Non-contacting ultrasonic specialists Pulsar Process Measurement have supplied a high-accuracy DUET transducer array to a Premier Foods owned company in Newport. The superb accuracy achieved has allowed the company to make a substantial saving on effluent charges. Siris Environmental of Co. Durham installed the transducer and its associated control unit to Premier Foods as part of an open channel measurement project.
Companies are charged on both volume and quality of the effluent being discharged and many either fail to appreciate the importance of accurate measurement or simply don’t know how to achieve a high standard of accuracy. The MCERTS scheme has introduced a way to benchmark the accuracy of a complete installation. Siris have introduced an ‘MCERTS Compliance Guarantee’ to reassure companies that their installation meets the standard, and in this case they handled design, installation, commissioning and also arranged 3rd party inspection of the installation for MCERTS certification.
As Simon Richardson of Siris put it: ‘Many companies see the MCERTS Certification Scheme as another additional expense, they often don’t appreciate that the scheme ensures accurate measurement of their effluent discharge and in this case we have proved that a well implemented installation can save real money.’
Paul Wiggins of the Environment Agency also commented: "It is excellent news that an industrial effluent flow monitoring installation meeting MCERTS requirements and using a MCERTS certified flow meter has had such a positive impact. Managing flow is crucial to effective effluent treatment, protecting the environment and can have considerable financial benefits to the industry."
Siris led the project, supplying and installing the primary measurement device together with the flow and sampling equipment. Richardson again: ‘to achieve the most accurate flow measurement system, both the design and the installation of the weir tank and associated equipment was undertaken to the highest possible standards. It is vital that upstream flow conditions are controlled, the weir tank was constructed to be very rigid, the weir plate was reinforced and the chamfering of the edges of the weir plate was closely controlled. The whole system was designed and installed to meet the requirements of British Standards.’
Pulsar’s DUET non-contacting ultrasonic transducer array was chosen for the extraordinary accuracy achievable. Ultrasonic systems work by bouncing a sound pulse from the surface being measured and calculating the distance from the time taken for the pulse to return to a transducer. The accuracy of the measurement depends on the speed of sound, which can vary with temperature. Temperature changes can be compensated for, but a temperature compensation circuit can’t respond immediately and there may be temperature variations in the column of air below the transducer face. DUET uses two transducers a known distance apart, and by comparing the returning signal from both transducers, variations in the speed of sound are dynamically compensated for. This was critical to the success of the project. A 2mm variation in measurement accuracy would result in an error of 40 cubic metres per day.
