Tag Archives: conveyor belt maintenance

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

Martin Engineering’s Mr. Blade service offering comes to US Mid-Atlantic region

The use of factory-trained, OSHA- and MSHA-certified experts for maintenance of bulk handling systems has taken another step forward as Martin Engineering establishes its newest Mr. Blade™ territory, serving the Mid-Atlantic region of the USA, the company says.

Introduced in 2015, the network is a “unique factory-direct service program”, delivering replacement belt cleaner blades, air cannon valves and other Martin products, specified and custom-fitted on-site and installed free of charge. Further, Martin service technicians will replace the main frame and tensioner of any belt cleaner as needed – also at no charge – as part of the Mr. Blade service relationship.

The new territory is part of a larger initiative to deliver factory-direct service to customers around the world. The Mr. Blade program is currently up and running in the USA, UK and Italy, with additional launches planned for next year. The company estimates that it is currently responsible for about 10,000 conveyor belts worldwide as part of its managed services program.

“Martin assures accurately-sized and professionally installed replacement blades that are matched to the specific application, providing optimum cleaning performance and service life,” the company said. “The company ensures customer satisfaction with its exclusive Forever Guarantee, which specifies that users will experience better cleaning, longer service life and lowest cost of ownership.”

Initial targets for the new territory will be facilities producing or handling sand, aggregate or cement.

Martin Engineering Senior Customer Support Specialist, Marty Smith, explained: “Plants in just about every industry are being asked to do more with limited resources. Maintenance personnel often don’t have the time or training to safely and efficiently perform belt cleaner inspections or air cannon service when needed. Customers really appreciate having a dedicated technician who makes regular visits, so employees can focus on core business activities.”

National Sales Manager for Wear Components, Alan Highton, says shifting the maintenance responsibility to a trusted partner through this kind of service relationship is one way that bulk handlers can continue to streamline their operations, improving the performance and safety of their bulk handling systems at the same time.

“Unlike most suppliers, we have chosen not to use third-party service providers, who typically don’t have the specific expertise to optimise these systems,” Highton said.

“The idea behind the Mr. Blade program is to deliver an unequalled level of service using highly efficient, regionalised systems,” he added. “Our technicians really get to know the conveyors they’re visiting, and with the monitoring systems we now have in place, we’re able to deliver proactive service in advance of a breakdown, replacing worn or failing components before they lead to an event that stops production.”

The company is also taking steps to help customers whose facilities have limited access during the COVID-19 pandemic by partnering with their maintenance staff to remotely train employees to effectively maintain their conveyor systems, offering guidelines on preventive maintenance, inspections and replacement blade ordering. Factory-direct technicians remain in close contact with periodic check-ins and provide key parameters to assure optimum performance, according to the company.

As part of the Mr. Blade service, Martin will install its Position Indicators on every primary cleaner free of charge to deliver remote monitoring for qualifying customers, allowing technicians and operations personnel to access detailed information on conditions and remaining service life via Wi-Fi or cell phone. The monitoring system alerts service personnel when re-tensioning or replacement is required, or when abnormal conditions occur.

Also included are regularly-scheduled inspections, adjustment and blade replacement as required on all Martin belt cleaning systems, as well as the company’s multi-point Walk-the-Belt audits based on worldwide best practices. All services are covered by the price of components, with no contract required, Martin claims.

Highton said the new territory will cover five states: Pennsylvania, New York, Maryland, New Jersey and Delaware. The company has begun serving customers with two technicians in specially-equipped vans, each outfitted with a fresh supply of 8 ft (2.4 m) blade lengths and equipped with a band saw, milling machine and all tools required to achieve a custom fit, accurate installation and precise tensioning.

The vans are designed as mobile business units, with technicians able to electronically enter and update data on each customer system right at the site. With a lifetime record of all belt cleaning equipment, customers will have access to details on the mounting assembly, tensioner and blade wear life, along with total annual cost information for budgeting purposes, the company claims.

Smith said: “Consistent attention to the cleaners helps deliver maximum performance and wear life, minimising component failures and unscheduled shutdowns. And, if there is a breakdown, service is available from MSHA-certified technicians capable of repairing any brand or style of cleaner. We can even supply retrofit blades to fit belt cleaners from any manufacturer.”

ScrapeTec-Trading boosts conveyor belt product flow with AirScrape

A new side sealing system for belt conveyors patented and manufactured in Germany is reducing material spill, dust formation and explosion hazards at transfer points and other critical sections in the conveyor chain, according to ScrapeTec-Trading.

The contact-free AirScrape® conveyor belt skirting system hovers freely above the conveyor belt, meaning skirt friction and belt damage is eliminated and service life extended, the company says.

Thorsten Koth, Sales Director, Scrapetec-Trading, said the system, which encompasses inward facing, hardened-steel diagonal blades, operates according to a new principle where it hovers 1-2 mm on the left and right side above the conveyor belt.

“These blades deflect larger particles inwards, while using the air flow of the conveyor belt and conveyed material to create an inward suction, flowing any dust and fine particles back into the product flow,” Koth said. “Through these diagonally fitted blades and the speed of the running belt, air is drawn from the outside inwards. As a result, neither the dust nor material can escape.”

Conventional skirting is pressed against a conveyor belt to keep dust and material in the middle of the belt, according to Koth. After a period, wear of the skirting and belt can be so severe that material and dust escapes, he said, adding that material spillage at transfer points needs to be removed and regular maintenance of belt skirting and transfer points is necessary.

“With the AirScrape dust-free and contact-free side sealing system for belt conveyors, there is no skirt contact and therefore no belt wear or damage,” he said. “Motor power requirements are reduced as there is no belt-skirt friction and, because there is continuous skirting with no gaps, product loss is minimal.

“Studies show that even three years after installation and with continuous use in harsh conditions, the AirScrape system hardly shows any signs of wear. Operational costs are also reduced because there is no need for spillage collection, regular maintenance, or replacement parts.”

This system comes in pairs of left and right hand two metre, inter-connectable pieces to form any required length, and is available in three different base widths of 100 mm and 55 mm to suit various belt widths and chute sizes. For flexibility on site, this system is completely extendable, according to the company.

AirScrape is fitted using spacers, floating the blades just above the belt, and is attached to the outside of the chute by using existing skirt clamps or a bolt and nut system. It is longitudinally adjustable to follow the contours of conveyor belt rollers and the belt trough angle.

This durable system consists of non-flammable and anti-static polyurethane materials and blades made from Hardox/stainless steel, the company said. FDA-approved materials are also available for specific conveyor handling applications.

Designed and manufactured in Germany by ScrapeTec Trading, the AirScrape system is available from BLTWORLD throughout Africa and the Indian Ocean Islands; from Grupo-ISC throughout South America and from Scrapetec-Trading for the rest of the world.

Martin Engineering brings automation to conveyor belt maintenance game

Martin Engineering has announced a belt cleaner position indicator that monitors the blade, tracking and reporting remaining service life in conveyor and bulk material handling applications.

The Martin N2® Position Indicator (PI) monitors primary belt cleaner blades, notifying Martin Engineering service technicians and plant operations personnel when re-tensioning or replacement is required and/or when abnormal conditions occur.

The PI can be part of a new installation or directly retrofitted to existing mainframes that use the company’s replacement blades, the company said, with managers and service technicians able to quickly access information on any networked cleaner via cell phone.

“With approximately 1,000 operating systems currently in service and installations continuing daily, the technology has been embraced by bulk material handlers in a wide range of industries and applications,” Martin Engineering said.

The N2 Position Indicator was designed in-house by the engineering team at Martin’s Center for Innovation, and the firm also engineered and built the proprietary equipment used to manufacture the new devices.

Martin offers the equipment, monitoring service and batteries free of charge to qualifying customers, it said. “The company will also support the PI components and provide customer alerts without cost as needed, with mainframes and tensioners replaced free for users of Martin belt cleaner blades,” the company added.

Martin Engineering Global Marketing Director, Brad Pronschinske, said: “There are no annual maintenance fees, and no add-on charges for cell phone access. Most customers using our cleaner blades can take advantage of this technology.”

Position indicators can be mounted anywhere from 3-800 m from the cellular gateway and the robust, sealed construction means it is virtually immune from damage, according to Martin Engineering. Up to 50 units can be monitored by a single gateway connecting to the Internet, usually located at the highest point in the plant, where the cell signal is strongest. The system does not require a cellular line for each PI, instead communicating via radio frequency from each sensor to the gateway.

Operating independently of any plant communications infrastructure, the small physical size and low power requirements deliver a projected battery life of two years, according to Martin Engineering, with the self-contained model developed by Martin Engineering in order to minimise the dependency on in-plant resources. Only the gateway requires a constant 110 V power point, it said.

The company explained: “The device eliminates the need for manual inspections by giving technicians precise information, delivering critical real-time intelligence and reducing exposure to moving conveyors, improving both efficiency and safety. Maintenance planning is simplified by having detailed information available on demand, allowing service personnel to deliver and install replacement wear parts during scheduled outages.”

Alerts are also provided automatically when a blade change is required; re-tensioning is needed; a cleaner has been backed off the belt; there is an abnormal condition; a substantial change in temperature occurs; and batteries need replacement.

The PI is just one component of the company’s push to develop new and evolving technologies to improve bulk material handling and reduce the associated hazards, Martin Engineering said. It is within the same product family as Martin’s automatic tensioning system to continuously maintain optimum blade pressure without any operator intervention.

“This capability is a true enabler, bringing a number of benefits,” Pronschinske said. “Belt cleaner inspection time is basically eliminated 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.”

Pronschinske described the innovation as a game-changer in the industry, with a positive impact on productivity, operating costs and safety. “Relying on actual operating conditions instead of human judgement to monitor blade wear and tension for optimal cleaning performance, the indicator maximises the blade’s usable surface area and reports with certainty when a blade is nearing the end of its useful life,” the company said. “Delivering instant, continuous feedback while eliminating guesswork – tracking the individual performance and status of each cleaner – the detailed history also provides a maintenance log with service dates and work performed.”

The result is an improved return on belt cleaner investments, according to Martin Engineering.

Replacement parts can be scheduled for just-in-time delivery, and installation can occur during planned downtime instead of emergency stoppages.

Pronschinske said: “By monitoring the rotation of the belt cleaner mainframe, the N2 PI helps managers plan tensioner adjustments and blade replacements during scheduled outages.”

Manufactured from a proprietary grade of polyurethane resistant to bumps, shocks and knocks, the PI device is extremely robust, according to Martin Engineering. It can handle a typical mining environment, the company says, and the device can be installed inside or outside the transfer chute. It has also been designed to operate in challenging ambient environments found at operator sites, such as handling wet and sticky materials.

“The system recognises how much rotation is acceptable before tensioner adjustment is required,” Pronschinske explained. “It allows our service technicians to know exactly when a belt cleaner needs replacement, even before the customer does. And, if excessive movement is detected on any cleaner, an alarm notice will automatically be sent to alert operators to check it immediately.”

The software tracks and displays blade status, remaining life, next scheduled tensioning, run time, wear rate, cleaner model, blade type and several other details, the company says.