46 CFR §56.30-30

1. (a)General (refer also to subpart 56.75). The minimum socket depth must be sufficient for the intended service. Brazing alloy must either be end-fed into the socket or must be provided in the form of a preinserted ring in a groove in the socket. The brazing alloy must be sufficient to fill completely the annular clearance between the socket and the pipe or tube.
2. (b)Limitations.
   1. (1)Brazed socket-type joints must not be used on systems containing flammable or combustible fluids in areas where fire hazards are involved or where the service temperature exceeds 425 °F. Higher temperature service must be approved by the Commandant.
   2. (2)Brazed joints depending solely upon a fillet, rather than primarily upon brazing material between the pipe and socket are not acceptable.