Pull Back Force


Definition - What does Pull Back Force mean?

Pull back force, in the context of horizontal directional drilling (HDD), can be defined as the tensile load that is applied to the drill string when it is withdrawn to the entry point through the bore hole. Usually when the drill string is pulled back, the pipe is simultaneously installed. Calculating the pull back force is therefore very important before a project is started. When the pipe is pulled back for installation through the hole, it will experience different stresses and load conditions which should be estimated to help prevent the failure of a pipeline project.

Trenchlesspedia explains Pull Back Force

HDD is still in its infancy in the field of trenchless construction. Often, engineers and owners rely extensively on the contractor to determine the feasibility of a project. These contractors usually consider factors influencing the drill rig, successful boring, reaming and pulling of product pipe back through the hole if it is within specified tolerance levels. However, the stresses on the pipe itself are often not considered. It is therefore essential for the engineers to give a design to the contractor that takes into consideration the stresses and load that a pipe will experience, and can withstand, rather than considering the forces that the HDD rig will experience. Some of the aspects of a bore that effect pulling loads include bore hole diameter, stability of surrounding soil, subsurface conditions, drilling fluid properties and buoyancy control measures.

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