Electromagnetic Level Indicating (EMLI) System Using Time Domain Reflectometry

A novel approach to monitoring levels in naval shipboard seawater ballasted fuel oil storage tanks has been developed at the David Taylor Naval Ship Research and Development Center of Annapolis, Maryland. The Electromagnetic Level Indicator (EMLI) uses the pulsing and high frequency sampling techniques of Time Domain Reflectometry (TDR) to interrogate a single no moving parts probe to accurately measure the height of seawater, fuel oil and air columns in the ballasted fuel oil tanks. In addition, the EMLI can be used to measure a broad range of single or multiple levels of immiscible fluids and flowing solids. The system also offers the potential of content identification, detection and measure of emulsion layers, and pollution control. Final system configuration is expected to be simple and automatic, requiring less maintenance than tank level indicators currently in use. This paper is intended to provide a general understanding of the theory of operation, describe the system components, present preliminary test and performance data, and propose applications for the EMLI.