The design standards of eccentric butterfly valves (especially triple eccentric butterfly valves) cover multiple dimensions such as structure, materials, and testing. The core standard system is as follows:
1. Basic design standards
API 609
Authoritative specifications for the oil and gas industry: specify the eccentric structural angles (such as stem offset, cone angle inclination), torque calculation methods, and bidirectional pressure-bearing design criteria for double flange/wafer-type butterfly valves.
Pressure classification: covers Class 150~1500 (American standard) or PN10~PN100 (European standard), and clarifies the wall thickness and strength calculation formulas.
ISO 10631
General industrial butterfly valve standard: defines the valve flow channel geometry, operating mechanism interface (ISO 5211 top flange) and structural length tolerance.
2. Interface and connection standards
Flange connection
American standard: ASME B16.5 (Class 150~2500) specifies the flange sealing surface type (RF/RTJ).
European standard: EN 1092-1 (PN10~PN400).
Wafer connection
The bolt hole span and structural length are specified in accordance with MSS SP-67.
Welding end
The bevel size of the welding joint shall be implemented in accordance with ASME B16.25.
3. Sealing and performance test standards
API 598
Mandatory test items: Shell strength test (1.5 times the nominal pressure), high and low pressure sealing test (two-way zero leakage requirement).
Leakage level: Metal hard seals must meet Class V (≤0.5 Nm³/hr gas leakage) or Class VI (bubble-level liquid seal).
Fire safety standard
API 6FA: The valve remains sealed after simulating a 650℃ fire (mandatory certification for hard-sealed butterfly valves).
Low leakage certification
ISO 15848-1: For VOCs working conditions, fugitive leakage must be ≤B grade.
4. Material and process standards
Valve body/disc material
Carbon steel: ASTM A216 Gr.WCB;
Stainless steel: ASTM A351 Gr.CF8M (316 stainless steel).
Sealing surface reinforcement
Overlaying Stellite alloy (Stellite 6, hardness ≥HRC 40) or HVOF spraying tungsten carbide (hardness ≥HRC 65).
Special working conditions adaptation
Deep cryogenic treatment (-196℃) is carried out in accordance with BS 6364;
Corrosive media must pass NACE MR0175 hydrogen sulfide stress corrosion test.
Summary
The design of eccentric butterfly valves must meet four standards simultaneously:
Structural: API 609/ISO 10631 defines geometric parameters;
Interface: ASME B16.5/EN 1092-1 specifies the connection method;
Reliability: API 598 tests the seal, API 6FA guarantees fire protection;
Material: ASTM material standards + special process certification.