Underwater wireless in-pipe communications system

Abstract

This paper reports on the development of an in-pipe underwater wireless communication system. The wireless system forms an inherent part of an inline tool for the internal inspection of pipelines within the Oil & Gas industry. The wireless system was specifically developed to address the restrictions associated with the use of umbilicals for the control of most state-of-the-art inspection tools. Towards this direction, a full duplex communication scheme was developed for communicating ASCII commands from the external user to the inspection tool. Wireless communication is performed in a "master-slave" mode with the master modem located on the entry point of the robot into the pipe and the slave modem travelling along the pipeline with the robot. The 7-bit ASCII code is employed to convert each text character into a string of 7 bits. Signal modulation is performed based on the Frequency Shift Keying (FSK) method. The exact characteristics of the implemented software were provided and the details of the transmission and reception state diagrams were discussed. Furthermore, details about the hardware implementation were provided. The performance of the wireless communication system was validated in a water-filled pipeline. It was shown that the wireless communication system can operate with voltages in the range 12V _DC -16V _DC , provided by a battery. During the experiments a data transmission rate of 21bps was achieved for a pipeline experimental set-up of 5m. It was shown that during transmission each modem requires 6.35W. Finally, the propagation range of the wireless communication was theoretically explored based on the fundamental sonar equations. The analysis indicated that wireless communication within the pipe is feasible for a propagation distance of 1000m.