Läppäventtiilin

Läppäventtiili, known in English as a butterfly valve, is a type of quarter-turn valve that is used to control or isolate flow. It consists of a metal disc mounted on a rod, which is centrally located in the path of the flow. The disc is rotated by a handle or actuator. When the valve is in the open position, the disc is rotated 90 degrees to allow fluid to pass through. When the valve is in the closed position, the disc is rotated back to its position perpendicular to the flow, blocking the passage of fluid.

Butterfly valves are characterized by their simple design and relatively low cost, making them suitable for a wide range of applications. They are commonly used in piping systems for water, oil, gas, and air. Their compact size and light weight compared to other valve types, such as gate valves or globe valves, also contribute to their popularity, especially in larger pipe sizes.

The sealing mechanism in a butterfly valve can vary. In wafer-type butterfly valves, the disc is pressed between two flanges of the pipe. Lug-type butterfly valves have threaded holes on their outer casing, allowing them to be bolted between two pipe flanges. These valves offer the advantage of being able to be used as isolation valves at the end of a pipeline.

Despite their simplicity, butterfly valves can offer good control over flow rates when partially opened, though precise throttling can sometimes be challenging due to the disc's inherent tendency to create turbulence. They are generally not recommended for high-pressure or high-temperature applications where more robust sealing and control are required. Maintenance is typically straightforward, as there are few moving parts.