A Installing the casing pipe B Attaching the reamer C Drilling the pilot hole D Widening the pilot hole E The purpose of HDD F Stages in the HDD process G Main components H Function of components Horizontal Directional Drilling (HDD) 33 _____ Horizontal Directional Digging is used by the oil and gas industry for installing casing pipes under rivers or other obstacles. 34 _____ The equipment consists of a portable rig, a drill string, a cutter, a reamer, and a casing pipe. 35 _____ The job of the portable rig is to provide power for the drilling operation. The rig is attached to the drill string, the cutter and the reamer. The drill string transmits a rotating movement to the cutter. The purpose of the cutter is to make the pilot hole. The function of the reamer is to widen the small hole to the correct diameter. 36 _____ There are four main steps involved in horizontal directional digging. Let’s look at these four steps one by one. 37 _____ First, a small pilot hole is made using the drill bit on the end of the drill string. The drill bit completes the pilot hole and exits from the other side. 38 _____ Next, the cutter is removed from the drill string and the reamer is fixed to it. 39 _____ The drill string with the reamer attached is then pulled back through the pilot hole. As the reamer moves backwards through the hole, it increases the diameter of the hole. 40 _____ Finally, the drill string pulls the casing pipe through the hole, and the tunnel is completed.