A flange adapter is provided for positioning an insert device within a pressurized fluid system. A flange adapter assembly includes a pressure containing boundary and a flange adapter configured to be selectively connected to the pressure containing boundary. The adapter is configured to interchangeably fit a plurality of flange standards for the same nominal size. The adapter may also interchangeably fit a plurality of pressure ratings for the same nominal size. The flange adapter may be manufactured separate from the pressure containing boundary to allow for utilizing less costly material and to increase standardization of safety heads. The present invention also includes a gasket design having multi-flange compatibility for use in pressurized fluid systems.