  Flow-reaction forces acting in hydraulic valves have been studied for many
decades. Despite this, they are difficult to account for due to the
complexities of the jet flow. This paper focuses only on the reduction, also
referred to as compensation, of the flow force as applied to a valve spool
featuring a profile of a turbine bucket. Fluid power textbooks explain the
compensation taking place on such a profile by applying Newton laws of motion
to the profile and deliver an equation for the magnitude and the direction of
the flow force. This paper shows that both the magnitude and the direction of
the compensating flow force are incorrect if calculated from the textbook
equation. A corrected analysis of the dynamic forces is presented that are in
agreement with earlier experiments by this author. It follows that the
compensating flow force should be calculated from the static-pressure imbalance
on the spool profile. That is, not Newton but Pascal law should be applied to
calculate the compensating flow force.
