2019. Vol.22. No. 3, pp. 12-16
Eddy Current Inspection of a Cone-Type Tool-Joint Thread of Drill Column Details
Models of eddy current probes of different design for thread testing, influence of inspected and interfering parameters on their readings are described. Reference blocks for metrological support of crack depth measurement in the thread pit are developed. The results of practical application of the flaw detector in non-destructive testing of the drill strings line pipe thread are shown. Mechanized scanners have been developed for line pipe thread testing, which allows increasing the testing efficiency.
The novelty of the work consists in application of a new eddy currents excitation method in the testing object, which allows to significantly reducing the influence of interfering parameters, as well as in application of mechanized scanners to increase the speed of control and reliable fastening of transducers on the threads of drill string elements.
The accurate evaluation of the NDT instruments and technologies metrological parameters is а problem. It should take into consideration, that the parameters (like accuracy, limit of sensitivity etc.) certified by delivery can differ significantly when the instruments and technologies are used in practice. If one doesn’t take into account this difference, he can be disappointed with testing results which appear significantly worse than had been expected. The NDT users must be qualified enough to avoid this. Requirements for the personnel skill are parts of standards and norms on NDT technologies of concrete objects and are analyzed with regard to the wire steel ropes NDT. Unfortunately, the users meet the requirements not always. This concerns all of NDT devices and methods but especially of the EM and MFL ones, when they are used for the ferromagnetic objects testing such as steel wire ropes, steel-cord conveyor belts, tubes, oil and gas tanks. The paper can be helpful for specialists by NDT of ferromagnetic objects like wire steel ropes especially.
Keywords: thread inspection, eddy current, cracks in thread, mechanization, scanner