The hydraulic-damping-device can completely eliminate the backward stroke impact collision.
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A descriptive statistical approach was introduced to maximize the actual stroke length.
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A parametric model was fitted to evaluate the probability that impact collision is sufficiently eliminated.
Abstract
Utilization of the rotary–percussive drilling tools can help to reduce friction along the drill string and improve drilling performance in hard rock formations. However, intrinsic vibration and shock loads may severely damage the bottom hole assembly (BHA) and measurement while drilling (MWD). This paper investigates the dynamic response of fluidic hammer with hydraulic-damping-device, a rotary–percussive drilling tool which can provide forward percussion while eliminating harmful backward impact collisions. Descriptive statistical methods are introduced to accurately estimate the required damping length (RDL) and maximize the actual stroke length. In order to evaluate the influence of hydraulic-damping-device on vibration elimination, this paper discusses the effect of principal operating and design parameters on the dynamic responses of the fluidic hammer. In particular, a parametric model is fitted, in which the probability that backward impact collision is sufficiently eliminated is restricted to follow the probability density function. According to this function, when the damping stroke equals 10 mm, it is better than 99.999% to fully eliminate the possibility of backward collision. The improved understanding of the dynamic responses and some optimization proposals of a fluidic hammer will lead to the system reliability enhancement and cost optimization of the drilling engineering by eliminating the harmful shock and reducing shock-related tool failures.
