System and method for preloading a valve tester control assembly

A valve testing apparatus with a preloading capability, comprising:

• a fluid supply configured to receive working fluid and provide a flow of the working fluid;
• a motor configured to be rotated by flow of the working fluid through the motor, the motor having a rotatable shaft connectable to an operating stem of a fluid controlling valve;
• a fluid control assembly configured to control flow of the working fluid between the fluid supply and the motor to control operation of the motor, the fluid control assembly comprising:
• an operation valve having an input fluidly connected to the fluid supply to receive working fluid from the fluid supply, the operation valve having an output;
• an adjustable pressure-responsive valve having an inlet fluidly connected to the output of the operation valve to permit flow of the working fluid from the operation valve to the pressure-responsive valve, the pressure-responsive valve having an outlet, the pressure-responsive valve having a normal condition in which the flow of working fluid entering the inlet of the pressure-responsive valve substantially completely flows out of the outlet of the pressure-responsive valve, the pressure-responsive valve having a diverting condition in which at least a portion of the flow of working fluid entering the inlet of the pressure-responsive valve is diverted to a bypass outlet of the pressure-responsive valve, the pressure-responsive valve changing from the normal condition to the diverting condition when the pressure-responsive valve senses that a pressure of the flow of working fluid entering the inlet of the pressure-responsive valve substantially equals or exceeds a threshold pressure, the pressure-responsive valve being manually adjustable to set the threshold pressure;
• a preload valve having an inlet connected to the outlet of the pressure-responsive valve to permit fluid communication between the outlet of the pressure-responsive valve and the inlet of the preload valve, the preload valve having an outlet fluidly connected to the motor, the preload valve having an open condition in which flow of working fluid through the preload valve is not blocked and the flow of working fluid is able to move through the motor, the preload valve having a closed condition in which the flow of working fluid through the preload valve is substantially blocked such that the pressure-responsive valve is exposed to a maximum pressure generated by the fluid supply without allowing flow of the working fluid through the motor.

A method of preloading a valve tester control assembly, comprising:

• providing a valve testing control apparatus comprising a fluid supply, a motor, and a fluid control assembly controlling flow of a working fluid between the fluid supply and the motor, the fluid control assembly comprising an operation valve fluidly connected to the fluid supply, an adjustable pressure-responsive valve fluidly connected to the operation valve, and a preload valve fluidly connected between the pressure-responsive valve and the motor;
• closing the preload valve so that fluid from the fluid supply does not pass through the motor;
• opening the operation valve so that the fluid supply is in fluid communication with the pressure-responsive valve;
• operating the fluid supply to supply fluid to the pressure-responsive valve;
• and
• adjusting the pressure-responsive valve so that a pressure-sensing gauge in fluid communication with an inlet of the pressure-responsive valve senses a desired maximum pressure for the fluid during testing of a valve.