A HELICAL FORMATION FOR A CONDUIT

摘要

A helical formation for a conduit (1). The helical formation includes an elongate member (4) defining at least a portion of a helix, the elongate member (4) comprising an inwardly extending portion (6, 7). The inwardly extending portion (6, 7) extends along the length of the elongate member (4) and extends inwardly from the internal side walls of the conduit (1) for a distance equal to between 10 % and 80 % of the distance (r) from the longitudinal axis (3) of the conduit (1) to an internal side wall (2).