What’s Flange API？

What’s Flange API？
The second type of commonly used casing head is a flanged casing head, which generally meets the standards of API Specification 6A, called Flange API or may have dimensionally compatible flanges meeting the requirements of the American National Standards Institute (ANSI). The flanged casing head permits direct mating to a tubing head having the same size lower flange, rather than to a lower thread connection. The production casing is typically cut off a few inches above the top flange of the casing head, and the flanged tubing head has a lower recess or socket within a rubber seal that slides down over the protruding casing until both flanges mate.