Choosing the Right Cryogenic Valves
There are five types of cryogenic valves that are ideal for cryogenic media. Each of these types has its own set of characteristics that make them suitable in some applications and unsuitable in others.
1.Globe Valves. Called such due to their spherical shape, these valves have an internal movable disc -- the obturator -- that rotates at 90 degrees to the plane of its coordinated body seat. These cryogenic valves offer greater reliability for long-term sealing performance but are susceptible to moisture and aren't good in situations where flow rate is paramount.
2.Ball Valves. These valves utilize a ball as the obturator and generally include a Polytetrafluoroethylene body seat. They have better flow characteristics than globe valves but are more prone to wear and tear along its seals and the ball itself. They are thus most valuable for applications in which an unrestricted flow path is necessary.
3.Top Entry Ball Valves. Similar to standard ball cryogenic valves, this newer model has a one-piece design with butt welded connections that makes maintenance easy. The lack of mechanical joints also makes it a preferred option in fire safe applications.
4.Gate Valves. Gate valves utilize a wedge-type gate as the obturator which swings to close parallel to the mating body seat. They're similar to ball valves in that they offer good flow characteristics but are hampered by wear and tear.
5.Butterfly Valves. Butterfly valves are a part of the quarter turn family and utilize a circular disk at their center. This disc allows butterfly cryogenic valves to be shorter in length than the aforementioned choices, making them lighter and cheaper as well as quick and simple to operate. But over-use leads to their shorter lifspan.