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And How do ASME Standards Compare to ANSI Standards

If you’ve ever specified a valve, ordered flanges, or reviewed a piping contract, you’ve likely encountered the letters “ASME.” But what exactly does this organization do, and why do its standards show up on nearly every equipment spec sheet? This guide breaks down everything you need to know about ASME, its codes, and its standards. We also compare ASME and ANSI standards.

Quick Answer: What Is ASME?

ASME stands for the. ASME is a non-profit organization that develops widely used engineering codes and standards, particularly for pressure equipment and mechanical systems. Founded in 1880, ASME is recognized as a leading international developer of technical standards that shape how industrial equipment is designed, built, tested, and inspected.

In simple terms, ASME standards are technical rules that govern the design, manufacture, testing, and inspection of a broad range of equipment, including boilers, pressure vessels, piping systems, valves, , elevators, cranes, and rigging equipment. ASME standards provide the specifications and quality standards that engineers, manufacturers, and inspectors rely on to ensure that equipment is built and continues to perform safely under demanding conditions.

ASME actually has two roles. It is a professional society for mechanical engineers, as well as one of the oldest standards developing organizations in the world. ASME documents are frequently incorporated into U.S. and international regulations, making them mandatory for many applications.

This article aims to outline the most relevant ASME codes and standards for valves and piping, and clarify how ASME standards compare with ANSI standards.

What Are Standards and Codes?

Before diving deeper, it helps to understand the distinction between “codes” and “standards” in engineering language. While these terms are sometimes used interchangeably, they serve different functions.

ASME Codes are typically comprehensive, legally mandated documents that address safety, design, and fabrication requirements. They tell you what must be done to ensure safe operation.

ASME Standards are voluntary technical guidelines that describe how to achieve compliance. They provide the specific dimensions, materials, procedures, and testing methods that codes reference.

Regulatory Adoption

ASME provides expert insights, recommendations, and analysis on technical issues to regulatory agencies and policymakers, directly shaping legislation and safety regulations. Many ASME standards are referenced directly by regulatory bodies. U.S. agencies such as OSHA require compliance with ASME codes. The ASME Boiler and Pressure Vessel Code, for example, is incorporated into regulations across most U.S. states, territories, and Canadian provinces.

ASME standards are recognized globally and are accepted for use in over 100 countries.

Why ASME Standards Matter

For plant owners, EPC firms, OEMs, and valve manufacturers, ASME standards provide several practical benefits:

• Clear specifications eliminate guesswork in design and procurement
• Standardized dimensions ensure flanges, valves, and fittings from different suppliers fit together
• Shared quality standards simplify communication between parties
• International recognition facilitates trade across borders

ASME compliance enhances public safety in industrial equipment, as ASME-compliant equipment has undergone thorough inspection and testing to meet quality and safety standards.

Key ASME Codes and Standards for Valves and Piping Systems

ASME publishes families of standards for piping systems, pressure equipment, and valves, which are important for anyone sourcing industrial valve equipment. Understanding these standards is essential for proper valve specification and regulatory compliance.

ASME Boiler and Pressure Vessel Code (BPVC)

The ASME Boiler and Pressure Vessel Code (BPVC) is perhaps the most famous and widespread standard that ASME has ever produced. First issued in 1914, the BPVC was created to protect public safety.

The BPVC is organized into multiple sections such as Section VIII for pressure vessels and Section IX for welding. The code establishes requirements for materials, design calculations, fabrication procedures, inspection, testing, and certification marking. Equipment bearing the ASME stamp has been verified to meet rigorous code requirements.

ASME B31 Piping Codes

The ASME B31 series of piping codes covers the design, materials, fabrication, inspection, and testing of piping systems across different applications. Common codes include:

• B31.1: Power Piping
• B31.3: Process Piping
• B31.4: Pipeline Transportation Systems for Liquids and Slurries.

For industrial valve applications, B31.1 and B31.3 are frequently referenced codes.

ASME B16 Series

The ASME B16 series provides detailed specifications for valves, flanges, fittings, and gaskets. These standards define dimensions, pressure-temperature ratings, materials, and testing requirements. Common standards include:

• B16.5: Pipe flanges and flanged fittings (NPS 1/2 through NPS 24)
• B16.10: Face-to-face and end-to-end dimensions of valves
• B16.34: Valves—flanged, threaded, and welding end
• B16.24: Cast copper alloy pipe flanges, flanged fittings, and valves

When someone talks about a “Class 300 flange” or a project specifies a “B16.34 valve,” they’re referencing ASME B16 standards.

For those in the valve and piping industry, the ASME B16 series is particularly important, as it defines the specifications that ensure valves, equipment, and piping components from different manufacturers work together seamlessly.

ASME vs ANSI: What’s the Difference?

A common source of confusion in industry involves the relationship between ASME and ANSI, with mix-ups between the two very common. Here's the difference:

ASME (American Society of Mechanical Engineers) is an engineering society that also develops codes and standards. ASME writes, maintains, and publishes the actual technical content for mechanical, pressure, and piping-related standards (amongst others).

ANSI (American National Standards Institute) is an umbrella organization that oversees and accredits U.S. standards developers. ANSI doesn’t write standards itself—it coordinates the voluntary consensus standards system and approves documents as “American National Standards.”

To summarize, ANSI doesn't develop standards but rather accredits standards, which includes standards developed by ASME as well as other organizations such as API, ASTM, IEEE, and many more. While ASME focuses on writing and maintaining technical standards related to mechanical engineering, ANSI accredits standards developers across a broad range of industries.

Common Misconceptions between ANSI and ASME

Many people casually refer to “ANSI flanges” or “ANSI valves,” but in most piping and valve contexts, they are actually referring to the ASME B16 standards. This confusion has historical roots.

• There is no separate “ANSI B16.5” and “ASME B16.5” flange standard. The current document is ASME B16.5, although older usage and some informal references might still refer to “ANSI flanges.”
• The pressure classes, dimensions, and ratings commonly called “ANSI” specifications are maintained by ASME standards today.
• ANSI may have historically approved some ASME standards as American National Standards, but ASME owns and maintains the technical content.

When you see “ANSI Class 150” or “ANSI 300# flange” on a valve data sheet or equipment spec sheet, the actual technical requirements come from ASME B16.5.

For a deeper dive into the role of ANSI and how ANSI standards are created, see our guide to “What are ANSI Standards”.

Why ASME Standards Matter for Valves, Flanges, and Piping Systems

Anyone who works with valves, operates plants, or maintains industrial equipment should know that ASME standards are far more than just paperwork. They directly influence safety, reliability, and your bottom line.

Key Benefits of ASME-Compliant Components

Safety: ASME design standards and guidelines, material rules, inspection, and testing requirements reduce the risk of leaks, ruptures, and catastrophic failures.

Compatibility: ASME standards ensure dimensional consistency across manufacturers. A Class 300 ASME B16.5 flange from 91ÊÓƵ will mate correctly with a Class 300 flange from Manufacturer X. The same applies to valve face-to-face dimensions as per ASME B16.10. This interchangeability simplifies procurement, reduces inventory complexity, and allows sourcing from multiple suppliers.

Legal and Regulatory Compliance: Using ASME standards helps satisfy requirements from:

• State and provincial boiler boards
• OSHA regulations
• Local building codes
• Insurance underwriters
• International regulatory bodies

Non-compliance can result in permit denials, insurance voidance, or legal liability.

Reliability: ASME standards and qualification testing translate to predictable performance levels over decades. Equipment designed and built to ASME requirements has a track record of durability that non-compliant alternatives often lack.

The Risk of ASME Non-Compliance

Installing non-ASME components into an ASME-specified system may create problems, such as:

• Dimensional mismatches: A valve with non-standard face-to-face dimensions may not fit the intended piping layout
• Flange sealing problems: Non-ASME flanges may have different surface finishes or bolt patterns, causing gasket failures
• Underrated pressure limits: Equipment not designed to ASME requirements may lack adequate safety margins in terms of pressure-temperature performance
• Inspection failures: Non-compliant equipment may fail inspections, delaying project completion

How to Incorporate ASME Standards in Your Next Project

You don’t need to memorize every clause in every ASME document. What matters is knowing which standards apply to your project and understanding how to interpret ASME standards at a fundamental level.

Step 1: Identify the Applicable ASME Code

Determine which code governs your system based on its service:

• Power plant steam systems → ASME B31.1
• Refinery process piping → ASME B31.3
• Gas transmission pipelines → ASME B31.8
• Pressure vessels → ASME BPVC Section VIII

Step 2: Confirm Regulatory Requirements

Check with contract documents, project specifications, local jurisdictions and your insurance carrier to identify any mandatory ASME code adoptions. Some states require ASME stamps on all pressure equipment; others reference specific editions of ASME codes for adoption.

Step 3: Standardize Component Selection

Build your specifications around commonly used ASME B16 classes and dimensions:

• Standard flange classes: 150, 300, 600, 900, 1500, 2500
• Standard valve specifications: pressure classes
• Standard dimensions: ASME B16.5 for flanges, B16.10 for valve face-to-face

Standardization simplifies sourcing, reduces lead times, and eases maintenance.

Step 4: Work with Qualified Suppliers

Partner with manufacturers and distributors who:

• Demonstrate compliance with relevant ASME standards
• Provide material test reports and certifications
• Supply proper documentation for your project files

ASME helps ensure that the components you purchase meet recognized quality standards, but product quality and performance verification requires working with reputable sources.

Continue Learning

ASME standards represent just one piece of the industrial equipment puzzle. Complex industrial piping systems, like those found in refineries or chemical processing plants, feature numerous types of equipment, valves, and piping. In contexts such as these, engineers apply ASME standards to ensure reliability, safety, and efficiency. Setups like this deal with an intersection of engineering disciplines and highlight the vital role of organizations like ASME in advancing technical knowledge within the global engineering community.

Continue building your knowledge by exploring related topics:

• Learn more about what are ANSI standards and how ANSI fits into the standardization ecosystem
• Review Valveman resources on valve classes, pressure-temperature ratings, and flange selection
• Conduct conformity assessment programs at your facility
• Consider ASME educational programs and related professional development initiatives that provide structured skills development

Frequently Asked Questions

What does ASME stand for?

ASME stands for the American Society of Mechanical Engineers. It is a professional organization that develops and maintains codes and standards for mechanical devices to ensure safety, reliability, and operational efficiency.

What is the main difference between ANSI and ASME?

The main difference is their function. ANSI (American National Standards Institute) is an administrator and coordinator for the U.S. voluntary standards system; it accredits standards developing organizations but does not develop standards itself. ASME is one of those accredited organizations; it actively develops and writes the technical standards for mechanical engineering.

Are ASME standards mandatory?

ASME standards are generally voluntary. However, they become mandatory when they are incorporated into a business contract or cited in government regulations (e.g., by OSHA). For example, many pressure vessel and piping regulations legally require adherence to specific ASME codes.

In Closing

Whether you’re designing a new process unit, replacing aging valves, or reviewing a contractor’s proposal, ASME standards provide the foundation for safe, reliable, and interchangeable industrial equipment. Investing the time to understand these documents pays dividends in reduced risks, smoother projects, and equipment that performs reliably for decades. If you need any help with ASME or ANSI standards, or if you'd just like to chat about valves, get in touch with the team at 91ÊÓƵ today!

Gilbert Welsford, Jr

Valve industry Engineering Business operations and leadership Sales and customer service Product knowledge Sector-specific knowledge Project management Innovation and industry trends

Gilbert Welsford, a renowned valve industry expert and third-generation owner of FS Welsford Company, is the visionary behind 91ÊÓƵ, a leading platform for valve-related products. Gilbert's profound understanding of fluid dynamics and precision engineering plays a pivotal role in designing and applying various valve types. Known for his collaborative approach and outstanding communication skills, he builds strong relationships across multiple sectors and consistently ensures successful project outcomes. Committed to innovation and excellence, Gilbert remains at the forefront of industry advancements, consistently delivering solutions that exceed expectations.