(under subclass 328) Boiler type glasses wherein improvements are claimed in the manner in which the glasses are provided with valves. The valves are usually manipulable so that the transparent portion may be cleaned by blowing off steam therethrough or whereby the transparent portion may be isolated from the reservoir to permit replacement of the transparent section.
SEE OR SEARCH CLASS
137, Fluid Handling,
559, for sight glasses combined with valves or other fluid handling apparatus.
251, Valves and Valve Actuation, appropriate subclasses for hand manipulable valves, per se.
