Abstract: A seal for flow passages has directional characteristics allowing gases or fluids to flow freely in one direction while restricting the flow in the opposite direction. The seal includes a flow diverter cone (or other inclined surface) which is spacedly mounted on a flow inverter cone (or other inclined surface) in a passage to effectively reverse the direction of undesired counterflow of gases without restricting normal gas flow. The seal has no moving parts but serves as an effective aerodynamic valve. Addition of this seal to the stack of a flare system, or to other chimneys, restricts the flow of air into the stack while allowing the waste gases to be exhausted with negligible restriction.

Abstract: A tall stack construction which may be used for the discharge of products of combustion or may be used as a flare stack with a burner at the top end for combustion of waste products from oil refineries or other chemical processes, the stack pipe being supported by a derrick in the form of a tripod with lateral support guy wires each extending over a pulley carried by one of the tripod legs and with their ends connected to a plate on the stack pipe. Additional stability is obtained by diagonal guy wires in tension extending from the bottom of the stack to the foundation in one embodiment. The stack pipe may be fixed to the derrick at the top or the bottom, may have a disentrainment drum at the bottom and may be supported in slidable engagement at the top of the derrick for expansion and for separation of the disentrainment drum.