In asphalt production, process temperature is a crucial factor in plant performance and the properties of the hot mix. To ensure long-term quality of the road surface, temperatures must be precisely monitored during the production process and as the hot mix is loaded onto trucks.

Dryer drum exit

In asphalt production, a crucial process parameter is the temperature of the mineral aggregate and the reclaimed asphalt pavement (RAP). As these materials enter the dryer drum, their temperatures can vary depending on weather conditions. To ensure that temperatures remain within specified limits as the material is fed to the mixer, temperatures are monitored at the point where the material exits the drum. Burners are controlled based on this data.

Mixer discharge and Truck loading operations

The hot asphalt mix is discharged directly from the mixer or from the hot mix storage silo onto trucks that deliver the asphalt to the road construction site. In order to achieve uniform quality and long-term performance of the road surface, it is essential that the hot mix exhibits a specific temperature as it arrives at the job site and when road paving operations begin. Asphalt temperatures are thus monitored and documented as the hot mix is loaded onto delivery vehicles. Common to all asphalt plants are the severe environmental conditions. A temperature detection device will be exposed to hot and aggressive vapours and dust.

Solution

Pyrometers are ideal for monitoring temperatures of a hot liquid material. A pyrometer detects the infrared radiation emitted from an object at a safe distance, without surface contact, and produces an accurate temperature reading. Most commercially available pyrometers will not hold up to the aggressive fumes and dust present at asphalt mixing plants. Lenses are especially sensitive to such harsh industrial environments. The CellaTemp PQ 11 AF 8x pyrometer was specifically designed for use at asphalt and concrete plants and features a stainless steel housing as well as a special lens whose surface is highly resistant to impurities. When combined with certain fittings and accessories such as an air purge and sighting tube, the PQ 11 AF 8x provides many years of reliability and precision. At proper operation the measuring system works maintenance and wear-free. The integrated digital display is very convenient during commissioning and plant maintenance procedures. During overhead load out onto trucks, a temperature reading is recorded for each load and saved in the plant’s data acquisition system as a matter of quality control and verification.