If you’ve ever submitted a bellows RFQ and had a procurement compliance question come back about EJMA versus ASME requirements, you’re not alone. These two standards govern overlapping parts of the same physical component — and the distinction between them matters directly to your procurement documentation, inspection requirements, and project compliance.

This guide explains what each standard covers, how they interact, and what you need to ask your bellows manufacturer to ensure your project is compliant.

EJMA stands for the Expansion Joint Manufacturers Association. The EJMA Standard — currently in its 10th edition — is the only industry standard written specifically for the design, fabrication, and testing of metal bellows and expansion joints.

The EJMA Standard covers:

• Bellows design calculations including cycle life, spring rate, pressure capacity, and squirm pressure
• Convolution geometry requirements and dimensional tolerances
• Material requirements and weld procedure requirements
• Hydrostatic test requirements and acceptance criteria
• Design documentation requirements including stress analysis and calculation sheets

When a manufacturer says their bellows are ‘designed per EJMA,’ it means the bellows geometry, material, and construction were selected using the EJMA design equations to ensure the part will meet its rated performance for pressure, movement, and cycle life.

ASME (American Society of Mechanical Engineers) publishes a much broader set of codes and standards. For bellows and expansion joints, two ASME standards are most relevant:

ASME B31.3 governs the design, materials, fabrication, assembly, examination, and testing of process piping — the pipes, fittings, valves, and expansion joints in chemical plants, refineries, and industrial facilities. When a bellows is installed in a B31.3 piping system, it must be designed and documented in a way that satisfies B31.3 requirements. B31.3 references EJMA for expansion joint design — so EJMA compliance is effectively the path to B31.3 compliance for bellows elements.

If a bellows or expansion joint is part of a pressure vessel, ASME Section VIII Division 1 may apply. This involves more rigorous documentation, third-party inspection (typically by an authorized inspection agency), and ASME stamp requirements. The manufacturer must hold the appropriate ASME U-stamp or similar certification to fabricate compliant components.

Think of it this way: EJMA is the technical specification for how the bellows is designed. ASME tells you what level of documentation, inspection, and certification the project requires.

These are the compliance questions to ask before you commit to a supplier:

• Do you provide EJMA design calculations as standard deliverable? (If no, walk away.)
• Are your engineers familiar with ASME B31.3 piping design requirements for expansion joints?
• Can you provide full material traceability (Mill Test Reports / Certified Mill Test Reports) for all materials used?
• What NDE capabilities do you have in-house? (radiographic testing, dye penetrant, hydrostatic testing)
• Do you hold ASME certification for your welding procedures (AWS certified welders)?
• Can you support a third-party inspection hold point if required by our project?

Bellows Systems designs per EJMA standards, employs AWS-certified welders, maintains over 150 qualified welding procedures, and can support project-specific NDE and documentation requirements. BSI’s in-house engineering capability includes 3D modeling and stress analysis to support full ASME compliance documentation.

For any project requiring EJMA or ASME compliance, your bellows documentation package should contain:

• EJMA design calculation sheet (shows cycle life, spring rate, pressure rating, squirm pressure)
• Material certifications (MTR or CMTR) for all bellows materials
• Welding procedure specifications (WPS) and procedure qualification records (PQR)
• Welder performance qualification (WPQ) records for welders who fabricated the part
• NDE reports (as applicable: radiographic, dye penetrant, visual inspection)
• Hydrostatic or pneumatic test records
• Dimensional inspection report

If your project requires third-party inspection by an Authorized Inspection Agency (AIA), this needs to be established before fabrication begins, not after.

• Custom Engineering Services — EJMA and ASME design documentation
• Testing and Qualification — BSI’s NDE and testing capabilities
• Certifications — BSI’s quality and compliance certifications
• EJMA Official Website (External) — Expansion Joint Manufacturers Association
• ASME Standards Portal (External) — ASME B31.3 and Section VIII standards