Monitoring & Servicing Remote Transfer Points on Long Conveyors

More and more, belt conveyors are being built that are miles (or kilometers) long.  They descend mountains and cross vast stretches of plains, forests or jungles.  Built to compensate for expensive, slow and potentially dangerous haulage by trucks, long conveyors travel at high speeds regardless of the weather.  This appeals to operators for several reasons: reduced maintenance, less labor, increased production, improved safety and a lower cost of operation. However, there are many logistical and maintenance considerations for long conveyors.

“We’ve observed that a fleet of trucks involves several logistical factors such as the need for experienced drivers, trained mechanics, safe roads and a lot of fuel,” said Andrew Timmerman, Engineering Supervisor at Martin Engineering.  “Long conveyor systems are designed to reduce some of the cost and safety issues.  But like any solution, they have their challenges, too.”

Intersecting Conveyors and System Accessibility

Access to a transfer point by vehicle is recommended, if not critical, because of the nature of the most common maintenance tasks which could involve heavy lifting and work with power tools such as cutters and grinders.  Discharge and loading zones experience the largest amount of spillage, and fugitive material can quickly pile up and encapsulate the belt, causing dust emissions and idler fouling.  Maintenance staff needs to access the area to make adjustments to remedy causes of carryback and spillage and clear away accumulation.

Properly engineered material transfer includes belt cleaning, sealing, chute clog prevention, impact management, tracking and monitoring to control the need for maintenance and unscheduled downtime.  A goal should be to minimize the number of trips and address all issues in a single visit.

Transfer Point Maintenance

Transfer points can take some care to maintain.  The most common ongoing transfer point maintenance tasks are:

• Primary and secondary belt cleaner blade replacement
• Cleaner performance monitoring and tensioner adjustments
• Spillage cleanup
• Transfer chute maintenance and clog mitigation

Having to frequently maintain a basic belt cleaner to make sure it is adequately tensioned and cleaning properly is costlier in labor over the long run than installing quality belt cleaning equipment upfront.  This is known as Return on Performance (ROP), which differs from Return on Investment (ROI) in that it calculates the savings in labor for maintenance and equipment life over the long term, instead of merely the period in which the initial capital investment is recovered regardless of increased costs and replacements afterward.  At a transfer point located miles away, having a reliable belt cleaner tensioning system that is self-adjusting and/or low maintenance drastically reduces the cost of operation.

Transfer chutes can experience buildup due to material properties, lump/particle size, moisture content, temperature, abrasiveness and corrosiveness.^[1]  When clogs happen, production stops and backflow fouls components in the discharge zone and spills over the edges of the system.  Due to the distance and equipment needed on extended conveyor lengths, the unscheduled downtime and associated costs can be excessive.

Equipment Reliability at Transfer Points

“Quality and durability are key elements for a sustainable remote transfer point,” Timmerman pointed out.  “Getting to the work site alone increases the cost of maintenance, so calculating the ROP on low maintenance equipment may be a better metric than ROI.”

Equipment geared toward mitigating common transfer chute issues can include service-friendly primary and secondary cleaners, autonomous tensioners, belt alignment devices, self-adjusting skirting, vibration and localized power generation.

Service-friendly primary and secondary cleaners are track-mounted components that pull away from the stringer for safe service outside of the system.  An example of this is the QC1™ Cleaner HD STS™ (heavy-duty) (safe-to-service).  After performing the proper lock-out/tag-out/block-out/test-out procedures, a single worker has easy access to safely service the blades using basic tools.

Low maintenance cleaners like the CleanScrape® primary and secondary cleaners are tensioned upon installation and with no need for further adjustment.  Positioned at an angle across the discharge pulley, it has a rubber strip constructed with tungsten carbide tips, requiring far less maintenance and delivering as much as 4x the blade life of conventional designs.

Belt alignment devices like the Martin® Tracker™ ensure that the belt and the cargo remain centered, which is especially critical in loading and discharge zones.  Standard belt training devices either impede the belt from drifting into the stringer or react to the belt drift. [Fig.2]  On long conveyors, belt trainers are required along the belt path both on the carrying side and the return to mitigate mistracking.

Self-adjusting skirting rides the belt to create an effective seal automatically.  Historically, skirting had to be adjusted when excessive dust and spillage escaped from the loading zone.  Self-adjusting designs prevent spillage and equipment breakdown caused by fugitive material, creating a constant tight seal to the belt.  The unit self-adjusts to rubber skirt wear, regardless of material volume and size diversity, delivering an adaptable and low-maintenance solution.

Applied vibration helps prevent the buildup of dust and fines on the inner walls of the transfer chute.  Clogging can bring the entire operation to a stop, causing excessive downtime, but disrupting and loosening the material helps prevent accumulation, which can lead to backflow and spillage.

Monitoring and Sensors

In addition to cameras that provide an overall view of conditions, sensors monitor operations and flow, delivering important data.  One thing to keep in mind is the need to relay the information to a central control center via Global System for Mobile Communications (GSM), which requires the proper equipment and power.

A N2® Position Indicator is an intuitive sensor that allows remote monitoring of the belt cleaner blade position and remaining service life, notifying operators when re-tensioning or blade replacement is required.  A position indicator can be mounted anywhere from 3-800 meters (10-2,625 feet) from the cellular gateway, and the robust, sealed construction means it is virtually immune from damage.  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.

Load sensors are specifically geared to communicate with automated tensioning systems so the unit can pull the blade away from the belt when there is no cargo.  Running a cleaner on an empty belt can reduce blade life, degrade the belt face and create potentially dangerous friction heat and static.

Flow indicators or “plugged chute detectors” can either alert operators to the need for maintenance or automatically activate flow devices like vibrators or air cannons to disrupt stuck material and commence flow without worker intervention.

Service and Safety

Each piece of equipment requires a knowledgeable and trained technician for safe service.  As a result, performing maintenance on a remote transfer point might involve the most experienced technicians in the facility for long periods to inspect and maintain it.  Additionally, it could require a fully equipped service truck with lifts and onboard power.

Many operators have turned to specialty service contractors who are trained and equipped to safely conduct regular inspections, provide maintenance and offer recommendations.  These highly trained and certified technicians can reduce replacement equipment lead times and perform maintenance tasks faster, minimizing downtime.

To improve response time, many systems can be set up so technicians can be alerted through the GSM to issues at the same time as operators.  Some service contractors can even maintain data logs on customers’ conveyors, recording system specifications, status details and service procedures performed.  The collected information is helpful in scheduling preventive maintenance activities and in determining when outside resources should be utilized.  This data can be used to better manage an operation’s equipment and budget.

Improving Efficiency and Operating Costs

Although there are several considerations and obstacles associated with installing and operating a long conveyor system, the improved safety and long-term cost savings over vehicle transport should be convincing.  Once the conveyor system is built, material transport is more predictable and easier to control and maintain, which reduces the cost of operation and improves the bottom line.

Well-monitored autonomous equipment can make a remote transfer point much more cost-effective to operate.  ROP-minded design and maintenance performed by trained service technicians can mitigate many of the disruptive issues and downtime associated with transfer points in general.

“Long conveyors with multiple transfer points have been around for several decades, and equipment designs for this unique environment have evolved in recent years,” Timmerman concluded.  “By focusing on safety, ease of service and reduced risk exposure, operators are realizing that many of the most troubling issues can be effectively resolved.”