Vlf Detection Technology Used In The Tracking & Marking System For Pipeline Inspection Operations

The pipe cleaner in the industry referred to as a Pig,which driven by the transmission medium in the pipe, such as crude oil, refined oil and natural gas, which is a special equipment used for pipeline cleaning. The outer edge of Pig’s leather bowl to the inner wall of the pipe is elastic seal, by the pipe medium to produce differential pressure as the driving force to drive along the pipeline tube. Relying on the Pig itself or the machine which carried by scraping, scouring action to remove the pipe scaling or sediment. The electronic pig is consists of pig and tracking & marking system.The Tracking & Marking System is a complete system for tracking and marking pipeline tools based on pulsed ELF(extremely low frequency) electromagnetic field transmission which can be received outside steel pipelines. It consists of receiver and transmitter. Because extraneous signals and noise are filtered out as it accurately detects, reports and stores pig passages, locations, times and dates. The system is independent of the pipeline medium, and it works equally well in all liquids, e.g. crude oil, water and refined products, and in gases such as methane, air, nitrogen, etc.The Tracking & Marking System in pipeline pigging operation process, plays an important role, its performance will directly affect the safety and cost of pigging operation. Along with the China’s “West second-line”, “West third-line” and other long and big caliber transmission pipeline have been built, Pig is not only to meet the strong anti-electromagnetic interference ability and the high probability of recognition performance requirements, at the same time which tracking the high speed performance put forward higher request. At present, more than 90% pigging operation engineering tracking speed average below 5m/s, but the large caliber tracking speed need to meet the requirements of 10m/s. The main work of this paper is to meet the special requirements of the large caliber pipeline cleaning pipe engineering, the research based on the characteristics of the ELF(extremely low frequency) electromagnetic field transmission in the pipe and when the pig via pipelines variation characteristics of electromagnetic field. Put forward an automatic recognition algorithm and the large dynamic logarithmic receiving detecting method, realizes high speed tracking when pigging the big caliber transmission pipeline and successful simulation verification on the ground.