Gasproofing leaking gas main

Claim 1

A METHOD FOR INTERNALLY SEALING A LEAKING JOINT BETWEEN LENGTHS OF PIPE COMPRISING THE STEPS: (A) LOCATING LEAKING JOINT BETWEEN ADJACENT LENGTHS OF PIPE; (B) MOVING A TRAVELING PLUG THROUGH SAID PIPES TO THE VICINITY OF SAID LEAKING JOINT, SAID PLUG BEING ADAPTED TO STRADDLE SAID LEAKING JOINT AND SEAL OFF AN ENVIRONMENT WITHIN SAID PIPE ON BOTH SIDES OF SAID JOINT FROM THE REMAINDER OF SAID PIPES; (C) FLOWING INTO SAID ENVIRONMENT A SEALING COMPOSITION HEATED TO A TEMPERATURE IN THE RANGE OF 200450*F. AND COMPRISING A TAR-RUBBER SOLUTION CONTAINING ACRYLONITRILE AND BUTADIENE IN COAL TAR PITCH TOGETHER WITH AN INERT FILLER; AND (D) MOVING ONE PORTION OF SAID PLUG RELATIVE TO THE REMAINDER OF SAID PLUG WITHIN SAID PIPES SO AS TO EXERT A PRESSURE ON SAID SEALING COMPOSITION GREATER THAN THE EXTERNAL PRESSURE AROUND SAID LEAKING JOINT WHEREBY SAID SEALING COMPOSITION FLOWS INTO SAID LEAKING JOINT AND SEALS THE SAME.