Heat from Brazing on Copper Air Line Causes Soft-Soldered LO Valve to Come Loose on 100 Psi Air Line
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Type:  Lessons Learned

Publisher:  Los Alamos National Laboratory, Los Alamos, NM (LANL)

Published As:  Public

Date: 

Topics:  Operations, Work Management/Planning, Welding/Hot Work - Grinding

Workers were brazing on copper process air line for a construction tie-in to an existing facility system. The process air was isolated with a lockout/tagout (LOTO) for personnel protection. The heat from the brazing softened the soft solder on the valve with the LOTO. The valve came off the existing facility piping, allowing process air to escape into the room. The process air was isolated after the event by utilizing another isolation valve.

Lessons Learned: Although there is no formal industry requirement or guidance on what distance should be between connections when soldering copper tubing/piping, careful consideration should be taken to ensure that heat applied to one joint being soldered does not impact another upstream. Hard soldering and/or brazing requires the filler metal melting point to be above 600 degrees, whereas soft soldering uses a low melting point of the filler metal below approximately 350 degrees. The high temperatures required to melt filler metal through the hard solder or brazing process can cause the failure of joints upstream in the system if these joints were soldered through the soft-solder process.

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