Development of a Curb Valve Flow Meter for Gas Theft Detection

摘要

Today, according to numerous gas utilities, significant revenues are being lost via theft of service, losses which are ultimately passed on to the businesses' honest customers. A method to detect such thievery developed was the design of a secondary flow metering device. Located outside a suspected concern, and placed within the small confines of a modified valve or pipe structure, its function is to act as a cross reference for the existing positive displacement meter. The concept chosen was the phenomena of vortex shedding, a fluid oscillatory instability which is used extensively as a measuring technique in the process control industry. Feasibility studies were carried out using a flat, non-moving bluff shedding element and a piezo-electric bimorph ceramic cantilevered behind it. Both elements were situated within a curb valve based prototype design having a test section inner diameter of one inch. As predicted, experiments demonstrate a repeatable, linear relationship between frequency of oscillation and volume flow for flow rates between 200 and 1000 CFH.