1. Definition and core role of the standard
API 609 is the design and manufacturing specification for double flange, lug and wafer butterfly valves formulated by the American Petroleum Institute (API), which is suitable for medium and low pressure conditions in industrial fields such as petroleum, chemical, and gas. The standard clarifies the structural parameters, material selection, performance testing and installation requirements of butterfly valves to ensure the reliability and sealing of valves under frequent opening and closing conditions.
2. Structural type and applicable connection method
Connection form: Double flange type: flange connection at both ends, suitable for conventional pipeline systems; Lug type: fixed by bolts through the valve body lug, easy to disassemble and maintain; Wafer type: clamped between pipeline flanges, compact structure and light weight.
Structural length: Short type and Long type are defined in the standard. The long type is mostly used for special working conditions or scenes requiring additional rigidity.
3. Material and performance requirements
Main material:
Key components such as valve body and butterfly plate are usually made of stainless steel (such as CF8, CF8M), nickel-based alloy or carbon steel (WCB).
Seal design:
Soft seal: non-metallic materials such as PTFE and rubber (NBR) are used, suitable for clean media at room temperature;
Hard seal: metal + graphite composite layer (such as 304 + graphite) is used, which is wear-resistant and can adapt to slightly granular media.
Performance test:
It is necessary to pass the shell strength test and sealing test of API 598 standard to verify the leakage-free performance of the valve at 1.5 times the rated pressure.
4. Typical application scenarios
Petrochemical industry: used for medium cutoff and regulation of oil refining equipment and storage tank inlet and outlet;
Gas transmission and distribution: sub-control valves in urban gas pipelines to meet frequent operation requirements;
Water treatment system: flow control of large pumping stations or pipelines, with high corrosion resistance requirements.
5. Certification and selection points
Certification requirements:
Manufacturers must pass the production system audit of API 609 standard, and some manufacturers are also required to provide performance test reports from third-party laboratories.
Selection considerations:
Prioritize matching flange standards (such as ASME B16.5) to ensure installation compatibility;
For high temperature or high pressure conditions, select valves that meet API 6D or API 608 standards