Both butterfly valves and ball valves give you a quarter-turn open/close action, and both are common in brewing, food processing, and fluid handling. But they work differently, and those differences matter for certain applications.
How Butterfly Valves Work
A butterfly valve uses a disc mounted on a rotating shaft through the centre of the bore. When open, the disc sits parallel to the flow direction and presents almost no obstruction, and when closed, the disc rotates 90° to sit perpendicular to the flow, sealing against a seat in the valve body.
The disc always stays in the flow path, so even when the valve is fully open there's a disc and shaft running across the bore. That creates a small amount of restriction and provides a surface that product can contact and that needs to be cleaned.
How Ball Valves Work
A ball valve uses a drilled sphere. When open, the bore of the ball aligns with the flow path and you have an unobstructed through-bore, and when closed, the solid part of the ball rotates to face the flow.
The key advantage of a ball valve is that when fully open the bore through the ball is roughly the same diameter as the pipe, so restriction is minimal and there's no protruding shaft or disc for product to contact or collect around.
Sanitary Considerations
In food and beverage processing, full-bore ball valves are generally preferred for product lines because the fully open position leaves no obstruction and is easier to clean. Butterfly valves are used extensively in these industries too, but require more attention to ensuring the disc seat and shaft area are fully clean and are better suited for applications where CIP capability is possible.