X series casing

casing tubes have a box thread at both ends and are connected together by a pin-to-pin coupling. Casing tube has a thinner wall than the coupling, allowing the overall weight of casing string to be minimized.

W series casing

Flush-jointed casing has a heavier wall section than coupled casing and has an integral pin and box section. The heavier wall section provides internal and external mating shoulders for the threaded portion to butt-up against, providing twice the contact area of coupled casing and helping to prevent the threads climbing under heavy torque loads. This is by far the most popular type of casing used in geotechnical applications.