CONVEYOR TECHNOLOGY DESIGNING FOR THE FUTURE BY INNOVATING THE PRESENT

Higher production demands across all bulk handling segments require increased efficiency at the lowest cost of operation, in the safest and most effective manner possible. As conveyor systems become wider, fasterand longer, more energy output and more controlled throughput will be needed. Add an increasingly stringent regulatory environment, and cost-conscious plant managers must closely review which new equipment and design options align with their long-term goals for the best return on investment.

Safety is likely to become a new source of cost reduction. The percentage of mines and processing facilities with a robust safety culture are likely to increase over the next 30 years to the point where it is the norm, not the exception. In most cases, with only a marginal adjustment to the belt speed, operators quickly discover unanticipated problems in existing equipment and work place safety. These problems are commonly indicated by a larger volume of spillage, increased dust emissions, belt misalignment and more frequent equipment wear/failures.

Higher volumes of cargo on the belt can produce more spillage and fugitive material around the system, which can pose a tripping hazard. According to the US Occupational Safety and Health Administration (OSHA), slips, trips and falls account for 15% of all workplace deaths and 25% of all work place injury claims. Moreover, higher belt speeds make pinch and sheer points in the conveyor more dangerous, as reaction times are drastically reduced when a worker gets clothing, a tool or a limb caught from incidental contact.

The faster the belt, the quicker it can wander off its path and the harder it is for a belt tracker to compensate, leading to spillage along the entire beltpath. Caused by uncentred cargo, seized idlers or other reasons, the belt can rapidly come in contact with the main frame, shredding the edge and potentially causing a friction fire. Beyond the work place safety consequences, the belt can convey a fire throughout the facility at extremely high speed.

Another workplace hazard – one that is becoming progressively more regulated – is dust emissions. An increase in the volume of cargo means greater weight at higher belt speeds, causing more vibration on the system and leading to reduced air quality from dust. In addition, cleaning blade efficiency tends to decline as volumes rise, causing more fugitive emissions during the belt’s return. Abrasive particulates can foul rolling components and cause them to seize, raising the possibility of a friction fire and increasing maintenance costs and downtime. Further, lower air quality can result in fines and forced stoppages by inspectors.

Correcting misalignment before it happens

As belts get longer and faster, modern tracking technology becomes mandatory, with the ability to detects light variations in the belt’s trajectory and quickly compensate before the weight, speed and force of the drift can overcome the tracker.

Typically mounted on the return and carry sides every 21 to 50 m – prior to the discharge pulley on the carry side and the tail pulley on the return – new upper and lower trackers utilise innovative multiple pivot, torque-multiplying technology with a sensingarm assembly that detects slight variations in the beltpath and immediately adjusts a single flat rubber idler to bring the belt back into alignment.

Case study

The conveyor belt at one of the major mining plant in India, was experiencing serious tracking issues, which caused damage to the belt and structural components, as well as spillage along the conveyor path. Operators had been using self-aligning idlers from a local manufacturer, but were unable to effectively control the belt wander. The company needed to correct the issue to avoid further damage and minimize fugitive material.

BEFORE Martin Tracking system: The mis-tracking problem caused belt damage and material spillage along the conveyor path. In some places the belt was so far off-center that it damaged structural components.

Martin Engineering technicians performed an audit on the conveyor and recommended four Martin® EVO® Trackers™ on the carrying side and five on the return side to stabilize the lengthy run. Rollers attached to the end of a sensing arm assembly ride both sides of the belt edge, detecting even slight variations in the belt path. Employing the force of the wandering belt, the arms automatically position a steering idler in the opposite direction of the misalignment. Transferring the motion to the steering idler through a unique parallel linkage requires less force to initiate the correction, so fine-tuning of the path can be continuous, active and precise.

Utilizing a troughed idler support system on the carrying side of the conveyor to retain the proper angle and keep the load centered, the Belt Tracker Upper Unit employs guide rolls that are mounted just one-quarter inch (6 mm) from the belt for high precision when making opposing adjustments to the idlers. Belt Tracker Lower Units are hung from the mainframe under the return belt and use a single flat rubber idler to bring the belt back into alignment. The customer reports that the belt is now properly centered, and the results have been so positive that the company is planning to install additional Martin Trackers on its other conveyors.

Rethinking belt cleaning

Faster belt speeds can also cause higher operating temperatures and increased degradation of cleaner blades. Larger volumes of cargo approaching at a high velocity hit primary blades with greater force, causing some designs to wear quickly and leading to more carry back and increased spillage and dust. In an attempt to compensate for lower equipment life, manufacturers may reduce the cost of belt cleaners, but this is an unsustainable solution that doesn’t eliminate the additional downtime associated with cleaner servicing and regular blade changes.

As some blade manufacturers struggle to keep up with changing production demands, industry leaders in conveyor solutions have reinvented the cleaner industry by offering heavy-duty engineered polyurethane blades made to order and cut onsite to ensure the freshest and longest lasting product. Using a twist, spring or pneumatic tensioner, the primary cleaners are forgiving to the belt and splice but are still highly effective ford is lodging carryback. For the heaviest applications, one primary cleaner design features a matrix of tungsten carbide scrapers installed diagonally to form a three-dimensional curve around the head pulley. Field service has determined that it typically delivers up to 4xthe service life of urethane primary cleaners, without ever needing re-tensioning. Taking belt cleaner technology into the future, an automated system increases bladelife and belt health by removing blade contact with the belt any time the conveyor is running empty. Connected to a compressed air system, pneumatic tensioners are equipped with sensors that detect when the belt no longer has cargo and automatically backs the blade away, minimising unnecessary wear to both the belt and cleaner.

Case study

One of the key mining sector companies in India was experiencing excessive carryback and spillage on four coal handling conveyors transporting 1500 tonnes (1653 tons) of cargo per hour.  Operators noticed that inadequate belt cleaning left material clinging to the belt, which caused carry back to drop spillage along the entire belt path.  This resulted in piling around the structure, obstructing access and creating a trip hazard.  Fines would also clog equipment, leading to premature failure and replacement.  In addition to the safety issues, the cost of operation increased through added labor for cleanup, product loss, excessive maintenance and reduced equipment life.  To improve efficiency, managers sought a solution.

The Martin Engineering India team visited the site and performed a Walk the Belt assessment, followed by installation of Martin CleanScrape Primary Belt Cleaners on all 4 conveyors.  The units are installed diagonally across the discharge pulley, forming a 3-dimensional curve beneath the discharge area that conforms to the pulley’s shape.  Designed for the heaviest applications, the design features a matrix of rugged tungsten carbide scrapers.  The Clean Scrape Cleaner protects the belt with its specific application of low force and is ideally suited for both slow and fast conveyor belts, including those with mechanical splices.  Field service has determined that it typically delivers up to 4x the service life of urethane primary cleaners.

A year after installation, the cleaners have removed carryback and improved safety significantly.  With the drastic reduction in spillage, the amount of material piling in walkways and fouling equipment has been nearly eliminated.  Reduced cleaning and maintenance, as well as minimized product loss, have lowered the cost of operation. After one initial tensioning, the blade requires no further adjustment. Downtime to replace seized idlers and other components has dropped considerably, and the small footprint is well suited to the confined space.

Images: Copyright 2022 Martin Engineering

– R. Todd Swinderman

CEO Emeritus of Martin Engineering

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