00:00 Apr-01-2009 Bruce McPherson Consultant MFL Services, United Kingdom, Joined Mar 2009 21
Determining magnetisation for WFMPI
In the new ISO standard on the inspection and classification of used drill stem elements ISO 10407-2 (AKA API RP7G-2), there is a section on determining the level of magnetisation required to carry out wet fluorescent MPI on the male and female threads (pin and box) of various types of drillstem components to detect circumferential cracks in the thread roots
A coil is used to produce the longitudinal magnetic field and the inspection is performed using the residual method.
The standard says that the field level in the component is acceptable if, when the fluorescent particles are applied to the surface, the particles remain mobile for 6-10 seconds. When this degree of mobility has been achieved, a gaussmeter is then used to measure the field at the end of the component and that all similar components should then be magnetised to the same field level (+/-10%)
Sorry for the long intro, but I am unfamiliar with this particle mobility requirement, and I can find no reference to it (or anything like it) in ASTM E1444, BS EN ISO 9934, or any of the specific oilfield inspection standards such as API RP5A5, DS-1 or NS-2
Can someone explain how this mobility test might be performed - bearing in mind that gravity will clearly cause the particles to run around the pipe threads and accumulate at the lowest point