Development of speed control algorithm for Instrumented Pipeline Inspection Gauge (IPIG) in high speed liquid petroleum pipelines

Abstract

Integrity management of cross country buried oil pipelines is one of the most challenging task of pipeline operators. Under integrity management program, in-line inspection of buried pipelines with Instrumented Pipeline Inspection Gauge (IPIG) tool is the only means to monitor the health of these pipelines. IPIG works on non-destructive techniques like magnetic flux leakage (MFL), eddy current (EC), ultrasonic (UT) etc. It uses any particular technique or combination based on the application. In-line inspection of pipeline involves inserting an IPIG into the pipe transporting liquid/gaseous petroleum cargo. IPIG houses an array of sensors (mostly magnetic flux leakage, eddy current, ultrasonic etc) that is used to sense the thickness (or change in thickness) of pipe as the tool travels. Offline analysis of this data reveals critical parameters necessary for pipeline health assessment and maintenance. For optimum performance of IPIG with respect to fault detection and tool integrity, it is mandatory for the tool to move at near constant speed. As motion of the tool is a function of differential pressure across it, which in turn depends on the flow-rate of petroleum cargo, a speed control mechanism is necessary to decouple the tool speed from varying cargo flow-rate. A prototype dynamic speed control mechanism is developed and integrated into an existing IPIG tool and tested in IOCL R&D Centre, Faridabad. The tool has successfully negotiated speed excursions with necessary control actions. The paper outlines the development of speed control algorithm based on IPIG tool dynamics, its implementation in 24 IPIG tool and analysis of results obtained in multiple field trials.