46 CFR §56.25-5

Each flange must conform to the design requirements of either the applicable standards of table 2 to § 56.60-1, or of those of Appendix 2 of Section VIII of the ASME BPVC (incorporated by reference; see § 56.01-2). Plate flanges must meet the requirements of § 56.30-10(b)(5). Flanges may be integral or may be attached to pipe by threading, welding, brazing, or other means within the applicable standards specified in table 2 to § 56.60-1.