A flow through fluid pressure vessel of the type containing filter bags formed by a tubular shell, a one-piece cast bottom closure with an integral outlet port fitting welded to one end of the shell, a one-piece cast combination bulkhead and flange ring welded to the opposite end of the shell, a cast inlet fitting inserted through an aperture in the shell and connected to an inlet opening through the bulkhead and welded to the shell aperture. A cast closure/lid forms an inlet plenum with the bulkhead and is releasably sealed over the flange ring.