Compressor Packages and the Machinery Exclusion: What Still Needs a CRN on a Compressor Skid

By Kopfkino Consulting Corp. · Published September 14, 2026 · Updated October 17, 2026 · 8 min read

The machinery exclusion covers only parts integral to the compressor itself. Scrubbers, coolers, pulsation bottles, piping, PSVs and fittings on the skid still need CRN registration.

The machinery exclusion removes only the pressure-containing parts integral to the compressor or driver itself, casings, cylinders, and machine-mounted chambers whose stresses come from the machine's function. Everything else on a compressor skid remains registrable: suction scrubbers, pulsation bottles, coolers, separators, filters, interconnecting piping, relief valves, and fittings each need a CRN or piping registration before installation in Canada.

Compressor packagers routinely hear a sales-level misconception: "it is a compressor package, so pressure equipment rules do not apply." Canadian regulations do contain a rotating/reciprocating machinery exclusion, but it is narrow, and misreading it leaves most of a typical skid unregistered. This article maps the exclusion component by component and shows a compliant registration scope.

What does the rotating machinery exclusion actually exclude?

Canadian jurisdictions share an exclusion pattern for pressure-containing parts integral to rotating or reciprocating machinery, where primary stresses derive from the machine's functional requirements:

• Ontario: O. Reg. 220/01, s. 2(2)(m)
• Alberta: Pressure Equipment Exemption Order (PEEO), AR 56/2006, s. 2(2)(j)
• Quebec: r. 6.1, s. 3(9): machinery-driven equipment such as pumps, compressors and turbines
• British Columbia: the same machinery concept within BC Reg. 104/2004

The exclusion covers the compressor block itself: cylinders, casings, crankcase chambers, liners, chambers cast into the machine, and driver pressure parts (e.g., a hermetic compressor shell), parts engineered under machine design standards (e.g., API 618), not ASME Section VIII.

Two cautions are non-negotiable. An exclusion from registration is never an exemption from the governing Act or code of construction. And the exclusion follows the part, not the skid, mounting excluded machinery on a frame excludes nothing beside it.

What remains registrable on a compressor skid?

Every pressure-retaining component outside the machine boundary falls back into the normal CRN regime, vessels, fittings, and piping above 15 psi (≈103 kPa):

• Suction scrubbers / knockout drums: vessel design registration (Category H fitting under the small-vessel thresholds: ≤42.5 L or ≤152 mm ID in Ontario and Alberta).
• Pulsation bottles (dampeners): code-stamped vessels; high-pressure and fatigue-sensitive.
• Interstage and discharge coolers: exchangers; both shell and tube sides addressed.
• Separators and coalescing filter vessels: vessels, or Category H items when small.
• Station and interconnecting piping, piping-system design registration to ASME B31.3 (or B31.1/B31.5), scoped by P&IDs, line lists, and calculations.
• Pressure relief valves: Category G fittings; primary overpressure devices must hold ASME certification; Ontario and Alberta register them individually.
• Other fittings: valves (C), flanges (B), strainers/filters (E), instruments (F), non-standard components (H). A/B/C/G categorical exemptions exist only in BC, SK, and MB (and QC for A/B/C piping accessories); Alberta and Ontario register all fitting categories.

Component-by-component scope tables

Typical reciprocating compressor package (gas service)

Typical rotary screw compressor package (compressed air)

Jurisdiction differences in interpreting the exclusion

The exclusion wording is similar across provinces, but its edges are not harmonized. At the boundary (a bottle flange-mounted to the cylinder, an oil separator cast into the airend) reviewers may differ on what is "integral." Interpretive guidance is thin outside the clause texts; treat the following as practice-level guidance and confirm current interpretation with the authority having jurisdiction (AHJ):

• Alberta (ABSA): PEEO s. 2(2)(j) applied conservatively; skid-mounted vessels register as vessels regardless of proximity to the machine.
• Saskatchewan (TSASK): the skid design registration program (IP-2016-07-04) captures the skid's piping and mounted equipment as a stand-alone design; the 0.5 m³ exemption does not apply.
• Quebec (RBQ): r. 6.1 s. 3(9) excludes machinery-driven equipment; the s. 2 subjection figures govern mounted vessels.
• Ontario (TSSA): s. 2(2)(m) mirrors the pattern; piping registers as P-numbers or P-standard designs.

The Alberta AB-96 reality for out-of-province fabrication

Alberta trips up the most packagers. Under the Pressure Equipment Safety Regulation, pressure piping fabricated outside Alberta must be registered regardless of volume, the ≤500 L system-volume exemption applies only to in-province fabrication. A package built in Texas, Ontario, or Germany therefore needs an AB-96 piping design registration sealed by an Alberta P.Eng., plus CRNs for every mounted vessel and fitting (no categorical fitting exemptions). ABSA is not a party to the Reconciliation Agreement, so another province's CRN still requires a separate ABSA National Registration review. Budget this before fabrication, never after shipment.

Nameplates and documentation for the registrable scope

• Each registered vessel (scrubber, bottle, cooler, separator) is stamped with its CRN per the registered drawing; the manufacturer's data report goes to the destination AHJ (e.g., RBQ requires the MDR within 30 days of signing).
• Saskatchewan-registered skids carry a nameplate with manufacturer, serial number, and TSASK skid design registration number.
• Fittings are marked or documented with their CRNs; Ontario piping submissions attest that only registered fittings are used.
• Alberta's AB-96/AB-83/AB-81 chain ties the registered piping design to construction and completion records.
• Keep a scope-of-registration register: every pressure-retaining component, its exclusion basis or CRN, and the registering jurisdiction. Inspectors increasingly ask for it.

Worked scenario: a 500 kW reciprocating gas-compressor package bound for Alberta

A US packager builds a two-stage reciprocating package: cylinders (excluded machinery); one 600 L suction scrubber; two pulsation bottles; an air-cooled discharge cooler; interconnecting B31.3 piping (~800 L aggregate); three PSVs; ~40 valves, flanges, strainers, and instruments.

Registration scope: the scrubber and bottles register as vessels (ABSA design surveys run hourly, $163.50/hr as of November 2025); the cooler registers as an exchanger; the piping needs AB-96 registration (out-of-province fabrication, Alberta P.Eng. authentication); all three PSVs and every fitting need Alberta CRNs, no A/B/C/G exemptions. Welding procedures register with the fabrication jurisdiction's AHJ. Sold into Saskatchewan, TSASK's skid registration applies with an SK P.Eng.-authenticated package; into Ontario, designs need PEO-P.Eng. authentication under s. 4(3). The cylinders register nowhere, excluded machinery in every province.

Common mistakes

• Treating the exclusion as skid-wide. It covers machine-integral parts only; mounted vessels, bottles, and coolers remain registrable.
• Forgetting Alberta's out-of-province piping rule, assuming the 500 L exemption applies to a foreign-built package is a common Alberta failure.
• Assuming fitting exemptions travel. A/B/C/G exemptions exist in BC, SK, MB (and QC for A/B/C), never in AB or ON.
• Overlooking pulsation bottles and small pots: they are vessels or Category H fittings, not "part of the compressor."
• Missing P.Eng. authentication: Ontario (s. 4(3)), Alberta piping, and Saskatchewan skids all require provincially licensed P.Eng. authentication.
• Retroactive registration: BC warns it can be very expensive, burdensome, or impossible.

Best practices

Engineering recommendations, not regulatory requirements:

• Build a component-by-component scope register at proposal stage, mapping each item to "excluded machinery / vessel / fitting / piping" per destination province.
• Freeze the registration boundary on the P&ID, marking excluded machine parts explicitly so reviewers see the logic.
• Register vessels and fittings before fabrication; engage the AHJ-accepted inspection agency before work starts on out-of-country builds.
• For Alberta destinations, run the AB-96 and National Registration reviews in parallel with other provinces.
• Confirm boundary components with the AHJ in writing before relying on the exclusion.

Frequently Asked Questions

Which components of a compressor package are exempt and which still need CRNs?

Only pressure parts integral to the compressor or driver (casings, cylinders, machine-mounted chambers) are excluded under provisions such as O. Reg. 220/01 s. 2(2)(m) and Alberta PEEO s. 2(2)(j). Scrubbers, bottles, coolers, separators, filters, piping, PSVs, and fittings remain registrable.

Does the rotating machinery exemption cover my whole compressor skid?

No. The exclusion follows the part, not the package. Anything mounted beside the machine is assessed under the destination jurisdiction's normal vessel, fitting, and piping rules.

Are pulsation bottles part of the compressor or separate vessels?

Separate vessels: code-stamped, pressure-retaining chambers distinct from the cylinder casting, even when flange-mounted. Register them in every destination province (Category H fittings if small).

My package is built outside Alberta with under 500 L of piping: do I still register the piping?

Yes. The ≤500 L exemption applies only to in-province fabrication; out-of-province piping needs AB-96 registration (Alberta P.Eng.-authenticated) at any volume.

Do relief valves on an excluded machine need CRNs?

Generally yes. PSVs are Category G fittings, registered individually in Ontario and Alberta; primary overpressure devices must be ASME/NB capacity-certified. Confirm machine-internal relief devices with the AHJ.

Does one CRN cover a compressor package sold Canada-wide?

No. A CRN is jurisdiction-specific. Nine jurisdictions reciprocate under the Reconciliation Agreement; Alberta always requires a separate ABSA review, and NB, NL, and NU route through ACI Central.

Is excluded equipment exempt from the Act entirely?

No. An exemption from registration is never an exemption from the governing safety Act or codes; the machinery must still be safely designed, constructed, and installed.

Key Takeaways

• The machinery exclusion (ON s. 2(2)(m); AB PEEO s. 2(2)(j); QC r. 6.1 s. 3(9)) covers only pressure parts integral to the compressor/driver.
• Scrubbers, bottles, coolers, separators, filters, piping, PSVs, and fittings remain registrable.
• Alberta registers all fitting categories and requires AB-96 piping registration for out-of-province-fabricated packages, regardless of volume.
• P.Eng. authentication are mandatory for Ontario submissions, Alberta piping, and Saskatchewan skids.
• Register before fabrication; retroactive registration is costly and sometimes impossible.
• A component-by-component scope register is the most effective compliance tool for packagers.

Related Guides

• CRN Registration for Packaged Skids and Modular Process Units: The Complete Canadian Guide
• What Needs a CRN in Canada? Boilers, Pressure Vessels, Fittings and Piping Above 15 psi
• CRN Registration for Compressor Packages in Alberta: ABSA Requirements for Packaged Equipment
• Compressor Station CRN Compliance: Scrubbers, Coolers, Bottles and Station Piping
• Welding on Compressor and Process Skids: WPS/PQR Registration with ABSA, TSASK and RBQ
• CRN for manifolds and skids
• CRN for air receivers and compressed air tanks
• Compressor Package CRN in Canada

Sources

• Ontario O. Reg. 220/01 (Boilers and Pressure Vessels), https://www.ontario.ca/laws/regulation/010220
• Alberta Pressure Equipment Exemption Order (AR 56/2006), https://kedkep.com/docs/Safety%20Code%20Act%20PEEO.pdf
• Quebec Regulation respecting pressure installations (r. 6.1), https://legisquebec.gouv.qc.ca/en/ShowDoc/cr/B-1.1,%20r.%206.1
• BC Reg. 104/2004 (PEBPV&R Safety Regulation), https://www.bclaws.gov.bc.ca/civix/document/id/complete/statreg/104_2004
• ABSA design registration and National Registration, https://www.absa.ca/design-registration/ ; https://www.absa.ca/design-registration/absas-national-registration-process/
• TSASK skid design registration (IP-2016-07-04), https://api.tsask.ca/wp-content/uploads/2024/07/IP-2016-07-04_-_Application_for_the_Registration_of_a_Skid_Design.pdf
• TSSA Fitting Registration Guidelines (Jan 2026, Rev 3), https://www.tssa.org/downloads/fittings-guidelines-jan-2026-rev-3

Defining a compressor package's registrable scope (and defending exclusion boundaries to multiple regulators) is where Kopfkino Consulting supports packagers and OEMs. Services include CRN applicability reviews, registration strategy, pre-fabrication design review, calculations, submission packages, P.Eng. coordination, multi-province registration, regulator-comment resolution, and international OEM support, engaged before fabrication, so the scope aligns with AHJ expectations from the start.

Contact us to discuss the registration scope for your equipment and its destination provinces.

Topics: CRN Registration, Compressor Packages, Machinery Exclusion, Packaged Equipment