Noninvasive Magnetic-Marking-Based Flow Metering with Optically Pumped Magnetometers

Abstract

We present a noninvasive procedure that measures the flow velocity of a fluid by using polarized hydrogen nuclei in the fluid. The measurement procedure is based on a time-of-flight method where magnetic information is applied on the fluid with a permanent magnet and an RF-pulse. In contrast to other methods, this magnetic-marking method works without tracers. The read-out of the magnetic information is performed by optically pumped magnetometers downstream. In order to function, the magnetometers have to be operated in a magnetic shield with magnetic field strengths lower than 100 nT, i.e., in the zero-to-ultra-low-field regime. In this regime, the magnetometers are capable of detecting induced magnetic signals of 10 pT or less with an inline-flow setup. The results presented in this paper demonstrate the viability of optically pumped magnetometers for flow metering. The first metering results yielded an average accuracy of 3% at flow velocities between 13 cm/s and 22.4 cm/s.

A6.1 - Magnetic Flow Metering with Optically Pumped Magnetometers (OPM)

“…The procedure allows flow detection through metal pipes, and, because the procedure does not require high magnetic fields, its implementation is effortless compared to the established high field NMR pendant [8]. The research presented is a continuation of the proof of principle for magnetic flow metering presented in [7]. As we continue to test the industrial potential of the procedure, we now analyze the viability of metering the flow of water flowing through industry standard steel pipes.…”

“…These aspects limit the methods applicability [5]. The recent commercialization of highly sensitive OPM [6] allowed us to develop a novel magnetic flow metering procedure in the zero-to-ultra-low-field (ZULF) regime [7]. The procedure allows flow detection through metal pipes, and, because the procedure does not require high magnetic fields, its implementation is effortless compared to the established high field NMR pendant [8].…”