When large industrial vacuum brazing furnaces begin to produce customer parts that show discoloration instead of a pristine stainless steel finish or joints where the brazing material has refused to flow properly, production is quickly halted. Easy-to-find-and-fix leaks can take the furnace down for a half of a day, and more downtime is likely. The topics presented in this article will help make your next leak-checking search a quick and successful one.

Vacuum brazing furnaces, whether continuous in-line or batch machines, are large complicated systems that must be able to pump down to the required vacuum level to produce high-quality heat-treated parts (Fig. 1). It is important that these machines be vacuum-leak-free if they are to produce parts with void-free braze joints and flawless surface finishes. Ideally, these requirements would suggest that routine leak detection be a part of the regular maintenance schedule on these machines. Yet real-world production demands force some users to occasionally delay regularly scheduled preventive-maintenance tasks and instead operate their equipment to failure.