Methods of sealing annular space between inner and outer gas mains for tie-overs

摘要

A method of tying over an individual customer service connection from a live outer gas main to an inner gas main inserted within the liver outer gas main comprises defining a generally annular region within the space between the inner and outer mains. The region is upstream from the customer service connection between the customer service connection and the source of gas for the outer main. The sidewall of the outer main is opened intermediate the ends of the region, and an amount of a high-density liquid foaming composition sufficient to fill the region is introduced into the opening. The foaming composition is permitted to foam and harden to a plug in the region. Before the foaming composition is permitted to foam and harden, a first end of a first conduit is inserted into the opening, and pushed into the space so that the first end lies upstream from the region. A section of outer main downstream from the region is then removed and the new customer service connection is placed through the sidewall of the inner main exposed by cutting away the outer main.