A ball valve consists of a hollow rotating ball placed in the middle of a stem. Thanks to the rotational movement of the stem, this ball rotates 90° degrees within the valve body, providing flow control.
Ball valves are reliable and robust. Even if they remain in the same position for a long time, they can safely perform their function. They also allow frequent changes in stem position. However, their intended use is generally either fully open or fully closed. Outside the fully open or fully closed positions, their flow control is poor. For this reason, their use as control valves is not recommended.
Ball valves can be manufactured by many brands in various material constructions — metal, plastic, ceramic — for pressures up to 1000 bar and temperatures up to 400°C. However, when ball valves are used for control purposes, fluid frequently becomes trapped between the body and the ball. In cold weather, this trapped water expands within the ball and valve body, causing cracking or damage to the valve. This is a significant disadvantage; if a ball valve is to be used in environments where the air temperature drops below 0°C, a cold-resistant (frozen/freeze-proof type) valve must be used.
For cryogenic fluids, or products that could expand inside the ball, a vent hole is provided on the upstream side of the valve.
One of the most critical problems in the use of ball valves is contamination. Particularly when valves are used in drinking water or food plants, water accumulating between the valve body and the ball can lead to bacterial growth or cross-contamination when different fluids are used. This, in turn, harms human health first and then the quality of production. To prevent this accumulation, the cavities formed between the ball and the body are closed off by extending the surfaces on which the ball seats.
This type of valve is called a cavity-free "Cavity Filler Ball Valve", and the gaskets and materials of valves used in food or drinking water applications must be suitable for food and human health.
