Dust Solutions: Conveyor Transfer Points

November 21, 2025|Dust & Fume Control, Industrial Hygiene in the Workplace

By: R. Todd Swinderman, P.E., Contributor

Dust can foul rolling components, machinery and equipment air intakes, necessitating extra parts and labor for cleaning and maintenance. These factors unnecessarily elevate operational costs, especially when there are methods and technologies designed to control and suppress dust emissions—before they become airborne and create these risks.

Most of the dust present in bulk materials originates from the reduction in particle size due to crushing or grinding, as well as from transfers between steps in the production process, such as conveyor transfer points or during discharging onto a stockpile.

Causes of Dust on Conveyors

Conveyors are a significant source of dust emissions, yet they can also help reduce fugitive dust. For instance, in pit-crushing and overland conveying at a surface mine, total site dust generation is lower compared to truck haulage. Some raw materials are easily wind-swept and, in some cases, an enclosed conveyor belt system may be necessary.

When the haulage involves a conveyor belt, dust generation depends on the loading and discharge processes, as well as the management of these processes. Closed conveyors are highly effective at preventing contamination and shielding the cargo from environmental elements, but they must still be opened and closed for loading and discharge.

Passive dust-reduction strategies include:

Shorter or directed drops – Transfer chutes over loading zones that minimize the impact of cargo on the belt below reduce the turbulence within the loading zone, thereby decreasing the amount of dust released.
Managing the flow – While rock boxes can be effective, they are also susceptible to clogging. Therefore, experienced engineers recommend a sloping system that slows material to minimize impact and induced air, along with loads in the center of the belt to reduce shifting and enhance belt training.
Preventing belt sag between idlers – The belt can dip slightly between idlers, creating gaps between the belt and skirting that allow dust and fines to escape in the loading zone. Using an impact cradle with shock-absorbent polyurethane bars reduces impact strain on the belt and ensures an even belt plane without gaps between the skirting and belt. Cradles can extend along the entire length of the stilling zone.
Fully enclosed transfers – By completely enclosing the loading and settling zone, dust is contained. Items like dust curtains and dust bags can then be added to control airflow and capture dust.

the Decision to Slow Belts Down

With lower belt speeds, the width of the belt must increase to convey the same tons per hour, creating a dilemma between capital costs and operating costs. Many sources suggest belt speeds of 2m/s (394fpm) or less for reducing dust generation.

It is worthwhile to closely compare the capital savings from a higher-speed belt with the long-term costs of maintenance, cleanup and safety. There are clear relationships among increased cleanliness, fewer safety incidents and more reliable production, so the trade-offs should be examined carefully. Foundations™ for Conveyor Safety—a comprehensive textbook for safe conveyor operation written by Martin Engineering—provides a detailed methodology and data sources for including direct and indirect costs in the financial analysis in section six.

Pay Attention to Belt Tension

At critical speed, the bulk material loses contact with the belt at the idler and is launched into the air, landing back on the belt at a slightly lower speed than the belt itself. This splashing action opens the profile, creating induced air flows that can release dust—resulting in turbulence, impact and degradation as the material lands and returns to belt speed. Maintaining a belt sag of 1% between idlers is a common specification. Typically, the concerns in conveyor design regarding these belt sag phenomena involve the increased belt tensions necessary to counteract the frictional losses.

Design choices often overlooked in a dust-reduction strategy can minimize dust creation from the undulations of the bulk material on the belt during transport. Managing belt tension to reduce sag between idlers mitigates the effects of material trampling and splash.

Material trampling refers to the particle-to-particle movement that occurs when the bulk material profile changes as it passes over the idlers. Both trampling and splashing can generate dust, due to the numerous times cargo crosses over idlers each hour. The higher the belt tension, the lower the trampling loss.

Control the Air, Control the Dust

If the material stream can be constrained so that it does not open up when discharged, the amount of air induced into the transfer point is minimized. As the material particles disperse, they create a low-pressure zone in the spaces, which encourages airflow into the transfer point.

The amount of dust that can become airborne is directly proportional to the volume and speed of the airflow through the transfer point. If the openings in the chute are restricted to the practical minimum, the inward airflow is limited. A useful dust-control strategy is to capture the material shortly after discharge and keep the stream coalesced as tightly as possible to minimize induced air.

Conclusion

Much emphasis is placed on planning the mine to maximize profitability, but little attention is paid during the initial feasibility studies to how the layout can affect dust creation and emissions. Conveyor transfer points have a history of being drafted rather than designed. Design tools are now readily available to address these critical details. How the conveyor is operated and maintained also significantly affects dust generation and release. IHW

About the Author:

R.Todd Swinderman, President Emeritus with Martin Engineering, joined the company’s Conveyor Products division in 1979 and then served as VP and GM, President, CEO and Chief Technical Officer. He has authored dozens of articles and papers; presented at conferences and customer facilities worldwide; and holds more than 140 active patents. He served as President of the Conveyor Equipment Manufacturers’ Association (CEMA).