Cold milling machine
With cold planers are asphalt , - concrete - or gravel layers ablated different thickness. The cold milling machine moves over the layer to be milled, whereby a rotating milling drum is lowered according to the milling depth and loosens the material. The machine can mill the road surface both parallel to and at a certain incline to the road surface. During the milling, the set milling depth can be regulated in relation to a previously defined reference height.
Depending on the construction method and the logistical requirements of the construction site, the milled material obtained is loaded onto a truck from a loading belt, placed on the side or left in the remaining milling track. In the case of small milling machines, which are used when smaller areas are machined or when milling in a confined space, work is often carried out without a loading belt.
Cold milling machines are available in different sizes. Small milling machines have working widths of approx. 0.30 m to 1.00 m. Large milling machines are available with working widths of up to 4.40 m. In Germany, for logistical reasons, milling machines over 2.20 m are rarely used, as such a milling machine, including low-loader and tractor unit, has a total weight of approx. 70 t and is also marginal in terms of transport height and width.
From fine milling is used when the asphalt layer should not be replaced, but can be driven after the operation immediately. Other rollers with a higher number of chisels are used for this. A subtype of fine milling is vertical fine milling , here a vertically milling chisel plate is used, which can mill out local unevenness (lane markings, bus bays ) or shaft covers.
The predecessor of the cold milling machine is the hot milling machine , which works according to the same principle, but can only process a strongly heated surface. Compared to the cold milling machine, this process has much higher energy costs (gas consumption for heating) and works more slowly or at shallower depths than is possible with the cold variant. Another point is the enormous oxygen consumption, which makes hot milling in closed buildings impossible. For example, a milling cutter passed out while working on an ice rink because the oxygen content of the air dropped too much during the work. Despite these disadvantages, hot milling was the first option for effective road rehabilitation, as high forces occur during cold milling, which place enormous stress on the entire machine. Not only the milling bits have to be made of highly stable special steel , the roller drive, bearings and protective plates have to withstand high mechanical loads. At the beginning of the 1980s, the first cold milling machines were mass-produced and the first companies specialized in this type of renovation. Today, cold milling is the most common construction method used in road renovation.
With cold milling, the stones used in road construction material can be crushed, which can release E-dust , A-dust , quartz dust and asbestos fibers (if mineral raw materials with natural asbestos content were used). The BG / BGIA recommendations evaluate the exposure of employees to these hazardous substances when removing paved surfaces from asphalt layer by layer using front-loading cold milling machines that have an extraction system with return. In addition, the recommendations provide practical information on how suitable protective measures can be used to ensure that the occupational exposure limits are complied with. Other requirements of the Hazardous Substances Ordinance , e.g. B. Information gathering, instruction obligation and preventive occupational medicine remain in place.
- German statutory accident insurance e. V. (DGUV): DGUV Information 213-720 - BG / BGIA recommendations for risk assessment according to the Hazardous Substances Ordinance: Use of road milling machines with extraction systems - milling of asphalt surfaces. Retrieved November 25, 2019 .