Improvements relating to the sealing of pipe liners

A method of joining a sheet of fabric together to form a pipe liner comprising a fabric sleeve with a barrier-coated inner surface and a longitudinal seam, the method comprising the steps of:

• a) providing a sheet of fabric comprising a barrier coating on one side;
• b) bringing two opposing side edges of the sheet of fabric together to form the fabric sleeve comprising the barrier coating on an inner surface of the fabric sleeve;
• c) applying a molten polymer to each of the two opposing side edges of the sheet of fabric on the inner surface of the fabric sleeve and to any gap in-between the opposing side edges;
• d) joining together the two opposing side edges of the sheet of fabric with the molten polymer to form the longitudinal seam in the fabric sleeve to provide the barrier-coated inner surface of the fabric sleeve and thereby provide the pipe liner;
• and
• e) applying a coolant liquid to the longitudinal seam on the inner surface of the fabric sleeve.

A method of testing a longitudinal seam of a pipe liner during manufacture on a production line, the pipe liner comprising a fabric sleeve with a barrier-coated inner surface and a longitudinal seam, the method comprising the steps of:

• receiving the pipe liner from a joining station of said production line;
• passing the pipe liner through a test station comprising an entry point, an exit point and a low point, wherein the entry point and the exit point are above the low point, and wherein the pipe liner comprises a test liquid comprising a dye at the low point which completely fills a section of the pipe liner passing through the low point, wherein the test liquid moves along the pipe liner as the pipe liner passes through the test station;
• and
• observing whether the test liquid penetrates through the longitudinal seam to an outer surface of the fabric sleeve.