Magnetic Field Exposure in a Nondestructive Testing Operation

Abstract

Nondestructive testing is any technique used to inspect the integrity of a manufactured item without diminishing its future usefulness. Magnetic particle inspection is one type of nondestructive testing that uses electromagnetism in the inspection procedure, thus potentially exposing the operator to magnetic fields. During magnetic particle inspection, investigators took peak magnetic field measurements of 8 turbine engine shafts at a turbine engine overhaul and repair center. They recorded 95 peak magnetic field measurements, ranging from < 0.1 to 29.27 mT. The exposure values measured were among the highest reported in the occupational setting. Further work is needed to characterize magnetic field exposures in magnetic particle inspection operations--in particular, by differentiating magnetic field magnitude by current frequency--and to understand exposure as it relates to different types of magnetic particle inspection devices.

Hazards and Mitigation Measures in Aerospace Non-Destructive Testing

“…Typical electromagnetic field (EMF) penetration frequencies in eddy current testing range from 100 Hz to 10 MHz (Ansley et al, 1992;García-Martín, Gómez-Gil, & Vázquez-Sánchez, 2011), although García-Martín et al reported inspection frequencies of up to 25 MHz. Lippert et al (2007) found that workers at a turbine engine overhaul and repair center had recorded electromagnetic flux densities as high as 29.27 mT while carrying out magnetic particle inspection using a 3-phase 1400-5000 A 60 Hz alternating current system. However, the World Health Organization (n.d.) recommends that workers not be exposed to EMF levels above 500 µT at the 50/60 Hz line frequency.…”