Tag Archives: Martin Engineering

Martin Engineering air cannon tech keeps the fines flowing at Lundin’s Eagle mine

Martin Engineering, a leader in industrial bulk handling, has helped Lundin Mining’s Eagle Mine in Michigan’s Upper Peninsula with clogging and downtime issues, resolving these problems and improving material flow with powerful and compact air cannon technology.

Martin Engineering installed the cannons in a chute carrying damp fines through the refining process at Eagle, with the cannons mitigating blockages and facilitating the movement of material. The result was improved safety, reduced labour costs, greater production, less downtime and a calculated circa-1,000% saving to the cost of operation over existing solutions.

“Safety is a top priority for us,” Ted Lakomowski, Lead Reliability Technician at Eagle Mine, said. “When we experienced clogging and downtime at the processing mill, our crew naturally swung into action to resolve it, but we immediately sought a safer long-term solution.”

Eagle Mine is the only primary nickel mine in the USA, producing 1.5% of the world’s total nickel production. The company extracts approximately 2,000 t/d from the underground nickel-copper mine using a bench-and-fill stoping process. Ore from the mine is stored in a covered coarse stockpile facility prior to transport to the Humboldt Mill. A former iron ore processing plant, the Humboldt facility’s three-stage crushing circuit reduces the material to 3/8 in-minus (9.5 mm-minus), then a single stage ball mill grinds it further and it is mixed into a slurry.

To liberate the nickel and other minerals from the waste materials, a refining process of selective flotation is used. During the crushing process, a mesh screen separates the fines from the remaining aggregate, which are fed back through the process. Fines that pass through a screen fall into a wide-mouthed hopper, leading to a chute that narrows to approximately 2.5-m wide by 0.6-m high and – after a dead drop of several feet – slopes in a circa-45º of decline. This slope slowed the descent of the fine material for a low impact and centred discharge onto a conveyor belt leading to the ore bins. Material buildup began at the hopper and at the discharge slope, but could also occur at virtually any point, blocking the chute, according to Martin Engineering.

Such accumulation would stop the entire crushing process approximately three-to-four times per shift for as long as an hour, blocking input of material all the way back to the ore storage area. Workers attacked the clog with 4.5-m long air lances from the top of the hopper and bottom of the chute. The method used a tremendous amount of compressed air and diverted manpower from other essential duties. Moreover, air lances caused excessive splash-back of wet material, which was extremely messy and potentially hazardous.

Eagle first installed a polymer lining in the chute. Offering a low coefficient of friction, the lining was bolted to the chute wall and acted like a smooth slide for the material to ride down. Less effective against the adherent qualities of the material than hoped, Eagle next installed pneumatic vibrators onto the vessel wall, intended to agitate the adhered material and promote its descent down the chute slope. But the fact that the polymer lining was bolted to the vessel caused it to dampen the vibration of the units, limiting the force to only the impact zone and not much farther.

“We were forced to default back to air lances, but kept on looking for a better solution,” Lakomowski explained. “Having worked with Martin Engineering in the past, we asked them to come in, examine the issue and offer a safe, effective and affordable solution.”

Lakomowski advocated for the initial installation of five 35 litre Martin® Hurricane Air Cannons, followed by two more placed in essential spots in the chute. One unit was placed at the area where material discharged into the hopper, two others were positioned at the hopper slope where the most accumulation was observed and two more were placed along the drop chute. All of the tanks were accompanied by a 101 mm pipe assembly ending in fan jet nozzles.

Offering more force output than designs double their size with considerably less air consumption, the compact air cannon tanks measure only 406 mm in diameter 633-mm long, weighing 35 kg each, Martin Engineering says. The units fire a shot of air at up to 120 psi (8.27 bar) through the pipe assembly to a fan jet nozzle. The nozzle spreads the air stream 304 mm at the exit point, distributing the blast pattern across the surface of the wall.

Operating on a regular firing schedule of every 1-10 minutes – readjusted for production volume, time of year and moisture level – revealed the seven-cannon configuration reduced clogging issues and downtime, according to the company. This significantly lowered the risk to operators and reduced the cost of operation.

“When I did the cost assessment, I was surprised to discover that there was a 1,000% compressed air savings in using the air cannons over the air lances,” Lakomowski said. “It’s a significantly lower effect on our system than initially predicted, and managers are very happy about that.”

The project also improved safety, as workers spent less time diverted from other assignments to use air lances or create vibration by beating on the vessel walls, Martin Engineering said. By being able to perform maintenance on wear parts like valves from the outside of the cannon without tank removal, upkeep can be safely performed by a single technician with no heavy lifting involved, it added.

“Just from a safety aspect, this solution has paid for itself,” Lakomowski concluded. “The Martin Engineering team was easy to work with, and they were cognisant of our budget restrictions. Overall, this was a successful project.”

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

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.”

Martin Engineering cleans up conveyor operations with DT2S, DT2H

Martin Engineering, a leader in bulk material handling technologies and training, has announced the availability of two rugged secondary conveyor belt cleaners, both engineered for fast and easy maintenance.

The innovative design of the DT2S and DT2H reversible cleaners from Martin Engineering reduces system downtime and labour for clean up or service, while helping to prolong the service life of other conveyor components, the company says.

The models feature a unique split-track blade cartridge that slides in and out on a stainless steel mandrel, meaning the cleaners can be serviced or replaced without stopping the belt when on-site safety approvals are in place, Martin Engineering claims.

Dave Mueller, Conveyor Products Manager for Martin Engineering, says: “Even when the cleaner is encrusted with material, one half of the split frame can be removed so the cartridge can be changed in just five minutes. This allows users to have a spare cartridge on hand and quickly change it out when the blades need replacement. Then they can take the used cartridge back to the shop, clean it up and change the blades so it’s ready for the next service.

These secondary cleaners serve a wide variety of applications, including miningBoth products significantly reduce material carryback, and arr engineered to accommodate reversing conveyors to avoid damage to the belt or splicing, the company says. With steel blades and tungsten carbide tips set into a flexible base, the DT2 cleaners offer simple, effective solutions that can solve a number of carryback-related problems.

Martin DT2H Reversing Cleaner XHD

Designed for particularly demanding conditions, the DT2H Reversing Cleaner XHD is suited for heavy material loads on belts ranging from 400 to 2,400 mm wide that operate at speeds up to 6.1 m/s. 

The company explains: “Carryback accumulations along the return run of the conveyor can occur when the cleaning systems on a conveyor fail to remove most of the material that adheres to the belt after unloading its cargo. Increased build up results in unnecessary labour costs for clean up, and can lead to premature failure of conveyor components if left unchecked.”

Mueller said: Carryback can have an extremely sticky texture and abrasive nature, which can muck up conveyor components and contribute to premature failure. One key to the success of these cleaners is the blade’s negative rake angle (less than 90 degrees). With a negative angle, you get a ‘scraping’ action that mitigates potential belt damage, while delivering outstanding cleaning performance.”

Martin DT2S Reversing Cleaner

Like its larger counterpart, the Martin DT2S reversing cleaner can be installed on belts ranging from 400 to 4,800 mm wide. But, unlike the DT2H, the DT2S is designed for a lower maximum belt speed of 4.6m/s on belts with vulcanised splices. Mueller pointed out that this is primarily due to the difference in applications:The DT2S has a slim frame that allows it to fit in spaces as narrow as 7 in (178 mm). As a result, the DT2S can be attached to belts that may be too small for primary cleaners.”

Both of the DT2 cleaners can be used in medium- to heavy-duty environments, providing a lasting solution to a diverse array of complex problems that are caused by carryback and minimising  fugitive material, the company says.

Pueblo Viejo case study

An example of the cleaners’ performance can be found at the Pueblo Viejo Dominicana Corporation (PVDC) mine in the province of Sanchez Ramirez, about 89 km northwest of the city of Santo Domingo in the Dominican Republic. Operators at the operation, majority owned by Barrick, were experiencing excessive carryback and dust on its conveyor systemresulting in expensive equipment failures, unscheduled downtime and increased maintenance. Production is 365 d/y, but, between April and October, moisture can cause cohesion in fine clay particles, causing the cargo to become sticky. The substance had the consistency of thick toothpaste, which was also able to adhere small chunks of aggregate to the belt, causing destructive carryback that damaged pulleys and headers.

In just two weeks, Martin Engineering technicians replaced the existing belt scrapers at 16 locations with Martin QC1 Cleaner XHD primary cleaners fitted with low-adhesion urethane blades specifically designed for tacky material loads, along with DT2H secondary cleaners. The secondary cleaner blades can endure hot summer temperatures, high moisture content and constant production schedules, according to the company.

Following the upgrades, operations are now cleaner, saferand more productive, giving executives and stakeholders more confidence in the sustained operation of the mine, which is projected to be profitable for the next 25 years or more.  

Martin Engineering on ‘carryback’ issues with conveyors

“Carryback” is defined as the material that fails to unload from a conveyor belt, adhering to the belt and typically falling off at some point other than the intended discharge, and it’s one of the main sources of fugitive materials, estimated to account for 85% of all conveyor maintenance issues, according to Martin Engineering.

Accumulation on moving components from dirty belts can cause premature wear and require frequent cleanup, which exposes workers to potential workplace injuries and respiratory diseases, it warns.

It can be shown practically and theoretically that a conveyor belt cannot be cleaned 100% because the surface of the belt and the blades are not without imperfections. However, this does not do away with the need for operators to take a proactive approach to keeping the belt clean. Most industries have gravitated to basic mechanical scraping with a metal or elastomeric blade for flat rubber or PVC belting as the best combination of effectiveness, ease of maintenance and low belt wear to yield the lowest cost of ownership.

Belt cleaning effectiveness varies day to day with changing conditions and the number and type of cleaners applied, as well as the maintenance they receive. Keeping the material in the process is always better than letting it accumulate on components and build up under the conveyor. Without effective belt cleaning, experience has shown that as much as 3% of the total cargo can be lost due to spillage, dust and carryback.

The exposure to hazards and injuries is also reduced when less cleanup is required, saving significant – but seldom considered – indirect costs. The key to consistent cleaning effectiveness is to control the process through proper selection, installation, inspection and maintenance of the belt cleaning system and establish a safe cleanup routine and schedule.

The use of multiple mechanical scrapers on a belt has been accepted for quite some time as an effective cleaning approach. In most operations, multiple cleaners are required to reduce the carryback to a safe, acceptable level while limiting manual cleanup to weekly or even monthly tasks.

Effectiveness vs efficiency

The undulating action of the loaded belt passing over idlers tends to cause fines and moisture to migrate and compact on the surface of the belt. The amount of carryback that clings to the belt can range from a few grams to a few kilograms per square meter. The level of belt cleaning required is a function of the operational schedule and method of collecting/disposing of the carryback that is cleaned from the belt or dislodged by return idlers and collects outside of the conveyor discharge chute.

When discussing the efficiency of a belt cleaner, it’s meaningless to talk about efficiency without stating the initial level of carryback. When considering the beginning and ending levels of carryback as a measure of improvement, effectiveness is a better term. Some guidelines do exist. The US Bureau of Mines states that an average of 100 g/sq.m of carryback is a reasonable level of performance for belt cleaning. At this level, a 1,200-mm wide belt traveling 2 m/s and operating 24/7 would create a cleanup workload of about 7 t/d, a significant labour investment that also increases worker exposure to a moving conveyor and the associated risks.

Carryback level determines the cleanup schedule, but, in reality, a typical belt cleaner loses effectiveness over time due to wear, lack of inspection and maintenance. On systems with average or poor maintenance, effectiveness values are generally in the range of 40-60%, thus the need for multiple cleaners.

Cleaning location

Unfortunately, designers often focus on the lowest installed cost of the structure around the head and snub pulleys, without allowing enough space for optimum cleaner installation. The figure below shows the clear areas needed on a discharge chute for installation of belt cleaners in the optimum positions. The installations should be at an ergonomic height above the work platform to encourage proper inspection and service. Consideration in the design stage for locating cleaners in the optimum locations will lead to more effective inspections, maintenance and belt cleaner performance.

Belt cleaning positions (© 2022 Martin Engineering)

Belt cleaners can be placed anywhere along the return run of the belt, as long as the belt is supported in some fashion. Since it’s desirable for the carryback cleaned from the belt to be returned to the main material flow, most belt cleaners are installed inside the discharge chute. Cleaning on the head pulley – labeled the ‘primary cleaning position’ – is preferred. Cleaning the dirty side of the belt before it reaches a snub, bend pulley or return idlers is considered less desirable, requiring a dribble chute for cleaners in the secondary position.

Typical installation of primary, secondary and tertiary cleaners (© 2022 Martin Engineering)

The secondary position is complicated by another fact: the nature of carryback is such that it can adhere to vertical surfaces and not flow down a sloped dribble chute. A tertiary position is sometimes required for difficult materials or critical applications such as conveying over wetlands. In such cases, the tertiary cleaners are often enclosed in a spray box and the effluent directed to a settling basin.

Belt cleaning pressure & blade wear

Without enough cleaning pressure, the blade cannot stay in contact with the belt, resulting in poor carryback removal effectiveness and increased blade and belt wear. With too much cleaning pressure, the cleaning performance declines due to deflection of the elastomeric blade or metal blade indentation into the rubber belt. Power consumption also increases dramatically with excessive cleaning pressure.

Elastomeric primary blade pressure at a positive rake angle (left) and metal secondary blade pressure at zero rake angle (right)

Keeping a belt cleaner properly tensioned is critical for maximum effectiveness and lowest cost of ownership. The cleaning pressure usually varies over time, based on the maintenance department’s attention or lack thereof. Some manufacturers have begun to offer automatic tensioners and wear indicators which maintain the optimum cleaning pressure and alert operators when blades are worn.

Automatic tensioner maintains optimum cleaning pressure without operator intervention (© 2022 Martin Engineering)

Conclusion

Many belt cleaner systems are installed and forgotten. A survey of technicians indicated that about 25% of all belts have cleaners installed, and of that percentage only about 25% are properly maintained. Lack of inspection and maintenance results in a gradually lower level of effectiveness, higher operating cost and an increased exposure to the hazards associated with cleaning up carryback.

Effective belt cleaning starts in the design stage, with adequate space for cleaners and well-positioned work platforms for ergonomic inspection and maintenance access. Service-friendly designs improve production, minimising carryback and prolonging the life of equipment. If the cleaners are located in the optimum positions and easy to access, it is more likely that regular inspection, cleaning and maintenance will be performed, delivering optimum results.

Martin Engineering compiles conveyor operation, safety educational resource

Martin Engineering, a leader in conveyor accessories and bulk material handling solutions, has launched what it says is a comprehensive digital educational resource for conveyor operation and safety.

The online Foundations™ Learning Center draws from the collective knowledge and expertise gathered over nearly 80 years solving bulk handling challenges. Aimed at apprentice technicians and experienced engineers alike, the non-commercial information is offered at no charge and is accessible by computer, tablet, or smartphone.

An extension of the Foundations training curriculum, the Learning Center uses a mix of text, photos, videos, webinars, online events, and live experts available to answer questions. The result is a unique central hub for industry professionals of all knowledge levels to use as a resource for building a deep understanding of material flow and safe, efficient conveyor operation, Martin Engineering says.

Not everyone learns by reading a textbook or following a lecture, so we set up the Learning Center as the place to go for all things conveyor and bulk handling for all types of learners,” Jerad Heitzler, Foundations Training Manager and curator of the Learning Center, said. “Technology allows us to accommodate different learning styles by offering several avenues to the same knowledge. The centre is designed in categories to provide easy access to the resources and organised so that people can find what they need quickly.”

The Learning Center is an online portal where plant operators, managers, and supervisors can send members of their teams to build their understanding of every aspect of conveyor operation and safety practices. The platform provides visitors with immediate solutions that are applicable and actionable, regardless of the equipment manufacturer. It is also a place to learn about the latest technologies, techniques, and compliance measures.

Building from its comprehensive training resources Foundations, The Practical Resource for Cleaner, Safer, More Productive Dust & Material Control and Foundations for Conveyor Safety, the Learning Center has been modelled on decades of knowledge from Martin’s experienced team of engineers and field technicians in every corner of the bulk materials handling industry. To start with, the creators have focused on the basics of conveyor operation and safety, with more advanced subject matter being added regularly.

The Learning Center resources supplement and enhance Martin Engineering’s extensive Foundations training program. The in-person training program combines the hands-on instruction and personal attention found in a classroom setting with the Learning Center technology, the textbook, and comprehension testing.

The modules of the Learning Center are split into nine categories:

  1. Material carryback & belt cleaning
  2. Dust management
  3. Material spillage
  4. Belt conveyor safety
  5. Conveyor belt & component damage
  6. Conveyor belt mistracking
  7. Material flow problems
  8. Belt conveyor system maintenance
  9. Basics of belt conveyor systems
Once the category is chosen, the learner is greeted with the core issues related to the module and examples of best practicesVideo overviews are immediately available to introduce the subject. The navigation bar to the right of each module page provides a detailed walkthrough of the subject from beginning to end with text information, topical webinars, videos and related articles.
“Our goal is comprehension and retention,” Heitzler pointed out. “Visitors might be pressed for time or may become distracted. While an experienced live instructor can see that and overcome it in a face-to-face training session, online learning is a different animal. So by providing visitors with options for learning and ways to break up the information rather than hours of reading or long videos, we’re able to better engage them, improving their experience and their learning.”

Once the Learning Center has been fully explored, users should have the foundation needed to operate belt conveyors safely and effectively. If managers choose, they can refer their employees to the Learning Center to gain professional development credits toward their certification to become qualified as maintenance technicians, operators, foremen, millwrights/fitters and so on.

The feedback from people who have already used the Learning Center has been excellent, according to the company. Users find it informative, easy to use, engaging, and an overall enjoyable experience. Managers and supervisors say they like having a trustworthy and cost-effective source for quick, unbiased information.  

“Of course, nothing replaces hands-on training and on-the-job experience, so that’s why the training system is called Foundations,” Heitzler said. “We provide the basic knowledge needed to work safely and efficiently in a platform that they can easily access when they need it.”

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, 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

Martin Engineering on resolving bulk material handling issues with flow aids

In order to achieve controlled and consistent flow on conveyors handling large volumes of bulk material, transfer chutes and vessels must be designed not just to accommodate – but to actually facilitate – the flow of the cargo they will be handling.

Unfortunately, because so many conditions can hamper effective cargo flow, engineering a conveyor and chutework that would handle every material situation is virtually impossible.

Even modest changes in moisture content can cause adhesion to chute or vessel walls or agglomeration at low temperatures, especially if the belt is stagnant for any period of time. Even during continuous operation, a bulk material can become compressed, and physical properties often change due to natural variations in the source deposits, suppliers or specifications, or if the material has been in storage. If left to build up, material can encapsulate belt cleaners and deposit harmful carry-back onto the return side, fouling idlers and pulleys, according to Martin Engineering. At worst, systems can become completely blocked by relatively small (and common) changes. To overcome these issues, a variety of devices collectively known as flow aids can be employed.

What Are Flow Aids?

As the term implies, flow aids are components or systems installed to promote the transport of materials through a chute or vessel, controlling dust and spillage. Flow aids come in a variety of forms, including rotary and linear vibrators, high- and low-pressure air cannons and aeration devices, as well as low-friction linings and special chute designs to promote the efficient flow of bulk materials. These modular systems can be combined in any number of ways to complement one another and improve performance. The components can be used for virtually any bulk material or environment, including hazardous duty and temperature extremes. One of the primary advantages is that an operation can obtain a level of control over the material flow that is not possible any other way.

When employing flow aids, it is critical that the chute and support components are sound and the flow aid be properly sized and mounted, because the operation of these devices can create potentially damaging stress on the structure, the company says. A properly designed and maintained chute will not be damaged by the addition of correctly sized and mounted flow aids.

It is also important that any flow aid device be used only when discharges are open and material can flow as intended. The best practice is to use flow aids as a preventive solution to be controlled by timers or sensors to avoid material build-up, rather than waiting until material accumulates and restricts the flow. Using flow aid devices in a preventive mode improves safety and saves energy, since flow aids can be programmed to run only as needed to control buildup and clogging.

Air cannons

One solution for managing material accumulation in chutes and vessels is the low-pressure air cannon, originally developed and patented by Martin Engineering in 1974. Also known as an “air blaster”, it uses a plant’s compressed air to deliver an abrupt discharge to dislodge the buildup. Cannons can be mounted on metallic, concrete, wood or rubber surfaces. The basic components include an air reservoir, fast-acting valve with trigger mechanism and a nozzle to distribute the air in the desired pattern to most effectively clear the accumulation.

The device performs work when compressed air (or some other inert gas) in the tank is suddenly released by the valve and directed through an engineered nozzle, which is strategically positioned in the chute, tower, duct, cyclone or other location. Often installed in a series and precisely sequenced for maximum effect, the network can be timed to best suit individual process conditions or material characteristics. The air blasts help break down material accumulations and clear blocked pathways, allowing solids and/or gases to resume normal flow. In order to customize the air cannon installation to the service environment, specific air blast characteristics can be achieved by manipulating the operating pressure, tank volume, valve design and nozzle shape.

In the past, when material accumulation problems became an issue, processors would have to either limp along until the next scheduled shutdown or endure expensive downtime to install an air cannon network. That could cost a business hundreds of thousands of dollars per day in lost production. Many designers proactively include the mountings in new designs so that future retrofit can be done without hot work permits or extended downtime. A new technology has even been developed for installing air cannons in high-temperature applications without a processing shutdown, allowing specially-trained technicians to mount the units on furnaces, preheaters, clinker coolers and in other high-temperature locations while production continues uninterrupted.

Engineered vibration

The age-old solution for breaking loose blockages and removing accumulations from chutes and storage vessels was to pound the outside of the walls with a hammer or other heavy object. However, the more the walls are pounded, the worse the situation becomes, as the bumps and ridges left in the wall from the hammer strikes will form ledges that provide a place for additional material accumulations to start.

A better solution is the use of engineered vibration, which supplies energy precisely where needed to reduce friction and break up a bulk material to keep it moving to the discharge opening, without damaging the chute or vessel. The technology is often found on conveyor loading and discharge chutes, but can also be applied to other process and storage vessels, including silos, bins, hoppers, bunkers, screens, feeders, cyclones and heat exchangers.

There is another innovative solution that prevents carry-back from sticking to the rear slope of a discharge chute. The live bottom dribble chute uses material disruption to reduce friction and cause tacky sludge and fines to slide down the chute wall and back into the main discharge flow. By addressing these issues, operators can experience a reduction in maintenance hours, equipment replacement and downtime, lowering the overall cost of operation.

Flow aid devices deliver force through the chute or vessel and into the bulk material. Over time, components will wear, or even break, under normal conditions. Most of these devices can be rebuilt to extend their useful life. Because clearances and fits are critical to proper operation, it’s recommended that flow aid devices be rebuilt and repaired by the manufacturer, or that the manufacturer specifically train plant maintenance personnel to properly refurbish the equipment.

This article was provided to International Mining by Martin Engineering

Martin Engineering expands conveyor training scope with LMS integration

Martin Engineering has added new online conveyor training content specifically designed to integrate with Learning Management Systems (LMSs) so users can assign, monitor and certify progress of all participants during its courses.

The new offering from Martin Engineering includes eight self-paced modules that address methods to identify, understand and correct common bulk conveying issues to improve safety on powerful and potentially dangerous systems, while complying with regulations, maximising productivity and achieving the lowest operating costs.

“Online conveyor training is delivering critical knowledge to companies around the world, and that’s never been more important than in these pandemic-restricted times,” Training Manager, Jerad Heitzler, said. “But, even as the popularity of these programs continues to rise, larger firms face challenges integrating the content into their LMSs so they can ensure thorough and convenient training for all employees – at all levels – across multiple sites. These modules create a verifiable record of employee training, so customers can track and confirm the participation of individuals company-wide.”

Organised into 90-120 minute segments, the virtual classes cover topics such as best practices for safety, fugitive material control and belt tracking.

With the training modules easily accessible and conveniently located in company-wide LMSs, the new Martin content gives customers complete control over scheduling and tracking, the company says.

“This is the type of training that everyone should have, and companies no longer need to rely on an outside vendor to schedule individual or group sessions,” Heitzler continued. “It delivers an in-depth and consistent understanding of conveyors and their hazards, ensuring that personnel at all levels can work safely and efficiently around these powerful systems.”

Martin Engineering has been providing training for much of its 75-plus year history, helping customers better control bulk material flows while reducing the risks to personnel. Designed to maximise employee engagement, the modules deliver topic-specific, non-commercial content that can be put to immediate use, and the new format allows even the most remote locations to take advantage, the company says.

The eight modules cover essential subjects that include an introduction to the concept of total material control, with content on transfer points, belting and splices, as well as belt cleaning, alignment and dust management.

“This system is created using a SCORM 1.2-compliant format, so it will integrate seamlessly with most existing LMSs,” Heitzler added.

SCORM is a widely used set of technical standards that provides the communication method and data models that allow eLearning content and LMSs to work together. All eight modules are currently available in English, Spanish and Portuguese, and can be provided in a variety of formats to meet the requirements of specific customers and their LMSs.

“Seven of the eight modules have a test at the end, requiring a minimum score of 70% to move on to the next module,” Heitzler said. “SCORM allows the content to interact with the LMS and leverage any features that a customer’s system has, which could include tracking the progress of each learner, providing reports or issuing certificates of completion.”

He concluded: “With this new effort in place, Martin has taken another step forward in global conveyor training. We’ve emerged as an LMS content provider to deliver greater flexibility and control over employee learning, helping customers attain the highest levels of efficiency and safety.”

Conveyor belt cleaner tension: the keys to optimal performance

While it is clear there is no single or ideal solution for conveyor belt cleaning and tensioner selection, Todd Swinderman* of Martin Engineering thinks companies need to put the due diligence hours in to make the optimal choice.

Conveyor belt cleaners have evolved over the last 50 years from mostly home-made designs to a wide variety of engineered solutions to suit virtually every application. The expectations have changed over time as the relationship between health, safety and productivity and clean belts have become more widely accepted. As development continues, a single solution to the problem of belt cleaning and tensioner design is unlikely to be found due to the numerous variables and conditions that affect belt cleaner effectiveness.

General requirements

A discussion about belt cleaner tensioners must include the basic approaches to belt cleaning, as the most effective approach is achieved through a combination of cleaner and tensioner designs. Industry has gravitated toward mechanical cleaners and tensioners because they are simple and economical. The most common mechanical belt cleaner designs present a blade or brush at various angles to the belt. Depending on the cleaner type and materials of construction, they can approach the belt at either a positive, negative or zero rake (Figure 1).

Figure 1 – Blade style cleaning angles

Regardless of the basic cleaning approach, maintaining the optimum range of contact pressure will result in the best balance between cleaning performance, cleaning element wear, belt wear and power requirements. CEMA Standard 576, ‘Classification of Applications for Bulk Material Conveyors Belt Cleaning’, provides a performance-based classification system for use in specifying belt cleaners.

Basic approaches to tensioning

There are two basic approaches to applying tension to the belt cleaner: linear and rotary (Figure 2). The blade’s angle of approach to the belt often dictates whether a linear or rotary tensioner is applied. The stored energy that creates the tensioning force most often comes from gravity, springs or actuators. CEMA defines the cleaning positions as Primary, Secondary and Tertiary (Figure 3). Most belt cleaners mounted in the primary position utilise a rotary style tensioner, while most belt cleaners mounted in the secondary or tertiary positions use linear style tensioners.

Figure 2 – Basic tensioning approaches
Figure 3 – CEMA-defined cleaning positions

Linear tensioners

Linear tensioners are most often applied where the compensation for wear is required in small increments, such as with hard metal-tipped cleaners located in the secondary cleaning position or with brush cleaners. The basic tensioner design approach is typically a carriage that constrains the support frame but allows linear movement along a guide or guides roughly perpendicular to the belt surface, with the support frame and blade design providing the cleaning angle. Some designs incorporate a relief ability for impact by splices or belt defects.

The advantages of linear tensioners include: 1) simple in design; 2) can be engineered to one setting for full blade wear; 3) access windows are easily incorporated within the mounting footprint; 4) can accommodate actuator deflection scales for accurate adjustment of cleaning pressure and; 5) delivers the ability to adjust for uneven mounting positions or asymmetrical blade wear.

The disadvantages of linear tensioners include: 1) the tensioner footprint can be large, restricting options for ideal belt cleaner installation; 2) there must be access to the far side for adjustment; 3) the guide mechanisms are subject to fouling from dust and corrosion; and 4) changing from bottom adjustment to top adjustment or providing for adjustment from one side complicates the tensioner design.

Rotary tensioners

Rotary tensioners utilising an actuator are principally designed using a lever arm or an elastomeric element that is concentric with the belt cleaner support shaft. They apply a blade-to-belt contact surface determined by the actuating force and linkage geometry. The energy source delivers a force to the lever arm which rotates the shaft and forces the belt cleaner blade(s) against the belt surface. Rotary designs tend to be compact and, in most cases, the actuator(s) can be mounted at any orientation, which provides options for installing the belt cleaner in the optimum position.

Counterweight tensioner

At one time the most common rotary tensioner was a counterweighted lever arm, with its position adjusted to apply the design cleaning force to a blade or blades that contact the belt. A counterweight can be mounted on one end of the shaft or both. Usually, the initial installation would have the arm angle set so that at the midpoint of the blade wear the arm would be horizontal, thus roughly averaging the design cleaning force over the life of the blade (Figure 4).

Figure 4 – Typical counterweight tensioner

The primary advantage of the counterweight design is that it is self-adjusting by gravity. The disadvantages of the counterweight design are: 1) the lack of damping which allows the blade and therefore the weight to bounce when struck by a splice, strongly adhered material, like ice or a defect in the belt. The unexpected movement of the counterweight can represent a safety hazard and uncontrolled bouncing can result in belt top cover damage; 2) the counterweight tensioner takes a significant amount of space; and 3) if the counterweight arm cannot be mounted horizontally there is a reduction in the force applied to the blade, because the effective lever arm is shortened.

Rotary lever arm and actuator tensioners

Rotary adjustment of the belt cleaning blade can be accomplished in several ways. The support frame is almost always in a fixed location but free to rotate. The required tensioning forces can be applied by many types of actuators, such as: springs, fluid cylinders, electric actuators or from torque stored in an elastomeric element. Rotary tensioners are often used with elastomeric blades, where the change in blade height and thickness as it wears is significant (Figure 5).

Figure 5 – Rotary tensioner types

The advantages of rotary tensioners are: 1) a compact design; 2) a single tensioner mounted on one side of the conveyor can often be used for a range of blade styles and belt widths; 3) they can be designed to minimise the number of times the tensioner has to be adjusted during the life of the blade; and 4) many types of actuators can be used.

The disadvantages of rotary tensioners are: 1) there can be a safety hazard if the support frame is mounted too far from the pulley and the cleaner pulls through; 2) the mounting location of the axis of rotation is critical for proper blade cleaning angle; 3) the constant force output by some actuators can result in a wide variance in cleaning pressure and blade life over time; and 4) when a tensioner is required on both ends of the support frame, it is often difficult to access the drive side of the conveyor for mounting and adjustment.

Other factors

The importance of proper installation should not be overlooked for the proper performance of the belt cleaner. Slight variations in the location of the support frame relative to the belt can cause significant issues with the effectiveness of the blades and can result in support frame bending. Most manufacturers provide detailed instructions for the location of the support frames and tensioners, which must be followed for optimal function.

To be effective, belt cleaners should be frequently inspected and maintained. In practice, the design of the conveyor structure and location of the drive and other equipment makes service difficult. Consideration in the design stage for easy access and ergonomic location of the cleaners for inspection and service will pay dividends in reducing carryback, maintenance time and potential exposure to injuries.

To maximise blade effectiveness and minimise rapid wear, the recommended adjustment protocols should be followed. Studies have shown that there is a critical cleaning pressure range for various types of cleaners and blade types. These studies demonstrate that over-tensioning the belt cleaner does not necessarily improve the cleaning effect, but often results in increased belt and blade wear as well as higher power consumption.

The future of cleaner tensioning

As technology continues to advance, suppliers are beginning to integrate an increasing level of functionality in belt cleaner designs. One such innovation is a belt cleaner position indicator that can monitor the blade and estimate remaining service life based on the current hourly wear rate. Able to retrofit directly to existing mainframes, the device is capable of sending a notification to maintenance personnel or service contractors when a cleaner requires re-tensioning or replacement.

This capability brings a number of benefits. Inspection and service time is reduced, as maintenance personnel no longer need to physically view the cleaner to determine the tension or wear status. It also reduces the time workers need to spend near the moving conveyor, helping to minimise the potential for accidents. By relying on data – not human judgement – to maintain the appropriate tension for optimal cleaning performance and monitor blade wear, the indicator maximises service life and reports with certainty when a blade is nearing the end of its useful life, delivering a greater return on cleaner investment. Replacement orders can be scheduled for just-in-time delivery, reducing the need to stock parts inventory, and installation can be scheduled for planned downtime instead of on an emergency basis.

Taking the technology a step further is another patent-pending device that combines the position indicator with an automated tensioner. This novel powered assembly incorporates sensors that constantly monitor blade pressure and adjust its position to maintain optimal cleaning tension. Maintenance personnel no longer need to visit each cleaner and manually re-tension. Instead, the tasks are performed automatically, reducing maintenance time while maximising the usable area of every cleaner. Analytics provide an unprecedented view and understanding of belt cleaner performance, with real-time data available remotely via a specially designed app.

Automated tensioner

Conclusion

While manufacturers continue to improve belt cleaner effectiveness, it has become clear that there is no single or ideal solution for belt cleaning and tensioner selection. Safety of personnel and the belt itself is an important consideration when selecting a tensioner. Ease of inspection and maintenance is critical for belt cleaner effectiveness, so the tensioner must allow for quick and safe service.

The selection of a belt cleaner should be based on the duty rating of the cleaner as provided in CEMA Standard 576 and then the appropriate cleaning system selected. The system should be selected based on life cycle cost and not just the initial price. The investment for effective belt cleaning is justifiable on direct cost reduction (clean-up costs), extended component life (often 25-40%) and reduced exposure to injuries, which is directly related to reduced clean-up frequency.

*R Todd Swinderman is CEO Emeritus of Martin Engineering

Addressing unsafe work practices around mining conveyors

Due to their size, speed and high-horsepower drive motors, conveyors pose a number of risks to personnel working on or near them. In addition to all the physical danger zones, when an injury occurs, ‘fault’ is often attributed to injured workers’ actions or inactions. However, safety experts point out that injuries generally occur due to a series of factors.

“Accidents are typically a result of a complex combination of probabilities, rather than a single unsafe act,” Martin Engineering Process Engineer, Daniel Marshall, observed. “Except for the unsafe act, it can be said that the accident would not have occurred if there was a safer design, better maintenance or less pressure for production.”

Assessing the risk of a conveyor

A thorough risk assessment by trained professionals is the ideal way to bridge the gap between workers and managers when the rules need review, to identify hazards and implement controls to reduce risks.

“A belt conveyor is a powerful machine with thousands of moving parts,” Marshall continued. “These moving components might severely injure a worker and can produce that injury in a fraction of a second.”

A typical conveyor belt moves at a relatively constant speed, commonly running between 0.5-10 m/s. At the very minimum, a worker who inadvertently touches a running conveyor belt – even with world-class reaction time and total focus on the danger of a conveyor – will come in contact with at least one carrying idler, and the potential is there to hit return idlers, chute uprights, stringer supports, pulleys and drives. The results are often disastrous.

Working around a moving conveyor

It has been estimated that two thirds of the fatalities involving conveyor belts take place while the belt is moving, usually because of a worker becoming entangled or crushed by moving equipment. Most of these take place when maintenance or housekeeping is being done on or around an energised conveyor.

Conveyor service should be performed only when the belt is properly locked, tagged, blocked and tested

These fatalities are generally caused by two compounding practices. The first is performing maintenance without thoroughly locking, tagging, blocking and testing the conveyor. Another unsafe practice is touching a moving conveyor belt with a tool or implement of any kind. When these two choices are combined, the results are usually severe and often fatal. Even working on a conveyor that is turned off, but not locked out, can lead to tragedy.

Workaround and shortcuts

“An intelligent and creative worker will often invent or discover ways to expedite certain functions or make work easier,” Marshall said. “Unfortunately, some of these shortcuts bypass safety hardware and/or best practices, putting the worker in harm’s way.”

The most common of these workarounds involves the “improper locking out” of a conveyor system, Martin Engineering says. The purpose of a lockout is to de-energise all sources of energy, whether latent or active. Failure to properly lockout can exist in many forms – varying from disregarding lockout requirements, to working on a moving conveyor, to improperly stopping the conveyor. An example would be pulling the emergency stop cord and assuming that the conveyor is de-energised.

Another common workaround involves entering a “confined space” without following established procedures. A confined space is any enclosure that is large enough and configured so that an employee can enter and perform assigned work, has limited or restricted means for entry or exit and is not designed for continuous employee occupancy. Very specific rules apply to workers when dealing with confined spaces. Failure to follow those rules can result in increased danger or death, Martin Engineering says.

Other potential unsafe behaviors include crossing a conveyor in a risky manner. Conveyor belts are often lengthy systems bisecting a production facility. Workers may be required to cross a conveyor line to get to an area in need of service or maintenance. To save time, a worker is likely to step over or cross under a conveyor.

“Crossing under” offers multiple hazards, according to the company. If any of the worker’s body parts come in contact with the moving conveyor, it will either act like a grinder and abrade the skin or pull the worker toward rolling components. Crossing under also places the worker at risk from falling objects.

Taking a shortcut by crossing over or under a conveyor can lead to injury

“Crossing over” a conveyor without using a designed and designated crossover structure comes with dangers, as well. There is a high potential for a slip and fall. If lucky, the worker may fall on the ground; if not, the worker will fall onto the conveyor belt. If the conveyor is in operation, the worker may be carried downstream. This can result in contact with the conveyor structure and rolling components or being thrown off the conveyor at the discharge. The safe approach to crossing a conveyor is to use a designated crossover or cross-under point engineered for that purpose, Martin Engineering says.

Anything in a worker’s line of travel is a potential “obstruction”. These can range from piles of spillage, items lying on the walkway or work areas, as well as low overheads. An obstruction can cause several hazards, the most obvious being the opportunity for a trip or fall. If the obstruction is in the middle of the walkway, a worker will have to go around it. If that revised path brings the worker closer to a conveyor, this decision places the worker closer to the hazards of the conveyor.

Neglected safety and control mechanisms

“Emergency stop pull cords are the last line of defence if the belt needs to be stopped quickly in response to an entrapment or impending equipment failure,” Marshall said. “The reaction time when such an event occurs is usually extremely brief, so workers need a way to stop the conveyor as fast as possible. In addition, the belt will not halt immediately and must coast to a stop. If the cord is broken, the switch is not working or the system is disabled, workers have lost the one final tool they have to protect themselves.”

The multiplying effect of unsafe practices

Often an accident occurs due to a combination of several poor work practices. A Mine Safety and Health Administration (MSHA) Fatalgram from 1999 in the USA recounts an event that caused a fatality at a mine when a worker entered an unguarded area alone, near an operating conveyor that was not locked out. The worker’s clothing then became trapped in the conveyor’s operating tail pulley. Four unsafe practices and two unsafe areas combined to produce a catastrophic event. Any individual factor may have led to injury or even death, but the combination essentially sealed the worker’s fate.

In a 2003 study, ConocoPhillips Marine found a correlation between fatalities and unsafe practices. The study showed that for every fatality there are an estimated 300,000 unsafe behaviors.

The research also quantified lost-time accidents, recordable injuries, and near misses. These are independent variables, so the numbers do not mean that lost day incident number 31 will be a fatality. But they do indicate that there is a statistical probability of a fatality for every 30 lost workday incidents. As a result, statistically speaking, an effective way to reduce fatalities is to reduce unsafe behaviors.

The most effective way to reduce fatalities is to minimise unsafe behaviors

“While even one unsafe practice has the statistical potential to lead to serious repercussions, conveyor accidents are rarely the result of a single action,” Marshall concluded. “More often, they result from a combination of company culture and unwise decisions. If workers can eliminate these unsafe practices and minimise their presence in danger zones, their chances of avoiding an accident will improve considerably.”