What is the Difference Between These American Industrial Standards ASTM vs ANSI vs ASME vs API:
When sourcing piping materials, valves, flanges, or pressure equipment for international projects, engineers and procurement professionals often encounter ASTM, ANSI, ASME, and API standards. These American industrial standards are widely used across oil & gas, energy, chemical, and infrastructure industries—but they are not interchangeable.
Understanding the differences between ASTM, ANSI, ASME, and API is critical for correct material selection, engineering design, compliance, and global trade.
This guide explains what each standard represents, how they work together, and how to apply them correctly in real engineering projects.
What Are American Industrial Standards?
In simple terms:
- ASTM defines what the material is
- ANSI provides national standard recognition
- ASME defines how the material is used safely in design
- API defines industry-specific requirements for oil & gas
Each organization plays a different role in the American standards system.
ASTM Standards: Material Specifications and Testing
ASTM International develops standards for materials, testing methods, and quality evaluation.
Key Characteristics of ASTM Standards
- Focus on chemical composition and mechanical properties
- Include material specifications, test methods, and practices
- Widely used as the base material standard worldwide
ASTM Material Designations
- Common steel materials use the ASTM “A” series, such as:
- ASTM A516 Grade 70 (pressure vessel steel plate)
- Other series include B, C, D, and E, covering non-ferrous metals and non-metallic materials
Practical Role of ASTM
ASTM standards define the material “recipe”, but do not govern engineering design or pressure safety. They are the starting point for material selection.
ANSI Standards: National Accreditation and Coordination
The American National Standards Institute (ANSI) serves as the official U.S. standards accreditation body.
What ANSI Does (and Does Not Do)
- ANSI does not usually write technical standards
- It approves and accredits standards developed by organizations such as ASME, ASTM, and API
- Approved standards become American National Standards (ANS)
ANSI in Piping and Flanges
Many engineers refer to flange standards as “ANSI standards,” but technically:
- The technical content is often written by ASME
- ANSI acts as the national approving authority
This is why standards such as ASME B16.5 flanges are sometimes informally called “ANSI flanges.”
ASME Standards: Engineering Design and Pressure Codes
The American Society of Mechanical Engineers (ASME) develops engineering codes and safety standards, especially for pressure-bearing equipment.
Core Focus of ASME Standards
- Pressure vessels
- Boilers
- Piping systems
- Mechanical equipment safety
ASME and ASTM Materials
ASME typically adopts or references ASTM material specifications within its design codes.
Example:
- ASTM A516 Grade 70
- ASME SA-516 Grade 70 (approved for pressure service)
Why ASME Requirements Are Stricter
Because ASME materials are used in pressure-containing applications, they often require:
- Additional inspection
- More stringent testing
- Enhanced traceability
ASME standards convert material data into safe, enforceable engineering rules.
API Standards: Oil and Gas Industry Authority
The American Petroleum Institute (API) develops standards specifically for the oil, gas, and petrochemical industries.
Typical API Applications
- Valves and actuators
- Pipelines and fittings
- Drilling and wellhead equipment
- Storage tanks
- Offshore and upstream equipment
API and Other Standards
API standards frequently:
- Reference ASTM materials
- Align with ASME design principles
- Add industry-specific performance requirements
For petroleum projects, API standards are often contractually mandatory.
How ASTM, ANSI, ASME, and API Work Together
In real-world projects, these standards form an integrated system:
- ASTM defines the material properties
- ANSI provides national recognition
- ASME governs engineering design and safety
- API applies specialized oil & gas requirements
Because ASME and API often adopt ASTM standards, similar content may appear under different standard numbers. The governing standard is determined by:
- Contract documents
- Design codes
- Industry regulations
- End-user specifications
Comparison Table: ASTM vs ANSI vs ASME vs API
| Standard | Organization | Primary Focus | Typical Use |
|---|---|---|---|
| ASTM | ASTM International | Material & testing standards | Defines material composition |
| ANSI | American National Standards Institute | National accreditation | Approves U.S. national standards |
| ASME | American Society of Mechanical Engineers | Engineering & pressure codes | Governs design and safety |
| API | American Petroleum Institute | Oil & gas industry standards | Petroleum equipment & practices |
