Cryogenic Ball Valves

As the name implies the ball valve uses a ball as the obturator and the body seats are usually PTFE, the ball has a port through the centre and the valve operates with a 90° turn of the hand lever or actuator.

Advantages
1. When the valve is fully open there is a clear unobstructed flow path along the pipeline, this gives better flow characteristics than globe valves. Typical resistance factors are between 0.3 and 1.0, the higher value being for reduced port valves.

2. The valve is quick and simple to operate with a 90° turn of the valve stem; this also makes the valve more suitable for automation as the 90° actuator is a low cost readily available item.

Disadvantages
1. Due to the sliding action of the ball over the body seats, wear of the seals and ball takes place especially if particulate contamination is present in the line, ball valves therefore have not been used in situations where tight shut off is critical over long service life.

Applications
The ball valve has been used where an unrestricted flow path is required and leakage at shut off is not critical or valve operation is infrequent. Typical application being fill and isolating valves used on CO2 trailers where the temperature is not low (-20° C). Also trailer fire block valves where the valve normally remains open until emergency shut off is required.