Eliminating Chute Entry with an External Wearliner

Daniel Marshall, Contributor

Copyright Martin Engineering 2024
Confined space entry requires a permit because it is deceptively
dangerous and has injured several workers in the past.

The wearliner on a belt conveyor transfer point is essentially considered a sacrificial layer.  Removal and replacement is a grueling job that could require multiple workers and days of scheduled downtime.  Conventional wearliners have historically been installed inside the chute, but modern designs are placed on the outside, improving skirtboard sealing and preventing spillage.

The Occupational Safety & Health Administration (OSHA) considers most transfer chutes to be “permit-requiring confined spaces,” mandating that an “authorized entrant” perform the work inside the chute.  An attendant must also stand outside monitoring the safety of the person inside while assisting in the removal of material from the chute.  In some cases, a supervisor further oversees this procedure.

The goal of the external design is to significantly cut the installation and service time while reducing risk and improving safety.  The result is excellent performance with fewer labor hours, no required certification for maintenance, and a lower cost of operation.

Rethinking Chute Design

Previous designs securely welded the wear liner to the inside of the chute, with only the skirt seal located on the outside.  The logic behind the conventional design is for the wear liner to protect the skirtboard, which is typically ¼ inch sheet metal and not strong enough to withstand the sustained force and abrasion from bulk material.

Instead, Martin Engineering designers came up with the idea of raising the chute work about 4” above the belt, out of the way of the material, then putting the wear liner on the outside.  Using this approach, the material still hits the liner and doesn’t damage the chute.  To engineers, it was a real light bulb moment.  The team was surprised that no one had tried it before, as it had some obvious benefits.

Copyright Martin Engineering 2024
The external wearliner and skirting system improve safety, maintenance costs, and equipment life.

After elevating the chute box above the material flow, a 3/8″ or 1/2″ (0.95 cm or 1.27 cm) thick abrasion-resistant liner plate (AR500) is mounted on the outside of the chute, followed by the skirt seal.  Mounting brackets with jackscrews provide a tight hold, with precision adjustment of the wear liner to reduce spillage.  This system closes the gap between the liner and the sealer, thus eliminating abrasion from trapped material without interfering with existing supports.  When accompanied by skirting and clamps, the system forms a tight belt seal, delivering outstanding fugitive material control.

Safer By Design

When a conventional wear liner loses its edge, the replacement procedure is what operators describe as an undesirable maintenance assignment.  The authorized entrant would go into the chute with a grinder to remove the welds and take off the sacrificial liner, which may have required a torch to cut away the existing material.

This can be extremely dangerous, for two reasons.  First, the liner can weigh several hundred pounds, and when a worker cuts it loose, it can fall and endanger the personnel inside the confined space of the chute.  Second, nearly any dust can be explosive under the right conditions, and having to grind or torch-cut the old liner introduces a spark or open flame.

Copyright  Martin Engineering 2024
Safety by Design helps avoid crossing the plane of the conveyor to perform maintenance.

Some companies thoroughly wash out the chute prior to entry to avoid any chance of combustible particulates, making the job even more time-consuming.  Once the old liner had been removed, the new wearliner was positioned to keep it as close to the belt as possible and welded into place.

Copyright Martin Engineering 2024
The dual skirting design runs the entire length of the chute and can be flipped for extended life.

Installing an External Wearliner

An external liner can be installed and adjusted faster and easier, without the need for a grinder or torch, through the use of special mounting tabs.  Clips for bolting the liner are initially welded in place but do not require removal when the liner wears out.  Since the work is done from the outside, without any grinding sparks or torch flame, the hazard of explosive dust from tool usage is greatly reduced.  Replacement liners come in a standard length of 72 inches (1829 mm), and Martin Engineering uses laser cutting technology to create the complex geometries necessary for a custom fit.

The new liner is easily retrofitted onto existing equipment.  Installers simply cut back the chute wall on existing chute boxes to accommodate the external wearliner.  On new installations, the chute is easily engineered to work with the new liner design, as well as other Martin Engineering components such as dust curtains, track-mounted idlers and cradles.

Case Study – ArcelorMittal Port Terminal

An ArcelorMittal port terminal in Indiana was experiencing excessive spillage, tail pulley fouling and belt tracking issues with a petroleum coke transfer point on the stacker/reclaimer boom conveyor.  Material spilled out the sides of the chute and piled onto the floor, creating a hazard and requiring workers to be reassigned from other duties several times per month to clean, increasing labor costs.  Moreover, the spillage was getting onto the return side of the belt and fouling the tail pulley, causing loading and tracking issues.  Operators attempted to remedy the situation by having a new transfer chute built.  However, once installed, operators realized that the problem was not with the vertical chute, but the loading zone and settling zone equipment.  These were onerous and time consuming to service requiring a maintenance team with confined space entry permits which extended downtime and diverted experienced staff from other important tasks.

Copyright Martin Engineering 2024
Mechanical air cleaners are low maintenance
and improve the air quality around the system.

Managers invited Martin Engineering to examine the issue and offer solutions.  After conducting a thorough Walk the Belt™ procedure, technicians installed external wearliners, ApronSeal™ Double Skirting HD (heavy-duty), Trac-Mount™ Idlers, Upper and Lower Trackers, and a V-Plow.  The wearliner protects the chute wall against punishing material as the double skirting forms a seal that rides lightly on the belt, keeping fines from escaping.  The wearliners and skirts are externally mounted for safe and easy maintenance with no confined space entry required.  To retain a true belt path, technicians installed upper and lower tracking technology and 35º idlers that slide out for faster one-person maintenance.  To protect the tail pulley, a V-Plow was installed to deflect fugitive material on the belt return.

Three Martin technicians and 6 contractors completed the installation project over 2 shifts (12-hour and 14-hour).  The chute was tested several times and adjusted until the proper trough angle and belt seal were achieved.  After several boatloads, the customer reported “not a single pellet has hit the deck.”  Along with a near-complete elimination of spillage, operators said that the tracking issues were also resolved and the tail pulley has had no incidents of fouling from return side debris.  Moreover, the reduction in labor reduced the cost of operation.  Managers are currently working with Martin Engineering on other projects.

Safety in Design

An external wearliner could be considered a safety device since it eliminates the need to expose maintenance staff to a potentially hazardous activity like confined space entry.  Moreover, the external wearliner and skirting configuration extend the life of the equipment and the chute, while reducing spillage and dust.  Retrofitting the transfer chute with updated equipment improves system performance with no required certification for maintenance, which reduces the number of workers and hours to replace and service, in turn lowering the cost of operation. IHW

Martin Engineering has been a global innovator in the bulk material handling industry for more than 80 years, developing new solutions to common problems and participating in industry organizations to improve safety and productivity.  The company’s series of Foundations books is an internationally-recognized resource for safety, maintenance and operations training — with more than 22,000 print copies in circulation around the world.  The 500+ page reference books are available in several languages and have been downloaded thousands of times as free PDFs from the Martin website.  Martin Engineering products, sales, service and training are available from 18 factory-owned facilities worldwide, with wholly-owned business units in Australia, Brazil, China, Colombia, France, Germany, India, Indonesia, Italy, Malaysia, Mexico, Peru, Spain, South Africa, Turkey, Japan, the USA and UK.  The firm employs more than 1,000 people, approximately 400 of whom hold advanced degrees.  For more information, contact info@martin-eng.com, visit www.martin-eng.com, or call (800) 544-2947.