Re: NDT gas distribution mains In addition to the techniques that you have listed, pulse/echo ultrasonic thickness gaging with a simple hand-held instrument is probably the least expensive, and usually highly sensitive to individual pits. Access to the outside of the pipe is required. See the application note linked below for further details.
Re: NDT gas distribution mains ----------- Start Original Message ----------- : At the moment I am conducting a literature survey of available NDT techniques for steel gas distribution mains. These mains suffer from general corrosion, pitting corrosion and cracks. : On the internet and in literature I find several NDT methods, but it is unclear to me which are the most suitable. : Possible options are : Remote Field Eddy Current : Ultrasonic Phased Array : Magnetic Flux leakage : Guided Wave Inspection : However, I don't know what can be used best. For example Remote Field and Ultrasonic Phased array seem to have the same capabilities : Can someone explain what the advantages and disadvantages of above techniques are? : Thanks in advance! ------------ End Original Message ------------ Eddy current is used for small thickness pipes say below 5 mm. Most of the burried pipelines i.e. gas distribution lines have thickness above 6 mm unless one is doing a precision engineering to save costs. the preferred NDT for burried pipelines are Ultrasoni tests using intelligent pigs, which is a costly exercise done once in 5 yrs on average and is based on regulatory guidelines in respective countries.
You could also consider the ultrasonic IRIS for wall thickness. It can be used as a free running ILI tool to inspect from the pipe ID. It would require a liquid for propulsion (as do most ILI tools) and for locomotion so may be a difficult choice in a gas distibution system.