Contamination in reflecting ultrasonic meters
Scientific investigations prove adverse effects from contamination in reflecting ultrasonic flowmeters are a myth
Exhaustive investigations at the E-ON Ruhrgas high-pressure gas testing facility in Lintorf (Germany) on possible effects of contamination on ultrasonic flowmeters (UFM) have irrefutably shown that the accuracy is not affected by the reflection principle. Indeed, the investigations substantiate a significant advantage of reflection technology; actually compared to direct path measurement the level of contamination can be recognised from the reflection properties of the acoustic signal.
- Reflectors: Left clean, centre slightly roughened, right considerably roughened
Part of the tests included the effect of roughness of the reflector surface. For this reflectors were made with medium and high roughness. Since the KROHNE ALTOSONIC V12 UFM is equipped as standard with reflectors, the investigators were able to vary the roughness of the reflecting surface to any desired extent, without having to change the roughness of the inside wall of the meter.
- Conditions - clean or contaminated - have no effect on the accuracy. Click graph to expand
Even with more severe roughness the automatic gain simply had to compensate a signal of 6 dB. Figure 2 shows the accuracy before and after the “contamination”. There was no adverse effect.
The increase in automatic gain is seen by defining the state on commissioning (the state under clean conditions) as the specified state and comparing it with the actual state after contamination. This reveals the advantages of the reflection principle: the design of non-reflecting UFM’s makes it impossible for them to detect such small quantities of contamination or corrosion inside the meter.
The results shown here are only a part of the comprehensive results that are to be published at the 2010 Flomeko Conference in Taiwan. Further results include the effect of bottom fouling, roughness in the entire meter, as well as roughness in the inlet run.