Abstract: A removable bore liner is provided that substantially increases the dependability, flexibility and field-serviceability of seismic vibrators and other hydraulically actuated devices. A method for installing the removable bore liner in a seismic vibrator is also provided.

Abstract: A preloaded vibrator assembly wherein each leg of a stilt structure is preloaded in compression during construction. The linear actuator is preloaded prior to operation by supplying hydraulic fluid under pressure between one end of the linear actuator piston and the hub of the stilt-structure spider. A structural deflection of the spider away from the piston rod is created by the hydraulic pressure. At a predetermined load, a mechanical lock is engaged, fixing the relative positions of the spider and the piston rod. Hydraulic pressure is removed leaving the structure preloaded.

Abstract: A small battery operated nuclear spectrum simulator having a noise source nerates pulses with a Gaussian distribution of amplitudes. A switched dc bias circuit cooperating therewith generates several nominal amplitudes of such pulses and a spectral distribution of pulses that closely simulates the spectrum produced by a radiation source such as Americium 241.

Abstract: An improved means for making up and breaking out sections of drill pipe is disclosed herein. The make-up and breakout system is adapted for drill rigs having powered rotaries and powered carriages for moving the rotary up and down the mast. A wrench is mounted to the carriage for gripping the first section of the pipe. Slips are mounted at the work table for gripping the second section of pipe to support the string of pipe and prevent its rotation. The wrench is powered independently of the rotary, and the wrench and rotary can also rotate a certain amount with respect to each other while the wrench is gripping the first section of pipe. The independent power of rotation allows the wrench to breakout the first section from the second section. It also allows the rotary to breakout the first section from the rotary while the wrench restrains the first section from rotation.