Alvin Markus 2014-01-08 07:06:58
Viable alternative The following information is particularly important to individuals switching from leaded brass to stainless steel as an option for installing no-lead brass piping that conforms to the new federal Reduction of Lead in Drinking Water Act (U.S. Senate Bill S3874), which went into effect in all 50 states Jan. 4. Normally making up ferrous threaded joints, the pipe and fittings are different materials, such as carbon steel threaded pipe, making a joint into a malleable or cast-iron threaded fitting. Since the materials are different, they are forgiving and will thread together without a problem. However, working in stainless where the pipe and fittings are made of the same materials, there is a tendency for thread galling. This threat of thread galling is recognized by the ANSI/ASME B1.20.1 “Pipe Threads General Purpose (Inch)” standard and is called to the attention of users in paragraph 1. 3.1 labeled “Sealing.” “Where pressure-tight joints are required, it is intended that taper pipe threads conforming to this standard be made ‘wrench-tight’ with a sealant,” the spec states. “To prevent galling on materials such as stainless steels, the sealant usually contains a lubricant.” The pipe sealant must specifically state it is suitable for stainless-steel connections. One qualifying sealant is a Series 0384 PTFE tape with nickel (90% PTFE and 10% nickel) with a .0045 thickness. Table 2 in ANSI/ASME B1.20.1 further demonstrates how to make the exact number of turns and length of threads to attain pressure-tight threaded joints. If you do not have access to the ANSI/ ASME standard, here is a simplified chart that provides similar approximate results for pressure-tight joints. Alvin Markus is head of PVF Engineering, a consultant to the PVF industry. He is a 30-year veteran in manufacturing as president of Sun weld Fitting Co.; 15 years in distribution with Smith-Cooper International as vice president, engineering and quality assurance among other industry positions.
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