Pneumatic Actuated Lug Butterfly Valve

Figure-1: typical photo and drawing for the pneumatic-actuated lug type butterfly valve.

Metalsin supplies versatile pneumatic-actuated lug butterfly valves for waterworks applications. These valves feature the pneumatic-actuated operation method: The butterfly valve is driven by a pneumatic actuator, which is a device that uses compressed air to automate the operation of the valve, enabling it to open, close, or modulate flow. Pneumatic actuators are widely used in waterworks applications due to their reliability, simplicity, and ability to provide precise control. The butterfly valve is usually made of ductile iron, characterized by lug style body construction and pinless one-piece through shaft.

Key Components of a Pneumatic Actuator

The pneumatic actuator with optional accessories: (1) positioner; (2) solenoid valve; (3) limit switch box; (4) manual device; (5) air filter pressure relief valve.

A pneumatic actuator consists of several key components: the cylinder, which serves as the main body for storing compressed air and converting it into mechanical motion, contains a piston or diaphragm that moves in response to air pressure. The piston or diaphragm transforms compressed air energy into mechanical force, with pistons moving linearly and diaphragms flexing to create motion. In spring-return actuators, a spring returns the piston or diaphragm to its original position when air pressure is released. The shaft connection links the actuator to the valve stem, transferring motion to the valve disc. Optional components include a positioner for precise valve control, a solenoid valve for automated air flow regulation, and limit switches for feedback on valve positions, etc.

Pneumatic Actuator Types and Working Principles

Pneumatic actuators for butterfly valves include single-acting actuators, which use compressed air to move the valve in one direction and a spring to return it to a default position, ideal for fail-safe applications. Double-acting actuators use compressed air to move the valve in both directions without a spring, requiring air pressure to maintain position and suitable where fail-safe operation is unnecessary. Rack and pinion actuators and scotch yoke actuators both convert linear motion into rotary motion, with the former commonly used for quarter-turn valves and the latter offering high torque output for larger valves. Single-acting actuators rely on compressed air to overcome spring force, returning to the default position when air is cut off, while double-acting actuators alternate air supply on both sides of the piston or diaphragm, maintaining position even if air supply is interrupted.

Technical Specifications

Materials Specification & Design Standards: The body is made from ductile iron ASTM A536 grade 65-45-12, while the disc available in ASTM A536 Gr.65-45-12, CF8/CF8M, CF3/CF3M, or aluminum bronze (ASTM B148 C95800). The valve seat ring is bonded on to the interior surface of body and is usually made of EPDM, NBR, FRM, or PTFE. The stem (shaft) is made from SS420 or SS431. The lug butterfly valve shall be designed in accordance with ISO 5752, BS 5155, EN 593, MSS SP 67, or API 609, etc.

Sizes, Pressures, Temperatures: Pneumatic-actuated lug butterfly valves are available in sizes DN50 through DN600. The rated working pressure can be PN10 or PN16, while the rated working temperature is ranging from -20°C to +120°C.

Flange Dimensions: Similar to the wafer butterfly valve, the pneumatic lug type butterfly valve shall be clamped between two pipe flanges when installed in waterworks pipelines. The flange dimensions shall be in accordance with EN 1092-1 PN10, PN16; ASME B16.5 Class 150; ASME B16.1 Class 125, Class 250; DIN PN10, PN16; BS 4504 PN10, PN16; JIS 10K, 16K; GB/T PN10, PN16.