Butterfly valve switch direction respectively?
If it is not to sound from behind, from large to small if that is in the open.
If there is no arrow on the handwheel, the indicator on the turbine has been damaged, you can put your ear on the wall of the pipe, turn the handwheel, and through the sound of the pipe medium to determine the direction of the switch.
First, if the butterfly valve has been installed on the pipe, you can first see the mark on the handwheel. Second, there is a switch indicator on the general worm gear.
