Abstract: A forging hammer employs compressible fluid to drive the ram into impact and a trapped volume of compressible fluid to cause the ram to be retracted from impact position when fluid driving the ram into impact is released. The velocity of impact is adjusted by the timing of the opening of a valve allowing variable amounts of compressed fluid into a cylinder from a compressible fluid supply. Various means are provided to sense one or more of following: pressure of the compressible inlet fluid, residual velocity of the ram at the position at which the at least one inlet port is uncovered by the piston, position of the piston at the time of fluid admission and pressure of the lifting fluid. The sensed parameters are correlated in connection with predetermined criteria. This correlation is used to determine a range of possible kinetic energy at impact and that range is compared with a preselected kinetic input demand.