API 598 vs API 6d standards for valve: Key Difference

When comparing API 598 and API 6D, it’s important to understand their key differences. Both standards apply to valves, but they serve different purposes and industries. Here’s a breakdown of the main distinctions between API 598 and API 6D.

Main Objective

• API 598 focuses on valve inspection and testing. It specifies the tests required for different types of valves, such as gate, globe, ball, plug, check, and butterfly valves. The goal is to ensure valves meet specific quality and performance standards.¹
• API 6D, on the other hand, sets standards for pipeline service valves. This includes ball, gate, check, and plug valves, often used in the oil and gas pipeline industry. The standard is more stringent than API 598, especially for applications where safety and durability are critical.¹

Industry Applications

• API 598 is a general valve testing standard that applies to various industries, including petrochemicals and refineries. Valves designed to meet API 602, 608, and 609 standards often undergo API 598 testing.²
• API 6D is specifically tailored for oil and gas pipelines. It ensures that valves meet the high-performance requirements for handling fluids under extreme conditions, such as in pipelines.²

Testing Requirements

• API 598 specifies several types of tests, such as visual inspections, backseat tests, shell tests, and closure tests. The tests focus on identifying leaks and ensuring the structural integrity of the valve.
• API 6D includes tests like casing hydrostatic tests, seat hydrostatic tests, and stem backseat tests. These tests are more rigorous, often requiring longer test times and stricter standards, especially for high-pressure applications.

For example:

• Rear seat test: Pressure at 1.1 times the valve rating for 2–5 minutes.
• Shell test: Pressure at 1.5 times the valve rating for up to 30 minutes.

Test Duration

• In API 6D, the duration of tests varies based on the valve size. For larger valves (20 NPS or larger), the casing test can take up to 1,800 seconds.
• API 598 tests are generally shorter. For valves up to 2 NPS, the housing test, backseat test, and closure check each take around 15 seconds, whereas larger valves may require longer times (up to 300 seconds for the body test).

Test Medium

• API 598 allows the use of various test mediums, including air, water, inert gas, kerosene, or other non-corrosive fluids. This flexibility makes API 598 applicable to a wider range of industries.
• API 6D, however, is more specific. It uses freshwater (with a corrosion inhibitor) for hydrostatic testing and inert gas for pneumatic testing. This is particularly suited for pipeline valves in the oil and gas sector, ensuring optimal performance under high pressure.

Stringency of Standards

• API 6D is more stringent than API 598, especially in terms of test times and pressure requirements. It is designed to handle the demands of pipeline service valves, which operate under more extreme conditions than the general-purpose valves tested under API 598.

Key Differences at a Glance:

• API 598: General valve testing standard for multiple valve types and industries.
• API 6D: Standard for pipeline valves in the oil and gas industry, with stricter testing requirements.
• API 598: Shorter test durations and more flexible test mediums.
• API 6D: Longer test durations and specific test mediums tailored for pipeline applications.

API 598 ensures that a wide range of valves meet performance standards. While API 6D focuses on the rigorous testing of valves used in pipelines. Understanding the differences between these two standards can help you choose the right valve specification for your project, depending on your industry and application.For businesses needing valves that meet API standards, Pans Valve is a global leader. The company provides high-performance solutions across several industries. These would include petrochemicals, power generation, and oil and gas. Their product lineup meets both API598’s general testing and API6D’s strider requirements.

References

1 API Valve Standards Defined and Explained – China Valve Manufacturer

(https://www.stvvalves.com/valve-standards-defined-by-the-american-petroleum-institute-api/) 

2 API – Valve Standards

(https://www.engineeringtoolbox.com/api-valve-standards-d_378.html)