Assessment of Electromagnetic Fields in Arc and Resistance Welding

Welding is used in a wide range of heavy and light industry, construction and maintenance, including vehicle construction. Workers using welding processes are exposed to electromagnetic fields (EMF). The International Commission on Non-Ionizing Radiation Protection (ICNIRP) has published guidelines on limits of the exposure to static magnetic fields and on guidelines limiting the exposure to time-varying electric, magnetic and electromagnetic fields. Moreover, the European legislation is based on these guidelines being the most recent and updated limits published in the Directive 2013/35/EU. The ICNIRP reference levels for magnetic fields may be exceeded in both arc and resistance welding. This study aims to assess the workers exposure to EMF in arc and resistance welding and compare the results with legal limits. Several measurements of EMF were carried out in different industries at workplaces using welding processes. The maximum measured field was near the cables with 1065 μT for single sided spot welding; 761,7 μT for arc welding (MIG) and 646,7 μT with resistance welding using a pneumatic “C” clamp. In some cases, the results were above the action levels (ALs) of the Directive 2013/35/EU. sure to magnetic fields and comparing these values with the limits established in the Directive 2013/35/EU. 2 MATERIAL AND METHODS This study was performed in three different companies from different sectors of activity. Company A is a small enterprise in the light metalworking, which works with two similar MIG welding machines: ESAB MIG C280. This company has 2 welders; one does welding tasks during approximately 4 h/day and the other during 1 h/ day. The first one has about 24 years of welding experience, and the second about 10 years. Company B is a medium-sized company with 70 employees, of which 31 are welders. They work in three shifts of 8 hours, with 11 similar MIG welding machines: ESAB MIG 5004i. All do welding tasks during 6 h/day. Concerning the 31 welders, 20 perform welding processes since 10 years ago in this company, 3 started their professional work as welders 4 years ago and 4 were already welders when they joined the company. Company C is from the sector of vehicle repair and maintenance. In this sector of activity, welders usually perform welding tasks for a short period of time. They used to use arc welding (MIG/MAG, SMAW, plasma and oxyfuel) and resistance welding. Nowadays, the most used are MIG/MAG and spot welding. In this company, some measurements of the EMF were carried out in a resistance welding machine using a single sided spot weld and a “C” clamp: Blackhawk/CompuSpot WEL 750. This company has 8 welders who weld on average 1 hour per day, distributed approximately as follows: 10 minutes with resistance spot welding, 10 minutes with MIG/MAG, 10 minutes with oxyfuel and 30 minutes with small sop welder. The measurements were performed in each company for 5 shifts of 8 hours each one. The welders were also observed during one shift without disturbing their jobs to analyze the welding process, the type of pieces welded and to check the periods in which the welding tasks were performed. The magnetic field data was acquired using a isotropic and triaxis magnetic sensor (Aaronia NF5035). This instrument measures magnetic fields in the range of 0,1 nT to 2 mT, from 0 Hz to 30 MHz and with an accuracy of 3%. Figure 1: Spectrum analyzer of the isotropic magnetic field (Aaronia). The measurements were conducted at several positions, close to the welders head, chest, waist and hand/electrodes and also near the welding cables and machine. In addition, a few measurements were carried out at distances of 20 cm, 50 cm, 1 m and 2 m from the welding cables and machine. Each measurement was carried out with a minimum period of 1 minute. The electric field was also measured, but the registered values were very low compared to the action levels defined in the Directive 2013/35/EU.