Abstract: A union nut is installed over a valve body between an outwardly flaring flange on a valve port and the valve itself. The union nut is uniquely characterized by installation threads cut into an inwardly flaring shoulder, and installation threads are also provided on the flange of the port. The shoulder can be screwed onto the flange until the union nut freely rotates about the port. A split ring is installed against a neck on the port, the neck being adjacent the flange, such that the union nut cannot threadedly engage the installation threads. The freely rotating union nut can be tightened into a suitable fitting that is part of a fluid system.