An operation monitoring apparatus capable of displaying right click menus varying in configuration from each other according to a select object on an operation-monitoring screen is realized. In one embodiment, a valve assembly includes a valve body having at least two ports comprising a purge inlet and an outlet, a valve seat surrounding one of the ports, an annular groove formed around the valve seat coupling the purge inlet and the outlet, and a diaphragm assembly. The actuating member is coupled to a magnetic circuit such that the driving force acting on the actuating member is created by the magnetic field of the magnetic circuit, said magnetic field being induced by the overcurrent. The present ink compositions have particular application in the printing of packaging for foodstuffs.