A mechanism in the body of the lock ensures that the lock rotates freely around the internal drive spindle of the body. No force is transferred to the spindle in this state and the valve cannot be operated. The coded key has to be inserted to engage the drive spindle and hence to open or close the valve.
HSV-AT anti-tamper locks are suitable for any type of valve (ball, butterfly, gate, globe, gear box driven, slide valves etc.) and come equipped with either a lever or a hand wheel.