How far can a flat disc in a butterfly valve typically rotate?

In a butterfly valve, the disc is designed to rotate in the plane of the valve body. Typically, this rotation allows the disc to either fully open or fully close the flow path when turned. The standard rotation for a flat disc in a butterfly valve is 90 degrees.

When the disc is rotated 90 degrees from its closed position, it aligns with the flow path, permitting unrestricted flow through the valve. This design is efficient for regulating and controlling flow in various applications, as it offers a quick and straightforward mechanism to either stop or allow flow.

The limitation to 90 degrees is primarily due to the design of the valve itself, ensuring that beyond this point, the valve stays in one of its two primary positions—fully open or fully closed—making it easy to operate and manage. Thus, the 90-degree rotation provides the necessary functionality while maintaining compact design and ease of installation.