CRN User's Survival Guide - Introduction to this Blog

At times I feel obliged to apologize to customers for how difficult Canada's CRN registration system has become. The emotions can run high when someone has been going up against our poorly documented and constantly shifting regulatory barriers. It is no longer possible for a person with prior pressure vessel design experience but no Canadian registration experience to expect an easy navigation of our system. CRNs are harder to get now than ever before, the waiting time is longer, the costs higher and the need for specialized knowledge has never been greater.

The original goal of this guide was to provide a set of rules to use for CRN submissions in Canada. By documenting accepted methods, we and our customers could work towards the goal of getting easier, faster and less expensive CRN approvals. Along the way it became apparent that single methods for use Canada wide, or even within one province were impossible. Each province is different, and within provinces sometimes individual reviewers have contradictory requirements. All this guide can do is list methods that usually work.

The CRN system is currently splitting in two directions in Canada. Some provinces are finding little value in the system and are looking for easier ways to get safe products in use in Canada. These provinces are accepting the internationally recognized National Board system as an alternative for vessel registration or reducing the scope of fitting requiring registration. Other provinces are currently making the review process more difficult, expensive and varied between provinces. A few are currently debating which direction to follow.

Approximately once a week we encounter new requirements for registration in Canada. It is not possible to track all of these requirements, and this blog would be far too long to be useful. Further, some issues are too sensitive to write about here. If you have anything to share on these topics you can contact me at or 519-880-9808 x223.

Wishing you the best of fortune with your Canadian registration challenges. If you have any questions please contact me:

Laurence Brundrett, BSc, P. Eng.

Laurence Brundrett, B.Sc., P.Eng.
519-880-9808 ext 223

Registration of Cold Stretched Vessels

Oct 26 2015, By: Matt Hiskett

Why Cold Stretching?

Cold stretching has been in use for more than 30 years, but not under ASME code rules until 2008. Cold stretching (or cold working) increases the yield limit of a stainless steel material by work hardening it after all forming and welded steps are complete. A vessel can be cold stretched by over pressurizing it 1.5 to 1.6 times the maximum allowable working pressure (MAWP) under careful control of the deformation vs pressure as outlined in VIII-1 App 44. The resulting permanent plastic deformation increases the diameter up to 7% and the volume by 14%.

Stainless steel stress strain curve showing an increase in yield strength after cold working.

The ASME allowed stress in a vessel made of SA-240 304 stainless is 20,000 psi for cryogenic applications. After cold stretching, the allowable stress is increased to 39,300 psi (Table 44-1-1 in ASME VIII-1). The higher allowable is a combination of both an increase in the yield stress and a decrease in the factor of safety.

A cold stretched cryogenic storage vessel. The cold stretched vessel is not visible, contained inside a non-stretched vacuum vessel that can be seen in this photograph.

To date the only cold stretched vessels we have seen are used for cryogenic storage and we do not think this process would be practical for a vessel without an outer containment vessel.

Cold Stretching and The CRN process

Cold stretched vessels are easy to register if you have all the required documentation, however much of the required information is not in writing on the jurisdictions websites - refer to this chart:

Requirement ASME App. 44 BC AB SK MN ON QC ACI*
Drawings (with additional notes). Drawings are a standard requirement of CRN registration. yes yes yes yes yes yes yes
Calculations. Calculations are a standard requirement of CRN registration. yes yes yes yes yes yes yes
Manufacturers Design Report (MDR) including U-DR-1 yes yes
Certificate of compliance (for MDR and UDS) yes
User design report unique to the specific vessel being registered yes
Signed letter from the owner of the vessel. yes yes yes yes yes yes yes yes
Cold stretch procedure (44-6-3) yes yes yes yes yes yes yes yes
ABSA IB13-016 yes yes
Limited Ownership yes yes yes yes yes yes yes yes
*ACI covers the registrations in MB, NS, PEI, NFLD, YK, NV and NT

The biggest problem with registering cold stretched vessels is App. 44-2: “The use of this mandatory appendix is contingent upon the approval from the user of the user’s designated agent.” Anyone building cold stretched vessels must have a letter from the customer stating that they understand that they are purchasing a cold stretched vessel built to appendix 44. Cold stretched vessels cannot be modified or repaired without re-stretching.

What’s included in the CRN submission?

As with all submission packages, the standard vessel drawings and calculations must be included in the submission. Drawings for a cold stretched vessel must have a few additional notes added:

What’s in a Manufactures Design Report (MDR)?

An MDR is a vessel design specific document that includes the design conditions for each design. It should include the following:

What about a User Design Specification (UDS)?

The UDS is also vessel specific; however it covers the entire process, including fabrication. In addition to the information found in the MDR, it also needs to include a document, similar to your standard CSP, but less generic. For example the edited CSP should make reference to the vessel diameter, nozzle sizes, and Pressure/Temperature ratings. As with the MDR, the UDS requires a certificate of compliance as found in ASME VIII-2, Table 2-A.1.

Is my current CRN valid for a different customer?

Based on our experience and discussions with the various registration agencies, we have concluded that you can submit multiple user acceptance letters with a CRN submission, which will allow that CRN to be used for multiple customers.

It is our opinion that after a registration is completed in a province a revision to the CRN can be obtained to include additional customer by submitting the following documents:

ABSA Survey Process Improvements

May 4, 2015, LRB

I used to read a Canadian magazine that would only discuss the safety and reliability of specific cars once they were determined to be good. "Manufacturer X overcomes safety and reliability problems in their brand Y model" No bad news about their advertisers would ever be printed. I hated them for it, but now that it's my turn to write about review agencies I can sympathize. Our line has been "some issues are too sensitive to write about here." The review process is improving in Alberta, so I feel it is safe to discuss the improvements.

A topic of debate in our office is that there are enough design surveyors in Canada to get all jobs registered in a reasonable time frame (one week), but we cannot do this because too much time is spent re-reviewing work that has already been registered in other provinces. This then leads to the observation that once a jurisdiction can no longer keep up with its review workload, it will get buried by the extra work in managing the backlog and never be able to recover. ABSA is making the effort to both recover and reduce the amount of time re-reviewing.

Noted changes

We have noted some improvements in the registration process at ABSA in the last 9 months. ABSA has posted policy changes making these improvements possible in The Pressure News Volume 20, Issue 1, March 2015. The complete article, (with our comments) is below:

Design Survey Process Improvements
The number of design submissions has increased by 45% since 2010. In 2014, we received a record number of 10,500 submissions which had been climbing steadily over the last 5 years. More than 50% of the submitted designs have deficiencies and cannot be accepted the first time around. This sends them into a loop that involves putting the review on hold, resubmission, and repeated reviews until registration requirements are met. The process is inefficient and frustrating for both the submitter and Design Survey.

We submit more than 250 applications a year to ABSA so we contribute to about 2.5% of ABSA's registration volume. The loop process was particularly bad at ABSA where by policy, submissions with issues were put to the bottom of the pile. This often resulted in 3+ month delays between rounds of questions, and due to the loss of continuity, the same questions would get repeated. This disastrously inefficient policy appears to have met its only just end - it has been abolished. This change on its own would be worth noting.

What are "design deficiencies" is a difficult topic, as what causes a project to be rejected varies by reviewer. We have seen a reduction in our rejection rate with the changes in personnel as noted below.

ABSA is actively working on improvements to design review processes in order to improve efficiency, reduce frustration, and decrease the turnaround time on design registrations:
1. More design surveyors are being hired - three new design surveyors started training in December 2014, and we are adding three more design surveyors in March.
2. For certain piping submissions , once we ensure that all required documents are submitted and have the required P.Eng. stamp and signature, we will register the design.
3. Design surveyors will use an 'audit' process to expedite design reviews for submissions from companies with a history of designs having few deficiencies.
4. Companies with a history of high deficiencies will see submissions rejected sooner.
5. Dedicated positions have been added to respond to general inquiries from clients.
6. We will continue to look for and implement improvements to the process for reviewing and registering designs.
7. We will accept designs registered by other jurisdictions provided that we receive the proper documentation.
8. We have added more administrative support staff.
9. ABSA technical staff have been seconded from the Inspections Department on a temporary basis to help with design reviews and registration.
10. Guidelines are being applied that will direct the ABSA review to higher risk items.

We have already experienced some of these changes. We have had projects reviewed by new surveyors. We have seen new applications processed much faster than in previous years. We have received reciprocal registrations based on review of other provinces:

This registration has been issued:
1. Based on TSSA's review
2. Based on the Association of Chief Inspectors Policy on Reciprocal Recognition of Design Review for Fitting Design Registration

The above quote is from an application that was submitted first to TSSA. The Ontario expedited review took one week. The reciprocal ABSA registration only took 3 weeks. This is an interesting development as TSSA and ABSA reviews differ. This provides new hope for applicants who's designs were rejected by ABSA, but obtained registration in the rest of Canada.

We feel that this change will result in more registration work being sent to other provinces first, in particular Ontario. The fastest review time from TSSA is a 2 week expedited registration (it sometimes happens faster). Followed by a reciprocal acceptance from ABSA without review which takes 2-3 weeks. The total review time of around one month is a considerable improvement. However TSSA is already very busy and removes expedited services when overloaded, but other provinces can also help.

Please note that this policy only applies to new ABSA applications. Applications currently in the stack still take up to one year for an initial partial review leading to full review or rejection, even if proof of registration from another province is included. Full review is being applied to the older submissions.

This change, when fully implemented takes us one step closer to the dream of someday only having to submit a design once, to one province or organization, to get complete Canada wide approvals...

Your Job

Back to ABSA's article:

Design submitters can help: A check list has been added to the AB-31 application so submitters can confirm that all requirements have been addressed. Please make sure that your submission is complete. Deficient information could lead to immediate rejection. Please help us to help you.

In our experience, the assigned reviewer is the most important variable determining success or failure of an application. However, the quality of an application is the second most important. Extra effort applied to making a quality submission has a beneficial impact on the whole registration process.

We would welcome a return by ABSA to the times of 2000-2007 when they were the most helpful and resourceful jurisdiction in Canada, but we have seen these current changes make a big improvement.

Updated Yet Again - A New Hope

File: File:PVE-4703, Last Updated: Mar 19 2015, By: LRB

In spite of the ever increasing rules and mountains of paperwork required to register vessels and fittings in Canada, five provinces have been working on alternatives to make the CRN system work better in their provinces.

British Columbia

British Columbia has two innovations to make life easier for people dealing with the CRN system:

1 BCSA has set up a Reciprocal Designs registration process. If your design has previously been registered in Alberta, Ontario or with ACI, you can get your design registered for less than $200 in a couple of days. BCSA relies on the review done by the original province of registration as allowed by the CSA B51 standard [B51-14 4.2.2]:

4.2.2 Initial registration with one regulatory authority may be accepted by the regulatory authority in another province if the latter is provided with an accepted copy of the statutory declaration form and the supporting documentation...

We have found that this process works fast - it only takes a couple of days and saves money. We have also noticed a reduction in registration times associated with regular registrations as more jobs are done this way. More Information. Note that some restrictions apply.

2 BCSA (like TSASK below) does not require registration of Category A, B, C and G fittings of standard design. We have seen whole piping systems get registered only requiring a CRN on one fitting. There are restrictions on what fittings are exempt. More Information.


TSASK has three innovations to simplify the registration process:

1 Like BCSA, TSASK does not require the registration of Category A, B, C and G fittings. The BC additional restrictions do not apply.

2 TSASK allows the use of National Board only registered vessels in some cases. More Information below.

3 Saskatchewan is one of two provinces that has joined CSA's CCRN program.

Canadian Central Registration Number (CCRN) — a registration number, allotted by a nationally recognized organization such as CSA in accordance with procedures accepted by more than one province, that allows a fitting to be used in such provinces.

With Manitoba opting out of the program, now Quebec is the only other province that is a member of this program.


Inspection and Technical Services Manitoba is now issuing reciprocal registrations. Like B.C., reciprocal registrations can be issued based on the review being done by other provinces. We do not know yet which provinces are acceptable, and under what circumstances the reciprocal process will be applied. When applied the registration time has be reduced to half. Per the first review we got registered this way:

Note: CRN registered under reciprocal agreements & is conditional based on compliance with the notes set by the original issuing Jurisdiction: TSSA. See attached stamped "this is part of CRN" for scope of registration. This registration expires Dec 16 2024"
Category A, B, C and G fittings do not need to be registered in BC and Saskatchewan (Some restrictions apply)


Quebec has two programs under way to reduce the scope of systems requiring CRNs and the complexity of registration:

1 Quebec is one of the two provinces that are a member of CSA's CCRN fitting program. Unfortunately Saskatchewan is the only other member province for this program. We at Pressure Vessel Engineering currently register fittings directly through Quebec and Saskatchewan. CSA is currently trying to get renewed interest in this program with additional provinces, we wish them good luck.

2 Quebec is currently rewritting its legislation to reduce the number of piping systems and machines with piping systems that need registration. Also Quebec is planning to exempt Category A, B and C fittings of standard type from registration. The legislation is in process, but can be applied to jobs currently on the go. Contact RBQ for more information or if you wish to implement this prior to the legislation being finalized. The changes go beyond this - more preliminary details here.


Many of our customers have the most trouble getting CRNs in Alberta. The reasons are: 1) the volume of work is greatest in Alberta leading to long wait times; 2) Alberta has many unique requirements not based on pressure codes, only some of which are documented; 3) (this policy is no longer being followed)ABSA’s policy of putting a job on the bottom of the pile every time the reviewer needs to ask a question and .4) registration requirements that vary by reviewer. Although at this time we have outstanding jobs waiting for review for more than 1/2 year, many new submissions are being reviewed in less than 4 weeks.

Last year there were some important personnel changes in the ABSA: 1) chief inspector Dr. Lau has retired. 2) The design review department has been reorganized under Po Fok the new Design Survey Manager. There has also been turnover in the review staff beyond these reported changes. These changes have had a huge impact making it easier to deal with ABSA.

ABSA accepts registrations based on other jurisdiction reviews without re-review as permitted by CSA B51-144.2.2:

Initial registration with one regulatory authority may be accepted by the regulatory authority in another province if the latter is provided with an accepted copy of the statutory declaration form (see Figure D.6) and the supporting documentation specified in Clause 4.2.8.

When these reciprocal registrations are accepted, the review time is less than 2 weeks. We do not yet know under what circumstances reciprocal registrations will be accepted. We continue to be optimistic about ongoing changes at ABSA.


These simple changes to the registration process show that there is considerable flexibility in the CRN system allowing many improvements to the system, when the jurisdictions are so inclined.

Updated: National Board Vessels in Saskatchewan

File:PVE-4711, Last Updated: May 26 2014, By: LB

More Updates (May 2014):

After discussing this topic with TSASK, we have some more useful information not currently covered by TSASKs web site:

Initially this alternative registration process was put in place to cover used vessels where the owner did not have fabrication drawings or calculations. The legislation was not written to exclude using this system for new vessels so TSASK allows this process on new vessels. Future versions of the legislation may be updated to exclude new vessels.

Once TSASK has reviewed your application and agreed that the vessel is within the scope of allowed vessels, a letter is drafted and returned to the owner as proof of filing.

A vessel filed this way can not be altered. At time of alteration, the vessel might have to be fully CRN registered to allow the alteration to proceed.

In light of these and other potential restrictions TSASK recommends anyone contemplating using this filing process call first.

Update (May 2014):

Saskatchewan allowing the use of ONLY National Board registered vessels remains an important experiment in Canada. Initially we were excited by this option. Currently our enthusiasm is tempered by a few issues: 1) The price has gone up substantially from the initial $110 to the current $371. This can still be a bargain compared to the cost and delays of CRN registration. 2) TSASK has added a series of restrictions on which vessels this method of registration can be applied to (see chart below). Check carefully, you must pay up front. If your vessel does not match the requirements you do not get your money back. 3) No other jurisdiction has followed along.

Once this program was installed, the volume of work we did with Saskatchewan dropped to about 1/3. It still made sense for companies with standard product lines to get CRNs and not need to register each vessel. This was at the old $110 price. Also, some customer wanted proof that their products were reviewed, which is built into the CRN system. When the additional restrictions were added our volume of work went up, but still not as high as it originally was. People are still using this alternative when they can.

Considering how long Registration takes and how much it cost at many jurisdictions, we need to be doing everything we can to make this CRN system work. This is just one of many experiments we can be trying. We have so much that we need to do, and are doing so little to make things better!

The updated restrictions on using ONLY National Board registration in Saskatchewan

More information: TSASK scroll down to the section on "Exemptions from Registration Requirements of Boiler and Pressure Vessels" and the registration form used.

Original Post (Jan 2012):

1. The boiler or pressure vessel: a. is constructed in strict compliance with the administrative and technical rules of the appropriate section of the ASME code; b. is stamped in accordance with the ASME code with the applicable code symbol stamp; c. is registered with the National Board of Boiler and Pressure Vessel Inspectors (NBBI); d. records the NBBI registration number on the data report required by the ASME code; e. and stamps the NBBI registration number on the nameplate of the boiler or pressure vessel.

To use this registration option as an alternative to the CRN process:

Before a boiler or pressure vessel mentioned above is installed, the owner must submit the data report for registration. The fee for the registration of the data report is $110.00 and shall accompany the data report.

Technical Safety Authority of Saskatchewan

2202 2nd Avenue


Make check payable to: Technical Safety Authority of Saskatchewan

For more information on National Board registration in Saskatchewan scroll down to "Exemptions from Registration Requirements" for New Designs and Other Registrations.

We are PVEng are grateful that Saskatchewan has put the effort into making this alternative to the CRN process available and wish other provinces joined in!

Design Code used in Alterations

Last Updated: Jan 16 2014, SMM/LRB

When registering a vessel alteration, you must use the correct section, edition and addenda of the ASME Code.


According to National Board RC-1020 (Construction Standards), if the "original construction is the ASME Code, repairs and alterations shall conform, insofar as possible, to the section and edition of the ASME Code most applicable to the work planned".

Similarly, CSA B51-03 paragraph 11.1 states, "In all repairs or alterations, the methods employed shall retain the factor of safety determined by the ASME Code section referenced when the unit was first manufactured".


A vessel originally designed to Section VIII-1, 1995 Edition is being modified with the addition of new nozzles. This vessel is already in service and CRN registered. The alteration also needs CRN registration before the work can proceed.

The 1995 VIII-1 edition is no longer in print, but the factor of safety used to calculate the stress values has only changed once in recent times. In the 1999 Addenda to the 1998 Edition, ASME changed the factor of safety from 4 times to 3.5 times, increasing the allowable stress values. In our office we use the stress values from our copy of the 1986 VIII-1 code book to represent pre 1999.

The alteration calculation set only covers the new nozzles. However, shell calculations are also required to run the nozzles, so they are also included. We have a variety of current code design programs to choose from based on current code rules. All offer some way of either lowering the allowed stresses or increasing the factor of safety to match the 1995 values. These programs use current code rules for items like slip on flange weld sizes and custom flange flexibility. The rest of the vessel would not pass these recently updated rules, but that is outside the scope of alteration. The original calculation set still covers the rest of the vessel.


There have been small changes in allowable stresses for some materials from edition to edition not related to the 1999 change in factor of safety. For critical applications photocopies of out of print code books can be purchased from National Board. For example, our copy of the 1971 VIII-1 code cost $591. Order Department: The National Board of Boiler & Pressure Vessel Inspectors, 1055 Crupper Ave., Columbus, OH 43229, P: (614)888-2463, F: (614)847-1147

Getting the original registration calculation and drawing set from the jurisdiction can be very useful. Usually the vessel owner does not own access to this registration information. You have to get permission to access the file from the original owner unless they are out of business. More than half the time the jurisdictions can find the files for registered vessels with better success for more recent submissions.

When the factor of safety on material tension strength was reduced from 4x to 3.5x in 1999, the hydro test pressure was also reduced from 1.5x to 1.3x to provide the same factor of safety during testing. An alteration of a pre-1999 vessel needs to be registered with a 1.5x hydrotest, but the Authorized Inspector on site often reduces it to 1.3x at time of test.

Generic Vessels

File: 4711, Last Updated: April 19, 2013, By: LRB

You Should Be Registering Generic Vessels!

Back in the pre-history* of the CRN system it was recognized that the cost and delay of registration was an unacceptable obstacle to business in Canada. These were the 2 week / $100 days, not our current era. A solution was worked out: jurisdictions could register generic designs.

What is a Generic Design?

A generic registration covers a range of possible vessel configurations in one CRN. Without changing the operating conditions, diameter, wall thickness and material, a huge variety of changes can be made to a vessel. It can be vertical or horizontal. Its length can change within an acceptable specified range. It can have a huge variety of nozzles on the heads and shell. The location and spacing of the nozzles can change. All these changes can be covered in one drawing and calculation set.

ABSA has written a guideline outlining what can and cannot change in a generic design. Reading the ABSA guide is a good start. Also please refer to our Generic Design sample.

The Balance

The designer needs to choose how much to include in the generic design. Not every option can be included; some unusual designs will still have to be registered one off. The number one option for generics is a large range of nozzle designs: configurations, sizes. Note that Alberta restricts the number of variations allowed on each nozzle size. ABSA:

...only one configuration of minimum nozzle neck thickness, minimum internal projection, minimum weld size(s) and added reinforcement shall be permitted [per shell or per head].

The largest problem is normally covering the location and spacing of the nozzles. This is covered in a nozzle spacing table (see our sample job). ABSA again:

Nozzle quantities and positions shall preferably be fixed. If this is not the case, tables specifying the minimum centre-to-centre distance in inches or millimetres between any two nozzles shall be provided.

More time is usually spent on the issue of nozzles than all others combined. Even with these restrictions a huge number of options are possible.

Also typically covered are options like vertical and horizontal mounting, varying shell lengths and varying mounting locations for external equipment. The generic drawing needs to have all the desired options documented.

Getting Registered

The calculation set covering all of the options tends to be long and the matching drawing dense.

The weight of paper of a generic registration is about 2.5x more than a comparable one-off.

We estimate that there is about 2.5x as much work for designer and the reviewer. The jurisdiction reviews often take twice as long. We budget 2x the registration fees.

Using the Registered Generic Design

Once registered, the work is not done. The registered generic drawing is usually too complicated to build from. Usually the fabricator makes a new drawing for each application, which refers to the registered drawing. The Authorized Inspector can verify that the new drawing falls within the scope previously registered and therefore it is acceptable to use the generic CRN number. No new registration is required!

The generic calculation set is reviewed by the shop and Authorized Inspector on a yearly basis, the same as for repeat production of unique CRN designs or regular National Board fabrication. For fabricators outside of Canada, National Board registration is also required on each production batch with vessels destined for Canada.

The cost

The photo here is from a generic registration for seven related vessels differing in diameter. The weight of paper shown is 38.5lbs, representing the mail out after the first province signed off. The total weight of submitted paper is 45 lbs (6.5 lbs per vessel). For reference, a full box of paper with 10 reams weighs 49 lbs. The registration process Canada wide took about one year. Registration fees totalled $16,800 (or $2400 per vessel), higher than would be expected for a series of related one-off designs. If these were not generics, the total weight would be around 15 pounds and the expected total review time about half a year.

Fabricators located outside of Canada still have to pay the National Board registration fees on each batch produced. This batch of 7 vessels can be National Board registered for $128 (cheaper if you file electronically). There is no registration delay with National Board.

The Benefit

Once the cost and delay of the first registration process is covered, the remaining production costs and times are the same as for vessels sent to countries other than Canada. Production can continue until the code changes or the manufacturer updates their design. Recent B16.5 flange weld size and Appendix 2 flange flexibility updates are examples of code changes that could lead to design changes ultimately leading to the need to update the generic design.

A Return to Sanity

Yes the process is long and expensive, but picture the upside - once complete you have a series of vessels that can be built the same as if the CRN system did not exist and Canada was only part of National Board. Future registration costs and delays - an unknowable variable - have been removed. Your designs have been locked down because different reviewers with differing requirements will not be looking at each job you are building. More companies should seriously consider generic registrations.

*The pre-history of the CRN system as used here is defined as the time before PVEng started up in 1999, but in this case it predates the spinning off of the safety organizations like ABSA and TSSA from their parent government departments in the mid-1990s.

Nozzle-Pro and CRNs

PVE-5522, Last Updated: May 22, 2014, By: LRB

Can I Use Nozzle-Pro for a CRN submission? Quick Answer: No.

FEA made easy
We love this program but we are not allowed to use it as often as we would like to.

Although Nozzle-Pro is a very good design tool for the use of designing pressure vessel nozzles and beyond, it does not follow one of the multiple finite element analysis standards recently required in various Canadian jurisdictions. Currently there are five different pressure vessel FEA guidelines in Canada. It would not be feasible to make a program like Nozzle-Pro meet all the different requirements.

We like using Nozzle pro for the project design phase, but when CRNs are involved, we remove the results from the final calculation package. Sometimes we can get the less accurate but more familiar WRC 107/297 methods to show a pass after we are done with Nozzle-Pro. These results are what get submitted to the jurisdictions. If the Nozzle-Pro results are required for the submission package, they have to be replicated in standard Finite Element Analysis packages with the report tailored to the reviewing jurisdiction.

Caution: Some reviewers require physical testing such as strain gauging to prove an FEA. See Evolving Acceptance below.

Finite Element Analysis - Evolving Acceptance

File: 3783, Original Post: June 7 2012, Last Updated: May 22 2014, By: Laurence Brundrett

Update Aug 2015

This article was originally written in 2012 because it became very difficult to use FEA to register fittings and vessels. The primary location not accepting FEA was Alberta, but with designs needing to be registered Canada wide, its usefulness became limited. We could only use FEA to prove the cycle life of vessels, not the structural integrity.

Three years later we note a counter change where FEA is being accepted for not just the proof of cycle life but ALSO proof of structural integrity in both vessels and fittings. The primary catalyst is the change in a number of personnel at ABSA, along with ABSAs increasing use of reciprocal registration, whether based on code calculations or FEA. Even without reciprocal registration, ABSA has been accepting FEA to prove items not covered by code rules. See individual updates below.

Original article last update May 2014

A product was successfully registered across Canada using FEA as the design basis. One year later FEA was again used as the design basis to register additional similar designs. FEA was used in both cases on the grounds that code rules do not cover its design. This time FEA was not accepted as a design basis in 2 provinces. What changed?

Green - as built and proven by FEA, Red - an analysis was required by two Canadian reviewers for a lower operating pressure. By removing the reinforcing from the scope of analysis standard code rules could be applied. Unfortunately this simplification reduced the allowed operating pressure to one half. FEA proved that the reinforced design was acceptable as with previous submissions, but the use of FEA was not allowed in all Canadian provinces. This varies by reviewer and by province.

The criteria of when FEA is acceptable have changed with some reviewers in two of Canada's provinces. The old criteria: Code rules do not cover design therefore use FEA or other methods like Burst testing to prove the design. Here is the interpretation from ASME:

Interpretation: VIII-1-01-12

Subject: Section VIII, Division 1 (1998 Edition, 1999 Addenda); U-2(d), UG-19(b) and (c), UCI-16, and UCD-16

Date Issued: December 5, 2000

File: BC00-131

Question: If there are no applicable Code rules in Section VIII, Division 1 for the design of a vessel or vessel part, may a finite element analysis be performed in lieu of a proof test?

Reply: Yes, see U-2(g).

New emerging criteria: code rules do not cover the design as manufactured; however, code rules can be made to apply if we pretend that material is removed from the product. In the above example, the green shape is the product as built. If we pretend that material is removed, the red shape emerges and the design can be analysed using standard code rules. (Because code rules can be applied this way U-2(g) is no longer necessary. By this logic FEA and Burst testing is not allowed.) Appendix Y can now be used on the flange without reinforcement and UG-34 for the now flat unreinforced head. The FEA rating was used in most provinces except two where a much lower calculated rating was used.

Update Aug 2015: With changing personnel at ABSA, this requirement has changed. There will always be times when weird things have to be done to a design to get a CRN, but this case was extreme, and now it is becoming rare.

Back to ASME:

Interpretation: VIII-1-98-116

Subject: Section VIII, Division 1 (1998 Edition, 1999 Addenda); UG-34

Date Issued: June 13, 2000

File: BC00-l55 [BC00-267]

Question: Does Section VIII, Division 1 permit the use of stiffeners in the design of unstayed flat circular heads, bolted covers, or flanges?

Reply: Yes, provided the requirements of U-2(g) are satisfied

Code interpretations cannot always be used in Canada to support your design case. They did not work this time. See below for comments on one province that does not always accept interpretations.

Code Cases

Aug 2013 Addenda:

When can Finite Element Analysis (FEA) be used? In our experience FEA can always be used to validate the cycle life of a product - in many cases this is the only way possible. Depending primarily on the reviewer, FEA can sometimes be used to justify the design of vessel or fitting features that are not covered by code books. This original post covered a case where the reviewer did not allow it for features not in the ASME code books. We also encounter cases where FEA is allowed, but its use is restricted to one time use only - no repeat production of identical units are allowed. The rejection of the use of FEA is on the rise - it is worth considering whether your product can be redesigned for the Canadian market to avoid the need to use FEA for other than cycle life purposes. If you must use FEA for pressure boundary design, try to get your jurisdiction to sign off on its use in advance. Update Aug 2015: we find that increasingly FEA is allowed to be used to prove that designs are acceptable when code passages covering the design are not available.

Will validation be required? In our experience, validation is never required if the FEA is only used to predict the cycle life. Some reviewers require validation if pressure boundary components are designed using FEA. Ideally, a CRN is applied for and issued prior to fabrication, but in this case the actual issuing would not happen until the reviewer accepts the validation results - after construction is complete. Not all reviewers require validation.

Update Aug 2015: Reviewers are rarely asking for validation, but it still happens and occasionally extreme validation is required: For a range of closures a jurisdiction asked for each size to be run by FEA (usually only some sizes representative of the range need to be run). One burst test must be done to validate a matching FEA run, and the FEA must predict the burst test pressure! So the requirements for using FEA are still not always consistent, but it is better than the alternative offered by the jurisdiction: burst test every size of closure!

Validation of a FEA model is done by strain gauge or displacement measurements. Testing is usually done during the hydro test at regular hydro test pressures - there is no need to destroy a product as you would with UG-101 burst testing. Additional FEA run(s) are required to mimic the hydro test conditions and predict strain or displacement results under hydro test.

There will be some variation between the FEA prediction and the test results. Our experience shows that locations with simple geometry like centers of heads and straight shells should provide strain gauge results within a few percent of the FEA predictions. Areas with complex geometry are extremely hard to gauge well and cannot be expected to match. Unfortunately, these are the areas that we are most interested in. There are no acceptance criteria on test results - you have to work out what is acceptable with your reviewer.

Past and Present CRNs

File: 3783, Last Updated: June 7, 2012, By: LRB

Q: I registered a part last year without any problem. Now the jurisdiction will not allow the same design method on a similar part. Should I reference my previous design as proof that the design is in use and safe?

A: No. Customers have lost registrations doing this. The reviewer can revoke the past registration stating that it was originally made in error. It is best to leave existing CRNs alone.

Q: I started my registration process in province X, now province Y says that the original review by province X overlooked important issues and is sending a letter to the original reviewer. What should I do?

A: Don't panic. If there is a real problem, be grateful that it has been found. Most of these complaint letters are coming from one province, and most reviewers in other provinces are just ignoring them. Experienced CRN applicants do not send proof of registration to certain provinces.

Q: My registration bill is four times higher than the last time for a similar design. What can I do to get this fixed?

A: Registration fees vary most by reviewer and secondly by Province. The leading cause of an increase in billing is a change of reviewer. Be cautious about complaining - some jurisdictions will re-review design files on receipt of a complaint. This can result in finding new design issues causing the immediate cancellation of the registration number. You now have more design work and further invoices.

Maximum Allowable Working Pressure

File: 3783, Last Updated: June 7, 2012, By: LRB

Design Pressure vs. Maximum Allowable Working Pressure (MAWP) Alberta (ABSA) and Saskatchewan (TSASK)

Typically when doing calculations for pressure vessels you start with a set of design parameters to determine your vessel characteristics. The design pressure, temperature, corrosion allowance and several other factors contribute to the calculations, affecting the wall thickness of the shell, heads and nozzles.

For example, you may have a design pressure of 150 psi with a temperature of 400° F, and no corrosion allowance. This is on a 20" carbon steel vessel with the shell made from SA-106 B pipe. You select 20" SCH 10 (0.25" wall) because it exceeds the thickness required by the calculations (0.154" wall), and it's a readily available material. For this scenario, we will ignore all other components, so the MAWP of the shell is 320 psi.

Most of the time you are able to list the Design Pressure as 150 psi and the MAWP as 320 psi. However, Alberta has a clause in AB-516 Rev. 3, 2011-08-22 that does not permit this. Section 15(2)(b) Calculations states the following: "The pressure used in the calculations must be equal to or greater than the MAWP to be marked on the vessel nameplate and manufacturer's data report. A lower pressure which must be met for process conditions must not be used in the calculations."

In our example, we have two choices:

Either method will be accepted in both Saskatchewan and Alberta.

So you can either rate your vessel's MAWP to be the same as the design pressure as in the first method, or you can run calculations at the higher pressure of the MAWP and then list the MAWP as both the Design Pressure and MAWP. The choice is yours, but you must abide by one of these methods in order to obtain a CRN in either Alberta or Saskatchewan.

Note: The MAWP from the calculation could be 320.8 or some other number as long as it is higher than the MAWP reported on the nameplate and drawing. Do not use decimal precision numbers for the MAWP on the nameplate or drawing. For example if your design program returns a MAWP of 320.8psi, you could re-run the design at 320.0 psi and declare that 320.0 is the MAWP even though your design software will report a slightly higher number. The design pressure and MAWP on your Alberta or Saskatchewan destination vessel will be the same number.

According to ASME Section VIII Division 1, the definitions for Design Pressure and MAWP are as follows:

Design Pressure - "The pressure used in the design of a vessel component together with the coincident design metal temperature, for the purpose of determining the minimum permissible thickness of physical characteristics of the different zones of the vessel. When applicable, static head shall be added to the design pressure to determine the thickness of any specific zone of the vessel."

MAWP - "The maximum gage pressure permissible at the top of a completed vessel in its normal operating position at the designated coincident temperature for that pressure. This pressure is the least of the values for the internal or external pressure to be determined by the rules of this Division for any of the pressure boundary parts, including the static head thereon, using nominal thicknesses exclusive of allowances for corrosion and considering the effects of any combination of loadings listed in UG-22 that are likely to occur at the designated coincident temperature. It is the basis for the pressure setting of the pressure relieving devices protecting the vessel. The design pressure may be used in all cases in which calculations are not made to determine the value of the maximum allowable working pressure."

In the document AB-516, ABSA defines maximum allowable working pressure (MAWP) as "the pressure authorized on the design registration or a lesser pressure as indicated on the manufacturer's data report. MAWP is the highest pressure at which the equipment may be operated at its design temperature. MAWP is measured at the top of the vessel in its operating position."

Another similar term commonly used is maximum allowable pressure (MAP). This refers to the maximum pressure in the new and cold condition. It does not take temperature effects or corrosion into consideration and therefore cannot be confused with MAWP or Design Pressure. It is best to avoid referring to this when submitting designs to Alberta or Saskatchewan.

As an example of the differences between Design Pressure, MAWP and MAP, we have run a set of calculations in Compress using the design conditions stated earlier. From the Pressure Summary output you can see that the Design Pressure is the same for every component (150 psi), however the MAWP and MAP are considerably higher.

The lowest MAWP for these components is 182.46 psi (rated at 182 on the drawing and nameplate), therefore the MAWP of this design is 182 psi. In this case the MAP and MAWP are the same for most of the components. This is mostly due to the fact that there is no corrosion allowance. Only the nozzles N1 and N2 have different values for MAWP and MAP. MAWP is in the hot and corroded condition while MAP is in the cold and new condition.

In most normal circumstances, such as our example above, the Design Pressure is lower than the MAWP. Typically a specification sets the Design Pressure based on the function of the vessel. The calculations are then run using this pressure, and the MAWP is derived from the calculations by taking the maximum pressure from the lowest rated component in the vessel. The vessel can be used up to the MAWP. This is the reason the ASME nameplate in Section VIII-1 depicts the MAWP instead of the Design Pressure.

As mentioned previously, in Alberta and Saskatchewan you cannot use this practice. You must have the Design Pressure set equal to the MAWP.

Registration of Fittings - Changes Since 2005

PVE, Last Updated: October 7, 2011, By: LRB

The requirements to register fittings have changed significantly. Around late 2004/early 2005 we started getting phone calls from companies having difficulty renewing their CRN registrations in various Canadian provinces. We started doing calculations and drawing sets to get lines of valves, sensors and other pressure products registered. Prior to this time we did almost none of this type of work.

What had changed? Why did these manufacturers need engineering help now, and not before? The manufacturers were providing the jurisdictions what they had always provided: signed statutory declarations; a copy of their product catalog; and a copy of their ISO or other QC certificate. But no longer was this enough to get their products registered. They now had to send in additional proof of burst tests and/or calculations along with detailed product drawings - the same requirements as if they were registering a pressure vessel.

The 1997 B51 standard outlined the requirements to get a CRN for a fitting (B51 - 4.2.5): As a minimum the following documentation in support of an application is required:

By the 2009 edition, the list had changed slightly but not significantly. The Canadian code had not changed; the jurisdictions decided it was time to enforce it.

Prior to 2005 CRNs were routinely being issued without items (vi) and (vii) above. It was so easy that the services of a company like ours were not required. As we did more fitting renewals, we found that there had been an earlier even easier registration method - submit a statutory declaration and a catalog (without proof of the QC program). The original intent of the statutory declarations became apparent - the manufacturer was swearing that the QC program and the calculations existed, but were not including them in the registration package. Companies still have to fill out statutory declaration forms, but their purpose is no longer to declare that the missing information exists - all information must be provided.

This change in requirements caused significant difficulties for some manufacturers as widely used clauses such as B31.3 304.7.2(a) - extensive successful service -were no longer acceptable. Other difficulties included providing material specifications acceptable under B31.3 323.1.2 and getting previously run proof tests accepted under the requirements of Section VIII-1 UG-101. We also believe that some companies were declaring that non-existent calculations or proof tests existed.

The changes resulting from this are twofold: 1) - some products that were previously registered in Canada are not being renewed; and 2) those that are being renewed are being done at a much higher cost. Manufacturers are now spending $10,000 to $50,000 to register a few pages out of a catalog which had previously been completely registered for $3000. The review times are also much longer. It is not unreasonable to budget one year to do the calculations and get Canada wide registration of a series of fittings.

It will be a few more years before all fittings registered under the old methods expire upon their ten year anniversary. At that point will Canada have the world's safest pressurized equipment or will we be trying to cobble together marginal systems from a selection of available parts that is too small?

Registration of Plastic Fittings

PVE-5246, Last Updated: June 17/11, By: LRB

FEA of Plastic Valve Body Plastic pipe that needs to be registered can be calculated to code rules found in B31.1 or B31.3. But a plastic pipe needs plastic fittings - how can they be registered? Plastic fittings are among the most difficult to get registered under the CRN system.

Burst Testing:

The good news is that TSSA has a standard to cover the burst test pressures used for unlisted materials (like plastics):


Burst test factor of safety from the guideline (Appendix D):

The bad news is that it is very hard to get a reviewer, even one from Ontario to accept the factors listed. Although moulded plastic parts are made with automated processes justifying a 4x factor, we invariably end up having to use a 10x factor. However we have seen rare cases where 4x has been allowed on moulded parts in Ontario. See more on CRN burst test problems here.

When more than one grade of plastic is used, each grade needs to be tested. That, combined with the need for conservative safety factors can make using burst testing unacceptable.


B31.3 provides allowed stress levels for calculating plastic fittings. B31.3 Table B-1 and B31.1 table III-3.2.1 provide HDS allowed stress levels for many common plastics. The Plastics Piping Institute has a larger list of HDS values here. Where the B31.1/31.3/PPI listings overlap, identical HDS values are provided. Most reviewers Canada wide allow the PPI values of HDS to be used with the occasional exception of some Alberta reviewers.

With an allowed HDS, the fitting can be calculated either by using standard code rules or as shown in the illustration above, by FEA. Simple or complex fittings can be registered at a higher operating pressure than would be allowed by burst test. When more than one grade of plastic is used, only the weakest has to be analyzed.

Registering Steam Heated Molds

PVE-5242, Last Updated: June 17/11, By: LRB

Photo of Steam Heated MoldIn some provinces, heated molds need to have CRN registration. For example, steam heated platens and steam heated cavity molds need CRNs in Ontario. Tire molds with steam cavities are registered in Quebec. Each province has its own requirements - contact your local jurisdiction.

A designer of a mold or platen would not normally consider the pressure vessel design rules unless specifically required to do so. The primary stresses in the mold normally come from the use of the mold, not from the steam in its heating passages.

VIII-1 U-l(c)(2) Based on the Committee's consideration, the following classes of vessels are not included in the scope of this Division... pressure containers which are integral parts or components of rotating or reciprocating mechanical devices... where the primary design considerations and/or stresses are derived from the functional requirements of the device.

I interpret this passage to mean that you can use the code rules to design these items if you like, but don't be surprised if the most important loads and stresses in your device are not pressure related. Design to code rules only could prove inadequate.

The registration process:

Tire molds have more complex internal cavities that require more difficult calculations. The calculated code stresses from internal pressure usually end up being a small fraction of the stresses that the mold experiences during operation.

Solid model of a rectanglar steam heated mold.
Registering a steam heated mold shown first as a mold, the passages in the mold, and finally passages modeled as pipes using available material. The equivalent pipes and intersections are calculated to piping code rules.

Moving or Changing Your Company Name?

PVE-4045, Last Updated: May 26, 2014, By: LRB

Overloaded MuleQ - If your company changes name or address, do you need to update the registration of your fittings?

A - Yes.

In Canada, fittings are considered to be small pressure vessels with the permission for inspection granted to the manufacturer under the control of the manufacturer's quality control program, as specified and sworn in the statutory declaration. When the companies name or address changes, the statutory declaration on file with the provinces is no longer valid. The statutory declaration for each CRN in each province needs to be updated.

Changing the brand name to be affixed on the product is another case where the statutory declarations need to be updated. This case is not discussed below.


The following is required to update the CRN applications:


Step 1 - get the original jurisdiction that did the first registration on the original CRN to update the CRN using the above listed materials.

Step 2 - included a copy of the updated CRN from step 1 with the above listed materials and send it out to all other jurisdictions.

Additional Information from ABSA:

The following clarification was received from ABSA regarding moving a company manufacturing fittings and vessels.

1. If a fabricator changes the name of the company, what is involved with updating the paperwork at ABSA?

2. Can a company own a CRN on a fitting or vessel and have multiple fabricators manufacturer the design for them? Assuming valid QC documentation and Stat Decs (fittings only) for each fabricator.

3. Can ownership of a CRN be purchased by one company from another?

Costing and Timeline:

For our job where the brand name to be affixed to the product needed to be updated, the re-registration process took about the same amount of time as the first submission with design review - 8 weeks for Canada wide. The renewal fees at about $2000 came in at 85% of the original registration cost. The product was registered Canada wide both times, except for BC and Saskatchewan where it was exempt from registration.

Update CRN for Flange Welds

File:PVE-4711, Last Updated: Jan 11/2011, By: LB

ASME changed the amount of weld required on a standard B16.5 slip on flanges with the 2009 VIII-1 code update. Per section UW-21 of VIII-1 all standard slip on and socket weld flanges need larger welds on the outside. The larger weld size is not required if there is no room for it on the hub.

UW-21(a) ASME B16.5 socket weld flanges shall be welded to a nozzle neck using an external fillet weld. The minimum fillet weld throat dimension shall be the lesser of the nozzle wall thickness or 0.7 times the hub thickness of the socket weld flange. See Fig. UW-21, illustration (4). UW-21(b) ASME B 16.5 slip-on flanges shall be welded to a nozzle neck using an internal and an external weld.See Fig. UW-21, illustrations (1), (2), and (3).
VIII-1 Fig UW-21 - flange attachment weld size

The weld size change is mandatory, but do you need to update your CRN? That depends - at the present time Manitoba and Saskatchewan say yes, Ontario says no. We will be adding more jurisdictions as we find out.

Province Update CRN? More Information
Ontario No Will be posted on TSSA's web site
Manitoba Yes  
Saskatchewan Yes  

ABSA - Impact Test Information on the Drawing

File:PVE-4711, Last Updated: Aug. 03/2011, By: LB

ABSA requires impact test information to be put on fabrication drawings whenever impact testing is a requirement of the design. This is information that is not usually put on a drawing, but if it is left off, the ABSA review process will be put on hold until it is added.

From ABSA's web site:

Identify which pieces of material must be impact tested and the temperature(s) at which the impact tests are conducted.
Identify whether production impact tests must be conducted for specific welds and the temperature(s) at which the impact tests are conducted.
For materials not impact tested, identify, by reference to the correct Code paragraph, the reason why this material is not being impact tested.**
It is highly preferable that the acceptance criteria (absorbed energy values or lateral expansion) for the impact tests be identified on the drawing since these change with material thickness and strength level.
This information is required to be on the Manufacturer's Data Report and must be communicated by the designer to the shop in some fashion. The means of communication might be notes on the drawing, separate instruction sheets that are referenced on the drawing (and submitted to ABSA with the drawings) or some equally positive means.

** This is also a requirement for all vessels that do not require impact testing, for all jurisdictions in Canada

Why ABSA Cares

Daily Avg Temp at Fort McMurray

As mentioned above, ABSA has stricter drawing requirements for minimum temperature information than other provinces, and reviews minimum temperature calculations in more depth. The graph above shows why. Fort McMurray winter air temperatures drop to negative 40 degrees C (also -40 degrees F).

Should You Care?

Assuming your vessel is not headed for Alberta, should you care about this? An actual example from our jobs: We designed a pressure vessel with a SA-350 LF2 class 1 forging greater than 3" thick. The vessel was designed to -20 deg F. LF2 material comes from the mill already impact tested to -50 deg F. - therefore it meets the code requirements - or does it?

SA-350 LF2 Class 1 material is impact tested to -50 deg F. The average minimum absorbed energy for three test specimens is 15 ft-lb, the minimum absorbed energy is 12 ft-lb (15 avg, 12 min). The minimum yield strength of the material is 36 ksi. Per Fig UG-84.1 The required average impact test requirements rises from 15 to 18 ft-lb because the material is greater than 2 inches thick. The minimum required is 2/3 the average or 12 ft-lb (18 avg, 12 min).

Fig UG-84.1
Fig UG-84.1 for SA-350 LF2 Class 1 material

The test requirement from the SA-350 standard is no longer adequate! However, this portion of the code has gone through many revisions and updates which have disguised the intent of the rules and left us only with a mess of code passages to follow. Note c on the bottom of figure UG-84.1 exempts this material from the requirements of figure UG-84.1. So the material tested to the SA-350 standard is acceptable!

We can hope for code rules that make sense, but instead with each revision we get more rules that contradict and confuse. How does your company deal with this tortured mess of requirements? Putting the impact absorbed energy requirements on the drawing is one way to make sure that the code requirements are considered during the design cycle and met during production.

Will I Need to Renew My CRN?

File: 4711, Last Updated: Jan. 24, 2013, By: LRB


CRNs for fittings expire after 10 years. If the registration is not renewed, no new pressure vessel or piping designs can be registered that use it, however end users keep using the same fittings and ordering spare parts and replacements for existing systems, even though the CRN is no longer valid.

The CRNs for fittings expire because provincial registration requirements vary vastly with time. Companies currently re-registering fittings (registered before 2003) now have to supply engineering proof that the design is safe, whereas before 2003 a statutory declaration, proof of QC program and a catalogue were often sufficient. When fittings currently being registered expire in 10 years, the requirements might be different again.

If a fitting is registered in one province one year it will be valid in that province for 10 years from the approval date. If the same fitting is registered in another province at a later date, it will expire at the 10th anniversary of the registration in the first province, not at the anniversary of the subsequent provinces.

Registrations of fittings shall be resubmitted for validation not more than ten years after the date of acceptance by the regulatory authority in the original registering province. (CSA B51-09 4.2.1)

Pressure Vessels and Boilers

Pressure vessel CRNs do not expire. The manufacturer can make as many copies of the design as they want without re-registering. If the code of design changes like the change from TEMA to UHX on heat exchangers, then the manufacturer will need to re-register the design to continue production. Similarly the change from 1998 to 1999 material strength changes required re-registration if the manufacturer wanted to take advantage of the allowed higher stress levels.

The pressure vessel calculations need to get reviewed yearly by an authorized inspector to check for compliance to the current code, the same as under a National Board registered production.

Any number of boilers, pressure vessels, fittings, fired-heater pressure coils, and piping systems may be constructed from a registered design until a change in the applicable Act, Codes; or Standards invalidates the design, in which case the design shall be obsolete and no further construction to the design shall be made after the effective date of the change as established by the Act. When the Act does not specify an effective date of change, the effective date shall be the date specified in the changed document or six months from the published date of the change, whichever comes first (CSA B51-09 4.1.2)

Piping Systems

Piping systems need to be re-registered for each installation unless it is a duplicate installation at the same address. If you are making multiple copies of skids, see if you can register your piping system as a fitting instead (it will need to be less than 1- 1/2 cuft for the whole piping system). If so, you can avoid having to register each item sold. Many duplicate machines classify as piping systems and need to be registered each time they are sold even though they are identical. Note that B51-09 4.1.2 (quote above) says that the manufacturer can make as many copies of the piping system as they want; the provinces require the piping installation address as part of the registration making this impossible. For example see TSSA) and ABSA.

Update on Piping Systems - Jan 2013

Due to ongoing registration problems with designs that are built multiple times and piping systems often on skids that need to be moved, the jurisdictions are working on various solutions. At this time none of this is finalized, but the following preliminary information is available: Ontario is working on Standard Piping registrations which will allow the piping system to be built more than once without need for re-registration, and/or allow the finished piping system to be used at more than one address. Saskatchewan will require the piping system to be registered for each address it will be used at. ACI is allowing piping systems over 1.5 cuft to be registered as Category H fittings which will allow them to be built multiple times or moved after installation.

Using Fittings in Vessels and Piping

File: n/a, Last Updated: Dec 13/2010, By: LB

Under the B51 program fittings need to be registered before they can be used on pressure devices. However, fittings on pressure vessels are exempted from requiring registration by B51-09 clause 4.2.1:

Fittings shall be registered in accordance with Clauses 4.2.2 to 4.2.9 unless they form a part of a boiler or pressure vessel that is subject to inspection by an authorized inspection agency. Registrations of fittings shall be resubmitted for validation not more than ten years after the date of acceptance by the regulatory authority in the original registering province or by a nationally recognized organization as specified in Clause 4.2.3.

In practice, all fittings on pressure vessels need to be registered except those listed in VIII-1 UG-44:

UG-44(a) ASME BI6.5, Pipe Flanges and Flanged Fittings [see UG-ll(a)(2)] UG-44(b) ASME B 16.9, Factory-Made Wrought Butt welding Fittings UG-44(c) ASME BI6.1l, Forged Fittings, Socket Welding and Threaded UG-44(d) ASME B16.l5, Cast Bronze Threaded Fittings, Classes 125 and 250 UG-44(e) ASME BI6.20, Metallic Gaskets for Pipe Flanges - Ring-Joint, Spiral-Wound, and Jacketed UG-44(f) ASME B 16.24, Cast Copper Alloy Pipe Flanges and Flanged Fittings, Class 150, 300, 400, 600, 900, 1500, and 2500 UG-44( g) ASME B 16.42, Ductile Iron Pipe Flanges and Flanged Fittings, Class 150 and 300 UG-44(h) ASME BI6.47, Large Diameter Steel Flanges, NPS 26 Through NPS 60

All other fittings will need registering. This exemption is applied to both ASME "U" vessels which are inspected by an authorized inspector and "UM" vessels which are not inspected by an authorized inspector. This exemption also applies to fittings which include any of the above.

In contrast B51-09 clause 8.2 demands the registration of fittings on piping systems:

Fittings used in piping systems shall be registered in accordance with Clause 4.2.

So these same fittings that are exempt on vessels which might be inspected by an authorized inspector are never exempt on piping systems that are always inspected by an authorized inspector. This made no sense to us so we made up a diagram to help illustrate:

The red items need registration*, the green items do not. Sense or nonsense, these are the rules as they are currently written and applied in Canada.

* Many of these fittings do not need to be registered for use in Saskatchewan or British Columbia (more here: Fittings).

Registering B16.9 Fittings

File: n/a, Last Updated: Dec 13/2010, By: LB

B16.9 fittings (elbows, tees, crosses, reducers, caps and stub ends) must be CRN registered before they can be used in Canadian CRN registered piping systems*. The 2009 B51 standard introduced a simplified approach to registering fittings found in table UG44 of the VIII-1 code book. B16.9 Fittings are one of these components in table UG-44:

At a minimum, the following documentation in support of an application for a new design registration or a reregistration shall be required: (a) for new applications for fittings that are built to a nationally recognized Standard (e.g., as listed in paragraph UG44, Section VIII, Division I, of the ASME Code or Table 326.1 of ASME B31.3) that specifies the dimensions, construction, materials, pressure/temperature ratings, and identification markings of the fittings (B51-09 4.2.6(a))

These components have a simplified registration process requiring only 3 items:

This would work for B16.5 flanges where the dimensions, materials and pressure temperature rating are fully specified by the B16.5 code. Likewise other fittings listed in UG-44 are also fully specified by the design standard so there is nothing for the manufacturer to design. The problem is that ASME Standard B16.9 does not specify wall thicknesses, so this simplified registration process cannot be applied.

The design of fittings shall be established by mathematical analyses (e.g. ASME B16.49 for bends) contained in nationally recognized pressure vessel or piping codes or at the manufacturer's option by proof testing in accordance with section 9 of this Standard. In order to meet design or manufacturing requirements, it is expected that some portion of formed fittings may have to be thicker than the pipe wall with which the fittings is intended to be used. The mathematical analyses, if used, may take into account such thicker sections. Records of mathematical analysis and/or successful proof test data shall be available at the manufacturer's facility for inspection by the purchaser. (B16.9-2001 Section 2.2 "Design of Fittings")

The user of a B16.9 fitting calculates its pressure rating as an equivalent piece of straight pipe. The manufacturer of the fitting has to provide proof that the fitting is the same strength as that straight pipe. A longer registration process is required:

	(B51-09 4.2.6(b))

Once the manufacturer provides this proof, along with other provincially required paperwork to each jurisdiction and gets the registration back, then the B16.9 fittings can be used in registered Canadian piping systems.

*B16.9 fittings do not need to be registered for use in Saskatchewan or British Columbia (more here: Fittings).

We Don't (Usually) Register Actuators

File:PVE-4711, Last Updated: Dec 3/2010, By: LB

We often get asked to register valve actuators, but usually we don't do it for a couple of reasons...


It is not possible to get many actuator designs to pass the ASME code rules which would be required for registration. For starters, picture this actuator being redesigned to use B16.5 flanges instead of its stamped steel flanges integrated into the housing. Not that there is anything wrong with this type of design, it just is not the way we usually design code pressure parts.

There is a class of actuator that has the piping system pressure on one side of the diaphragm. These actuators do need to be registered, which means that the actuators need to pass code rules.

Some valves have built in regulators where the housing for the regulator is the same part as the valve body. The stresses from the regulator need to be included with the stresses from the valve when the this type of valve is analyzed.

ASME VIII-1 - the bible of pressure vessel design - states this about the design of actuators:

U-l(c)(2) Based on the Committee's consideration, the following classes of vessels are not included in the scope of this Division; however, any pressure vessel [or actuator] which meets all the applicable requirements of this Division may be stamped with the Code U Symbol:
U-l(c)(2)(c) pressure containers which are integral parts or components of rotating or reciprocating mechanical devices, such as pumps, compressors, turbines, generators, engines, and hydraulic or pneumatic cylinders where the primary design considerations and/or stresses are derived from the functional requirements of the device;

Or to paraphrase ASME - you can use pressure vessel rules to design valve actuators if you want, but because the primary loading is from the force on the valve stem, the use of only code rules in the design of actuators will probably not be adequate.

CRN Rules:

The actuator on a valve is not part of the piping system for the fluid that the valve is regulating. It is part of the instrumentation piping system. These piping systems are usually small diameter and contain air. Each province has its own piping rules, but most do not require registration of small diameter air piping systems. For example in Ontario any air line 3/4" diameter or less does not need registering. (See piping charts for all provinces here ). An actuator is a fitting attached to a line and a fitting does not need registration if the line that feeds it does not need registration. Similar exemptions usually can be found for hydraulic actuators.


There will always be exceptions, occasionally your actuator will need registering, but most of the time it will not. Also, the valve might still need registering even if the actuator does not.

Code Updates

File:PVE-4711, Last Updated: Nov 17/2010, By: LB

It's that time of year again. The weather is getting colder, Christmas displays are in the stores and pressure vessel engineers are thinking about code updates.

Under National Board registration, a manufacturer will create a production drawing and state "latest code and addenda" under the code conditions block. A calculation set will be made to the current code and addenda. Copies of the vessel can be manufactured for the rest of the calendar year. After the year end rolls around one of two things happens. Either the code calculations are re-run (easy to do with commercial software) or the calculation set is reviewed and signed off that no code changes affect the calculation set. Production continues for another year. The drawing does not get updated until a code update forces a design change or some manufacturing detail changes.

Those familiar with the CRN system will realize that we crazy Canadians have succeeded in making this simple process more difficult and more expensive. In Canada we do not allow the words "latest code and addenda" on pressure vessel drawings when they are being registered. When the vessel is submitted for CRN registration, the drawing states an actual year and addenda. The calculation set is also done to the same year and addenda. After getting a CRN, non-Canadian manufacturer often revise the drawing set to show "latest code and addenda" so that the drawing does not need to be unnecessarily updated every year.

If the vessel is registered in one province in one year, and then the manufacturer wants to register it in another province in a later year, then the calculation set needs to be updated. The drawing no longer matches the calculation set so it needs to be updated. The updated calculation no longer matches the one registered with the first jurisdiction. Two choices are available: 1) update the registration with the first province, then register in the second - the CRN number is the same in both provinces - or - 2) Get a new CRN number in the second province. The vessel will end up with two CRN numbers. This becomes a nightmare if the vessel ends up in a province that does not match the CRN number on its nameplate (think shipping a vessel to a customer in one province who puts it on a skid and ships it on to a different province).

I have been told that the jurisdictions have been trying for years to work around this unnecessary and expensive complexity. For now we wait.

Comments on AB-520

File:PVE-4711, Last Updated: Jan 3/2010, By: LRB

We came across ABSA AB-520 the usual way. We submitted a job with a bunch of FEA reports and were told that ABSA now had an FEA guideline and we would have to re-do and re-submit our work. Unlike other times our work was rejected for undocumented reasons, this time was different... the guideline was in writing. AB-520 started its first couple of years as an anonymous document. It was quickly adopted by other provinces as an unofficial guide to how to do FEA. A couple of years later it was reformatted a bit and officially released as AB-520.

Because of the way it was introduced to us, we did not like it at first. We did however learn to work with it and the difference can be seen in our reports. We accept that this is an improvement in how FEA reports are done, but AB-520 still leads to confusion when we submit reports for ABSA review. One example, the article states:

The following figures must be presented (coloured prints): 4) Plot with element stress and compare nodal (average) stress vs. element (non-averaged) stress (If the small difference is less than 5%, the accuracy should be OK);

We have always taken this to mean that we should show an error plot and the error should be less than 5%. This is good and easy to include in the report. What the article does not mention is that in areas of surface contact reported errors will be above 5%. Sharp corners have theoretically infinite errors. We often explain this, and point ABSA reviewers to our articles on this effect. (More information on this topic can be found here hereand here. This standard is written by reviewers to make the review process easier which is very important. However, it is not written by FEA users who know what can and can not be done. If we knew that the original release was going to be revised and officially released later we would have liked to made a few suggestions. There is still time to make changes before it gets added to a national standard like CSA-B51 and improvement becomes impossible.

This guide would be better if it did what ASME does in some of the better areas of the pressure vessel code - include an example of what is considered to be good work or good method. Under current practice ABSA reviewers are asking for many incremental re-writes of reports. Samples of good working practice could reduce this.

As a postscript, AB-520 now has a partner. ACI has produced their own FEA guideline that is completely different from AB-520. We are now in the process of re-writing reports done to AB-520 to meet the ACI guidelines. Although we have confidence that we can create reports that can harmonizing the two standards, this requires more flexibility from review engineers than is sometimes given. Let's hope no other provinces come up with additional FEA guidelines in the future.

Code Cases and Interpretations in Alberta

File:PVE-4340, Last Updated: Oct 6 2010, By: LB

Alberta does not automatically accept either ASME code cases or Interpretations. See Alberta document AB-51 page 23:

Interpretations and code cases are not part of the code, and are not automatically adopted for use in Alberta. Use of interpretations and code cases may be accepted on an individual basis upon application to ABSA. Check with ABSA Design Survey before attempting to apply interpretations or code cases.

For example code case 2596/cold stretched vessels is not accepted in Alberta. **

Interpretations for ASME VIII-1 can be found at cstools VIII-1 (2007) ASME VIII-2 Interpretations can be found at cstools VIII-2 (2007) and VIII-3 at cstools VIII-3 (2007).

** Update Aug 19 2013: ABSA will now accept code case 2596 for limited use - see Bulletin IB13-008

Miniature Vessels in Alberta

File:PVE-3854, Last Updated: March 25/11, By: LB

Pulsation Damper Example "The Pressure News" published by ABSA has a write up on registering miniature pressure vessels for use in Alberta (Volume 13, Issue 22, June 2008, Page 4). Alberta no longer allows vessels small enough to be classified as fittings to be registered if they are not designed and built in accordance with ASME VIII-1. Under some circumstances the shop inspection will also have to be done by an Authorized Inspector. Each jurisdiction sets the rules for the products under their control. ABSA has set a rule for small vessels in Alberta and put it in writing. Conform and your products can be used.

This is an age old trade-off. What level of restriction do we place on free trade to achieve our safety standards? Do we allow a wide range of products into Canada, and accept the standards that they are built under, or do we restrict ourselves to using a smaller selection of products that meet our local standards? Alberta is the only jurisdiction to insist on VIII-1 for miniature vessels. We have never had a fitting rejected for this reason anywhere else in Canada, and could register them in Alberta this way until the summer of 2010. Further, it was another jurisdiction that taught us to register miniature vessels with unlisted materials this way.

The primary motivation for not using VIII-1 to register miniature vessels is to allow the use of non-code listed materials. Typically piping codes like ASME B31.3 are used which provide methods of adopting unlisted materials. It is a reality that many miniature vessels are made around the world out of non ASME listed materials. This is often done for pulsation dampers as shown in the picture.

See also the burst testing problems page for another issue that treating fittings as small vessels raises.

This is a major change for Alberta, and the rest of Canada if any other provinces go along. Some fittings can be registered across Canada except Alberta. The manufacturer has a choice to make, redesign the product to get access to the Alberta market, or accept registration for the rest of Canada without the re-design. Alternately, two products can be used - a custom product for Alberta and the standard part for the rest of Canada, registered under separate CRN#s.

Update Oct 2011: As of this year ABSA is still occasionally advising some manufacturers to use B31.3 to design miniature vessels for use in Alberta for limited applications. We suggest contacting ABSA to get permission in writing before attempting to use B31.3 on your miniature vessel destined for Alberta.

Possible Crazy Future CRN Directions

File:PVE-3854, Last Updated: Aug 20/10, By: PVE

Fitting Registration Problems We have had 2 jobs where fittings that carried current CRNs were refused by two jurisdictions because the Code of construction of the piping system did not match the code used to calculate the fittings. In one case we had to change the design code of the piping system to match the fittings. In the other case we had to re-register the fittings to match the piping system. The piping system was put on hold until the fittings duplicate CRNs were complete. Although this has only happened to us twice we have experienced many CRN requirements that initially seem unnecessary but end up becoming standard practice. (Our files PVE-2736 and PVE-3786.)