Läppäventtiili

Läppäventtiili, known in English as a butterfly valve, is a type of quarter-turn valve. It is used to control or isolate flow. The valve works by inserting a disc into the flow path, which is then rotated by a stem connected to an actuator. When the disc is perpendicular to the flow, the valve is closed. When parallel, it is open. In intermediate positions, it can be used to regulate flow.

The design of a läppäventtiili is relatively simple, consisting of a valve body, a disc, a stem, and an actuator. They are popular due to their compact size, lightweight construction, and lower cost compared to other valve types, especially in larger sizes. Läppäventtiilit are suitable for a wide range of applications, including water supply, wastewater treatment, chemical processing, and HVAC systems.

There are several types of läppäventtiile, differing in how the disc seals against the valve seat. Common types include concentric, eccentric, and fully-lined butterfly valves. Concentric valves have the disc centered in the bore, with the stem passing through the center. Eccentric valves have the stem offset from the center of the disc and the bore, providing better sealing and longer seat life. Fully-lined valves have a rubber or PTFE liner that encapsulates the entire internal surface, offering excellent corrosion resistance.

While läppäventtiilit are efficient for on-off control and some throttling, their throttling capabilities can be limited, especially in precise applications. They are generally not recommended for high-pressure or high-temperature services where more robust valve designs are necessary. Maintenance is typically straightforward, often involving occasional lubrication of the stem and checking the seal.