Published March 2016
Level measuring specialists Hycontrol have designed and installed a multi-point bitumen level measuring and overfill protection system for Aggregate Industries at their Express Asphalt plant at Botley, near Southampton, England.
The system, utilising microwave and capacitive technologies, has been fitted to four 36.5tonne tanks containing hot bitumen, replacing the existing ‘cat and mouse’ level system. This out-of-date mechanical arrangement, based on pulleys and counterweights, was becoming increasingly maintenance-heavy, raising serious concerns over its long-term reliability.
The Hycontrol instrumentation for this application has been designed to fall within strict budget restraints whilst also ensuring the systems meet the latest Eurobitume / RBA (Refined Bitumen Association) guidelines designed to prevent spillages and accidents during the filling and operation of hot bitumen tanks.
The RBA guidelines are very clear, mandating that hot bitumen tanks must be fitted with a continuous level measuring system, a high-level alarm (HLA) and a totally independent high-high level alarm (HHLA). To avoid product spillage whilst the delivery hose/line is being cleared, the HLA should be set to trigger at the available capacity of the tank less 10%, whilst the HHLA should be set to warn operators that there is only 7.5% of the available tank capacity remaining.
The accurate and reliable measuring of bitumen presents a number of challenges. Traditional ultrasonic technology cannot cope with the high temperatures, pressure changes and product build-up on the transducer heads encountered in such harsh environments. Any invasive measurement technology can be susceptible to product build-up on the sensors, rapidly resulting in degradation in performance.
