Effect of ultrasonic noise generated by pressure control valves on ultrasonic gas flowmeters

Natural gas imported to Korea has been provided and distributed by the pressure regulating and metering stations of Korea Gas Corporation (KOGAS) to domestic customers which include the power plants and city gas companies. The supplied natural gas is pressure-controlled to 10 and 40 bara by pressure control valves of several types, such as globe and axial types, pressure regulating and metering stations depending on customer's needs. In Custody Transfer Measurement System (CTMS) of KOGAS, ultrasonic flowmeters, instead of orifice and turbine meters, have been applied to newly established metering stations since 2011. However, the ultrasonic frequency range noise generated by a pressure control valve in a pressure regulating and metering system can interfere with the operating signal of the ultrasonic flowmeter. The aim of the present work is to investigate the effects of ultrasonic noise generated by the pressure control valve, including globe and axial type valves, on ultrasonic gas flowmeters. To this end, ultrasonic noise measurements for various pressure drop conditions and types of pressure control valves used in metering stations were conducted in a high pressure gas flow standard system of Korea Research Institute of Standard and Science (KRISS). Characteristics of the generation and propagation of ultrasonic noise in the pressure control valves were examined as well as the interfering effects on the performance of the ultrasonic flowmeter, which had a 125 kHz operating frequency.