API Flange Dimensions - Complete Reference Guide

API flanges are specialized high-pressure flanges designed according to American Petroleum Institute standards, primarily used in wellhead equipment, Christmas trees, and critical oil & gas applications. Unlike standard ASME B16.5 flanges used in normal piping systems, API flanges are specifically engineered for wellhead and Christmas tree equipment, offering superior pressure ratings and reliability in demanding petroleum industry environments.

API 6A flanges feature six distinct pressure ratings: 2000, 3000, 5000, 10000, 15000, and 20000 psi, significantly higher than conventional ASME flange classes. The three main types include API 6B flanges (most common), API 6BX flanges (compact design), and segmented API flanges for specialized applications. All 6BX flanges must have a raised face with a minimum height of 1/8 inch, while 6B flanges can feature either raised face or full face configurations.

These flanges are manufactured from high-grade carbon steel and alloy materials, designed to withstand extreme pressures and temperatures encountered in upstream drilling operations and downstream refining processes. API flanges utilize ring joint gasket sealing systems for maximum integrity, ensuring leak-proof connections in critical hydrocarbon service applications.

Our comprehensive dimension tables below provide detailed specifications for all API flange types, including bolt patterns, weights, and pressure ratings to support your engineering and procurement requirements.