is mounted with the retainer and extends upwardly through the center of a spring adjustment bushing 26 the bushing 26 enables and guides reciprocating movement of the stem 24 for enabling opening movement of the ball 20 and ball retainer 22 from the seat ring 18 concentrically disposed about the stem 24 is a helical spring 28 which engages the ball retainer 22 at one end the upper end of the spring 28 engages a spring retainer 30 which is thereby held against the adjustment bushing 26 the bushing 26 is secured to the valve body 10 by engaged helical threads 32 by rotating the bushing 26 the helical threads 32 will control the distance between the spring retainer 30 and the ball retainer 22 and thereby the magnitude closing force of the spring 28 on the ball member 20 by selection of an appropriate spring constant force produced per unit of spring deformation the closing force of the pressure relief valve may be carefully controlled and since the closing force must be overcome by the inlet pressure created opening force such spring adjustment arrangement also controls the force at which the ball 20 will lift from the seat 18 to open the pressure relief valve v the opening force is provided by the projected area.