Methods for detection and tracing of in-line PIGs which are moving or had stack inside a pipeline
Advantages and shortcomes of four the most developed methods for PIG tracking and detection are described. These methods are: acoustic, nuclear isotope, magnetic and electromagnetic on frequency 22Hz.
Some recommendations about use of low-frequency electromagnetic transmitters and locators for tracking of in-line PIGs during pipeline cleaning or diagnostics
It is briefly explained why frequency 22Hz is selected for in-line transmitters and receivers by the majority of manufacturers. Described also factors and effects which influence the strength of signal from transmitter fixed on a PIG which moves inside a pipeline. Shown a diagram for detection distance for any 22Hz transmitter depending from thickness of metallic pipes constituting the pipeline. Also shown the patterns of magnetic field lines for the signal emitted by a transmitter installed in a PIG by different ways. Based on this information some practical recommendations are written concerning correct installation of transmitters inside in-line PIGs in order to increase the detection distance.
Method for in-line pig tracking in an off-shore pipeline
Process of PIGs launching and receiving while cleaning and diagnostic of an off-shore pipeline is described. Application of specialized equipment and devices for automatic tracking and monitoring of PIG motion inside off-shore pipeline are demonstrated. Also two examples of systems for marker points equipment including floating buoys and hydroacoustic emitters are shown.
About methods and devices which enable to increase quality of gas pipelines diagnostic
Possible reasons of accidents on gas outlet pipelines are considered. Difficulties connected with compressibility of gas that influence the quality of diagnostics are analyzed . Typical diagram velocity vs. distance for PIG moving in gas pipeline is shown. Recently developed methods for diagnostic of major gas pipelines are described including application of PIGs with controllable by-pass. Reasons are written according to which use of PIGs with by-pass are not effective in gas pipelines with relatively low pressure and gas flow rate. As alternative for PIGs with by-pass it is proposed to use PIGs with movable cuffs. Working of moving cuffs is explained. Short video about testing of PIG with movable cuffs is demonstrated.
About features of detection of stress-corrosion cracking of main transportation pipelines
Brief description of gas pipeline stress-corrosion. Known methods of in-line inspection for stress-corrosion detection. Fundamental drawback of transverse field inspection method (TFI). Economical unprofitability of inspection in water plug. EMAT - "dry ultrasound" method. Electromagnetic acoustic transducers (EMAT) review. Lorentz EMATs. Horizontally and vertically polarized shear waves. Advantages and drawbacks of SH and SV shear waves. Monitoring of stress-corrosion cracking in gas pipelines. Opportunities of EMAT-method.