Technical specification Design reference: API or ASME Design standard: API 6D or ASME B16.34 Structural length for flanged ends: API 6D or ASME B16.10 Structural length for welded connection: API 6D or ASME B16.10 Flanged ends: ASME B16.5 Butt-welding end: ASME B16.25 Test & inspection: API 6D or API 598