Tag Archives: conveyor belt cleaning

Controlling dust at mine conveyor belt discharge points

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.

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

Multotec’s MATO boosts conveyor refurbishment capacity

Multotec’s conveyor belt lacing subsidiary, MATO, has recently expanded its offering with the addition of new service and repair facilities.

Andrew Frank, Operations Manager at MATO Products, highlighted the recent completion of a new spray-painting booth, which has doubled the firm’s capacity to finish refurbished items.

“To keep up with market demand, we have expanded our spray booth significantly in terms of size and throughput capability,” Frank said. “It can now accommodate components up to a length of 2.2 m and provide a more productive environment for operators.”

This allows for all repair and finishing work – even on the longer diagonal belt cleaners – to be spray-painted in-house, he says, improving turnaround time, quality control and cost to customers.

“We pride ourselves on the functionality and longevity of our products,” he said. “We base this on our technical quality in repairing and refurbishing equipment to ‘as-new’ specifications. Upgrading our facilities ensures that we continue doing this as cost effectively as possible, as our customer base grows.”

Complying with the highest standards of health and safety, the new spray booth is equipped with the latest filtration technology, according to the company. This ensures fumes and chemicals are filtered before air is expelled from the building. A powerful fan unit enables an extraction capacity of 18,000 cu.m/h.

Known as a leader in conveyor belt lacing, MATO also offers a range of belt cleaning solutions.

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.