API TR 6AF3 pdf download High-pressure High-temperature (HPHT) Flange Design Methodology Scope The scope of this document is to provide design guidelines for AP1 6BX style flanges utilized as end and outletconnectors in high-pressure， high-temperature (HPHT) surface and subsea applications. For this document,HPHT applications are intended to mean Flanges assigned a temperature rating greater than 350° F or apressure rating...