Radar checks up on asphalt levels

Solartron Mobrey is working with a leading supplier of asphalt products to trial its MRL700 noncontact radar level transmitter in an asphalt (bitumen) application.

Solartron Mobrey is working with a leading supplier of asphalt products to trial its MRL700 noncontact radar level transmitter in an asphalt (bitumen) application.

The radar serves a dual purpose in helping monitor tank asphalt levels as well providing a safety measure to avoid tank fires should contents levels fall too low.

It is the first noncontact level transmitter to provide a reliable, continuous level measurement in this notoriously difficult application.

The measurement of asphalt levels has always been a problem for the industry, as the environment inside container vessels is hot and vaporous and there is turbulence at the surface due to agitation or a static mixer in the tank.

Agitation is essential to limit product build-up and/or hardening, making contact level measurement technologies inappropriate.

To keep the asphalt in its liquid state, it is stored at high temperatures, by using heated "fire tubes" in the base of the tank.

It is critical for the supplier to manage the asphalt level in order to prevent messy overspills.

Furthermore, should the asphalt level fall too low, it will be heated too quickly above the asphalt's flashpoint and begin to burn, causing a maintenance problem and potential fire hazard.

Solartron Mobrey's MRL700 radar technology has enabled the asphalt supplier to measure asphalt levels in the tank, continuously for the first time.

Previously personnel had to drop a weighted string into the tank from the top and look for a ripple on the surface, then measure the string.

This approach was both time consuming and potentially dangerous.

MRL700 uses the FMCW (frequency modulated continuous wave) technique to ensure the consistency of measurement accuracy.

A continuous microwave is transmitted from the antenna down to the product surface below where it is reflected back.

The distance in frequency between the received and transmitted signal is a measure of the distance travelled.

FMCW produces more data and therefore a higher accuracy measurement than pulse-based devices which use short bursts of energy at lower frequencies.

The customer invited Solartron Mobrey to install the MRL700 radar unit for trial with some scepticism after a competitor's radar unit had been tested and failed.

The success of this trial demonstrates a significant step forward in safe, reliable and accurate asphalt level management.

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