Do You Have to Test valve's Appearance?

Why is the valve such as Pneumatic Drive Type Butterfly Valve always faulty, do you have to test its appearance?

1. There are defects such as blisters and cracks on the inner and outer surfaces of the valve.

2. Whether the valve seat and the valve body are firmly connected, whether the valve core and the valve seat are in agreement, and whether the sealing surface has defects.

3. Whether the connection between the valve stem and the valve core is flexible and reliable, whether the valve stem is bent or not, and whether the thread is damaged or corroded.

4. Whether the packing and gasket are aging and damaged, and whether the valve is flexible or not.

5. There should be a nameplate on the valve body. The valve such as DIN Angle Globe Valve body and nameplate should include: manufacturer name, valve name, nominal pressure, nominal diameter and other signs.