Every spring, crews head out onto our roads and highways to repair all the cracks and potholes that otherwise mar our driving experience. Milling machines that prepare sections for repaving are a familiar sight. In the past few years, significant technological advances have significantly reduced the airborne dust from the milling process. In this edition of Experts Corner, SMS Equipment milling expert Chaunce Edwards, Technology Support Specialist for our construction division, explains how Bomag’s Ion Dust Shield (IDS) raises the bar for roadbuilding air quality.

How does the milling process expose people to dangerous particles?

The milling process removes material from sections of existing roadways so that you can repair cracks and potholes and all that terrible stuff. Milling machines allow us to target only the layers that need repair. To do the cutting, we use a rotating drum with carbide picks. That produces a lot of dust, some of which is silica dust, essentially very fine sand. This material can be hazardous, especially to workers who could be exposed to it for extended periods of time, but also to people walking by.

How has this been dealt with in the past?

The older technology, which has been around for a long time, uses water to cool the picks on the drum, and that also helps to keep the dust down. It uses a pressurized system and spray bars situated across the drum.

There have been several improvements to that. One is the use of water additives that are added to the water tank. Those are very expensive, but it is imperative to use them to reduce the dust and cool the drum.

Another technology is the vacuum cutting system (VCS), which vacuums the dust as it comes off the drum and sends it up through the conveyor onto the truck. Finally, some vendors use pressurized cabs to protect the operator from dust.

Machines with these technologies meet ISO standards and the current NIOSH testing requirements for safety. Bomag’s Ion Dust Shield (IDS) adds to that existing technology to make the air even safer.
 

How does the Ion Dust Shield work?

The IDS is situated at the end of the conveyor. What we do, is force that dust-filled air through the sealed conveyor into a box. Inside the box are electrically charged blades that attract the really fine particles. So, they go into the truck instead of going into the air. Interestingly, it is not a filter, so it doesn’t have that maintenance requirement.

The IDS removes the most dangerous particles – they are so tiny that you don’t see or feel them, but they can get down deep in your lungs and cause silicosis. The IDS removes more than 80% of those harmful particles, so that’s a substantial improvement on top of the measures we already have in place with the older technology.

A big advantage is that instead of just protecting the operator who has the most exposure, the IDS protects people nearby by keeping these particles out of the air altogether. Those microscopic particles can stay in the air for a long time – if there is no wind, they can remain airborne for up to 30 hours. So, if you’re milling around a school or in a residential area, that could be a public hazard.