Solar Powered Thermal Mass Flow Meters For Flare Gas Measurement at Remote Fracking Sites

To comply with local and worldwide initiatives and regulations attempting to reverse global warming, oil/gas production field engineers are required to monitor and report on emitted (flared) gases occurring at these remote sites. Because FCI’s constant power technology meters require very low power compared to the alternative constant deltaT (variable power) technology, they are uniquely capable of being powered with a small solar panel and provide field operators with an accurate, reliable solution to comply with these regulations.

A recent specific application involved the waste gases that resulted from the separation of hydrocarbon fluids at the well head. This waste gas is unsuitable for commercial use and is sent to a tank with a flare unit to be burned off (flared) as necessary. This gas is a mixed combination of flammable gases that include methane, ethane, propane, isobutene, butane, isopentane, pentane and hexane as well as trace amounts of nitrogen and carbon dioxide. Often there is moisture in this gas, too. The gas line from the tank to the flare was a small 1- inch diameter pipe and had a very limited straight-run.

With its no-moving parts thermal dispersion mass flow sensing element, a solar power-able FCI Model ST75V Flow Meter with built-in Vortab® flow conditioner provides direct mass flow measurement of the gas at this site without the additional equipment required with other flow measurement technologies. Its non-clogging sensor design operates over a wide flow range with low-flow sensitivity. The integral Vortab flow conditioner provides a fully developed flow profile in just seven total pipe diameters.

The ST75V Flow Meter is compatible with solar power systems that provide 24Vdc power without any special modifications. A typical solar power system supporting up to 28 meters in an oil/gas production field requires two 50-Watt solar panels to provide 24 hour power, even during cloudy, rainy or snowy winter days. The site engineers also recommended the additional installation of two large 12 Volt, 40 Amp hour backup batteries that are housed in a rugged 16 x 16 x 10 inch [406 x 406 x 254 mm] enclosure.

The ST75V Flow Meter, with its rugged NEMA 4X/IP67 rated enclosure, is ideal for dirty oil and gas production field installations. It features an inline-style flow body providing accuracy to ±1% of reading with flow ranges from 0.04 to 560 SCFM (0.07 to 950 NCMH), depending on pipe size, and repeatability of ±0.5 percent of reading. It is suitable for line sizes from 0.25 to 2 inches (6 to 51 mm) diameters. For larger diameter pipes of 2.5 to 200 inches [63 to 5000 mm], FCI provides insertion-style flow thermal flow meters such as models ST98 and ST100.

The ST75V Flow Meter’s flow element is constructed with a 316L stainless steel body and Hastelloy C-22 thermowell sensors to resist corrosion. The instrument is approved for use in hazardous/explosive oil/gas production environments and carries global approvals that include: FM/CSA, Class 1, Div 1, Groups B, C, D; Class 1, Div II, Groups A-D, ATEX/IECEx Zone 1, II 2 G Ex d IIC T6 …T3, II 2 D Ex tD A21 IP67 T90°C…T300°C.

The ST75V meter’s transmitter outputs include dual 4-20mA analog outputs, which are user assignable to flow rate and/or temperature, a 0-500 Hz pulse output for totalized flow and a serial RS-232C I/O port. The optional digital display/readout is a two-line LCD displaying flow rate and totalized flow or flow rate and temperature. In applications with difficult access or display readability, the ST75V’s transmitter is also available to be remote mounted up to 50 feet (15m) away from the flow element inserted in the pipe.