Patent ID: 8091580

Claim:
A pilot assembly comprising: a pilot body defining a pilot body interior, and defining a first and second supply gas inlet and a single output gas outlet for providing output gas to a process control valve to regulate the flow of liquid from a vessel having liquid therein; a switch movable between first and second positions for selectively switching the pilot valve from a first to a second mode, wherein in the first mode supply gas is communicated to the first supply inlet and in the second mode supply gas is communicated to the second supply inlet; a pilot plug disposed in the pilot body interior, the pilot plug comprising an upper sealing ball engageable with an upper seat in the pilot body interior, and a lower sealing ball connected to the upper sealing ball by a pilot plug stem; a movable actuator disposed at least partially in the pilot body interior and defining a lower seat engageable with the lower sealing ball, the upper sealing ball being engaged with the upper seat and the lower sealing ball being disengaged from the lower seat to define a passage for supply gas from the second supply inlet when the pilot valve is in the second mode and supply gas is directed through the output gas outlet to position the process control valve in a fully open position, wherein the actuator is movable upwardly in response to a mechanical force applied thereto as a result of a liquid level change in the vessel so that the actuator will engage the lower sealing ball and close the passage for supply gas and move the pilot plug upwardly to disengage the upper sealing ball from the upper seat to vent the output gas and move the process control valve to a fully closed position; and a biasing means for applying a force to the upper sealing ball in a direction toward the upper seat to oppose the mechanical force applied to the actuator, wherein the biasing means is adjustable such that the amount of force applied to the pilot plug can be adjusted thereby adjusting the amount of opposing mechanical force that must be applied by the actuator to disengage the upper sealing ball from the upper seat and move the process control valve to the fully closed state.