Once the drilled hole is enlarged, the product pipeline can be pulled through it. The pipeline is prefabricated and usually tested on the bank opposite the drilling rig. A reamer is attached to the drill string and then connected to the pipeline pull head via a swivel. The swivel prevents any translation of the reamer's rotation into the pipeline string, allowing for a smooth pull into the drilled hole. The product pipe has to be supported for the pullback operation. This is usually accomplished on rollers or with some type of crane or backhoe. Caution has to be exercised during the pullback to ensure that the product pipe or its coating is not damaged. Often breakaway links that fail before pullback loads exceed the safe limits of the product pipe are utilized. The drilling rig then begins the pullback operation, rotating and pulling on the drill string and once again circulating high volumes of drilling slurry. The pullback continues until the reamer and pipeline break ground at the drilling rig. If possible, there should be enough work space on the pull side so that the product pipe can be assembled in one continuous length. This reduces the chance that the pipe may get stuck during the pullback operation. A schematic of the HDD pullback process is shown in Figure 1-7.
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What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.