In the industrial world, valves are used to isolate or shut off systems. There are ball, gate, globe and plug valves, which are used for the majority of services. Other valve types, such as knife gate and pinch valves, have a much more specific application. For this discussion I will focus on the ball valve and why it is preferred.
Ball Valve Functionality
The ball valve is a simple device. It has a 90 degree operation and is easy to determine which position the valve is in: when the handle is cross line, the valve is closed; when the handle is in line, the valve is open. The 90 degree operation means there is no stem that rises and descends through rings of packing, which often drags whatever product is in the pipe up with the stem. The valve’s 90 degree operation allows for ease of automation with either electric or pneumatic actuators. Ball valves also have an inherent low pressure drop and offer bubble-tight shutoff. While primarily considered as on/off valves, ball valves can be used in throttling service by using coated balls and hard seats. Ball valves are also considered to be downstream sealing, as they utilize the system pressure to push the ball into the downstream seat to achieve their shutoff. There are exceptions to this, but generally this is the case.
Basic Ball Valve Designs
There are three basic ball valve designs . . .
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