Method for controlling creep in spirally expandable profile

An elongated web or strip comprising a wall portion bounded by edge portions and adapted to form a conduit by spirally winding said web and joining adjacent edge portions, said edge portions including a primary locking formation and a secondary or sacrificial locking formation being adapted to permit relative movement of adjacent edge portions of said spiral conduit to thereby provide radial alteration of said conduit upon severing or disengagement of said secondary/sacrificial lock formation, said web further comprising a compensation portion to alter the dimensions of said web upon radial alteration of said conduit and thereby compensate for creep (as hereinbefore defined) in said spiral conduit, said compensation portion being provided at or directly adjacent one of said edge portions such that apart from the joint between adjacent webs, the interior surface of the web is substantially smooth and free of dislocations.

A method of compensating for creep (as hereinbefore defined) in a conduit constructed from a spirally wound web, said method comprising providing said web with a compensation portion at or directly adjacent one or more edge portions of the web, said compensation portions being adapted to compensate for variation in length of said conduit liner resulting from expansion or contraction of the conduit liner diameter.

A method of installing conduit comprising providing an elongated web or strip bounded by edge portions and adapted to form a conduit by spirally winding said web and joining adjacent edge portions, wherein said conduit is expanded or contracted to the desired diameter, said method comprising compensating for creep (as hereinbefore defined) during said expansion or contraction by providing said web with a compensation portion at or directly adjacent one or more edge portions of the web, said compensation portions being adapted to alter the dimensions of said web during and/or after said expansion/contraction.

A method as claimed in claim 20 wherein upon application of creep, said compensation portion alters the dimensions of said web in a substantially identical fashion around the circumference of said conduit.

A method as claimed in claim 20 wherein said compensation portion is selectively engageable such that it remains deactivated during spiral winding of said web and is activated upon expansion or contraction of said conduit.