Introduction
The American Petroleum Institute (API) standards are among the most widely referenced specifications for industrial valves in the oil and gas, petrochemical, and power generation industries. API 600 and API 602 are two fundamental standards governing steel gate valves, and understanding their requirements is essential for engineers, manufacturers, and end users. This article explains the scope and key technical requirements of both standards.
1. API 600 Overview
API 600, Steel Gate Valves—Flanged and Butt-Welding Ends, Bolted Bonnets, covers bolted bonnet steel gate valves with flanged or butt-welding ends. It applies to valves in nominal pipe sizes NPS 1 through NPS 24, corresponding to pressure classes 150 through 2500.
The standard specifies detailed requirements for valve design, including wall thickness, bonnet design, stuffing box dimensions, and the use of packing. It is widely used in refinery and petrochemical piping systems where wedge gate valves provide reliable isolation service.
2. API 602 Overview
API 602, Steel Gate, Globe, and Check Valves, Sizes DN 8 to DN 100 (NPS 1/4 to NPS 4), covers smaller-sized forged steel gate, globe, and check valves. These compact valves are commonly used in instrumentation, small-bore piping, and process connections.
API 602 valves are typically made from forged steel (such as A105, LF2, F11, F22, F316) and are available in socket-weld, threaded, and flanged end connections. The standard addresses three pressure classes: 150, 800, and 1500.
3. Face-to-Face and Flange Dimensions
Both standards reference ASME B16.10 for face-to-face and end-to-end dimensions of flanged and welding-end valves. Flanged valve dimensions follow ASME B16.5, with B16.47 for large-diameter flanges above NPS 24.
For butt-welding ends, the ends are prepared according to ASME B16.25. Manufacturers must ensure strict compliance with these dimensional standards to guarantee interchangeability and proper installation in piping systems.
4. Pressure-Temperature Ratings
Pressure-temperature ratings are critical for valve selection. For flanged valves, ASME B16.34 provides the working pressure ratings by class and material group at various temperatures. The ratings decrease as temperature increases, reflecting the reduction in material strength at elevated temperatures.
For API 602 Class 800 and Class 1500 valves, the standard specifies working pressures directly. Engineers must verify that the selected valve's rating exceeds the maximum operating conditions, including pressure, temperature, and any expected transients.
5. Material Requirements
API 600 Appendix A provides a comprehensive list of acceptable body, bonnet, and trim materials. Trim includes the wedge, seat rings, and stem. Common trim combinations include 13% chromium steel (Cr13) for general service, with harder alloys or overlays for severe service.
API 602 references ASTM forging specifications such as A105, LF2, F11, F22, and F316. Both standards require marking per MSS SP-25 and hydrostatic testing per API 598. Compliance with NACE MR0175/ISO 15156 may be required for sour service applications.