Raised Face (RF)
Ring-Type Joint (RTJ)
RTJ for API 6A Type 6B, BS 1560 and ASME B16.5 Flanges
The seal is made by plastic deformation of the RTJ gasket into the groove in the flange, resulting in intimate metal-to-metal contact between the gasket and the flange groove. The faces of the two opposing flange faces do not come into contact because a gap is maintained by the presence of the gasket. Such RTJ flanges will normally have raised faces, but flat faces may also be used or specified.
RTJ for API 6A Type 6BX FlangesAPI 6A Type 6BX flanges have raised faces. These flanges incorporate special metal ring joint gaskets. The pitch diameter of the ring is slightly greater than the pitch diameter of the flange groove. This factor preloads the gasket and creates a pressure-energized seal. A Type 6BX flange joint that does not achieve face-to-face contact will not seal and, therefore, must not be put into service.
Flat Face (FF)
Note: Both ASME B16.5 and BS 1560 specify flat face flanges and raised face flanges as well as RTJ flanges. API 6A is specific to RTJ flanges only. Male and Female Facings. The female face is 3...-in deep, the male face is 1..-in high, and both are smooth finished. The outer diameter of the female face acts to locate and retain the gasket. Custom male and female facings are commonly found on the heat exchanger shell to channel and cover flanges.