Recent reports from several natural-gas utility companies reveal concerns regarding failure experiences on HDPE pipes installed by horizontal directional drilling. These failures were attributed to deformation of the pipe due to the use of excessive pulling force during installation. A mitigation measure adopted by some gas companies involves the use of breakaway swivels to limit the amount of force used when pulling PE products. The weak link used can be either a small-diameter pipe (but same DR) or a specially manufactured breakaway link. The latter consists of a breaking pin with a defined tensile strength incorporated in a swivel. When the strength of the pin is exceeded, it will break, causing the swivel to separate. The use of breakaway swivels is warranted particularly when installing small-diameter plastic pipes (up to 4 inches OD). Application of such devices in the installation of larger-diameter products is currently not a common practice. If the drilling equipment rated pulling capacity is less than the safe load, the use of a weak link may not be required. Exceeding the product's elastic limit can be avoided simply by following good drilling practices, namely: regulating pulling force; regulating pulling speed, proper ream sizing, and appropriate amounts of drilling slurry fluid.
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