Locks can be used to lock the manual valve when it is fully open or closed so as to prevent non-working personnel from pulling the handle which may result in misoperation of valve.It can also avoid opening or closing of valve resulting from the shock from pipelines or unpredictable factors that may cause an accident.For working pipelines such as combustible and explosive oil, gas and chemical medium, or for field piping site, the locking mechanism is especially useful. www.valve-cn.com