Duct leakage control

Abstract

The invention provides an apparatus and methods for duct leakage control wherein a sealing element is introduced into the duct and is automatically drawn or otherwise guided to the locality of a leak, the element being caused, by reason of a pressure differential attributable to the leak, to move into and stem or seal the leak. The sealing element may comprise a plurality of individual members of differing buoyancy, each capable of being carried along at a predetermined level in the duct by the flow of fluid therein. The sealing element may carry a tagging device which can be used to assist in locating the leakage site.

1 . A method of controlling leakage of fluid from a duct along which said fluid is constrained to flow, wherein a plurality of individual sheet sealing elements are introduced into the duct and carried along the duct by the flow of said fluid; and
 wherein, at the locality of a leak, at least one of said sheet sealing elements is captured by a pressure differential associated with the leak and is thereby drawn to and held in position at the leak for stemming or sealing the leak.   
     
     
         2 . Apparatus for controlling leakage of fluid from a duct along which said fluid is constrained to flow, said apparatus comprising a plurality of individual sheet sealing elements for introduction into the duct and capable of being carried along the duct by the flow of said fluid, wherein, at the locality of a leak, at least one of said sheet sealing elements is capable of being captured by a pressure differential associated with the leak and thereby drawn to and held in position at the leak for stemming or sealing the leak. 
     
     
         3 . Apparatus according to  claim 2 , wherein said individual sheet sealing elements are in the form of a flexible membrane comprising a sheet of plastic. 
     
     
         4 . Apparatus according to  claim 2 , wherein each of said individual sheet sealing elements has a pair of opposing sides joined together and each is cut so as to present open ends so as to adopt a frustoconical form in the shape of a windsock when filled with fluid in the duct. 
     
     
         5 . Apparatus according to  claim 2  wherein said individual sheet sealing elements are in the form of flexible membranes having differing shapes. 
     
     
         6 . Apparatus according to  claim 5  wherein said individual sheet sealing elements are in the form of a flexible membrane rectangular in shape. 
     
     
         7 . Apparatus according to  claim 5  wherein said individual sheet sealing elements are in the form of a flexible membrane tubular in shape. 
     
     
         8 . Apparatus according to  claim 2  wherein said individual sheet sealing elements are in the form of flexible membranes having differing sizes. 
     
     
         9 . Apparatus according to  claim 2  wherein the sealing elements support a medium capable of adhering strongly to the duct when forced into contact therewith, thereby anchoring the sealing elements firmly in place across the leaking area of the duct wall and sealing the leak. 
     
     
         10 . Apparatus according to  claim 9  wherein said medium comprises a bonding agent. 
     
     
         11 . Apparatus according to  claim 10  wherein the bonding agent is contained in microcapsules which burst in response to the pressure imparted to the sealing elements when in position to seal the leak. 
     
     
         12 . Apparatus according to  claim 2  further comprising a location device capable, either by itself or in co-operation with another element or component, of providing a signal indicative of the location of the sheet sealing elements. 
     
     
         13 . Apparatus according to  claim 12  wherein the location device comprises a passive device including a loop of electrically conductive material, the proximity of which can be sensed by a mobile intelligent unit inside the duct or an external pick-up. 
     
     
         14 . Apparatus according to  claim 12  wherein the location device comprises an active device including an infra-red, acoustic, radio and/or optical sender configured to relay signals either directly to the environment outside of the duct or to a mobile intelligent unit inside the duct. 
     
     
         15 . Apparatus according to  claim 2  wherein two or more of the sheet sealing elements of equal or predetermined relative buoyancy are linked together by a link and encouraged to flow at a selected position within the duct depending in part upon the length of the link. 
     
     
         16 . Apparatus according to  claim 15  wherein the link between said two or more sheet sealing elements is constructed to dissolve or change in length during exposure, over a prescribed period of time, to the fluid content of the pipe.