Tag Archives: conveyor belts

Martin Engineering delves into the danger zone for conveyor belt best practice

In bulk material handling applications, a conveyor is typically a massive, complex and extremely powerful system. It is usually constructed of rubber belting, set on rolling idlers, wrapped around large steel drums at each end and driven by a high-torque motor. As such, a conveyor presents enough danger zones that the entire system should be considered a hazard, according to Martin Engineering.

In most applications, a conveyor belt moves at a relatively constant speed, commonly running somewhere between 0.5-10 m/s. An Olympic sprinter has a reaction time of about 0.18 seconds when poised at the starting line and totally focused on the race. If this athlete becomes tangled in a conveyor belt traveling 1.5 m/s, the person would be carried 0.27 m before even realising what has happened.

A ‘regular’ worker would likely require a longer time to react, Martin Engineering says. For simplicity’s sake, assume it would be twice the athlete’s reaction time, so the worker would be pulled twice as far, introducing the potential to strike many more components or to be pulled farther and harder into the first one.

In addition, most conveyors are engineered with the ability to start remotely. The system may go from dormant to active at any time at the push of a button, and that ability can suddenly catch a worker unaware, leading to serious injury or death, the company says.

Martin Engineering Process Engineer, Dan Marshall, said: “When a conveyor belt is moving, there will usually be more tension on the carrying side. If the conveyor is merely stopped and de-energised, that tension may remain in the belt in the form of stored energy.”

A system under tension will always try to approach equilibrium, according to Marshall; that is, it will try to release the energy. This release will likely come in the form of a pulley slip, which occurs when the belt slides around the head pulley to equalise the tension. The distance the belt will move is proportional to the amount of tension stored and the belt’s modulus (elasticity), possibly several feet. If a worker is on the belt or close enough to be pulled in during this sudden release of energy, injuries or death can occur.

“There’s a simple rule of thumb regarding conveyors: if it’s moving, don’t touch it,” Marshall continued. “The most common way to prevent inadvertent contact is with suitable guarding that renders the moving components inaccessible.”

For maintenance or repairs, procedures for lockout/tagout/block-out/test-out should always be followed when working on a stationary conveyor, and systems should be equipped with anti-rollback devices (also known as backstops) on the head pulley.

Many of the moving parts on a conveyor belt system are rotating components. These parts include idlers, drive shafts, couplings, pulleys and speed sensors. Items rotating at a high speed pose the risk of entanglement or entrapment.

“All moving machine parts should be guarded with adequately constructed, properly installed, functioning and well-maintained guards,” Marshall said.

There are many pinch points on a conveyor, components that the belt touches or comes near, including the drive pulleys, snub pulleys, idlers, stringer, chute walls and deflectors. If a worker’s limb travels with a conveyor belt, it will meet one of these components. The limb, as well as its attached worker, will become trapped between the belt and the obstruction.

The same thing can happen with a tool, which can pull a worker into the entrapment faster than the person can let go.

“Effective fixed guards should be absolute in their protection; workers should not be able to reach around, under, through or over the barrier separating them from moving components,” Marshall added.

Many of the fatalities around conveyors have happened when a worker was cleaning fugitive material from the structure or components of a conveyor system. The process of cleaning may put a worker in proximity to a very dangerous machine, according to Martin Engineering. The need to shovel, sweep or hose off accumulations puts the worker within arm’s length of the conveyor, and often closer.

Airborne dust can cause numerous health risks, ranging from material build-up in the lungs to explosions. Categorised as either respirable or inhalable according to particle size, dry, solid dust particles generally range from about 1 to 100 microns in diameter.

According to the EPA, inhalable coarse particles are 2.5-10 microns in size. They are typically caught by the human nose, throat or upper respiratory tract. In contrast, fine respirable particles (under 2.5 microns) can penetrate beyond the body’s natural cleaning mechanisms (cilia and mucous membranes), traveling deep into the lungs and causing long-term or chronic breathing issues.

While it is virtually impossible to prevent all fugitive material from escaping a conveyor structure, taking practical steps to minimise it as much as possible helps reduce the dangers it can introduce, the company says. When clean-up is necessary, performing the job while the conveyor is running should not be an option. Operators concerned with the cost of lost production from stopping a conveyor to clean need only consider the consequences of an accident to confirm the wisdom of this rule.

Until recently, the engineering of belt conveyors to carry bulk materials hadn’t changed much in the last half-century, despite the fact that virtually every requirement for safety, regulatory compliance and production performance has been raised during that time. Standards continue to tighten and industry best practices now often exceed government requirements.

“Using these new and emerging technologies, even poorly performing conveyors often don’t need to be replaced or rebuilt, but merely modified and reconfigured by knowledgeable and experienced technicians installing the right modern equipment,” Marshall concluded. “Specialised conveyor training and trusted resources from global suppliers are helping to raise operator awareness to make conveyor systems cleaner, safer and more productive.”

ASGCO, WAGNER-Schwelm and NILOS combine conveyor belt expertise

ASGCO® “Complete Conveyor Solutions” says it has signed a tri-lateral distribution, manufacturing and intellectual partnership agreement with WAGENER-Schwelm® and NILOS® to extend its ability to service and provide ASGCO products to servicing distributors, end-users and original equipment manufacturers around the world.

Aaron Gibbs, President of ASGCO, said the integration of highly precise German engineering from WAGENER and NILOS, combined with the manufacturing, marketing, sales and service strength of ASGCO will bring customers “excellent, highly engineered, ‘best in the world’ conveyor belt vulcanising products” manufactured in the US.

“By providing our ASGCO conveyor products through the NILOS service branches and then also incorporating the WAGENER and NILOS range of products into ASGCO’s product line, this will provide the ‘best in class’ range of conveyor material handling solutions for our customers,” he said.

Thomas J Ziller, Owner of WAGENER-Schwelm and NILOS, said the partnership will provide the “strongest and most innovative range of products in the conveyor belting industry”.

“The knowhow transfer in both directions guarantees sustainable and high-end production as well as increases our after-sales service around the world,” he said.

WAGENER-Schwelm has decades of experience in the development and manufacturing of portable and stationary vulcanising presses, for splicing and repairing conveyor belts, while NILOS is known for the application-oriented development of high-quality and innovative hot and cold vulcanising materials, compounds, cements and other conveyor belt related products.

ASGCO, founded in 1971, is a leading manufacturer, distributor and service provider of proprietary conveyor and screening equipment and accessories to improve the safety and performance of bulk material handling systems.

Mato Products makes its mark on conveyor belt cleaning market

Mato Products, a Multotec company, says it has expanded its bulk handling equipment reach into the design of innovative belt cleaning systems for a number of mineral and metals markets.

The company has long been a household name in clip fasteners for conveyor belts, especially in the underground coal sector. It company operates one of only three high production Mato machines in the world, and significantly the only one outside of Germany.

After over 30 years of operation, this Mato unit was overhauled in 2016 in an intense six-month refurbishment. It was upgraded from 180 t to 360 t capacity, speeding up production and ensuring both ongoing cost-effectiveness and reliability of supply for customers, according to the company.

Mato said: “The company’s exciting line of belt cleaning equipment has for some time now been gathering momentum. Its popularity has extended well beyond the coal sector into other materials handling and mineral processing applications, even in diamond mining.”

According to Benjamin Sibanda, Managing Director of Mato Products, over-feeds at transfer points often lead to material build-up on the inside of a belt.

“As mines and other industrial facilities raise their environmental standards, they want to avoid problems like duff heaps under conveyors, which can cause pollution,” Sibanda said.

The Mato MCP3-S primary cleaner, installed at the head pulley is designed to be an aggressive head pulley cleaner, yet friendly to the conveyor belt surface and suitable for use with mechanical fasteners, the company said.

“It offers a high level of cleaning due to its blade profile, and the spring tensioning system ensures the blade is in constant contact with the belt for the life of the blade while achieving up to a maximum of 75% cleaning.”

Sibanda said: “The secondary Mato MUS2 belt cleaner is one of our latest design belt cleaners and offers an M-TRAK slide on cushion and blade for easy installation and maintenance.”

The M-TRAK is designed to eliminate lengthy maintenance downtime and ensures blade alignment is 100% true across the entire conveyor belt width, according to the company. Blade replacement is simple with the design of the slide-on and slide-off principle, eliminating the need for special tools or training when maintenance is performed, Mato said.

Sibanda continued: “The unique design of our MUS2 cushion is based on the principle of a parallelogram whereby the cushion also stays true to the conveyor belts surface ensuring the angle of attack is maintained. This cleaner’s primary duty is to remove fines and duff, to almost zero carry-back.”

Blades on the cleaners come in a range of materials suited to different applications, including polyurethane and tungsten.

While the application in South Africa was initially mainly underground, equipment variations for surface have now also been developed and introduced to market, Mato said. The plant tail-end cleaner is based on the same concept but is mounted on channels rather than on stringer pipes.

“This product includes innovative blade stoppers,” Sibanda said. “When the blade is worn to a certain level, the mounted flat plate does not touch the belt, for better protection.”

Mato has also engineered closer integration between its fastener clips and the belt cleaners.

“For instance, we have added a profile to the clip which optimises the life of both the clip and the tungsten tip on our secondary belt cleaner,” Sibanda said. “The skiving process embeds the clip slightly into the belt ensuring the mechanical splice is on the same surface as the conveyor belt thereby minimising the impact on the tungsten tip as well as lowering noise levels. Longer life of both means less downtime for the customer and greater reliability.”

Sibanda said all the offerings in Mato’s conveyor belt systems range helps to improve the lifespan of equipment at loading points. The energy of ore transfer is absorbed, and wear resistance is increased by Multolag ceramic products.

Martin Engineering’s tips for cleaner, safer and more production conveying

Martin Engineering, a supplier of bulk material handling solutions, is urging mining companies to take another look at their conveyor belt cleaners and devise a strategy that can reduce operator and operational risk, as well as overall operating costs.

The company says: “Given the number of conveyor-related accidents that occur during routine maintenance and cleanup, every bulk material handler has a vested interest in technologies to help reduce hazards and prevent injuries.

“Seemingly mundane tasks such as adjusting belt cleaners and removing spillage often require employees to work near the moving conveyor, where even incidental contact can result in serious injury in a split second. Further, spillage can contribute to the risk of fire by interfering with pulleys and idlers and by providing potential fuel. Even worse, in confined spaces, airborne particles can create the right ingredients for an explosion.”

The buildup of fugitive material can occur with surprising speed, according to the company.

“As the table below illustrates, spillage in an amount equal to just one sugar packet (about 4 g) per hour will result in an accumulation of about 700 g at the end of a week. If the rate of escape is 4 g/min, the accumulation will be more than 45 kg/week, or more than 2 t/y. If the spillage amounts to just one shovelful per hour (not an uncommon occurrence in some operations), personnel can expect to have to deal with more than 225 kg/d of fugitive material.”

Reducing carryback

Although there are several belt cleaning technologies available to conveyor operators, most designs in use today are blade-type units of some kind, using a urethane or metal-tipped scraper to remove material from the belt’s surface, according to Martin Engineering.

“These devices typically require an energy source – such as a spring, a compressed air reservoir or a twisted elastomeric element – to hold the cleaning edge against the belt. Because the blade directly contacts the belt, it is subject to abrasive wear and must be regularly adjusted and periodically replaced to maintain effective cleaning performance.”

The ability to maintain the proper force required to keep the blade edge against the belt is a key factor in the performance of any cleaning system, the company said. Blade-to-belt pressure must be controlled to achieve optimal cleaning with a minimal rate of blade wear.

The company said: “There is a popular misconception that the harder the cleaner is pressing against the belt, the better it will clean. Yet, research has shown there is an optimum range of blade pressure, which will most effectively remove carryback material. Increasing tension beyond this range raises blade-to-belt friction, thus shortening blade life, increasing belt wear and increasing power consumption – without improving cleaning performance.

“Operating a belt cleaner below the optimum pressure range also delivers less effective cleaning and can accelerate blade wear. A belt cleaner lightly touching the belt may appear to be in working order from a distance whereas excessive amounts of carryback are being forced between the blade and the belt at high velocity.”

This passage of material between the belt and the blade creates channels of uneven wear on the face of the cleaner, according to the company, with these channels increasing in size as material continues to pass between the blade and the belt.

The company continued: “A common source of blade wear that often goes unnoticed – even with a properly installed and adjusted cleaner – is running the belt empty for long periods of time. Small particles embedded in the empty belt’s surface can create an effect like sand paper, increasing the wear rate of both the blade and the belt. Even though the cargo may be abrasive, it often has moisture in it that serves as a lubricant and coolant.

“Another potential source of wear is when the cleaner blade is wider than the material flow, causing the outside portion of the cleaning blade to hold the centre section of the blade away from the belt. As a result, carryback can flow between the belt and the worn area of the blade, accelerating wear on this centre section. Eventually, the process creates a curved wear pattern sometimes referred to as a ‘smiley face’ or ‘mooning’.”

As urethane cleaner blades wear, the surface area of the blade touching the belt increases, according to Martin Engineering. This causes a reduction in blade-to-belt pressure and a corresponding decline in cleaner efficiency. Most mechanically-tensioned systems, as result, require periodic adjustment (re-tensioning) to deliver the consistent pressure needed for effective carryback removal.

“To overcome the problem of the blade angle changing as the blade wears, a radial-adjusted belt cleaner can be designed with a specially-engineered curved blade, known as CARP (Constant Angle Radial Pressure),” Martin Engineering said. “With this innovative design, the changes in contact angle and surface area are minimised as the blade wears, helping to maintain its effectiveness throughout the cleaner’s service life.”

Air tensioning

New air-powered tensioning systems are automated for precise monitoring and tensioning throughout all stages of blade life, reducing the labour typically required to maintain optimum blade pressure and extending the service life of both the belt and the cleaner, Martin Engineering said.

“Equipped with sensors to confirm that the belt is loaded and running, the devices automatically back the blade away during stoppages or when the conveyor is running empty, minimising unnecessary wear to both the belt and cleaner,” it said. “The result is consistently correct blade tension, with reduced power demand on start-up, all managed without operator intervention.”

For locations lacking convenient power access, one self-contained design uses the moving conveyor to generate its own electricity. This powers a small air compressor to maintain optimum blade pressure at all times.

Maintenance

Even the best-designed and most efficient of mechanical belt cleaning systems require periodic maintenance and/or adjustment, or performance will deteriorate over time.

Martin Engineering said: “Proper tensioning of belt-cleaning systems minimises wear on the belt and cleaner blades, helping to prevent damage and ensure efficient cleaning action. Belt cleaners must be engineered for durability and simple maintenance, and conveyors should be designed to enable easy service, including required clearances for access. Service chores that are straightforward and ‘worker friendly’ are more likely to be performed on a consistent basis.

“The use of factory-trained and certified specialty contractors can also help ensure that belt cleaner maintenance is done properly, and on an appropriate schedule. Further, experienced service technicians often notice other developing system or component problems that can be avoided if addressed before a catastrophic failure occurs, helping conveyor operators avoid potential equipment damaging and expensive unplanned downtime.”

The company concluded: “By setting the cleaning goal necessary for each individual operation and purchasing a system adequate for those conditions, as laid out in CEMA standards, it’s possible to achieve carryback control and yet obtain long life from belt cleaners.

“The bottom line is that properly-installed and adjusted belt cleaners help minimise carryback and spillage, reducing risk and overall operating costs.”

New SICK LMS111 conveyor belt tool measures up the competition

SICK has extended its LMS Bulkscan laser scanner offering with the SICK LMS111 measurement tool, allowing more users to benefit from continuous monitoring of volume and mass throughput of bulk materials on conveyor belts.

The LMS111 Bulkscan provides highly-accurate, delay-free volume and mass flow measurements to maximise throughput of a wide range of bulk materials including gravels, sands and cements, according to the company.

Compact, and easy-to-integrate, it can be designed into new lines or easily retrofitted on to existing conveyors.
It is a cost-effective alternative to a conventional beltweigher, SICK says, offering wear-free, low-maintenance advantages of non-contact, real-time measurement. The multi-echo, time-of-flight laser scanning technology enables a reliable output of the material’s volume and mass flow, while the material’s centre of gravity is continuously monitored to help avoid uneven loading and resultant belt wear.

Darren Pratt, SICK UK’s National Product Manager for Industrial Instrumentation, said: “The new SICK LMS111 Bulkscan presents a value-added alternative to a standard belt scale and is a robust and consistent performer even in dusty production environments or when mounted behind glass.

“By measuring the load height profile every 20 milliseconds, the LMS111 Bulkscan delivers an accurate, continuous profile measurement. It then works out the volume of the material using the belt speed which can be provided as a fixed value or input via an encoder in the case of a variable speed belt. The mass is computed from the volume and a known density of the material.”

Volume is more important than mass for many production processes, according to Pratt. This makes Bulkscan an ideal alternative to beltweighers in conditions where the density of material changes significantly.

The LMS111 Bulkscan is easy to install and set up in a vertical (nominal 5°) alignment for accurate profile measurement, according to SICK. Using the pulsed, time-of-flight laser measurement system with a 190° wide field of view, the unit can be applied to the narrowest and widest conveyors.

The instrument outputs three analogue signals via the BAM100 processing unit accessory, or delivers three digital signals that can be assigned to a bulk quota or for condition monitoring. A TCP/IP interface ensures connectivity with a PC, factory SCADA and PLC communications networks.

The unit measures only 152 mm x 102 mm x 105 mm, so is easy to install in a wide variety of locations. It can be mounted up to 10 m above the conveyor, while ambient operating conditions range from +50°C to -30°C. Environmental protection is rated at IP67.

SICK says the LMS111 complements the LMS511 Bulkscan PRO which provides additional measurements and is designed for operation in more challenging dusty and dirty conditions, including the most arduous ambient conditions.