Do I Need A Fitting With a CRN?

Updated Oct 13 2015

Fittings are small pressure containing devices, either stand alone or attached to piping or vessels. In most countries these fittings do not require registration. The Canadian B51 based CRN system is a more restrictive, more inclusive system that requires registration on many of these 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. This unfortunately increases the registration costs but has allowed BC and Saskatchewan to declare categories A, B, C and G as not requiring registration. 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.) (Also, Quebec has future plans where category A, B and C will not require registration - contact RBQ for more information on your project.)

CSA B51-14 Table 1: Categories of Fittings
Category Type of Fitting
A Pipe fittings, including couplings, tees, elbows, wyes, plugs, unions, pipe caps, and reducers
B All flanges
C All line valves
D All types of expansion joints, flexible connections, and hose assemblies
E Strainers, filters, separators, and steam traps
F Measuring devices, including pressure gauges, level gauges, sight glasses, levels, and pressure transmitters
G Certified capacity-rated pressure relief devices acceptable as primary overpressure protection on boilers, pressure vessels and pressure piping, and fusible plugs
H Pressure-retaining components that do not fall into Categories A to G
(1) These categories do not take into account size, materials, end connections, ratings, schedules, and methods of fabrication.
(2) Category H can include
2(a) small pressure vessels registered and inspected as specified in Figures 1(a), (b), or (c). Such pressure vessels shall be designed and constructed in accordance with Clause 7, except that items that fall under Figures 1(a) and (b) may be designed and constructed to Clause 8, provided that the pressure vessel
2(a)(i) does not require full radiography in accordance with the ASME Code;
2(a)(ii) does not have a quick-actuating closure;
2(a)(iii) is not in cyclic service; and
2(a)(iv) is 4 NPS or smaller;
2(b) an assembly of components (including piping components), provided that the diameter of any component does not exceed 152 mm (6 in) and the total volume of the assembly does not exceed 42.5 L (1.5 ft3). Such an assembly is considered a single Category H fitting for the purposes of fitting registration; and
2(c) condenser coils and evaporator coils as defined in CSA B52 and air heater coils, provided that the diameter of any component does not exceed 152 mm (6 in) and the design pressure does not exceed 4.14 MPa (600 psig).

Notes 1 and 2 bring Canada wide registration closer to the current Alberta practices. Clause 7 is for pressure vessels, clause 8, piping and fittings. The addition of clause 8 to fittings 4" or less diameter now makes it possible to register category H items like filter housings made of die cast aluminium in Alberta.

Where provinces have legislation requiring items like medical/dental autoclaves of fitting size to be registered, they are now registered as vessels (clause 7) instead of fittings (clause 8). This can be an important change for both the manufacturers and end users. The fittings as vessels require authorized inspector sign-off and National Board registration.

Refer to the CSA B51 Graphs (Fig 1a, 1b, 1c) to determine if you have a vessel or a category H fitting. The above dimension limitations only apply to category H fittings. Category A-E fittings can be any size and remain a fitting.

Standard Fittings that are Exempt from Registration (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 which are not subject to inspection by an Authorized Inspector. This exemption does not apply to Assemblies of Components.

Assemblies of Components

A fitting can also be a collection of other fittings. Per CSA B51-14 Table 1 Notes(2):

Category H can include (b) an assembly of components (including piping components), provided that the diameter of any component does not exceed 152 mm (6 in) and the total volume of the assembly does not exceed 42.5 L (1.5 ft3). Such an assembly is considered a single Category H fitting for the purposes of fitting registration;

This is like a miniature piping system. A recent requirement is that these assemblies of components must now be made from registered components. Sections of pipe are calculated. Custom components made by the manufacturer require calculations or burst tests or separate CRN registration. All other parts need CRNs.

Fittings in Piping Systems

Manufacturers of the above UG-44 listed standard components would need CRNs for use in registered piping systems or assemblies of components. 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: 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.