The properties of laid asphalt are dependent on application and climatic conditions.
The asphalt mixture for a sealing project in the Northern Territory, for example, needs a different structural make up to that for strengthening upgrades in central Melbourne.
Mixed asphalt silos therefore have to accommodate significant variability, which when paired with asphalt’s innate viscosity and temperature, means plants require advanced level reading equipment.
VEGA Managing Director John Leadbetter says while radar level technology is relatively new to the asphalt industry, it’s gaining traction for reliability and accuracy.
“Radar level transmitters have been used in the process industry ever since VEGA developed a unit in 1991,” Mr. Leadbetter says.
“Their use in asphalt production is more recent however, only really taking off after the introduction of 80 gigahertz [GHz] units in 2014.”
Since 1991, the German measurement technology company has provided the international market with radar level measuring sensors for material production.
“Initially the units were operated with a 6GHz frequency,” Mr. Leadbetter says.
The original units weighed several kilograms and could only be operated from an alternating current power supply.
According to Mr. Leadbetter, VEGA released the world’s first true loop powered radar level transmitter in 1997, meaning the unit didn’t need to be connected to an alternating current power supply.
Mr. Leadbetter says in doing so, VEGA created a transmitter suitable for a wider range of industry applications.
VEGA continued researching and innovating, releasing a 26GHz transmitter in 1999.
In the second decade of the 2000s, VEGA began looking into the potential of a 80GHz frequency radar transmitter.
“As with all developments, we soon reached a point where the components and physics of the 26GHz technology had been maximised,” Mr. Leadbetter says.
During the testing phase, VEGA carried out a number of real-life customer trials, where Mr. Leadbetter says it was found that the higher frequency delivered superior radar beam focusing.
According to Mr. Leadbetter, this opened radar technology up to applications not previously practical, such as bitumen emulsion.
“Applications that have a relatively low DK level, with a low level of oxygen transmissibility, had not previously been considered suitable for radar level reading,” Mr. Leadbetter says.
“80GHz changed that and really paved the way for widespread radar uptake.”
In addition to high frequency, an effective radar transmitter needs components that provide a high level of dynamic range sensitivity. This is due to dynamic range sensitivity facilitating the detection of even the smallest pressure signals.
Radar level transmitters typically had a dynamic range of roughly 90 decibels. In 2014 VEGA developed the VEGAPULS 69 for solids in 2014, with a dynamic range of 120 decibels. This was followed up with a unit for liquids in 2015.
“The release of the 80GHz transmitter for liquids increased the capacity of radar measurements for bituminous material, which has traditionally proved challenging given its unpredictable nature,” Mr. Leadbetter says.
For every three-decibel increase, the power of the transmitter doubles.
“An increase of 30 decibels over previous and existing radar frequencies meant the sensitivity level of the VEGA 80GHz was 1000 times higher than previous transmitters,” Mr. Leadbetter says.
“With this increase, VEGA transmitters were now able to measure extremely low DK products such as plastics, which is significant given the rise of recycled material in asphalt.”