Making Non-ASME Stamped Vessels Legal—and Safe—in the U.S.
In U.S. plants, the default assumption is simple: if it’s a pressure vessel, it was built and stamped to ASME Section VIII, Division 1. That’s what most state laws require, and it’s the baseline most owner/operators work from. When equipment is not U-stamped, you’re typically looking at an exception process—often called a “State Special”—to secure installation or continued operation.
This post distills a recent conference paper into a field-ready playbook. We’ll unpack the regulatory context, then walk through two case studies: (1) importing CE-marked (PED) vessels and (2) securing approval for an older, non-code flare drum that now sees higher pressure. Along the way you’ll see what evidence actually convinces a state board and chief inspector, and how to set yourself up for a smoother approval.
Why this matters (and who’s really in charge)
Jurisdictions—not the ASME Code—decide what must be used. ASME Section VIII provides rules, but only a jurisdiction can mandate their use or allow alternatives.
OSHA requires RAGAGEP, but does not prescribe a specific code. That means recognized codes/standards (ASME, API, NBIC, ANSI) or rigorously followed internal standards may satisfy federal obligations—even in states that don’t require U-stamping.
“Code States” vs. “Non-Code States.” Most states require U-stamping for Section VIII vessels; some do not. In non-code states, you have more latitude—but still owe RAGAGEP. Local building codes (wind/seismic) can layer on top.
When a vessel’s design pressure or configuration falls outside typical scope—e.g., operating above 15 psig without prior certification—state law often pushes you into a formal approval pathway. For existing vessels, design changes are treated as rerates/alterations under NB-23 in code states; API 510 practices may be used in non-code states.
What is a “State Special”?
Think of it as a structured variance: you demonstrate, to the state’s satisfaction, that non-ASME-stamped equipment is safe at defined conditions. If approved, the board/chief inspector issues a unique State Special ID that goes on a new nameplate.
Typical triggers:
You’re importing CE-marked (PED) vessels designed per VIII-1 but lacking a U-stamp.
A legacy vessel (<15 psig) now faces new conditions above the jurisdiction’s threshold and can’t be U-stamped retroactively.
Both scenarios showed up in the case studies summarized below.
Case Study 1 — Installing CE-Marked (PED) Vessels in a U.S. Code State
The situation. A U.S. site bought unused vessels fabricated in Europe. They were designed to VIII-1, but certified under the EU Pressure Equipment Directive (PED) and carried CE marks, not U-stamps—an immediate permitting problem in a code state. The team engaged the chief inspector/board to pursue State Special approvals.
PED vs. VIII-1—why the board listened. While VIII-1 generally maps well to PED, PED is more restrictive in key areas. Two examples that resonated with the board:
Toughness: PED requires impact toughness for all materials; VIII-1 does not universally require it.
Hydrotest: PED minimum is 1.43× MAWP; VIII-1 requires 1.3× MAWP.
Documenting these deltas helped establish that CE-marked equipment could meet or exceed U-stamp rigor.
The dossier that worked. PED demands robust documentation—hydrotest certificates, MTRs, as-built drawings, calc packages, PWHT reports, hazard analyses, NDE reports, and more. For higher hazard categories, a Notified Body (NB) issues a Certificate of Conformity after a formal Conformity Assessment. In this case the vessels were Hazard Category IV, the most comprehensive NB review—analogous in weight to an AIA’s role for U-stamping.
What sealed approval. The team maintained open dialogue with the chief inspector/board, provided ASCE wind/seismic checks for the installation site, presented at the annual board meeting, and secured conditional State Special approvals. After state-witnessed inspections, the State Special nameplates were affixed and the vessels were installed.
Takeaway. For CE-marked equipment, document parity or superiority relative to VIII-1—and show how PED processes (NB oversight, hydrotest factor, toughness) achieve equal or higher safety margins.
Case Study 2 — Keeping a 1950s Non-Code Flare Drum in Service (Now to 30 psig)
The situation. A refinery’s low-pressure flare drum (installed in the 1950s with no nameplate/U-stamp) had historically operated below 15 psig. A recent PHA showed an upset scenario could drive pressures much higher; mitigations capped credible upset at 30 psig—which triggered state registration. You can’t assign a U-stamp after the fact, so the team pursued a State Special instead of a lengthy vessel replacement.
Engineering evaluation—what the state cared about. Without original calcs or full records, the team built a defensible evaluation:
Assumed E = 0.7 (no RT) per VIII-1 Table UW-12,
Committed to a hydrotest at 1.5× maximum operating pressure (pre-1999 VIII-1 basis), and
Demonstrated a calculated MAWP > 80 psig—well above the new maximum pressure.
These steps framed a conservative, code-consistent margin of safety.
Over-the-top evidence (that helped). While not required, the site added PAUT of all weld seams (no crack-like indications), an API 510 external inspection with UT, and hardness tests showing material strength at/above assumed properties. This increased confidence without claiming extra credit in the rating (they kept E = 0.7).
Outcome. After a board presentation and state-witnessed tests/inspections, the board approved the drum at the requested conditions and issued a State Special number for a new nameplate.
Takeaway. When data are sparse, codify conservatism (joint efficiency, test factor), prove thickness/quality with modern NDE, and tie everything back to VIII-1/API 510 practices to satisfy RAGAGEP.
Your playbook for State Specials (imported or legacy equipment)
Engage the chief inspector early. Ask how they prefer to see the case framed and where flexibility exists. Early alignment avoids rework and surprises.
Map the jurisdiction. Confirm whether you’re in a Code State or Non-Code State and what local building code loads apply (wind/seismic).
Assemble a complete dossier. For PED equipment, emphasize NB certificates, hydrotest, toughness, and calc packages; for legacy equipment, compile dimensions, thicknesses, materials, joint details, support details, internal hardware, levels, and any inspection/test history available.
Perform a transparent engineering evaluation. Anchor to VIII-1 rules where applicable; if documentation is missing, use conservative assumptions (e.g., joint efficiency) and state them plainly. Plan a hydrotest aligned with the applicable code basis.
Add credibility with targeted inspections. Use PAUT, UT thickness surveys, hardness testing, and API 510 external inspections as appropriate—even if not strictly required. This often tips decisions in your favor.
Address site-specific loads. Provide ASCE wind and seismic checks for the installation location.
Prepare the board package and plan for witness points. Expect a board presentation, state-witnessed hydrotests/inspections, and issuance of a State Special ID/nameplate at the end.
When to stop and replace
Pursuing a State Special isn’t always the right answer. If the measured thicknesses can’t support the requested MAWP with credible corrosion allowance, if materials do not meet minimum properties even with conservative assumptions, or if modifications required to pass evaluation rival the cost/schedule of a new U-stamped vessel, replacement can be the safer and faster path. (In code states, a brand-new vessel with a U-stamp can also simplify future rerates under NB-23.)
Bottom line
State Special approvals are achievable—and often faster than many expect—when you (1) align early with the chief inspector, (2) present a rigorous, transparent engineering case, and (3) proactively close documentation gaps with modern inspections and conservative assumptions. Boards want to say “yes” when they trust the safety case and see a responsible owner/operator standing behind it.
How Refined Engineering can help
Refined Engineering has the cross-disciplinary chops—pressure equipment design, fitness-for-service, API/NBIC practice, PED/CE documentation reviews, NDE planning, and board-level advocacy—to shepherd non-ASME-stamped vessels through approval or help you choose the smartest path (rerate, State Special, or replacement). We’ll build the technical case, prepare the board package, coordinate witness points, and see it through to a nameplate.
Explore what we do on our Services page to see how this support fits with your project needs—and let’s talk about your specific equipment and jurisdiction.
