Non-invasive, clamp-on ultrasonic flow measurement is transforming the way that the chemical industry monitors and manages utility services. Once considered an almost insurmountable measuring task for clamp-on flowmeters, this innovative technology is accurately and reliably measuring steam without interrupting normal system processes.
Two pairs of ultrasonic sensors are mounted on the pipe at a defined distance from each other, forming two acoustic measuring ‘gates’. Ultrasonic signals are then radiated into the pipe and modulated by the vortices of the turbulently flowing steam. Because the vortices are carried along by the flow, they pass between the two measurement gates with a time delay. And through cross-correlation of the modulation signals over time, the flow velocity of the steam can be determined, with the mass flow being calculated based on the geometry of the measuring point and the physical parameters.
Low accuracy results in paying more for consumption –
At a sprawling chemical hub in the southeast of the Netherlands, a cooperative approach to utility services is in operation, including the supply of essential energy sources such as electricity, compressed air, natural gas, pure gases, water and steam. The utilities are meticulously tracked and accounted for in a document known as the ‘measuring book’ – setting the rules for utility transactions on the industrial park.
Operators were searching for a more cost-effective and reliable steam measurement system, as previously installed meters were proving unreliable. In fact, they were classified as the lowest accuracy class (D). This meant that a significant amount was paid for steam consumption, while less revenue was received for the steam contributed to the network.
FLEXIM was tasked with proving the effectiveness of clamp-on steam meters as a viable alternative. Following a detailed technical review and discussions with the utility provider, it was clear that clamp-on technology would require verification in order to be accepted.
Tests, calibration, on-site testing and implementation –
The calibration process involved using compressed air as the medium, and ensuring that the conditions closely matched the actual steam application. The calibration setup differed from the customer’s in terms of medium, pipe size and temperature, but this was not critical for validation. The calibration process ran for two days and effectively showcased the technology’s accuracy, with all test points well within its accuracy statement.
Following the successful calibration and additional on-site tests, the purchase and installation of two clamp-on steam meters went ahead. The meticulous installation process took into account factors that can influence accuracy, such as pipe diameter and wall thickness. With the meters connected to the process computer, the total uncertainty of the measurement was calculated, classifying the meter solution as a class B (better than 5%) solution.
Reduced costs and increased revenue –
Ever since installation, the clamp-on flowmeters have continued to prove their reliability, with the measurements typically agreeing within a 1% margin. This level of accuracy has been invaluable to the utility provider, reducing the cost of steam import and increasing revenue from steam production. The implementation of clamp-on technology has delivered a much clearer picture of the 3 bar steam network across the chemical site, helping to recover the mass balance.
To find out more about the capabilities and benefits of clamp-on ultrasonic steam measurement in the chemical industry, contact Simon Millington – www.flexim.co.uk | firstname.lastname@example.org | +44 (0)1606 781 420
By FLEXIM Instruments UK Ltd