Do I Need A Fitting With a CRN?

Fittings are small pressure containing devices, either stand alone or attached to piping or vessels, which in most countries do not require registration. The Canadian B51 based CRN system is a more restrictive, more inclusive system that requires registration on many of these smaller fittings.

The B51 Charts (Table 1 below) indicate whether a pressurized device is a fitting or a vessel. Do you need to use a registered fitting for your application? Unfortunately this is a difficult topic.

Fitting Classification

Fittings are broken down into categories for registration. A manufacturer must apply separately with different statutory declarations for each category that their registered product line covers. Although this unfortunately increases the registration costs, it has allowed BC and Saskatchewan to declare categories A, B, C and G as being a waste of time to register. They no longer provide CRNs in these categories, and they no longer require them on registered vessels or piping systems. Other provinces still require these items to be registered. (BC Safety Authority and Technical Safety Authority of Saskatchewan.)

Categories of Fittings

Standard Fittings that are Exempt from Registration in Vessels Only

Every fitting on a registered pressure vessel or a registered piping system needs a CRN unless it is exempted. B51 clause 4.2.1 provides an exemption:

"All fittings shall be registered... unless they form a part of a boiler or pressure vessel that is subject to inspection by an authorized inspection agency..."

This exemption is universal in its scope - exempting any fitting. In practice provincial jurisdictions will only use this exemption for items found in ASME VIII-1 table UG-44 which covers:

All other items not found on this list require CRNs for use on pressure vessels. Contrary to the B51 standard, CRNs are also not required for these same fittings when used on a UM vessels or made into other fittings, neither of which are subject to inspection by an Authorized Inspector. This exemption does not apply to piping systems.

Fittings in Piping Systems

Manufacturers of the above UG-44 listed standard components would need CRNs for use in registered piping systems. This picture shows when the same fittings require registration or not.

Categories of Fittings

The standard flanges, couplings and elbows listed in UG-44 located on the CRN registered UM vessel (not subject to authorized inspection) do not require CRNs. The identical flanges, elbows and couplings located on the registered piping system which will be inspected by an Authorized Inspector do require CRNs. Although it does not make any sense, this is how the rules are currently being applied.

Special Rules on Stand Alone Fittings

Fittings not attached to piping or vessels do not require registration. Most provinces also have special rules requiring and exempting classes or types of fittings in specific services. These requirements are usually outlined in the provincial vessel/piping safety rules. (Provincial Contacts)

Example: a fitting sized dental or medical autoclave not attached to a piping system would not require registering. However, some provinces have special requirements to register these stand-alone fittings written into their provincial legislation.

Example: air powered shell launchers for avalanche control are stand-alone fittings that have to be registered in some provinces.


Primarily due to confusion, customers will request registration on items that cannot be registered, like pipe (which is not a fitting but a calculated part of a pressure vessel or piping system), or items that do not require registration for the service that they are in. It can be easier for a customer to request a CRN than determine if it is required or not. A manufacturer often cannot determine if a fitting needs a CRN without knowing their customer's intended service.

A CRN is often used as a marketing tool. Competition with a registered competitor can lead to CRN registration even if it will never be required for the service the fitting will see. It is also less confusing to have a CRN even if it is not required.

Flowchart for Fittings

Disclaimer: While every effort is made to make these pages accurate and up to date as the CRN system changes, this information is only the opinion of Laurence Brundrett P. Eng., President of Pressure Vessel Engineering Ltd. Please consider this an introduction - the first 20% of the information you require to navigate the CRN system.