Post-Fabrication CRN: As-Builts, Alterations, Rerates

By Kopfkino Consulting Corp. · Published September 11, 2026 · Updated October 17, 2026 · 9 min read

When fabricated equipment differs from the registered design, the question becomes the lawful path: a design revision, alteration, rerate, used-equipment submission, or variance.

When fabricated pressure equipment differs from the design offered for CRN registration, the problem is no longer filing speed; it is identifying the lawful path for the steel that already exists. Depending on the jurisdiction and the change, that path may be a design revision, an alteration, a rerate, a used-equipment submission, or a variance, each with its own forms and evidence. TSSA, ABSA, Technical Safety BC, TSASK, RBQ, Manitoba ITS, and ACI Central each describe their own tools; the forms cannot be mixed. Expedited 24-hour and 48-hour review can organize as-built evidence and support path selection. It cannot legalize an undocumented change, and it cannot issue a CRN.

The 24-hour and 48-hour options are expedited engineering review, technical validation, documentation review, dossier preparation, and submission-readiness services. They are not a promise that a provincial regulator, authority having jurisdiction, or registration body will issue a CRN within 24 or 48 hours.

Definitions: as-built, alteration, rerate, variance

• As-built: the equipment as actually fabricated or modified, which may differ from the drawing filed for registration.
• Alteration: a physical change to pressure equipment after construction, handled under the AHJ’s alteration process rather than as new construction.
• Rerate: a change, in either direction, to the design pressure or temperature of existing equipment, based on the equipment’s present condition.
• Variance: relief from a specific regulatory requirement where the jurisdiction’s legislation allows it; it is not a substitute for missing calculations or registration.

Exact terms and forms differ by province and territory. Confirm the current definitions and forms with the applicable authority having jurisdiction.

How this article differs from a design-change addendum

A planned design change on paper (with the as-built still matching a drawing you control) is the addendum/revision territory covered on Kopfkino’s managing-design-changes service page. This article starts one step later: the equipment has already been built or modified and no longer matches the registered design. The first case is document control; the second is evidence about steel. If your drawings still describe reality, you need the addendum process, not this page.

Emergency CRN Support for Equipment Already Fabricated is the emergency intake page. This article is the technical map of post-fabrication paths so project teams stop calling every shop deviation a “minor revision.”

Four different events (do not mix the forms)

Calling a rerate a revision, or a variance a CRN, is how recoveries fail.

As-built differences that trigger this article

• Extra or relocated nozzles
• Different head type or thickness
• Material substitution (CRN Material Documentation: MTRs, Specifications, Substitution Risk)
• Missing PWHT
• Added jacket or coil
• Different corrosion allowance
• Shop “improvements” not on the filed drawing
• Nameplate already stamped with a non-issued number

If the as-built matches the filed design, you do not need this page. You need Clock 3 patience.

Evidence pyramid

1. Photographs of the unit, nameplate, nozzles
2. As-built drawing (or red-line converted to as-built)
3. Data report if it exists
4. MTR/traceability
5. NDE for present thickness if rerate/used
6. Recalculation of the as-built geometry
7. AHJ-specific alteration/rerate/variance forms
8. Honest transmittal

TSASK’s rerate list is the clearest official illustration that present condition, not original intent, is the design basis. Confirm the current evidence list with TSASK before filing.

Expedited-service relevance

24-hour: evidence triage if photos, U-1, and drawings are in hand. 48-hour: as-built drawing/calc reconciliation plan and index. Not 48-hour: performing UT, running a new PQR, or promising a variance will be granted.

Practical scenario

A vessel registered in Ontario is modified in the field in Alberta with an extra nozzle. That is not “the Ontario CRN still covers it.” It may be an Alberta alteration plus a design that is no longer the Ontario registered design. Two AHJs, two objects. Clock 1 should say so. ABSA and TSSA each have their own alteration/revision tools: confirm, do not mix forms.

Documentation checklist

• As-built vs registered comparison table
• Path selected (revision / alteration / rerate / variance / used)
• Destination AHJ forms for that path
• NDE if condition is the basis
• Stop-work on further mods
• No guessed nameplate numbers

Common mistakes

1. Filing the original design after the extra nozzle
2. Using TSSA variance language in an ABSA upload without checking ABSA’s path
3. Rerate without UT
4. Calling used equipment new
5. “We will note it in the MDR” as a substitute for design registration

Frequently Asked Questions

What happens when fabricated equipment differs from the design submitted for CRN?

The as-built equipment must be brought back into registration through whichever path the authority having jurisdiction provides: a design revision, an alteration, a rerate, a used-equipment submission, or a variance where the legislation allows one. Operating modified equipment under the original registration is a compliance exposure that can result in the equipment being ordered out of service. The correct path depends on the jurisdiction and the change, confirm with the applicable AHJ before filing anything.

Is this the same as emergency CRN for already fabricated new equipment?

Related but not identical. Emergency intake (Emergency CRN Support for Equipment Already Fabricated) covers equipment fabricated before registration where the as-built may still match a design that can now be frozen and filed as new construction. This article covers the harder case: the steel no longer matches any registered or fileable design, so the question becomes which lawful path (revision, alteration, rerate, variance, or used-equipment) applies in the destination jurisdiction.

The shop says the extra nozzle is “the same as a registered coupling.” Is that enough?

No. If the nozzle is not shown on the registered drawing and covered by the registered calculations, it is a design change. Similarity to another registered detail is not identity. Manitoba ITS describes identical-unit production as requiring an identical design, and the same logic applies to deviations: the registered envelope, not shop judgment, decides what is covered. Confirm the change path with the applicable AHJ.

Can we derate instead of repairing thin steel?

Possibly, but a derate is a registration event, not a silent nameplate edit. TSASK describes rerates as requiring design registration supported by present-condition evidence such as data reports, NDE results, and calculations for the vessel as it currently exists; confirm the current list with TSASK. The new, lower conditions must be justified by the actual remaining thickness, and the nameplate and records must be updated through the proper process.

What if two provinces already registered the old design?

A physical or design change can orphan both registration letters. Mutual recognition under the 2020 Reconciliation Agreement covers reviews of the design that was reviewed; it does not automatically extend to a new as-built configuration. Expect to run a revision, alteration, or rerate path in each jurisdiction where the equipment is used, with forms specific to each authority having jurisdiction. Confirm the sequence with both AHJs before modifying further.

Key Takeaways

• As-built mismatch is a path-selection problem.
• TSSA, TSASK, and TSBC describe different tools; do not mix them.
• Expedited review organizes evidence.
• Only the AHJ accepts the as-built.

Next Steps

Have a complete technical package and an urgent Canadian project? Kopfkino’s expedited review service can assess documentation, identify submission gaps, and prepare a submission-ready CRN dossier under available 24-hour or 48-hour service options, subject to project scope, technical complexity, and documentation completeness. Final registration remains with the applicable Canadian authority. Contact us to send your package for a completeness and submission-readiness review.

How to choose the path without mixing forms

Stand in front of the steel (or the photographs) and answer these in order:

1. Was a CRN already issued for this geometry? If no, you may still be in ordinary new-construction registration, but only if the as-built matches a complete design you can now freeze. If the as-built is a moving target, stop.
2. Did the geometry or materials change after a filing or issuance? If yes, it is not “the same CRN.” It is a revision (if still pre-construction in the AHJ’s sense), an alteration (if physically changed in service or in the shop after construction), or a rerate (if only conditions changed).
3. Are you raising or lowering design pressure/temperature on existing equipment? TSASK says rerates require design registration and typical vessel evidence includes MDR, repair/alteration report, NDE (UT preferable), and ASME calculations for the vessel in its present condition. That is present steel, not original intent.
4. Is the unit used, surplus, or of unknown history? TSBC discusses used vessels and non-full-ASME construction evidence. Do not file a 20-year-old U-1 as if it were a new unused design without a condition path.
5. Does Ontario post-construction change language apply? TSSA distinguishes pre-construction revisions (new application with a letter describing changes) from post-construction changes that may need a variance, with a variance attestation among supporting documents. Confirm current forms. Variance is not a missing-calculation tool.

Write the chosen path on the transmittal. Mixing a TSSA variance attestation into an ABSA new-construction portal upload is how recoveries fail.

Field vs shop alterations

A nozzle added in an Alberta module yard before first use and a nozzle added on a live Ontario plant are both geometry changes; they may not be the same statutory event. Shop changes before the unit has operated can still be “construction” in one AHJ’s vocabulary and “alteration” in another’s. Confirm. In all cases:

• Stop further modification until the registered design is redefined.
• Photograph.
• Recalculate the as-built.
• Use the destination AHJ’s current alteration/revision forms.
• Do not operate unregistered altered equipment because “it is only a two-inch nozzle.”

If welding occurs in a Canadian jurisdiction, joining-procedure registration may appear as a second file (CRN Welding Documentation: WPS, PQR, and Procedure Registration).

Nameplates after change

If a number is already stamped and the design changed, the plate may no longer describe the equipment. Do not add handwritten suffixes. Do not restamp a guessed number. Follow the AHJ’s restamping/nameplate rules after the new registration or alteration is accepted. RBQ’s requirement that boiler and pressure vessel nameplates include the CRN still means the correct issued number.

Expedited review in this article’s habitat

24-hour: triage if photos, data report, and last drawings are in hand, output is a path recommendation and a missing-evidence list. 48-hour: as-built vs registered comparison table, index of rerate/alteration exhibits, first recalculation coordination if the manufacturer can actually revise calcs. Not either timer: performing UT, running a new PQR, granting a variance, or promising ABSA/TSSA/TSBC will accept the as-built.

Related Guides

• Emergency CRN Support for Equipment Already Fabricated
• CRN Review Before Fabrication: Sequence and Hold Points
• Saskatchewan CRN with TSASK: Exemptions and Alternatives
• Ontario CRN Registration: TSSA Submission Readiness
• Pressure Vessel CRN Canada: Submission-Ready Dossier Guide
• CRN Welding Documentation: WPS, PQR, and Procedure Registration

Sources

• TSSA About CRN
• TSSA National Service
• ABSA
• TSBC
• TSASK
• Manitoba ITS
• RBQ
• ACI Central
• CSA B51

Regulatory references in this article were checked against publicly available authority pages as of 11 September 2026. Confirm current requirements with the applicable AHJ.

Topics: CRN Registration, CRN Documentation, Post-fabrication CRN Challenges