A method of threading an elongate flexible element through an elongate passage

摘要

String (2) is threaded through a pipe or conduit (1) by attaching it to a pig (3) and drawing the pig (3) through the conduit (1) by suction. The suction is applied by a pump (4). The string (2) may be a leader for an electric or fibre optic cable. The pig (3) may comprise a spring loaded scissor linkage (Fig. 4 not shown) or discs having spring loaded balls or wheels (Fig. 5 not shown). A membrane or diaphragm (11, Figs. 4,5) is employed. IMAGE