proposed equipment in terms of its ability to deliver the desired quality and quantity of aggregate. Also, you must get a feedback on the quality of after-sales services offered by the vendor from existing customers. Ideally, a contractor would like the crushing process to be achieved by a single machine. As this entails a reduction ratio of about 50, when a piece of 1 cu m is crushed into 20 mm pieces, which is practically not feasible, it becomes necessary to use an appropriate number of crushing stages and equipments to reach the required product size. “Primary crushers are chosen after considering the size of the intended feed and the transport services or conveyor belt facility that is available or can be created between the primary and secondary crusher,” explains Satya Raju. “Usually, a jaw or gyratory crusher capable of reduction ratios of 2-3 and 3-4 respectively is used as the primary crusher. But as many plants are expected to accept large intakes, we often find ourselves recommending a primary crusher of higher capacity than the rest of the installation.” This helps customers with substantial indirect savings in mining costs. But he observes that most of the time customers do not go for bigger size jaws because of the initial investments involved; they fail to realise the potential savings at the end of their projects. Some Sandvik customers like Rock-N-Rock of Hyderabad, Ravi Hitech Stone Crusher near Nalgonda (Andhra Pradesh), and other customers in Kerala, procured bigger jaw crushers (CJ411) to handle bigger lumps, even though their secondary (CH430)/tertiary crushers are somewhat smaller than the primary - they were driven to take this decision by virtue of being fully aware of the benefits of this arrangement. Secondary crushing generally employs a secondary type cone crusher, so chosen that it can handle the top size and capacity of the jaw crusher. After scalping the product from the cone crusher through a screen, the required product is sent to the tertiary stage and the oversize is re-circulated. A fine cone crusher is generally employed in the tertiary stage. Where a superior product shape is required, such as aggregates for concrete, sand, road surfacing, etc., a vertical shaft impactor (VSI) is used. The final products are screened to ensure their suitability using a product screen. Locate right It’s not enough only to select the right equipment. Installing crushing and screening equipment at the right spot is vital to improve its performance, productivity and profitability. “The aim is to locate the equipment so as to lower the cost per tonne of finished products; this requires a thorough knowledge of the whole quarrying process,” explains Raju. “Of course, these objectives also call for support to reduce downtime, optimise uptime, and sufficient trained operators.” For his part, Rajbir Singh, Director, C & C Constructions, observes, “In choosing a spot for a static crusher, you first need to comply with state government regulations. These differ from state to state. Some typical norms are that the plant has to be 500 m away from the passing main road, 2 km away from the nearest inhabitation, which is applicable in Rajasthan, and so on.” As the location of crushing and screening equipment plays such an important role in maximising yield, manufacturers like LZ Crushers and Sandvik offer assistance in selecting the right spot. According to Lu, “Crushing and screening equipment should be installed in a dry environment, both near the source of raw material and to a road to facilitate deliveries, and where there is regular power supply.” Optimise performance “Crushers must be used within the prescribed design limits and be maintained as per the recommended regimen to maximise uptime and minimise the operating costs and, thus, the cost per tonne of the yield,” opines BV Raisinghani, President, Jaiprakash Associates Ltd. “By and large, jaw crushers have the lowest operating costs, followed by cone crushers. VSIs are most expensive to run.” As crushers have a long life, say 20 to 35 years, some contractors may still be using machines driven by old technologies. They would benefit more from using the latest range of crushers based on advanced technology as these also improve productivity. “Such machines cut down on power costs and consumables, and use improved parts such as gearboxes, drives and fluid couplings (vis-à-vis mechanical couplings) that safeguard systems against mechanical overload,” he adds. “Proper feeding is another important aspect. It enhances productivity, reduces maintenance costs, and helps correlate power draws, crushing force and volumetric capacity (for a desired reduction ratio) to have them peak simultaneously.” The key to getting the most returns out of a crusher is to control the rate of feed by using a variable speed belt, variable frequency vibrating feeder and variable gate opening, irrespective of whether the crusher is fed by direct discharge from a belt, a feed bin, vibrating feeder, rock box, chute or combination of the above. Also, the crusher should be fed with a homogenous mix of rocks that is evenly distributed all around the feed chamber. This helps prevent fines accumulating in one area. Else, as fines can’t be crushed as much as solid streams, they end up causing fluctuation in the crushing forces generated around the cavity and reducing the efficiency of the process. Fines in a jaw crusher also cause breakage of the swing-stock. Use of a mechanised rotating feed distributor helps avoid problems caused by segregated feed. “If the feed gradation permits a cone crusher to be used as the primary crusher, you benefit from consistent choke feeding, more consistent power draw and larger crushing surface area,” says Raisinghani. “If a jaw crusher is used as the primary crusher, a grizzly feeder helps improve throughput by providing constant feed and separating the fines.” ‘Green’ aggregates Crushed stone, sand and gravel are vital for the economic development of the country. “Still, environmental concerns also need to be looked into; the construction industry must bear the responsibility for depleting natural aggregates and adopt recycling methods in a bigger way,” observes Niyogi. “Recycled asphalt from worn-out roads can be mixed with additives to ensure that its strength is comparable with natural aggregates. This protects the environment because the oil in dumped worn-out asphalt otherwise it seeps into the ground and enters underground water streams. Other raw material sources for recycled aggregates are concrete from demolished buildings and construction and demolition debris. Secondary construction aggregate like blast-furnace slag is also environment-friendly.” What do contractors make of the concept of eco-friendly aggregates? “It makes sense to use Mitsubishi or Rockster machines to produce recycled aggregates, especially if the raw materials comes from worn-out city roads as you can’t keep raising the level of inter-city roads [unlike highways],” responds Singh. Still, the reuse must be worthwhile - the material must pass appropriate tests.” While there were no tests available to verify the quality of materials for recycling until a few decades ago, now there is a range of tests to evaluate whether this material is fit for use. “The MORST also prescribes the use of laboratory tests to ensure the quality of infrastructure constructed that makes use of recycled aggregates. It’s a safety hazard to recycle unworthy raw material as well as a waste of public funds.” Recycling advantages Recycling is faster and less expensive than the traditional method of producing aggregates as it does away with preliminary operations like drilling and blasting. The process typically uses mobile machines that are far more compact than conventional crushers. Such machines are also less cumbersome to operate; Niyogi points out that the Rockster Recycler track-mounted mobile crusher and screener, which is imported as is and needs no reassembly in India, may be operated by remote control. “One operator can handle both the recycler and excavator, thus saving on manpower costs and also enhancing safety,” he explains. “Its performance is also not hampered by the snapping of the belt used for the conveyor feeder systems; its belt is barely 2-3 m long and integrated within the recycler with the screening box mounted on the discharge conveyor. As the machine is based on the patented ‘duplex’ system, it produces both recycled and natural aggregate and can thus supplement recycled aggregate produced at site with natural aggregates.” Rockstar model R-900’s ‘duplex’ system is what attracted Girish Bhatkhande, Director, Popular Construction, to the brand. A division of Popular Infra Resources, Belgaum, the company currently crushes 1.3 million tonne per annum in four different locations. It is targeting 2.0 million tonne by year-end, after expanding its activities to eight locations. Rapidly expanding operations called for an innovative, cost-effective, compact, high-performing, engineered track-mounted mobile crusher. “We’ve used more than 15 mobile crushers and screens, global brands, too, but saw benefit in Rockstar’s machine because it supports switching over from impactor to jaw crushing and vice-versa in two-and-a-half hours flat at site,” he says. “The machine’s versatility is well supported by readily available spares and technical expertise made available at site.” Indeed, smart choices are helping Indian contractors crush more, faster. If the present rate of expansion is anything to do by, crushing is set to grow more powerful in the near future. Mobile vs static crushers “Although the yield of stationary crushers is superior to mobile machines, the latter offer significant savings when they are used near ground excavations,” says Rajbir Singh, Director, C&C Constructions Ltd. “You can crush excavated rocks as you excavate. Static machines that take six to nine months to set up can’t serve the same purpose.” Nevertheless, he points out that the scope for mobile crushers and screeners will increase if state governments change their approach towards issuing licenses for their use. “At present, they only issue licenses for one particular place, as in the case of stationary crushers,” he adds. “But that defeats the very purpose of the mobile machine. The commercial angle According to BV Raisinghani, President, Jaiprakash Associates Ltd, “Contractors executing long-term projects, that is, of three to five years duration, would benefit from buying their own crusher and screener. Usually, you break even by the third year, which means you save on costs during the remaining duration of the project. Plants may be relocated to a new project site thereafter. Besides the commercial aspects, using company-owned crushing and screening plants helps ensure quality aggregates, uniform costs and savings on transportation costs. Market prices of aggregates fluctuate a lot.” Role of conveyors In the wake of improved construction standard specifications and larger projects, using two to three-stage crushing plants has become the norm. In such scenarios, Rajbir Singh, Director, C & C Constructions Ltd opines that conveyors play a huge role in ensuring the right flow of feed at the intermediary stages. Fortunately, conveyors of larger modern machines now available are far superior and safer to the rubber belts in vogue in past decades. Conveyors or belts used to transport the intermediate products affect plant performance. Such transport mediums must transport the output of one machine continuously and evenly to the next in the process, says Leo Lu, Marketing Director, Shanghai Longzhen Heavy Industry Co Ltd.

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