Process for everting a lining into a conduit utilizing two injection fluids

A process for internally lining a conduit, comprising the following steps:

• (a) cleaning of the inner wall of the conduit;
• (b) forming an inner lining sleeve from a single flexible and fluidtight sheet whose surface intended to be the inner wall is smooth and whose surface intended to be the outer wall is fibrous, the length of said sheet being substantially equal to the conduit to be lined and the width of this sheet being at least equal to the periphery of the inner section of said conduit;
• said sleeve having a cross-section capable of increasing when a pressure is applied to the inner wall thereof;
• (c) coating the inner wall of said conduit with a first resin;
• (d) introducing a light, flexible, fluidtight envelope, provided with at least one closable pipe at each of its ends, into said sleeve either before formation of this latter or after formation thereof, so that each of the ends of said envelope extends beyond the corresponding end of said sleeve;
• the cross section of said envelope being such that when it is inflated it may exert a pressure on the sleeve without undergoing plastic deformation so as to apply it against the conduit;
• (e) coating the outer fibrous wall of said sleeve with a second resin;
• (f) introducing the resin-coated sleeve and envelope disposed therein into said conduit
• (g) placing a flexible cap, comprising a tubular portion and a bottom over each of the ends of the envelope to retain said envelope in said sleeve, the length of said tubular portion being substantially greater than the external diameter of the bottom of the cap;
• said external diameter being smaller than the inner diameter of said sleeve so that, when said envelope is inflated, the tubular portion of said cap is firmly applied against said sleeve, said cap being held in position by the frictional force between the outer wall of said tubular portion thereof and the inner wall of said sleeve;
• (h) introducing a first pressurized fluid into said envelope through a first pipe disposed at a first end of said envelope, while the pipe(s) disposed at the other end of the envelope is (are) closed;
• continuing inflating said envelope until said sleeve is firmly applied against the inner wall of the conduit with a resin coat therebetween;
• (i) introducing a second hot fluid under pressure into said envelope, before polymerization of the resin(s), through a first or through a second pipe disposed at said first end of said envelope, the pipe or pipes disposed at said second end of the envelope being maintained sufficiently open to allow the first fluid to escape at least partially;
• continuing said introduction of said hot fluid until a sufficiently high temperature is reached in said envelope to cause complete polymerization of the resin(s) disposed between the outer wall of the sleeve and the inner wall of the conduit,
• (j) deflating said envelope and withdrawing said envelope from the sleeve when said inner lining sleeve is firmly bonded to said inner wall;
• (k) removing the water which has accumulated in the envelope during step (i).