BS ISO 24497-1:2020 pdf free.Non-destructive testing一Metal magnetic memory.
Equipment and structures (IOs) should be inspected by MMM in in-service state (under load) as well as in the maintenance state (after removal of operating loads). If possible, the initial magnetic service state of the I0 should be determined.Surface dressing and preparation are not required. It is recommended to remove insulation to reduce sensor to surface lift-off to gain reliability and avoid SFI from the insulation. In particular cases, non-magnetic insulation can be allowed during inspection. Any permissible insulation layer shall be verified experimentally. The results shall be attached to the test report.Limiting factors for the application of MMM testing are the following: de-magnetization and intentional magnetization of the I0; foreign external [electro-)magnetic fields near to the inspected object, near the inspected region of interest; temperature changes can influence the test results (e.g. at Curie temperature); Sensor to I0 surface distance (lift-off) and its changes during the measurement.Strong temperature changes in the I0 cause changes of the thermoremanent magnetization and should be taken into account during processing of the inspection results.If the dominant SF direction of the I0 is not parallel to the measurement line, the measurement shall be repeated along this direction. Otherwise, the subsequent evaluation steps shall be calculated between the measuring lines and along the principal direction of the (internal) field after the change of basis. The rotation of the SF direction between periodic measurements can indicate magneto-mechanical effects. If the I0 in operation is part of a magnetic circuit (in contact with other ferromagnetic objects) and is removed for inspection, additional demagnetization fields in the I0 are enabled. If the I0 is removed from its operation position, the magnetic fields in operation position as well as in inspection position shall be determined and documented in the test report.The magnetic stray field diagrams (and or mappings) and the I0 logfile with indications of the inspection areas and detected SFIs shall be attached to the report.BS ISO 24497-1 pdf download.