a valve operator is connected to a pipeline valve to control the throughput flow therethrough . a plurality of chambers are formed in the housing including control , balancing , bleed and regulator chambers . a poppet valve and an orifice device are disposed in the bleed chamber to be independently shiftable therein to vary the discharge from the orifice device which is shifted responsive to the pressure in the control chamber , while the poppet valve is shifted responsive to the pressure in the regulator chamber . a reset valve is connected in a reset loop connected between the control and balancing chambers to produce a predetermined delay in balancing the pressure gradient therebetween . the regulating chamber is formed in a regulator section of the housing to be detachably connected thereto so that a plurality of regulator sections can be formed each having a different operative pressure range so that the valve operator is selectively usable for example for high , medium and low pressure operation . the reset valve is adjustable to permit the delay to be set as desired .