A two-year study of the maintenance log of jaw crushers used in a cement plant to crush raw material (limestone, clay, etc) showed that wear-related failures, such as jaw plate wear and bearing failures, accounted for more than 60 per cent of breakdowns, while lubrication problems contributed to 25 per cent of failures. According to the researchers of this study, published earlier this year in Communications on Applied Nonlinear Analysis, this underscores the use of predictive maintenance and premium spares to reduce downtime and operating expenses.“Most breakdowns of 3-stage stone (basalt and weathered rock) crushing units are due to damaged bearings,” affirms Chetan Prakash Verma, General Manager - P&M, Ahluwalia Contracts (I).As timely greasing helps protect bearings, Pramod Joshi, P&M Head, All India, Ahluwalia Contracts India, proposes mandating the use of automated greasing systems, a feature in cone crushers and vertical shaft impactors from leading companies such as Metso, Puzzolana and Terex. He also confirms the utility of predictive maintenance in reducing breakdowns. However, he believes sensors and alerts indicating that key running parts need replacement would be a desirable addition to existing crushing models.Maintenance regimenProper routine maintenance plays a key role in enhancing the productivity of the crusher. Sai Krishna Naidu, Plant Owner, Sri Murali Krishna Stone Crushers, explains that this entails following the original equipment manufacturer (OEM) standards of maintenance, conducting regular inspections to identify wear or damage early to avoid costly downtime, reducing friction and extending component life with correct lubrication, maintaining an optimum level of wear and spares inventory, and removing material buildup quickly to maintain smooth operation. “Operators and the maintenance teams must be properly trained for safe, efficient use,” he adds.Verma emphasises upon proper maintenance of the crushing unit’s primary hopper/jaw and fitting a mesh of an appropriate size and a metal detector. Adding a separate conveyor after primary crushing would help to separate dust and reduce the content of silt in the crushed sand. To avoid any quality deterioration of the aggregates and sand, he also recommends that only screens from the OEM, fully calibrated with respect to their sizes, should be used. Mismatched screens may reduce the production output. Feature wiseAn online telematics system is a useful feature to understand the crushing hours, engine hours, wear life, location, etc, in real time, believes Rajkumar Chavan, Managing Director, RKC Infrastructure. “By implementing the Powerscreen Pulse telematics system on a crusher, we can monitor the plant from anywhere, anytime.”“Within our fleet of Terex Powerscreen crushing and screening plants, we are effectively using the Powerscreen Pulse, a telematic system to monitor the machines online, and effectively plan our need for spare parts and wear parts well in advance so that changeovers happen faster and site productivity is remarkably higher,” says Ajay Gujar, Managing Director, Rajsetu Projects, and Chairman, Building Association of India, Pune Centre. Naidu lists three essential features to maximise productivity: The crusher should be engineered to handle tough materials with high throughput and consistent output. It should have intuitive controls for user-friendly operations and accessible components to reduce downtime and make servicing straightforward. And it should have built-in safeguards to protect operators and the equipment, ensuring safe and efficient operations at all times.Verma says a crusher unit should be capable of being customised so that a sander or washing unit can be added if there is a need for more aggregate or crushed sand.Maximise outputUninterrupted power supply is vital to optimise production, says Verma, because it takes 45-50 minutes to restart operations after a single power cut. The starting and restarting of a crusher unit is a crucial feature, he believes, specifically the starting and restarting of a primary hopper. Hydraulic jacks with a vibrator can easily remove big boulders during these critical steps. It also helps to make boulders available very near the primary hopper to avoid idling. Preferably, incorporate the stock pile with the conveyor belt to feed the boulders into the primary hopper.He emphasises the need for conveyor belt rollers to be fully operational as they govern their constant speed. “Most belts get displaced because of damaged rollers,” he says. “Properly aligned conveyor belts are vital to feed raw material to the plant and transport the finished output. Further, covering the belts helps slippages during the rainy season and dust from accumulating when it isn’t raining.”Business-friendly sales and service support is vital to maximise output, adds Chavan. “With UMPESL - Voltas and Powerscreen’s support, we have achieved about 240 tph of granular slab base and 180 tph of wet-mix macadam, both of which are a good volume of production.”Verma has used a plant of 200 tph rated capacity (35-40 per cent of 40 mm/60 mm and 65-70 per cent below 25 mm) to produce 200 mt/hr of 150-200 mm boulders, 170-180 mt/hr of 40 mm aggregate, and 80-90 mt/hr of 25 mm and below produce. Essentially the output was 100 per cent for primary crushing. To produce 40 mm/60 mm aggregate, a vertical shaft impactor isn’t needed, in which case he got 90-95 per cent output from the unit.Naidu emphasises upon the need to ensure the correct or recommended feed size and gradation. His focus is sand because its production has garnered importance in recent years owing to its selling price. With a 250 tph plant with a secondary 250 tph cone crusher PCC26110 and tertiary vertical shaft impact crusher PVSI 800 MDR to produce maximum sand, and some aggregates, he has achieved 45 per cent sand production and the remaining aggregates (40/20/12/8 mm).Gujar attests to comfortably getting above 180 tph of GSB and 115 tph of crushed aggregate from his Powerscreen 200 tph (+/- 10 per cent) plants.Cut costsComplete electricity-driven track mobile crushing and screening plants (with a transport engine for mobility) are Chavan’s choice because most sites are dependent on grid power or gensets and opting for this variety, such as the recently developed Terex Powerscreen track plants, can reduce power and other operating costs by 35 per cent, based on his experience of the past eight years. “Dual-powered, hybrid-track mobile crushing and screening plants help to drastically cut down the power cost and operating cost over hydraulic models,” says Gujar. “Also, the same cone can be used to produce artificial M-sand, an engineering marvel by Powerscreen.” “Costs depend a lot on the technology used,” avers Purushotham Patel, Founder, Bharat Rocks and Mines. “We use a vertical shift impactor with REMco technology that Proman has brought to India. Using a vertical shaft impactor is vital to produce the quality output sought by the construction industry both for highways and high-rise buildings. In a decade of using the plant to make M-sand and aggregates, we have incurred low maintenance costs and seen less wear and tear because of the technology we chose. It keeps our cost low and profitability high, which is what every plant owner wants.”QuotesDual-powered, hybrid-track mobile crushing and screening plants help to drastically cut down the power and operating costs. - Ajay Gujar, Managing Director, Rajsetu Projects, and Chairman, Building Association of India, Pune CentreThe use of automated greasing systems should be made mandatory. - Pramod Joshi, P&M Head, All India, Ahluwalia Contracts IndiaOperators and maintenance teams must be properly trained for safe, efficient use. - Sai Krishna Naidu, Plant Owner, Sri Murali Krishna Stone CrushersOnly screens from the OEM, fully calibrated with respect to their sizes, should be used. - Chetan Prakash Verma, General Manager - P&M, Ahluwalia Contracts (I)Business-friendly sales and service support is vital to maximise output. - Rajkumar Chavan, Managing Director, RKC InfrastructureThe right technology keeps costs low and profitability high, which is what every plant owner wants. - Purushotham Patel, Founder, Bharat Rocks and Mines