Today there is an increasing need to monitor emissions and improve energy efficiency in order to meet new environmental and economic challenges. This is driving the requirement for better and cheaper methods of measuring gas flow in difficult applications such as shale and coal seam gas well heads, flare gas stacks, landfill and biogas. The gases in these applications are usually dirty and wet and they can contain corrosive gases and liquids. Until now, there have been no suitable flowmeters for many of these applications.
The new FMU ultrasonic flowmeters use the patented Broadband Continuous Wave© signal process and high-efficiency titanium transducers to provide reliable and precise flow measurement even in the most extreme applications. The FMU is a multipath ultrasonic flowmeter with sensor pairs arranged in four chordal paths ensuring good interrogation of the flow profile. The titanium encapsulated sensor technology assures reliable and maintenance-free performance even in extreme applications.
Four Paths for Accuracy and Reliability
The FMU has four paths as standard. It has been tested to meet the international standards for custody transfer metering including AGA-9 and OIMLR137. Integration of the flow across the paths provides accurate measurement even with varying flow profiles caused by changes in flow velocity, gas composition and pressure or upstream pipe configuration. Fast response is maintained by the simultaneous transmission on more than one path using Broadband Continuous Wave processing. The measured flow profile provides a diagnostic tool. Should one path fail, the Path Substitution Algorithm uses historical flow data to continue reliable flow measurements until the path recovers or remedial action is taken.
Broadband Continuous Wave
Most ultrasonic flowmeters transmit a short burst of ultrasonic energy consisting of between one and four pulses or cycles. A few ultrasonic meters use a short code consisting of a few cycles to as much as a few dozen cycles. The FMU ultrasonic flowmeter transmits many thousands of cycles in an almost continuous stream of encoded pulses. At the receiver, the signal is decoded in real time to reconstruct the receive signal that is precise and resistant to signal noise and interference in difficult applications. Extending the transmitted power over a long period rather than a few short pulses means that much lower transmit voltages are used, resulting in safety and low power. In addition, other ultrasonic flowmeters can only transmit on one acoustic path at a time. The Broadband Continuous Wave system, using codes that do not interfere, can transmit on two or more paths simultaneously. Simultaneous transmission means a faster response time and better performance in fluctuating or pulsating flow.