Shut-off valve for pipelines or equipment transporting polymers has a piston which is moved into a pipeline of greater diameter and is cooled to freeze the flowing material

摘要

A sleeve(3) mounted on the pipeline wall guides a freezing piston(7) in and out of a pipeline. The piston has a different diameter to that of the pipeline and when in the retracted, resting position does not restrict the pipeline cross-section. When moved into the pipeline the piston purges material in the latter and cooling fluid flowing through the piston solidifies material in the pipeline to halt the flow. The pipe cross-section in the pipe at the seat of the piston is not round and equals the cross-section or its dynamic equivalent in the pipeline in front of and behind the valve. A piston face(8) which contacts the flowable material can be either smooth, convex, concave, elliptical or circular arc shaped. arc-shaped arch. Freezing of the flowable material can be achieved when the gap between pipeline wall and piston wall is 5-100mm, preferably 8-40mm. No corners or angles exist on surfaces which contact flowable material and rounded areas have a minimum radius of 6mm. Conical enlargement(11) of the piston area in contact with flowing material corresponds to a seating angle of the cone in the guide sleeve(3) so that material entering a gap between piston and sleeve is forced back into the pipeline and the piston lies flush with the pipeline wall when in the resting position. Separate heating fluid(2) and cooling fluid(1) channels pass through the piston. The piston-guiding sleeve has a stripping seal(12) which, on retraction of the piston, ensures that flowable material cannot penetrate the sleeve. A jacket(5) surrounding the shut-off valve allows heating and cooling of the pipeline in this area. Piston movement between resting and shut-off positions is effected mechanically. A stop prevents movement onto the opposite side of the pipeline and in the resting position the piston is secured against accidental opening. When two pistons oppose each other the pistons have flat faces.