Magnetic field from spot welding equipment--is the basic restriction exceeded?

Area of Science:

• Biophysics
• Occupational Health
• Electromagnetics

Background:

• Spot welding machines generate significant magnetic fields (MF).
• International Commission on Non-Ionizing Radiation Protection (ICNIRP) sets reference levels and basic restrictions for MF exposure.
• Previous assessments often focus on spatially averaged MF, potentially overlooking localized effects.

Purpose of the Study:

• To assess if basic restrictions for induced body currents are exceeded during spot welding operations.
• To investigate the relationship between proximity to the welding machine and induced current density.
• To determine if localized high MF can exceed restrictions even when whole-body averaged MF is below reference levels.

Main Methods:

• Point measurements of magnetic flux density near a spot welding machine.
• Calculation of induced body currents using a full 3D human model.
• Comparison of calculated current densities with ICNIRP basic restrictions.

Main Results:

• Magnetic flux density near the machine exceeded the ICNIRP reference level.
• At 34 cm, the maximum induced current density was below the ICNIRP basic restriction.
• Closer proximity to the machine resulted in exceeding the ICNIRP basic restriction.
• Basic restrictions were exceeded even when the spatially averaged MF over the whole body was below the reference level.

Conclusions:

• Operator proximity to spot welding machines is critical for assessing exposure risks.
• Localized high magnetic fields can lead to exceeding basic restrictions, even with low whole-body averaged fields.
• Current dosimetry assessments should consider non-uniform MF exposure and induced currents.