DIRECTIONAL DRILLING MACHINE AND METHOD OF DIRECTIONAL DRILLING

摘要

A system, apparatus and method for automatically limiting the thrust force applied to a drill string during an underground boring process, in order to prevent deformation or collapse of the drill rods due to reaching the yield point of the rods and to prevent unthreading of drill string rods during reverse rotation of the drill string. One or more drill string characteristics that have an impact on the yield point of the drill string, or portions of the drill string, are determined. The yield point of the drill string or portion is computed, where the yield point is computed as a function of the drill string characteristics. The thrust force imparted to the drill is adjusted in response to the computed yield point. The thrust force imparted to the drill string is also adjusted to prevent unthreading of drill string rods during reverse rotation of the drill string.