CSA B51 explained
CSA B51 is the Canadian standard for boiler, pressure vessel and pressure piping construction. Every CRN is issued against it. It defines what must be registered (generally pressure equipment above 15 psig) and, for fittings, assigns a category from A to H that determines exactly how the design is accepted.
The 15 psi threshold
As a rule of thumb, pressure equipment operating above 15 psig falls within CRN scope; below that it usually does not require registration. Boundary cases matter, so confirm before assuming you are exempt.
Fitting categories A to H
For fittings (which includes valves, flanges, expansion joints and hoses), the category is the single most important decision. It dictates the evidence the authority needs.
| Cat | Typical basis | Acceptance route |
|---|---|---|
| A | Fittings proven by a recognized standard (e.g. ASME B16 series). | Standard-based acceptance. |
| B | Fittings designed to a code with calculations. | Calculation-based acceptance. |
| C | Fittings proven by proof test. | Proof-test acceptance (no ASME Code stamp shortcut). |
| D | Fittings proven by burst test. | Burst-test acceptance. |
| E | Expansion joints / flexible connectors. | Specialized review. |
| F | Hose assemblies. | Assembly-level registration. |
| G | Line fittings of a category not otherwise covered. | Case-specific routing. |
| H | Fittings registered by a manufacturer's quality program / statutory declaration. | QMS-based acceptance. |
Simplified for orientation. The authoritative classification depends on your specific product and the current edition of CSA B51, which we confirm during scope review.
Register your fittings, valves or hoses with the correct category from the start.