Self purging expansion joint can include first annular seal sleeve connecting bellows to first conduit and second annular seal sleeve connecting bellows to second conduit. Flow-restricting orifice(s) can allow a higher pressure external fluid to flow through the annular passage to purge the bellows and into the primary fluid flow passage of the expansion joint containing a lower pressure fluid. Self purging expansion joint can be utilized in a disengager vessel of a fluid catalytic cracking unit, for example, between primary and secondary stripping cyclones.