Method for lining a branch pipe of an underground pipe

A method for lining a branch pipe of an underground main pipe comprising the steps of:

• (a) preparing a tubular liner bag made of a nonwoven fabric soaked with a hardenable liquid resin, one end of said tubular liner bag being closed;
• (b) turning outwardly the open end of said tubular liner bag to form a collar which is so curled as to have a curvature equal to that of the inner wall of the main pipe;
• (c) curing the liquid resin in said collar to thereby harden the collar;
• (d) embedding stopper tacks in said collar at appropriate locations, each of said stopper tacks having its bottom end exposed from the back face of said collar and connected with a string;
• (e) facing the back face of the collar of the branch pipe liner bag with the upper face of a flange of a fluid pressure sealing nozzle, which comprises a hollow cylindrical part, through which the liner bag is passed, the flange extending perpendicularly from the side of said cylindrical part, at least one endless sealant laid on the upper face of said flange, and a string pull means provided in said flange;
• (f) engaging said strings with said string pull means of the flange;
• (g) causing said string pull means to pull said strings so that the collar and the flange are moved toward each other until sufficient sealing effect is obtained at the juncture between the collar and the flange by means of the endless sealant;
• (h) packing that portion of said liner bag which is tailing out from the fluid pressure sealing nozzle in an everter, which is a tubular body with one end closed;
• (i) connecting the open end of said everter with the bottom end of the cylinder part of the fluid pressure sealing nozzle in a manner such a closed space is defined by the inner wall of the everter, the inner wall of said cylindrical part and the outer surface of the uneverted part of the liner bag;
• (j) positioning said fluid pressure sealing nozzle together with the everter at the opening of the branch pipe in the main pipe such that the collar is fitted on the inner wall of the main pipe around the opening of the branch pipe;
• (k) everting said branch pipe liner bag into the branch pipe from the fluid pressure sealing nozzle toward the surface of the ground by supplying pressurized fluid into said closed space from the closed end of the everter;
• (1) hardening said hardenable liquid resin impregnated in the branch pipe liner bag while keeping the liner bag inflated by means of the fluid pressure;
• (m) severing said strings and detaching the fluid pressure sealing nozzle from the collar of the branch pipe liner bag;
• and (n) cutting off that portion of said liner bag which protrudes outside the branch pipe.