Miller Brewing Company's massive brew kettles, located at the company's Milwaukee Plant. Inset photo: Electrolytic, mechanical and chemical erosion had degraded kettle joints between the copper sidewall and the stainless steel dome.

When the 150-year old Milwaukee-based Miller Brewing Company needed assistance with its extensive brew kettle repair project, the company called Pro Engineering & Manufacturing Inc. (www.prowm.com/). Pro Engineering & Manufacturing has extensive experience in fabricating stainless steel and aluminum products for the beverage, food, material handling and construction industries.

Miller Brewing's project was a particularly unique and difficult welding application. It involved repairing damaged copper and stainless steel joints in its six massive brew kettles. Over a period of time, mechanical, chemical and electrolytic erosion degraded the copper and stainless steel interface where the brew kettles' side-walls and domes meet. In certain areas of the brew kettles, the original copper weld used to bond the stainless steel dome to the copper kettle was showing serious signs of wear.

To repair the damaged interface, Pro Engineering & Manufacturing engineers designed and fabricated a 6-in. wide copper band to bridge the original stainless steel/copper weld seam.

The upper portion of the band was attached to the ¹/₄-in. stainless steel dome by first TIG welding a root pass using a Weldcraft torch with ³/₃₂-in. diameter tungsten and .035-in. diameter silica bronze (AWSA5.7/ER Cu Si) filler rod. Because TIG welding produces lower deposition rates, fabricators used MIG welding to complete the remaining fillet welds. They used silica bronze solid wire operating at 275 amps and 25 volts.

Due to copper's excellent heat transfer, fabricators used a secondary heat source to achieve and maintain the weld pool. "We manually used Mapp torches to heat the area either directly below or on the opposite side of the work piece," said Ed Michalski, cofounder and co-owner of Pro Engineering & Manufacturing.

The fabricators then MIG welded the bottom portion of the copper ring to the ³/₈-in.thick brew kettle copper sidewall with .035-in. diameter copper solid wire, and XMT 350 inverters operating at 325 amps and 25 volts, with an S22A wire feeder. Fabricators also used Smith Equipment gas regulators to deliver 100-percent helium shielding gas.

The XMT 350, made by Miller Electric Manufacturing Co. (www.millerwelds.com), features AutoLine Management Technology, which allows the unit to produce a stable, steady arc with any type of primary power supply (190V to 630V, single- or threephase, 50 or 60 Hz) — even through primary power fluctuations. The system ensures that the inverter has sufficient power as long as the primary power remains within a +37/-59 percent of the nominal 460V power.

Pro Engineering fabricators value the XMT 350's primary power flexibility when they are working at off-site projects such as the brew kettle project, where Miller Brewing's brew house was running 230V service.

"In the past we've lost machines because of voltage problems," says Michalski. "I can move my XMT 350s from place to place without having to worry about the primary power supply."