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B 31.3 Special flange CRN

B 31.3 Special flange CRN

B 31.3 Special flange CRN

Hello friends
if nozzle fitting made by special flange ( by doing machining)
it is design under B 31.3 COME UNDER PIPING FLOW , do i have to register for CRN.
I think if any std.flange OR Special flange design calculation is done under regular piping no need to be register for CRN.

need your opinion.


RE: B 31.3 Special flange CRN

Depends on the province. Which one is yours?

RE: B 31.3 Special flange CRN

qubec ( RBQ)

RE: B 31.3 Special flange CRN

Are you making one, or many?

One may have its design registered with the piping design registration. You obtain a CRN for the entire piping system including that unusual component, providing design information to the satisfaction of the provincial registration agency for the entire piping design including the design of that part.

If you want to make many of them and offer them for sale, you will require something akin to the Category H Fitting registration, where you obtain a CRN for the component.

RE: B 31.3 Special flange CRN


In general, all flanges fall under Category B fitting per Table 1 of CSA-B51. Any special flange shall be registered with Authority having Jurisdiction, in this instance, RBQ in Quebec.

Where this special flange is connected? What is special about it and why not to use regular ASME flange?


RE: B 31.3 Special flange CRN

A common misunderstanding of the rules. There is no need to separately register one unusual part used in a pressure piping system, unless you later intend to produce them in quantity and sell them to others, in which case it becomes a Category H fitting and needs separate registration.

RE: B 31.3 Special flange CRN

Thanks to all.

RE: B 31.3 Special flange CRN

Category B Fitting for Flanges.

RE: B 31.3 Special flange CRN


You are correct! If a special flange is part of another assembly welded together, in this case it will be treated as a part of this H-fitting.

However, if you need a companion flange, you need in your piping to attach to this special flanged assembly, you will need B-fitting registered for the special flande. In latter case you will need two CRN registrations - H-Fitting + B-Fitting.


RE: B 31.3 Special flange CRN

curtis 2004: we do this on a routine basis. Any special component for one-off use in piping subject to the design registration requirement does not need to be separately registered as category H, category B or anything else- it can be, and routinely IS in our experience, registered with the piping system design, and its testing witnessed by the AHJ along with the balance of the piping system. The documentation that you need to submit to validate the component's design doesn't differ- what does differ is that you don't need to make a Statutory Declaration and have it separately legally witnessed etc., i.e. you can skip some of the regulatory paperwork exercises required of you to register a Category H fitting. It only needs to be registered separately as a fitting if it will be produced for sale as a loose component, in which case it needs its own CRN like every other pressure retaining component offered for sale.

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