When the butterfly valve is installed, can the stem be downward? What are the criteria?
According to the direction of the pipeline and easy to operate.
Not only can the transmission device at or above the level of 90 degrees, the transmission device is not allowed to download is in the valve below, it's too dangerous. This does not require any standard.
The valve stem can be installed vertically or horizontally, but the drive should be on top of the vertical installation. The stem should be downward and it is prone to accidents. This doesn't need any standard. It's the installation notes.
