The Floating Cushion Sub Model PD6-2 is designed to be installed on rotary drills below the top drive as a shock absorbing, thread saving and maintenance reduction device. It is available with all the popular thread configurations for drill pipe and steel up to and including six (6”) diameter. The telescopic action of the piston permits the drill operator to rapidly make-up and breakout threaded connections with minimal axial loading and no thread damage. In tension or compression, the transmission of axial vibrations created by the bit or D.T.H. hammer are minimized.
Function & Operation
The Floating Cushion Sub Model PD6-2 was developed primarily to allow a limited amount of axial travel between the drill string and the rotary drive while making up and breaking out threaded connections and also to reduce shock and vibration induced by the rotary bit or DTH hammer bit. Typically the pin up, box down threaded configuration machined into the upper cap and piston will suit most drills and drill string combinations without any modifications to the drill.
The spline drive system that transfers the torque from the rotary spindle by means of drive pins provides 100% displacement to the drill string and the bit. Located within the housing cavity are upper and lower cushions that absorb the shock displaced into the piston from the drill string when the piston is at either the upper or lower limits of its stroke within the housing. Drilling fluids and or air are isolated from the housing by means of a washpipe and seal arrangement that prevent corrosion from taking place on the internal components.