Flare Gas Flowmeter

Flare gas is one of the hardest flow measurements on a plant. The header is large, the pressure is barely above atmospheric, the composition changes with every upset and the flow ranges from a trickle of purge gas to a full emergency blowdown within seconds. Thermal mass technology handles this because it measures mass directly, responds at very low velocities and has a turndown that no differential-pressure device can match.

The flare gas flowmeter is an insertion probe for headers from 2½" to 99", mounted through a retractable packing gland so it can be installed and withdrawn with the flare in service, or with flanged or fixed-welded mounting. Ranges run from 0.07 to 305 Nm³/h at pressures to 69 bar and temperatures from −40 to +454 °C. Wetted parts are 316L stainless steel as standard, with Hastelloy C-276 for sour and corrosive gas.

A dual-element averaging system improves accuracy on large headers, and mixed-hydrocarbon gas reporting adjusts the reading for the actual composition. Calibration verification, a data logger, optical touch buttons for use without opening the enclosure and a sun shield for outdoor installation are available. Communication is 4–20 mA HART, RS-485, FOUNDATION Fieldbus H1, PROFIBUS PA, pulse, USB or Ethernet.

Applications are flare-gas measurement, leak detection through passing relief valves, upset and blowdown monitoring and emissions reporting in onshore and offshore oil and gas, refining and petrochemical.