“The basic configuration of a half-lane milling machine starts with a cutter drum inside a cutter housing where the asphalt is milled up off of the road,” Lyons says. “The drum is constructed so that it augers the millings to the center of the housing where kicker paddles eject them out through a window in the front of the cutter housing onto a ‘pick-up conveyor.’ The pick-up conveyor then transports the millings and dumps them onto a ‘discharge conveyor’ that can be raised and lowered and swings from left to right for loading trucks.”
With the Wirtgen unit, there is a primary transition area where the millings are loaded out of the housing onto the pick-up conveyor and a secondary transition area where the millings are dumped from the pick-up conveyor onto the discharge conveyor. Additional improvements include improved cutter housing sealing and sealing around the primary transition area and improved sealing between pick-up conveyor and the frame of the machine.
“Better sealing helps confine airborne dust within the cutter housing and pick-up conveyor chute and maximizes efficiency of the vacuum system,” Lyons says. “Vacuum system ducting is incorporated into the framework of the machine directly above the pick-up conveyor.
“This ducting exits the forward frame of the machine where flexible ducting is installed and routed to a high performance fan located on top of the discharge conveyor chute. The fan pulls the dust through the ducting and discharges it into the discharge conveyor chute to continue out the end of the discharge conveyor away from the tractor and operators.”
Contractors must still be aware that the water system of milling machines is the primary dust control system while the vacuum system provides a secondary level of dust control.
Price, maintenance and retrofits
Contractors can expect to see a few changes with the implementation of the new components to the milling machines. Changes to any type of equipment often results in changes in price, maintenance and the possibility to retrofit older units.
With the new components, a price increase of about 3% is expected for both Roadtec and Wirtgen milling equipment.
“When you add additional components to a machine, in this case this system, there will be additional cost,” Musil says. “We want to arrive at the best solution we can to protect our workers health — that’s number one. We are all in this together to improve our workers health.”
Roadtec’s new system will be available for purchase as an equipment option in January 2013. “The new system won’t be mandatory until NIOSH sets the date,” Richmond says. “Contractors need to be prepared when the regulation is written, and they need to be aware that in our opinion this process will move forward in the not too distant future making fans the industry standard.”
Additional maintenance will be required for the changes made to the milling machines, and manufacturers will release handbooks with new sections on the proper maintenance. Richmond doesn’t expect contractors to see a considerable increased cost in time or maintenance of the milling machines.
As for older units, contractors will be able to retrofit various manufacturers’ models. According to Lyons, contractors will be able to retrofit some older Wirtgen models. Richmond expects to see some third-party manufacturers distribute retrofits of the new system for various milling machines.
It’s essential for contractors to be aware of the importance in maintaining and operating their equipment’s dust control systems properly to ensure the safety of their workers.