The core differences between API 600 and API 602 gate valves lie in their applicable diameters, pressure rating coverage, material diversity, and design structure. The specific differences are as follows:
1. Diameter and Application Differences
API 600 Gate Valve: Designed for large-diameter pipelines (typically DN ≥ 50mm or NPS ≥ 2 inches), suitable for trunk pipelines such as industrial water systems or large steam lines, emphasizing versatility and high-pressure adaptability.
API 602 Gate Valve: Primarily featuring a compact design and smaller diameters (NPS ≤ 4 inches), it is often used in space-constrained applications such as equipment inlets and outlets or small process pipelines. It utilizes a tapered neck structure to reduce weight and volume. ️
2. Comparison of Pressure Classes and Material Selection
Pressure Coverage:
API 600 supports a full range of pressure classes (Class 150 to 2500), suitable for ultra-high-pressure applications such as power plant main steam systems.
API 602 covers only a limited range of pressure classes (such as Class 150, 300, and 600), but its forging process optimizes sealing reliability under high pressure.
Material Diversity:
API 600 offers fewer material options, primarily standard carbon steel, suitable for non-corrosive media such as water and oil.
API 602 offers a wider range of material options, including stainless steel (F304/F316), alloy steel (F11/F5), and corrosion-resistant alloys, suitable for harsh media such as chemical and marine environments.
3. Manufacturing Process and Design Features
Manufacturing Method: API 602 explicitly requires the use of a forging process (forged steel body), which provides dense grains and strong impact resistance, extending valve life. API 600 does not have this mandatory requirement and may include a combination of casting and forging.
Bonnet Structure: API 602 emphasizes diverse sealing designs, such as bolted (wound-wound gasket), welded (all-welded leakproof), or self-sealing (high-pressure self-tightening), to enhance reliability in flammable and explosive media. API 600's design is more standardized, focusing on universal bonnet styles.
4. Trim Configuration and Performance Standards
Sealing Component Differences: API 602 trim (such as the valve stem and sealing surface) often utilizes a hard alloy overlay (e.g., cobalt-chromium alloy) with a hardness of HB350, ensuring zero leakage under high temperature and high pressure. API 600 trim configuration is relatively simple, primarily using basic metal seals, suitable for conventional operating conditions. Testing Requirements: API 602 requires an impact toughness test report (e.g., -29°C impact energy ≥ 34J) upon shipment to verify low-temperature toughness. The API 600 testing standard focuses more on pressure testing and general performance verification.
Operation and Selection Considerations
The two standards overlap within the 4-inch diameter range, but API 602, due to its compact design, is more suitable for frequent openings and closings or in space-constrained environments, while API 600 is primarily used for high-flow, high-pressure main lines.
During welding maintenance, API 602 requires local heat treatment to restore performance, while API 600 does not have this mandatory requirement.