Tag Archives: R Todd Swinderman

Controlling dust at mine conveyor belt discharge points

Bulk handling, Equipment maintenance, Mineral processing, Mining equipment, Mining services, , ,

The design and function of belt cleaners have come a long way. In the past, belt cleaners were rigid, linear pieces of hardware made out of various materials from brick to plastic that earned the name “scrapers” or “wipers” because that is what they did. They had a low operational life, broke or cracked frequently and contributed significantly to belt wear, Todd Swinderman, President Emeritus, Martin Engineering, says.

Modern primary cleaners are usually mounted at the head pulley and made from engineered polyurethane. This specially formulated material is forgiving to the belt and splice, but still highly effective for dislodging cargo, according to Swinderman. Typically supported by mechanical or pneumatic tensioners, the designs require significantly less monitoring and maintenance of blade tension.

Some primary cleaner designs require no tensioning at all after initial installation. The single primary cleaner strips feature a matrix of tungsten carbide scrapers installed diagonally to form a three-dimensional curve around the head pulley and typically delivers up to four times the service life of urethane cleaners without ever needing re-tensioning, he claims.

As conveyor speeds and cargo volumes increase to meet production demands, secondary belt scrapers are often installed immediately after the belt leaves the head pulley to address dust and fines that escape the primary cleaner. Generally equipped with spring or air tensioners that easily adjust to fluctuations in the belt, secondary cleaners are particularly efficient for applications that produce wet, tacky or dusty carryback, Swinderman says.

Some innovative secondary cleaners take a different approach from the standard secondary cleaner. They feature independent 6-in (152 mm) wide blades with carbide tips set on a stainless steel assembly. Each tip is supported on spring-loaded arms at both ends with a wide range of motion that provides equal load pressure across each blade and requires less tensioning over its lifespan. This design absorbs obstructions, responds to belt fluctuations and is able to arc safely in the event of a belt rollback.

Innovations in both blade design and tensioner engineering have improved cleaning ability, increased equipment life, reduced the need for tensioning and blade changes, and decreased labour for maintenance and clean up. Along with lowering the cost of operation, the most noticeable change is less dust along the belt path and in work areas. This improves employee morale and retention and results in better compliance, Swinderman concludes.

Safety pays with mining conveyor maintenance, Martin Engineering’s Swinderman says

Bulk handling, Equipment maintenance, Mining equipment, Mining maintenance, Mining services, , , ,

Conveyor safety is not a modern trend bred by government regulation, it’s a common-sense idea as old as the first conveyor design, R Todd Swinderman, CEO Emeritus, Martin Engineering, says.

In the modern age, safety is a key factor in worker protection, reduced insurance rates and a lower total cost of operation. There are several hurdles to the installation of safety equipment, the biggest of which is the near-universal use of the “Low Bid process”, he says.

“When companies buy on price (Low Bid) the benefits are short-lived and costs typically increase over time,” Swinderman says. “In contrast, when purchases are made based on lowest long-term cost (Life Cycle Cost), benefits usually continue to accrue and costs go down, resulting in a net savings over time. Safer and more reliable equipment is easier to service, has a longer life and is less expensive to maintain.”

Organisations that embrace safety show significant performance advantages over the competition, according to Swinderman. The proof is reflected in reduced injuries and greater productivity, along with above industry average financial returns and higher share prices.

Justifying safety investments is greatly enhanced by quantifying what most financial managers refer to as “intangible costs”, ie injuries, lost labour, insurance, morale, legal settlements, etc. However, managers and accountants have been trained to think about saving direct costs to justify investments, Swinderman says.

When conveyors don’t operate efficiently they have unplanned stoppages, release large quantities of fugitive materials and require more maintenance. Emergency breakdowns, cleaning of excessive spillage and reactive maintenance all contribute to an unsafe workplace.

Safety pays

Numerous case studies revealing the positive relationships between safety and productivity are backed up by organisations that gather global statistics on accidents and incidents. The simple formula for return on investment (dividing savings by cost) does not capture the potential savings from safety investments, according to Swinderman. Several organisations provide detailed and regional statistics on the cost of accidents.

Regional statistics on costs of accidents

Lacking specific historical data, managers can turn to numerous reliable sources that provide the probability of incidents that can be used to estimate tangible and intangible future costs.

Accident rates per 100,000 industrial workers per year

The financial technique used to compare options is a “net present value” (NPV) analysis. NPV compares different investment options with varying costs and savings (cash flows) over time, discounting them by the company’s cost of money.

Swinderman explained: “For example, an internal risk analysis shows a facility has 30 workers exposed to conveyor hazards. The estimated probability of the different classes of accidents (fatal, lost time and first aid) is multiplied by the cost of these accidents to reveal what could be invested to reduce the incident rate by half.”

Estimated total annual cost for all accidents

Assuming the life of the conveyor is 20 years and the cost of money (discount rate) is 5%, the available additional investment would be about $750,000 more in design time to accomplish the 50% improvement in safety, he says. By choosing the lowest-priced bid to meet the minimum safety requirements, the short-term expenditure ends up costing considerably more over the 20-year lifecycle.

Annual accident costs for years 1 to 20

By spending $750,000 more to exceed the minimum safety and design requirements and reduce the accident rates by 50%, the annual projected cost of accidents drops from $140,813 to $70,407, Swinderman says.

Measured in today’s dollars – including the additional investment of $750,000 – the projected savings over the 20-year term at 5% are about $1.2 million by investing more upfront.

Swinderman concluded: “If, after further analysis, the savings are found to be less – perhaps only a 25% reduction in the cost of accidents – the upfront investment is still justified over the long term. Even though it takes a little more effort to collect data and do a financial analysis, in the end, NPV consistently proves that safety does indeed pay.”

Conveyor technology: designing for the future by innovating the present

Automation, Bulk handling, Equipment maintenance, Mining equipment, Mining maintenance, Mining services, , ,

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, R Todd Swinderman, CEO Emeritus of Martin Engineering, writes*.

As conveyor systems become wider, faster and 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 (ROI).

Safety at higher belt speeds

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 workplace 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 workplace 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 belt path. Caused by uncentred cargo, seized idlers or other reasons, the belt can rapidly come in contact with the mainframe, shredding the edge and potentially causing a friction fire. Beyond the workplace safety consequences, the belt can convey a fire throughout the facility at extremely high speed.

When a conveyor isn’t centre-loaded, the cargo weight pushes the belt toward the more lightly-loaded side

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 detect slight 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 70 to 150 ft (21-50 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 sensing arm assembly that detects slight variations in the belt path and immediately adjusts a single flat rubber idler to bring the belt back into alignment.

The pivoting ribbed roller design grabs the belt and uses the opposing force to shift it back into alignment

Modern chute design

To drive down the cost per tonne of conveyed material, many industries are moving toward wider and faster conveyors. The traditional troughed design will likely remain a standard. But with the push toward wider and higher-speed belts, bulk handlers will need substantial development in more reliable components, such as idlers, impact beds and chutes.

A major issue with most standard chute designs is that they are not engineered to manage escalating production demands. Bulk material unloading from a transfer chute onto a fast-moving belt can shift the flow of material in the chute, resulting in off-centre loading, increasing fugitive material spillage and emitting dust well after leaving the settling zone.

Newer transfer chute designs aid in centring material onto the belt in a well-sealed environment that maximises throughput, limits spillage, reduces fugitive dust and minimises common workplace injury hazards. Rather than material falling with high impact directly onto the belt, the cargo’s descent is controlled to promote belt health and extend the life of the impact bed and idlers by limiting the force of the cargo at the loading zone. Reduced turbulence is easier on the wear liner and skirting and lowers the chance of fugitive material being caught between the skirt and belt, which can cause friction damage and belt fraying.

Longer and taller than previous designs, modular stilling zones allow cargo time to settle, providing more space and time for air to slow down, so dust settles more completely. Modular designs easily accommodate future capacity modifications. An external wear liner can be changed from outside of the chute, rather than requiring dangerous chute entry as in previous designs. Chute covers with internal dust curtains control airflow down the length of the chute, allowing dust to agglomerate on the curtains and eventually fall back onto the belt in larger clumps. And dual-skirt sealing systems have a primary and secondary seal in a two-sided elastomer strip that helps prevent spillage and dust from escaping from the sides of the chute.

Modern stilling zones feature components designed to reduce maintenance and improve safety

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 on site 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 for dislodging carry back. For the heaviest applications, one primary cleaner design features a matrix of tungsten carbide scrapers installed diagonally to form a 3D curve around the head pulley. Field service has determined that it typically delivers up to four times the service life of urethane primary cleaners, without ever needing re-tensioning.

Taking belt cleaner technology into the future, an automated system increases blade life 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. Additionally, it reduces labour for the constant monitoring and tensioning of blades to ensure peak performance. The result is consistently correct blade tension, reliable cleaning performance and longer blade life, all managed without operator intervention.

Power generation

Systems designed to operate at high speeds over considerable distances are generally powered only at vital locations such as the head pulley, disregarding adequate power for autonomous ‘smart systems’, sensors, lights, accessories or other devices along the length of the conveyor. Running auxiliary power can be complicated and costly, requiring transformers, conduits, junction boxes and oversized cables to accommodate the inevitable voltage drop over long runs. Solar and wind can be unreliable in some environments, particularly in mines, so operators require alternative means of reliable power generation.

By attaching a patented mini-generator to idlers and using the kinetic energy created by the moving belt, the accessibility obstacles found in powering ancillary systems can now be overcome. Designed to be self-contained power stations that are retrofitted onto existing idler support structures, these generators can be employed on virtually any steel roller.

The design employs a magnetic coupling that attaches a “drive dog” to the end of an existing roller, matching the outside diameter. Rotated by the movement of the belt, the drive dog engages the generator through the outer housing’s machined drive tabs. The magnetic attachment ensures that electrical or mechanical overload does not force the roll to stop; instead, the magnets disengage from the roll face. By placing the generator outside the material path, the innovative new design avoids the damaging effects of heavy loads and fugitive material.

Bulk handling, safety and automation in the future

Automation is the way of the future, but as experienced maintenance personnel retire, younger workers entering the market will face unique challenges, with safety and maintenance skills becoming more sophisticated and essential. While still requiring basic mechanical knowledge, new maintenance personnel will also need more advanced technical understanding. This division of work requirements will make it difficult to find people with multiple skill sets, driving operators to outsource some specialised service and making maintenance contracts more common.

Conveyor monitoring tied to safety and predictive maintenance will become increasingly reliable and widespread, allowing conveyors to autonomously operate and predict maintenance needs. Eventually, specialised autonomous agents (robots, drones, etc) will take over some of the dangerous tasks, particularly in underground mining as the ROI for safety provides additional justification.

Ultimately, moving large quantities of bulk materials inexpensively and safely will result in the development of many new and higher capacity semi-automated bulk transfer sites. Previously fed by truck, train or barge, long overland conveyors transporting materials from the mine or quarry site to storage or processing facilities may even impact the transportation sector. Stretching vast distances, these long bulk handling networks have already been built in some places with low accessibility but may soon be commonplace in many areas around the world.

*This story was written by R Todd Swinderman, CEO Emeritus of Martin Engineering