Adapter Ring Mean?
An adapter ring is used to connect two flanges that have connections which are incompatible with each other. For example, if you wish to connect a socket connection flange to a blind connection flange, you would use an adapter ring between the two flanges to make a connection. The adapter ring forms a watertight bridge between the two flanges, allowing liquids to pass freely through the flanges (in the adapter ring without leakage or the incursion of air into the pipeline.
Trenchlesspedia Explains Adapter Ring
Adapter rings coming two forms: The double studded adapter ring (DSA) and single studded adapter ring (SSA). Both can be used to connect flanges of different sizes, different pressure ratings, and different configurations. Both are steel rings with an outside diameter and thickness equal to the larger of the two flanges to be connected. One side of the single-studded adapter is equipped with the union-type connection. The other side of the SSA has studs around the perimeter of its bore (sized to fit the smaller flange), which fit into the tapped stud on the smaller flange to which it’s connected.
The DSA has tapped stud holes around its perimeter to connect with the larger flange and a raised portion about 1/4" high on the opposite side for the smaller studded connection; unless tapped stud hole intersection and drilled hole depth necessitate additional thickness to satisfy the API design requirements for stud thread engagement.