RF Welding

Welding is a process of bonding two metallic materials together by the use of an Arc, created by high voltage applied to a welding rod. The welding rod itself is a combination of a soft metal core, and an outer layer of flux, used to clean and ensure a solid bond during the welding process. One method of welding is Radio Frequency welding. Here is an excellent resource that explains RF welding: web page.

Another similar one of several types of welding process is used by wire-fed welders, where a high voltage is applied to the materials, and as the welding wire contacts the surface (thus closing the circuit), an arc is created and melts the welding wire onto the surface of the object being bonded. While this is a simplistic explanation of the welding process itself, for our topic of welding, and how it affects RF, we'll concentrate more on the "RF Noise" generated by the welding process.

Lesson Learned: Several years ago, a customer of a large carrier was complaining that their data circuit would bounce up and down throughout the day. Once the carrier was contacted, they shortly ran loop-back tests to the DSU (data service unit) at the customer's location. Over and over, the line tested clean, and would come right back up for no apparent reason. To abbreviate the story, this customer's next-door neighbor in this commercial strip center was a custom fabricator, and used arc welding off and on throughout the day. After sufficient testing, we learned that every time the arc welder was actively generating an arc (while bonding two pieces of metal together) the customer's data circuit would fail. We sent a spectrum analyzer to the location just to see what amount of noise was generated from the arc welder. To our surprise, a wide splash of frequencies from about 50Khz through 450Khz (RF band) was generated in random fashion across the entire frequency band. Other that asking the welder to move, we solved the circuit problem by engineering a shielding solution for the customer that effectively isolated the circuit from all the RF noise generated by their neighbor.

In general, welding generates an unpredictable RF noise pattern that can interrupt both wired and wireless communication. Even some poorly isolated telephone systems will pick up a 'buzz" when an arc welder is activated close by. Effective RF shielding is the only way to protect communications equipment from the effects of RF noise. Grounding, isolation, and even phase inversion are effective techniques for reducing the affects of arc welding on RF communications.

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