A slam-shut safety device including a valve body defining a flow path extending between an inlet and an outlet, a bonnet including a sleeve extending into the flow path and having one or more flow ports, an actuator arranged to detect an overpressure or underpressure condition, a control element movable between an open first position and a closed second position, a reset pin operatively coupled to the control element and movable between an un-tripped position, placing the control element in the open first position, and a tripped position, placing the control element in the closed second position, the reset pin configured to move from the un-tripped position toward the tripped position responsive to the actuator detecting the overpressure or underpressure condition, and a seal arranged to substantially prevent accumulation of particulates carried by fluid flowing through the one or more flow parts on the outer surface of the control element.