Titan Ultrasonic Liquid Flow Meter for Low Flow Rates

Across the industrialised world there is an increase in demand for liquid flow meter systems operating at low flow rates. The range of applications that might benefit from such systems is very wide and includes offshore, industrial, medical, food, beverage, pharmaceutical and laboratories. The requirements on flow meters to fulfil these applications are also becoming more demanding. An ideal flow meter might have through flow design with minimum pressure drop and improved accuracy as well as offering operation at higher pressures / temperatures and across wide flow ranges with greater accuracy. A meter which can be easily cleaned either chemically or with a “pig” and be able to operate over a wide range of Reynolds numbers would be a great advantage.

Typically the three most popular current technologies for such liquid flow meters are electromagnetic, Coriolis and ultrasonic. Electromagnetic meters are restricted to conductive fluids and Coriolis meters are expensive which leaves ultrasonic as being the most widely viable meter type for these applications.

Of the two liquid flow meter ultrasonic technologies, Doppler shift and time-of-flight (TOF), the latter offers the best performance over the widest range of operating conditions. Time-of-flight ultrasonic flow meters are generally suited to larger pipe sizes but they offer the potential for smaller tube sizes.

This paper describes the design and performance of a novel, small bore ultrasonic liquid flow meter which operates in pipe diameters where traditional meters of this type stop working. Initially the meter was developed as a replacement for small turbine meters in laboratory, industrial and beverage applications. The achieved performance has far exceeded expectations making the meter suitable for a far wider range of applications. The patented technological approach has enabled a wide variety of different flow measurement, dosing and control applications to be addressed. Using the same electronics with an appropriately sized flow tube it is possible for the meter to monitor a range of flows from 3m3/hr to 0.12l/hr with an accuracy of better than ±1% over a flow range of exceeding 200 to 1 when used with pipe sizes as small as 1mm in diameter. The described ultrasonic flow meter is capable of providing an update rate of 0.05s and is therefore suitable also for batching type applications.