API and ISO Standards for Large Bore Butterfly Valves Design Large bore butterfly valves are critical components in industrial piping systems, particularly in applications involving high flow rates, such as water distribution, oil and gas, and chemical processing. To ensure reliability, safety, and performance, these valves must comply with internationally recognized standards, primarily those set by the American Petroleum Institute (API) and the International Organization for Standardization (ISO). API Standards for Large Bore Butterfly Valves 1. API 609 – This is the most widely used standard for butterfly valves, covering design, materials, pressure-temperature ratings, and testing requirements. It applies to both lug-type and wafer-type butterfly valves, including large bore designs (typically above 24 inches). API 609 ensures that valves can withstand high-pressure conditions while maintaining tight shutoff. 2. API 6D – While primarily for pipeline valves (e.g., ball and gate valves), API 6D includes provisions for large bore butterfly valves used in hydrocarbon services. It specifies requirements for fire-safe design, fugitive emissions control, and extended body configurations. 3. API 598 – Defines valve inspection and testing procedures, including pressure tests (shell, seat, and backseat) to verify leak-tightness and structural integrity. ISO Standards for Large Bore Butterfly Valves 1. ISO 10631 – Focuses on general-purpose metallic butterfly valves, covering dimensions, materials, and pressure ratings. It ensures interchangeability and compatibility across global markets. 2. ISO 5752 – Specifies face-to-face dimensions for flanged butterfly valves, ensuring proper fit within piping systems. Large bore valves must adhere to these dimensions to avoid installation issues. 3. ISO 5211 – Standardizes mounting interfaces between valves and actuators, crucial for automation in large bore applications. 4. ISO 15848-1 – Addresses fugitive emissions testing, an essential requirement for valves in environmentally sensitive industries. Key Design Considerations - Materials: API and ISO standards require corrosion-resistant materials (e.g., ductile iron, stainless steel, or exotic alloys) based on service conditions. - Seat Design: Resilient or metal-seated designs must meet API/ISO leakage classifications (e.g., Class VI for soft seats, Class IV for metal seats). - Pressure-Temperature Ratings: Valves must be rated per ASME B16.34 or ISO 7005 for flanged connections. - Testing: Hydrostatic and pneumatic tests per API 598 or ISO 5208 ensure durability under operational stresses. Conclusion Compliance with API and ISO standards ensures that large bore butterfly valves meet stringent safety, performance, and environmental requirements. These standards provide a framework for design consistency, reliability, and global interoperability, making them indispensable in industrial valve engineering.