Standards: Design and Manufacture: Cast steel check valve to BS 1868, ASME B16.34 and API 6D; Forged steel check valve to API 602. Inspection and Test: API 598 or API 6D. End flange dimension: ASME B16.5(for NPS≤ 24); ASME B16.47 series B, API 605 or ASME B16.47 series A, MSS SP-44(for NPS>24). BW end dimension: ASME B16.25. Socket-weld dimension: ASME B16.11. Face to face and end to end: ASME B16.10. Pressure-temperature ratings: ASME B16.34. Wall thickness dimension: API 600 and BS 1868. Features Bolted Bonnet; Swing and lift disc; Metallic seating surfaces. Body and Bonnet Connection The body and bonnet of Class150~Class900 check valves are usually with studs and nuts. And the body and bonnet of Class1500~Class2500 check valves are usually of pressurized seal design. Body-To-Bonnet Joint Stainless steel + flexible graphite wounded gasket is used for Class150 and Class300 check valve; Stainless steel + flexible graphite wounded gasket is used for Class600 check valve, And joint gasket is also optional for Class600 check valve; Ring joint gasket is used for Class900 check valve; Pressurized seal design is used for Class1500~Class2500 check valves. Seat For carbon steel check valve, the seat is usually forged steel. The sealing surface of the seat is spray welded With hard alloy specified by the customer. Renewable threaded seat is used for NPS≤ 10 check valves, And welded on seat can be also optional if being requested by the customer. Welded on seat is used for NPS ≥ 12 carbon steel gate valves. For stainless steel check valve, Integral seat is usually adopted, or to weld hard alloy directly integrally. Threaded or welded on seat is also optional for stainless steel check valve if being requested by the customer.
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