What is the difference between API 598 and API 6D?
API 6D is a quality management system standard for pipeline valves, while API 598 is an inspection and testing standard for various types of valves. In API 6D, the test medium is fresh water, and light oil with a viscosity not exceeding that of water can be used upon negotiation. Compared to API 598, there are significant differences in the selection of test media. API 598 specifies either high-pressure liquid sealing tests or low-pressure gas sealing tests depending on the valve type, diameter, and pressure rating. API 6D, however, does not include low-pressure gas sealing tests in its standard pressure tests; these tests are only performed when specifically required by the user.
1. Standard Nature and Scope
API 598: Applicable to various industrial valves such as gate valves, globe valves, ball valves, and check valves. Its core function is to verify the integrity and sealing performance of valves through shell testing and sealing tests.
API 6D: Focuses on the design, manufacture, and quality management of pipeline valves and is a core standard for long-distance pipeline systems such as oil and natural gas pipelines.
2. Test Medium and Pressure Test
API 598:
Shell Test: Use water or air, pressurized to 1.5 times the maximum working pressure. Holding time depends on valve size (e.g., ≥60 seconds for DN≤100mm).
Seal Test: High-pressure seal test uses water or air (1.1 times maximum working pressure). Low-pressure seal test uses air or inert gas (0.5–0.7 bar).
API 6D:
Shell Test: Test medium is fresh water or light oil. The hydrostatic pressure test time is longer (e.g., 30 minutes for valves with a nominal diameter of 20mm and above).
Seal Test: Routine pressure tests do not include low-pressure gas seal tests; these are only performed upon special user requirements.
3. Test Duration and Leakage Criteria
API 598: Shell test holding time is shorter (e.g., 60 seconds for DN≤100mm).
Strict sealing requirements apply. Liquid tests must achieve zero leakage, and gas tests must meet standards for leakage (e.g., ≤20 bubbles/minute for DN50 valves).
API 6D: The hydrostatic test time for the shell is longer (e.g., 30 minutes for valves with a nominal diameter of 20 mm or larger).
Zero leakage is required for sealing tests, especially for valves with resilient seats.
4. Application Scenarios
API 598: Applicable to industries with stringent valve quality requirements, such as oil, natural gas, and chemical industries, ensuring valve reliability under extreme conditions such as high pressure and corrosion.
API 6D: Primarily used in long-distance pipeline systems, it is the core standard for valves in long-distance oil and natural gas pipelines.
API 6D Valve and API 598 valve in stock
