Pulsating-Flow Measurement with an Orifice Flange

摘要

This paper resulted from a measurement problem encountered during instrumentation of a Geothermal air drilling operation on the Baca Ranch in the Jemez Mountains in New Mexico. The problem was how to measure the flow of ammonia water solution injected into the air line. The flow is pulsating as the pressure in the ammonia line fluctuates above and below the pressure in the air line. The pump that develops the pressure in the ammonia line is not a positive displacement pump, therefore, counting pump strokes does not determine the number of gal/min of ammonia flow. The flow was measured using an orifice flange differential pressure technique but, the range of flow measured, exceeded the 4:1 range ability of an orifice. A computer smoothing of the differential pressure and the line pressure together with a scaling factor, determined by the shape of the raw differential pressure, provided a smoothing of the flow data which was checked against the actual flow over a long time period to determine the volume of solution injected into the system per hour. An instantaneous reading of ammonia flow was thereby determined. It showed small variations in corrosion rate measured in the standpipe that may have been caused by a momentary variation in the flow of ammonia solution. (ERA citation 06:021971)