Transducer Technologies

Gases are used in a variety of industrial operations as ingredients. They are also produced as disposable harmful chem­icals. To avoid any gas leaks, it is important to regularly monitor places where gases are stored. Gas transducers can detect a variety of gases and convert them into an electrical signal that may be read by indicators, regulators, alarm systems, and other analytical systems. Gas transducers are used to monitor carbon dioxide levels in order to determine what action should be ta­ken if the limit values are surpassed.

Flexim has pioneered developments in the field of non-invasive gas flow measurement. The com­pany provides natural gas transport pipelines from DN 40 up to DN 1600 with no limitations on wall thickness or pipe material. There are two proprietary ultrasonic transducer technologies for gas flow metering applications. They act independ­ently of pressurisation level, with no upper pressure limitation. Moreover, they have an unlimited turndown ratio with high accuracy from very low to high flow rates (0.01m/s to 60m/s). The oper­ational flow is calculated through a normal volume calculator in the transmitter.

User experience

Shell Queensland Gas Company (QGC) produces coal seam methane in the Surat basin from 2,600 wells. The gas is collected in 24 first-stage compressor stations, where the pressure is raised to 12 bar. It is then sent to six central processing plants, where it is compressed twice to a transit pressure of 60-100 bar. QGC operates a two-train liquefied natural gas (LNG) facility that serves 10 per cent of east Australia’s domestic gas demand. The Fluxus dual-channel G704 with GRH transducers (300 kHz) is mounted in the twin sound pathways/dual planes.

Brunei Shell Petroleum (BSP) is by far the largest oil and gas producer in Brunei. BSP supplies about 350,000 barrels of oil and gas equivalent per day. Various technologies, including gas lifts, play a big role in maintaining this high output. In 2012, BSP partnered with Flexim to overhaul its dated gas lift flow measurement systems for its largest oil and gas field, Champion East. The initial groundwork performed was an extensive flow survey over 60 measurement points with portable flowmeters. The results have saved over $400,000 in the initial three months, with optimum gas lift injection set points. Eleven sets of permanent clamp-on flowmeter type G801 have been installed at various strategic measurement points for continuous monitoring of the gas lift network. The West Fields, consisting of Ampa and Fairley, embarked on a similar gas lift optimisation project in 2016. Thirty-six sets of G801 have been ordered over three phases.

E.ON Hanse’s underground gas storage (UGS) in Reitbrook utilises four reciprocating compressors to inject gas into a porous limestone reservoir. The compressors work at varying pressures from 30 to 180 bar and can deliver flow rates between 5,000 and 1,00,000 normal cubic metres per hour. They were recently upgraded and equipped with variable speed drives and an advanced ca­pa­city and energy control system. The older averaging pitot tubes needed to be replaced after vibrations caused fatigue and failure. Their limited turndown capability excluded the differential pressure method from the search. After evaluating Flexim’s references in larger E.ON greenfield UGS projects, the engineers decided on a field performance trial. Eventually, E.ON Hanse equipped all four compressors with a clamp-on solution and replaced the pitot tubes successfully. E.ON qualified Fluxus gas solutions via Lintorf gas flow laboratory and extensive field experience between 2008 and 2011. Flexim supplied and installed 20 units during the construction of the Etzel project in 2011. E.ON reported substantial cost saving compared to high pressure inline ultrasonic flowmeters.

Unloading cryogenic LNG is a sophisticated operation, with safety being the outmost priority. Ningbo’s LNG terminal needed to monitor and control the flow velocities in the main DN 900 transfer line. Previously installed Venturi metering proved instable and inaccurate, and eventually the Flexim cryogenic wave injector was installed to control -162 °C LNG offloading plus low flow medium recirculation to keep the transfer line system refrigerated between cargo offloading.

In sum

Chemical detectors are often used to classify gas sensors. To transform a desired chemical re­action into a measurable electrical signal, such as a change in resistance, frequency, current or voltage, a transducer and an active layer are required. Device sensitivity, selectivity, precision, detection limit, resolution, accuracy, rever­sibility, recovery time and reaction time are all used to evaluate a sensor’s performance. In ad­di­tion, gadget downsizing and power consumption, cost efficiency, extended lifetime and future wireless network integration are all regarded as important elements for a sensor’s use in diverse applications.

Based on a presentation by Claus Weihermueller, Senior Consultant, Asia Pacific and India Business Units, Flexim, at a recent India Infrastructure conference