Rising stem ball valves for some applications. These are hard to come by and only manufactured by a very, very limited number of companies.
Does anybody know of ball valves that have similar properties,very good tightness and wear properties?
In services where we have used Orbit (successfully) but are trying to reduce cost and weight we have begun to specify Zwick, Tyco Vanessa, FCX Orton triple offset butterfly valves and for the smaller valves, metal seated floating ball valves like Mogas, Valvtechnologies, Valvtron work well (but require a comparatively large actuator).
The rising stem ball valve is an adaption of the quarter turn ball valve. The ball is turned by means of a sliding helical guide. Example: Grove Omega Rising Stem Ball Valve. As I understand the ball rotates away from the seals until the final closing movement.

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