T. R. Marti
Papers # 2018 Las-Vegas
Horizontal Directional Drilling, or HDD, is now a common technique for installation of PVC pipe. This was not always the case. The fused PVC use in HDD has grown from an initial installation of 500’ (150M) in 2004 to installation lengths over 7000’ (2.14 KM) today. Advancements in connection properties taking into account full scale testing were necessary to reach these installation lengths with plastic pipe.
Horizontal Directional Drilling (HDD) incorporates many techniques of the more classic vertical drilling that is used for natural gas, petroleum, and water resources. HDD differs in several ways. The bore alignment has an entry and an exit giving access to both ends of the drill stem. The drill navigates horizontally through the geologic strata allowing for drilling in the same formation or layer. The steering can be done monitored and followed from the ground surface allowing for very accurate alignments.
The basic components of an HDD installation are featured in Figure 1 and include the are the pilot bore, the reaming passes, the cleaning swab, and the pull back of the product pipe. The pilot bore is typically a 9” to 11” diameter. The reaming passes open the pilot to 1 ½ times the new pipe outside diameter. The pull back of the new pipe is done immediately after verification that the bore is free of any large drilling debris that could compromise installation.
The connection between the new PVC pipe and the steel drill stem is accomplished with a pull head that is mechanically connected by smooth shank high strength bolts. These bolts provide a high capacity shear connection between the pipe and the tell shroud portion of the head.