When producers combine preventive maintenance programs with modern material handling methods, the result may be a resounding return on investment.
Today’s automated conveying solutions are literally on-target when programmed to build stockpiles in any desired volume or configuration; or to load bins, silos, and surge tunnels; or to streamline loading, unloading and stockpiling at barge, railcar, and marine distribution centres worldwide. These systems are customised to meet an operation’s exact requirements while minimising more costly haul truck and loader use.
Alternatively, the latest wheel loader releases are designed for tougher digging, faster loading, higher breakout forces, increased fuel efficiency, less maintenance requirements, and significant improvements in productivity compared to earlier models. Additionally, models can be combined with mechanically attached wear plate systems, as well as new bucket teeth systems engineered to boost productivity in quarry applications.
These new developments are critical responses to rising maintenance and operating expenditures, ongoing labour shortages, and an unending fuel cost crisis ? issues which may keep some producers swirling in the vortex of a perfect storm. So with that said, if your material handling mantra is ?that?s the way we?ve always done it,? don?t be surprised if you go down with the ship.
Method Before Maintenance
Without the appropriate material handling methods in place, a maintenance program may simply be chasing good money after bad. Uncovering the optimal solutions for an operation requires an analysis of current situations and future goals against the best available modern material handling technology.
When is it best to minimise wheel loader and haul trucks in favour of conveyor transport? Or, when is the flexibility of wheeled transport the better choice? Experts point to many factors. What is the size and age of the quarry? Is the operation blending on multiple benches? What is the length and grade of the haul? Does material have to cross over streams, roads, or tracks? What is age of the current loader fleet? Might selling older equipment help in the acquisition of new technologies?
Most operators will agree that it is best to limit haul truck and loader use to level applications, as opposed to stockpiling. Studies indicate that lifetime (8000 to 12,000-hours) loader owning and operating costs are no less than 2.25 times higher than the unit’s initial purchase price – and that figure does not even include the effects of labour and fuel costs, and an ongoing tyre shortage. Using a loader is a very expensive way to stockpile as loader component and tyre wear accelerates when the machine is operated on inclines exceeding 6 per cent.
Consider that conveying solutions, which may include automated telescoping radial stackers, portable jump conveyors, tripper conveyors, mobile stackable units, stationary overland systems, and more, streamline material handling maintenance requirements, while delivering key cost-cutting benefits in the following areas:
Environmental impact. Conveyors are environmentally friendly, while individual trucks or loaders emit and stir pollutions along the entire transfer path.
Improved product quality. Conveyors eliminate the multiple handling of material, while preventing the compaction and contamination typically caused by trucks and/or loaders. Importantly, telescoping radial stacking conveyors eliminate segregation and material degradation by stockpiling in very thin lifts and spreading material evenly across the entire length of the pile. The stockpile remains uniform and desegregated even if the nature of the material changes.
Lower operating expense. Conveyors cut labour and training costs. They are not reliant upon humans. They require no breaks or shift changes, and will operate at maximum efficiency during every hour of operation, conveying at capacities ranging from a mere trickle to 30,000 tonnes per hour (on major overland systems). Trucks and loaders require operators and intensive, costly day-to-day maintenance. Plus, with a lifespan of more than 20 years, conveyors deliver a long-term savings benefit.
A limited inflationary effect. Luckily, rising fuel and energy prices have little effect on conveyor operating costs. Conveyors are not sensitive to fuel shortages. Consider that electricity costs are fairly stable compared to diesel prices ? and conveyors can move material during off-peak energy intervals.
To minimise costly truck and loader use, quarries are turning to highly automated, customised conveyor systems in record numbers. This trend is also prevalent at asphalt and concrete production sites where, most likely, aggregate material must be trucked in from some distance away. The demands placed upon today’s producers are dramatically different from that of just a decade ago, a factor that has changed the face of modern material handling within the processing facility, and from the pit to the point of use.
Eliminate Material Spillage
It is estimated that 85 per cent of conveyor maintenance is a result of fugitive material spillage material at transfer points. A transfer point is any point on the conveyor where material is loaded onto or unloaded from the conveyor, and the cost reductions from eliminating spillage at just a single transfer point are significant.
“Material spillage is a costly proposition in tonnes of lost material per year, additional labour for cleanup, significant safety risks, and excessive wear and damage to conveyor components caused by any resulting belt mistracking. Yet, material spillage is common to many operations due to a lack of good preventive maintenance,” says Lyle Hettver, customer service and support technician for Superior Industries, a US-based manufacturer of conveyor systems and components. He offers the following key tips toward eliminating spillage:
Reduce impact. Loading zone impact causes wear and damage to the conveyor belt, weakening the belt carcass. To reduce impact at transfer points, impact cradles can be positioned under the conveyor. Or, impact idlers may be used at a transfer point. These are troughing idlers that have rubber-cushioned rollers to absorb impact.
Load in the centre. Ideally, each transfer point should be designed to load the belt in the centre and at a uniform rate. Off-centre loading can be corrected by using systems such as deflectors, liners, baffles, screens, grizzly bars, or a curved loading chute – all of which are designed to consistently direct material flow onto the centre of the belt.
Maintain proper belt scraper tension. For effective cleaning, belt scrapers should be installed at the appropriate locations and at the proper angles. Since multiple belt cleaning systems are often factory-installed, operators need only concern themselves with maintaining accurate belt scraper tension and replacing worn scrapers. The majority of blade-to-belt cleaning systems feature some form of tensioning device, which should typically be checked or adjusted on a weekly basis. An improperly adjusted belt scraper will lead to material carryback, premature wear to components, and eventual spillage and belt mistracking headaches. When retensioning is required, the cleaner and tensioning unit should allow for easy access and maintenance, without the need for special tools or multiple service technicians. Tensioning instructions are often located on the side of the belt scraper manufacturer’s bracket.
Select and maintain proper skirtboards. Skirtboards are key to preventing material spillage in and around the loading zone ? from the moment that material leaves the loading chute and until it reaches belt speed. So skirting usually extends from the loading chute and along some distance of the conveyor. Skirting should make slight contact with the belt, and should be mounted close enough so that the gap can be sealed with flexible rubber or urethane strips. Multiple-layer edge seals (a primary seal against the chute wall and a secondary seal that lies on the belt surface outside the chute) are best as they can contain any escaping fines. Note that seal wear life is dependent upon minimising belt sag, which can allow material entrapment. Wear liners should be installed inside the chute to protect the sealing strips from the forces of the load. To prevent spillage and maintain skirting life, hoppers should be lined and/or checked for wear areas. Skirtboards, and loading and discharge chutes be selected and installed to match the characteristics of the material as well as the conveyor.
Maximise Idler Performance
It only takes one idler roll malfunction to delay material throughput or cause potential damage to costly belting. “Maximising idler performance is just one more way that producers can lower costs per tonne,” says Mike Domnick, component sales manager for Superior Industries. He offers the following simple tips on getting the most from idlers:
Access replacement rolls. The market is shifting toward the use of replacement/ retrofit rolls over the practice of discarding the entire idler. Typically, idler malfunction involves only one of three rolls ? and if producers choose to replace the entire idler due to time and labour factors, they are wasting 75 per cent of their investment. Everyone wants to minimise conveyor downtime and few want to move the belt out of the way to replace one roll. Consequently, many operations are choosing to replace rolls in the shop during maintenance hours. The task is far simpler than it used to be, made easier by new idler design innovations that streamline installation. Plus, growing replacement roll demand has resulted in the affordability of built-to-order retrofit rolls that fit any frame brand or type. The use of readily available, adaptable, and easily changeable replacement rolls will undoubtedly cut costs.
Pay attention to seal design. The heartbeat of an idler lies in the integrity of its seal and the protection of the bearings. Since an idler’s seal is typically its first fail point, it’s always best to closely scrutinise seal design. For example, current seal innovations may involve improved contact seals that result in less seal drag; triple labyrinth seals that increase the distance that contaminants must travel; and grease fills that easily trap contaminants.
Eliminate idler pinch points. Avoid premature roll failure by using idlers that have no pinch points between the end stand and the outside roll. Pinch points will allow foreign material to lodge within them, causing the roll to seize up.
Ensure adequate frame support. It’s critical to have extra idler frame strength and support where you most need it ? at loading and transfer points where forces and impact may cause frames to bend or twist. Consider the use of idlers with ‘flared’ end stands, which deliver added strength especially in applications with large material lumps or where material feed is sideways versus straight on.
At ConExpo 2008, notes Mr Domnick, Superior Industries introduced its new Moxie Rolls, an idler roll that promises durability and cuts operating costs. Designed with a specially formulated, high-density polyethylene (HDPE) material, Moxie Rolls were developed to solve expensive problems caused by abrasive material and buildup. “Also, they are manufactured with a seal system that is one of the best defenses against contaminants getting to the bearing. These new rolls produce low roll resistance, saving producers from extra horse power and out of pocket expenses,” he says, adding that they can be retrofit into any competitor’s idler frame or bracket.
Mr Domnick stresses that as the idler’s job is to support and protect the conveyor belt, it is a key component. “Certainly, knowledge of the factors that affect idler life will greatly aid in choosing the best idlers for one’s operation,” he says.
Contamination Control
Because producers demand improved efficiency and longer life from their hard-working wheel loaders, Caterpillar says it has designed its high-performance, low-emission models with advanced electro-hydraulic components and high-pressure fluid systems – designs that incorporate extremely tight tolerances. This makes them especially vulnerable to contamination that cannot be detected by the human eye. Contaminants can be introduced during assembly, when being serviced, or while on the job ? and they can impair machine performance and reduce component life. Microscopic particles suspended in the fuel can be particularly damaging to injectors and control valves, causing premature wear. Subsequently, engine power drops off, fuel consumption rises, emissions increase, and so too, the odds of a costly breakdown. Contaminants accelerate wear and shorten component life. Caterpillar reports that a three-year independent study of hydraulic systems found that some hydraulic components lasted up to 10 times longer with proper contamination control.
Preventing fluid system contamination is a big priority for Caterpillar, which has instituted effective and extensive contamination control programs within its factories and dealer locations, and at customer mine and quarry sites.
“As particulates build up on metal surfaces and impede hydraulic flow, system efficiency erodes. Even a skilled operator may not notice a drop in responsiveness until the system has lost nearly 20 per cent of its power,” says Carmen Rose, senior consultant with the Caterpillar Product Support Division. “With a reduction of that magnitude, you’d be getting just four days worth of production for every five days on the job,” Ms Rose adds.
Ms Rose explains that most manufacturers assess the cleanliness of their fluid systems by counting and measuring the particles present in the oil and comparing those results to an International Standards Organisation (ISO) code. An ISO contaminant code contains three numbers, but Caterpillar only uses the last two ? the first number refers to the number of six-micron and larger particles in a 1mm oil sample.
The second indicates the quantity of 14-micron and larger particles in that same sample. A rating of 21/17, for example, means that 1mm of oil contains up to 221 (about two million) particles that are six microns and larger, as well as 217 (130,000) particles 14 microns and larger. A 1mm oil sample that earns a 21/17 rating is equivalent to a 210-litre drum of oil contaminated with a half-teaspoon of very fine dust. “Although that’s considered ‘clean’ by ISO standards, it’s not acceptable for our new machines,” says Ms Rose. “In fact, if your machine meets the 21/17 standard ? and the hydraulic pumps operate at 120 litres per minute, eight hours a day, 200 days per year ? you are actually running more than 285 kilograms of dirt through the hydraulic system annually. By improving cleanliness to ISO 18/15, you can reduce the amount of dirt in your system to about 35 kilograms per year. Achieve a 16/13 rating, and the number drops to 10 kilograms,” she says.
Equipment owners should do their part in controlling contamination during maintenance. Ms Rose recommends the following maintenance practices:
? Control operating temperatures to reduce internal wear.
? Fix leaks immediately, as if oil is leaking out, particles are getting in.
? Replace worn seals without delay, as a bad seal makes a perfect entry point for dirt.
? Remove old filters carefully as they hold sludge that can fall back into
the system.
? Keep new filters packaged until they are ready for installation.
? Drain oil when it’s warm and agitated and make sure to drain the dirty fluid as thoroughly as possible.
? Use a filtered fluid transfer cart to add new oil.
? Enroll in an oil-analysis program. When collecting samples, use proper procedures and clean materials, and follow the recommendations you receive after your samples have been analysed.
Ms Rose also suggests owners find out what their dealers are doing to reduce the risk of contamination during service work.
?Also, learn more about your manufacturer’s commitment.
?A world-class company will not only operate clean facilities and ship clean products, but it will work in partnership with its dealers and customers to minimise contamination over the life cycle,? Ms Rose said.
?When all parties focus on contamination control, your equipment will deliver better performance and longer life ? at a lower cost,” she says.