The Butterfly valve – a valve used for regulating flow or isolating. This type of valve has a disc which is mounted on a rotating shaft. When this valve is fully closed, the disk completely blocks the line. But, when the butterfly valve is fully opened, the disc is at a right angle to the flow of gas or liquid. They are lower in cost compared to the other valve designs. Also they are lighter in weight which means that it doesn’t require a lot of support.