ANSI vs API Valve Standards: Who Writes the Rules and Which One Applies

Anyone who has read a valve data sheet has seen both “ANSI” and “API” attached to requirements — an ANSI B16.34 pressure rating here, an API 600 gate valve spec there. The abbreviations get mixed up in everyday conversation, but they are not the same thing. Understanding the difference between ANSI standards and API standards makes it much easier to read a specification and to know what the vendor is actually being asked to build.

The Short Answer

ANSI is an umbrella organization that accredits standards bodies; in valve work, the standards you actually meet are published by organizations such as ASME (under ANSI-accredited processes). API is an industry association that publishes its own standards for oil and gas equipment, including specific valve designs like API 600, API 602, API 603, and API 6D. In simple terms: ANSI/ASME standards tend to define generic pressure-temperature ratings and dimensional rules that apply across industries, while API standards tend to define specific valve types with design, materials, testing, and inspection requirements aimed at the oil and gas and refinery service. A single valve can and usually does comply with both — for example, an API 600 gate valve is built to ASME B16.34 pressure ratings and face-to-face dimensions.

What Each Standard Family Covers

ANSI / ASME standards

ASME B16.34 gives pressure-temperature ratings for flanged, threaded, and welded valves of all types. ASME B16.5 covers flange dimensions, ASME B16.10 covers face-to-face dimensions. These are horizontal standards: they apply to any valve type and are used across water, steam, chemical, and general industrial service.

API standards

API 600 covers bolted bonnet steel gate valves for refinery service. API 602 covers compact steel gate, globe, and check valves. API 603 covers corrosion-resistant bolted bonnet gate valves. API 6D covers pipeline valves, including ball, gate, and check valves for petroleum and natural gas pipelines. API 598 covers inspection and testing of valves. These are vertical standards: they start with a specific valve type and add design, material, inspection, and testing requirements on top of the generic rules.

Key Differences

Characteristic	ANSI/ASME standards	API standards
Publisher	ASME under ANSI-accredited process	American Petroleum Institute
Scope	Generic ratings, dimensions, flanges	Specific valve types for oil and gas service
Typical examples	B16.34, B16.5, B16.10	API 600, API 602, API 603, API 6D, API 598
Design detail	Ratings and dimensions mostly	Adds materials, design, inspection, testing detail
Industry use	All industries	Refinery, upstream, pipelines
How they relate	Provide the rating and dimension baseline	Built on top of the baseline for specific valve types

Which to Specify

For general industrial piping, specifying the relevant ANSI/ASME standard — typically B16.34 for ratings — is the baseline. For refinery, upstream, and pipeline service, the client or project specification usually names an API standard for the valve type plus the applicable ANSI/ASME standards for ratings and dimensions. Read the project spec carefully: it often requires both, and vendors quote against the full combination.

Common Pitfalls

• Treating “ANSI” and “API” as interchangeable; they cover different layers of the same valve.
• Assuming an API designation automatically includes a pressure rating; the rating still comes from the ANSI/ASME class.
• Mixing editions — specifying API 600 from an old edition while the rest of the project uses the current one; always confirm the edition in the datasheet.
• Overlooking the inspection and testing requirements in API 598, which are separate from the design standard.

Practical Recommendation

When you review a valve spec, split the requirements into layers: pressure class and dimensions from the ANSI/ASME standards, and design, materials, and testing from the API standard (if named). Check the edition and the class together, and confirm with the vendor that the quoted valve meets both layers. That two-layer check catches most specification mismatches.

Conclusion

ANSI/ASME standards give a valve its rating and dimensions; API standards give a specific valve type its design and quality requirements for oil and gas service. Most refinery and pipeline valves need both. Reading a spec in layers — generic first, type-specific second — is the fastest way to keep the requirements straight.

This article provides general educational knowledge only and is not professional engineering advice.

Sources & Further Reading

API, ASME

Tags: Valve Standards