Completely, draining, nonleaking pneumatic valve

摘要

A valve system is provided for completely draining a vessel which may contain corrosive liquids and for preventing leakage until the vessel is to be drained. This is accomplished by providing the vessel with a throat at the bottom, an outlet tube connected to the throat and a pressure tube connected to the outlet tube with a source of fluid or gas pressure connected to the outlet tube between the throat and the pressure tube to force gas upward against (and/or through) the throat, thereby preventing the flow of liquid downwad through the throat. Agitation of the vessel contents can be achieved by flow of gas through he throat. The pressure tube is arranged to produce a positive pressure head greater than or equal to the maximum expected height of liquid in the vessel so that the pressure of air or inert gas upward prevents any liquid from draining from the throat of the vessel until the air or gas pressure is turned off, at which time complete drainage of the vessel takes place because of the absence of any chambers or cavities such as may be present in a conventional mechanical type valve.