Welch® Self-cleaning PTFE vacuum systems quiet and rugged vacuum pumps that provide work horse duty for years between service intervals. The self cleaning feature keeps the membranes and valves clean and dry, allowing the pump to achieve excellent base pressures and return to base pressure rapidly. The Welch Self Cleaning vacuum systems are the first choice for the vacuum savvy researcher with heavy work load rotary evaporator neeeds. The Welch Self Cleaning pumps have fine tunable control along with an anti-bumping/foaming feature.