Welds Assure Sanitary Piping for Draft Beer
Welds assure sanitary piping for draft beer
Pilchuck Mechanical, a general contractor in Seattle, applied orbital arc welding to install 6,000 linear feet of stainless-steel piping for cold-filtered Rainier Draft and Rainier Draft Light, introduced early last year by G. Heileman's Rainier Brewery in Seattle.
Unlike pasteurized beers, packaged draft beer is cold-filtered to eliminate spoilage organisms, retain fresh taste and extend unrefrigerated shelf life. Piping systems for handling draft beer must be exceptionally smooth and free of crevices that can harbor spoilage bacteria.
Orbital welding does this by fusing metal without adding filler material to the weld, creating a smooth inner bead. Both the inside and outside diameters of the weld are purged with argon gas to prevent oxidation of weld surfaces.
The new piping system maintains the beer's purity between cold filtration and cleanroom filling. An APV sheet filter, composed of diatomaceous earth bonded to cellulose paper fiber in layers of 240 plates per frame, removes particles down to one micron, including bacteria, as the beer flows through at 36° F. In the filling room, the beer passes through a final Pall filter which removes particles down to 0.65 microns. Filling is accomplished on new equipment at 1,200 cans or 900 bottles per hour in a HEPA-filtered air-locked Class 1000 cleanroom. A manifold-connected bank of Tuchenhagen dual block-and-bleed double-seat valves, pneumatically controlled by DMAX software, regulates product flow and CIP/SIP cycles through the piping system.
Pilchuck welders, installed the new piping from November 1991 to February '92 without disrupting the brewery's production schedule.
The welders used orbital weld heads and portable power supplies from Arc Machines, Inc. (AMI) to weld tubes ranging from 1/2-inch to 4 inches in overall diameter (OD), and from 0.035 to 0.085 inches in wall thickness.
The portable power supply provides precise control of welding variables such as current, travel speed, pulsation and time, which are programmed into a control panel on the machine. These parameters are accurate to within 1 percent of programmed values to assure consistent and repeatable welds.
AMI weld heads were used to weld pipes, elbows, tees and other fittings varying in OD from 1-1/2 to 4-1/2 inches. A typical 2-inch OD weld takes about 1-1/2 minutes of arc plus minute of purge to complete.
More than 90 percent of the several hundred welds were accomplished with orbital equipment. Inaccessible locations or configurations (such as elbow-to-elbow welds) were manually welded.
Pilchuck President Arch E. Van Belle estimated that orbital welding reduced manhours by 15-20 percent as compared to manual welding and reduced fabrication time by 50 percent.