Ball valve lockout is required by OSHA (1910.147) in order to isolate an equipment or machine from liquid or gas flow before it is repaired or overhauled. Ball valve lockout is installed to avoid miss operation or unintended operation of the ball valve.
Unintended operation of ball valve can cause serious problems from fire, severe chemical exposure to explosion. These problems will lead to people injury and death, and property damage. In this case, ball valve lockout is of importance to avoid such problems.
The following video will remind on how important ball valve lockout and tagout is.