A ring groove is basically a closely dimensioned groove cut into the face of a pipe flange. Together with a gasket, a groove helps create a seal between parts, so it is important that a groove meets designated specifications.  

       API 6A ring grooves are divided into three ring types, BX, R, and RX. Each type has different configurations and is designated by the type and a number, i.e. BX 150, R 41, etc.

API mandates the inspection of ring grooves. The necessary dimensions of a groove are clearly specified in API 6A. To pass API requirements, these dimensions must be met. For BX Grooves, the groove’s major diameter and width are specified. For R and RX Grooves, API specifies the groove’s pitch diameter and width.