Successful Reduction of Dust & Spillage

Transfer Point Improvements

To address the issue, Martin Engineering technicians removed troublesome sections of the air-supported conveyor and replaced them with specially-engineered transfer points. They also modified existing transfer points, installing drop chutes to help eliminate dust and transfer chutes with a hood-and-spoon design to improve the material flow.

Reducing the material turbulence during transfers is key to preventing fugitive dust. By managing the material speed and direction, transfer chutes help minimize impact and wear on liners and belts, while containing the dust and spillage that are often generated at transfer points .All of the chutes were field-fabricated, which helped get an exact fit and minimize lead time.

The transfer chutes employ special geometries that capture and concentrate the material stream as it travels through. Each unit is customized to suit the specific material characteristics and conveyor systems of the individual customer. They provide the dual benefits of minimizing aeration and preventing buildup within the chute, particularly important when dealing with combustible materials.

The installation team also placed electric rotary vibrators in key locations inside drop chutes to reduce the potential for plugging. To further ensure control of fugitive material, settling zones were created at the transfer points to slow the air speed, with dust curtains to contain airborne particles.

Dual Sealing at Loading Zones

Finally, skirtboard sealing systems were installed on the sides of the loading zones to contain dust, eliminate spillage and reduce cleanup. Martin Apron Seal Skirting was the first dual-sealing system on the market, as it incorporates a primary seal clamped on the steel skirtboard to keep lumps on the belt and a secondary or “outrigger” strip to capture any fines or dust particles that pass beneath the primary seal. The secondary seal lies gently on the belt and self-adjusts to maintain consistent strip-to-belt pressure, despite high-speed material movement and fluctuations in the belt’s line of travel.

Martin Engineering’s Apron Seal Skirting provides two wear surfaces on a single elastomer sealing strip, installed along the bottom of the skirtboard. When the bottom side of the strip against the belt is worn, the sealing strip is inverted, providing a second service life.

With the modifications in place, HPU reports significant reductions in spillage and airborne dust. “We’re very pleased with the results we’ve seen in fugitive material control,” Myers concluded. “We’re now reviewing several other conveyor sections to determine the opportunities for additional dust control measures. Our goal has always been to provide the Hibbing area with safe, reliable power that’s produced and delivered in an environmentally-responsible manner, and this work is a reflection of that commitment.” n