A flexible lined butterfly valve is a specialized type of valve designed for controlling the flow of fluids in various industrial applications. It combines the functionality of a standard butterfly valve with the added benefits of a resilient, corrosion-resistant lining, making it suitable for handling abrasive, corrosive, or high-purity media. Design and Construction The valve consists of a circular disc or vane mounted on a rotating shaft, which acts as the flow control mechanism. When the disc is parallel to the flow, the valve is fully open, allowing maximum fluid passage. Rotating the disc 90 degrees positions it perpendicular to the flow, effectively shutting off the passage. The key feature of a flexible lined butterfly valve is its elastomeric or polymer lining, which covers the internal surfaces of the valve body and the disc. This lining serves multiple purposes: 1. Corrosion Resistance – Protects the metal body from aggressive chemicals, acids, or alkalis. 2. Abrasion Resistance – Extends valve life when handling slurries or particulate-laden fluids. 3. Bubble-Tight Sealing – Ensures zero leakage when closed, critical for process control and safety. 4. Smooth Flow Path – Reduces turbulence and pressure drop, improving efficiency. Materials and Lining Options Common lining materials include: - PTFE (Polytetrafluoroethylene) – Excellent chemical resistance and high-temperature tolerance. - EPDM (Ethylene Propylene Diene Monomer) – Suitable for water, steam, and mild chemicals. - FKM (Fluoroelastomer) – Resistant to oils, fuels, and harsh solvents. - Natural Rubber or Nitrile – Used for abrasion resistance in slurry applications. The valve body is typically made from ductile iron, carbon steel, or stainless steel, providing structural strength while the lining ensures compatibility with the process fluid. Applications Flexible lined butterfly valves are widely used in industries such as: - Chemical Processing – Handling acids, alkalis, and solvents. - Water and Wastewater Treatment – Resistant to chlorine and other disinfectants. - Mining and Slurry Transport – Withstanding abrasive particles. - Pharmaceutical and Food Processing – Meeting hygienic standards with FDA-approved linings. Advantages - Cost-Effective – Lower maintenance and longer service life compared to unlined valves. - Lightweight and Compact – Easier to install and operate than gate or globe valves. - Bi-Directional Flow – Can be installed in either flow direction. - Low Torque Operation – Requires less force to actuate, reducing wear on actuators. Conclusion Flexible lined butterfly valves offer a reliable and efficient solution for demanding fluid control applications. Their combination of durability, chemical resistance, and tight shut-off makes them a preferred choice in industries where corrosion, abrasion, or contamination are concerns. Proper material selection based on the operating environment ensures optimal performance and longevity.