Basic Knowledge of Sanitary Butterfly Valves

Generally, many customers purchasing sanitary butterfly valves rely on the design department's specifications without having much understanding of the actual product. This can leave purchasing managers feeling like they know the "what" but not the "why."  Therefore, this document provides a basic overview of sanitary butterfly valves.

A sanitary butterfly valve consists primarily of a disc-shaped valve flap that rotates around an axis through its center to control the flow. It is a simple regulating valve that can also be used for on/off control of low-pressure pipeline media.

Sanitary butterfly valves are mainly used in pipelines transporting various corrosive and non-corrosive fluid media in systems such as mineral water projects, beer machinery, filling machines, rice wine projects, chemical machinery, food machinery, and dairy machinery, for regulating and shutting off the flow of media.

The rotation angle of the sanitary butterfly valve is directly proportional to the flow rate; in simple terms, it is a linear relationship. To reduce the flow rate, the opening angle of the valve flap should be reduced.  The pipe diameter must also match the diameter of the sanitary butterfly valve; otherwise, it's like a small engine pulling a large load, preventing the valve from functioning properly and causing losses.

If the medium used in the sanitary butterfly valve is corrosive, the valve should generally be either fully closed or opened to an angle greater than 15° to ensure a high flow rate. This prevents corrosion of the valve flap due to low flow velocity, thus extending the service life of the sanitary butterfly valve.

When the sanitary butterfly valve is in a partially open position, approximately 45°, the leading edge of the butterfly plate on one side moves with the flow direction, while the other side moves against the flow direction. This can easily cause the rubber seal to detach. This is because one side of the valve body and valve flap forms a nozzle effect, while the other side forms a throttling effect, creating convection and a pressure difference.