Seal the Joints Some brazing shops use standard plumbing-type threaded fittings to connect the piping from their gas tanks to the furnace. Such fittings, even those sealed with Teflon® tape or “dope,” are not gastight to the atoms of gaseous atmosphere and can leak. These plumbing-type fittings can also open up with time, resulting in more significant moisture and air leaks into the system — even when the piping is highly pressurized. Run Gas Piping Underground Gas lines that are positioned over driveways and along the outside walls of buildings are subjected daily and seasonally to wide temperature variations. The repeated heating and cooling cause the tubing to expand and contract putting the connections under continual stress. This, over time, can cause the joints to open up and leak. I recommend that gas-piping be run underground until it is inside the plant to avoid these temperature swings. Many production plants run their gas tubing and electrical cables through concrete-gutters covered with metal grates to shield them from the sun and temperature extremes. Insulate the Pipes Whether the piping is run underground or above ground, wrapping the pipes with insulation will reduce the effects of temperature extremes on the piping and connections. Insulating pipes is not difficult and will ensure the piping remains leak tight longer. An Additional Option Consider installing a desiccant stage in the line to remove moisture from the the gas just prior to it entering your furnace. Conclusions The optimal ways to minimize the amount of moisture that a liquid or gas picks up when piped is to use highquality, certified, gas-piping materials with all connections soldered, brazed, or welded. Avoid using plumber-type threaded fitings. Insulating the pipes and running the pipes underground are also worthwhile. It is cost effective to take all the steps necessary to ensure the gas entering your furnace is as dry as possible. The time and expense incurred to install a properly designed gas-piping system, as described here, will pay for itself in higher-quality brazements. 32 WELDING JOURNAL / APRIL 2015 This column is written sequentially by TIM P. HIRTHE, ALEXANDER E. SHAPIRO, and DAN KAY. Hirthe and Shapiro are members of and Kay is an advisor to the C3 Committee on Brazing and Soldering. All three have contributed to the 5th edition of AWS Brazing Handbook. Hirthe (timhirthe@aol.com) currently serves as a Brazing & Soldering Manufacturers Committee (BSMC) vice chair and owns his own consulting business. Shapiro (ashapiro@titanium-brazing. com) is brazing products manager at Titanium Brazing, Inc., Columbus, Ohio. Kay (dan.kay@kaybrazing.com), has more than 40 years of experience in the industry, and operates his own brazing training and consulting business. Post your questions for use in this column on the Brazing Forum section of the BSMC website www.brazingandsoldering. com. For info, go to www.aws.org/adindex WJ
Welding Journal | April 2015
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