A method of operating an on-off valve comprises closing one of two openings of a valve body with a seal member of a closure element within the valve body, the valve body being within an evacuation pipe connected between a process chamber and an evacuation apparatus; moving the closure element, using a linear driver, so that the seal member is moved away from the one of the two openings; and positioning the closure element into a retreat portion in an surface of the valve body, using the linear driver and a pivotal driver adapted to pivot the closure element between the one of the two openings and the retreat portion, so that the seal member is closed inside a protection seal member of the closure element to surround the seal member, thereby preventing the seal member from being directly exposed to the process gas.