There are certain requirements for the selection and purchase of ball valve during the manufacturing of ball valve damper, which must comply with the following points:
1. The radius of the ball valve is 0.4 times of its height under rated load;
2. The ball valve shall have a certain additional stroke, at least equal to 50% of the rated static radius;
3. The number of ball valve coils shall not be too small, generally not less than six.