CRN Survival Guide

Maximum Allowable Working Pressure

For Alberta and Saskatchewan, 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. PRINT EXPAND SHRINK LINK

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. 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:

  • Have the drawing only state 150 psi. Design Pressure equals 150 psi. If MAWP must be listed on the drawing or the nameplate states MAWP, then the MAWP also equals 150 psi.
  • Run the calculations at 320 psi. The design for the shell will still pass. Now our Design Pressure equals 320 psi and the MAWP also equals 320 psi.

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 320.8 psi, 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 (VIII-1 App 3):

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.

Updated CRN Requirements for Flange Welds

ASME changed the amount of weld required on standard B16.5 slip-on flanges with the 2009 VIII-1 code update. Slip-on and socket-weld flanges need larger welds on the outside. PRINT EXPAND SHRINK LINK

Updated CRN Requirements for Flange Welds

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

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. 

Registration of Cold Stretched Vessels

Cold stretching has been in use for more than 30 years, but not under ASME code rules until 2008. PRINT EXPAND SHRINK LINK

Registration of Cold Stretched Vessels

Oct 26 2015, By: Matt Hiskett

Why Cold Stretching?

Cold stretching (or cold working) increases the yield limit of a stainless steel material by work hardening it after all forming and welding 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 as outlined in 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:

  • The minimum and maximum cold stretching pressure (1.5xMAWP and 1.6xMAWP)
  • A note referencing the Cold Stretching Procedure (CSP)
  • Reference to Appendix 44
  • Warning: Cold-Stretched Vessel: Do not weld, grind, or in any way modify the pressure boundary

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:

  • A completed U-DR-1 (User Design Requirements) form, found in Appendix K-K of ASME VIII-1
  • Alberta Specific Information to include:
    • Reference to the design drawing
    • Number of units to be built
    • Serial numbers for the units
    • Reference to the CSP
    • A Certification of Compliance, as found in ASME VIII-2, Table 2-B.1

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 customers by submitting the following documents:

  • A New CRN application form or a revision to existing CRN.
  • One user acceptance letter for each new customer to be added.
  • A cover letter stating that a new customer is being added and that the registered design remains the same.

Using Registered Fittings in Vessels and Piping

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. In contrast fittings on piping systems must be registered. PRINT EXPAND SHRINK LINK

Using Registered Fittings in Vessels and Piping

Last Updated: Mar 27 2018, By: LB

Fittings on pressure vessels can be exempt from registration even when the same fittings used on piping attached to the vessel are not.

FlangeUnder 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, this exemption from registration is only applied to standard fittings – those listed in VIII-1 UG-44:

UG-44(a) ASME B16.5, Pipe Flanges and Flanged Fittings [see UG-ll(a)(2)]

UG-44(b) ASME B16.9, Factory-Made Wrought Butt welding Fittings

UG-44(c) ASME B16.11, Forged Fittings, Socket Welding and Threaded

UG-44(d) ASME B16.15, Cast Bronze Threaded Fittings, Classes 125 and 250

UG-44(e) ASME B16.20, Metallic Gaskets for Pipe Flanges – Ring-Joint, Spiral-Wound, and Jacketed

UG-44(f) ASME B16.24, Cast Copper Alloy Pipe Flanges and Flanged Fittings, Class 150, 300, 400, 600, 900, 1500, and 2500

UG-44( g) ASME B16.42, Ductile Iron Pipe Flanges and Flanged Fittings, Class 150 and 300

UG-44(h) ASME B16.47, Large Diameter Steel Flanges, NPS 26 Through NPS 60

This exemption is also applied to ASME “UM” vessels which are shop, but not authorized inspector inspected. All other non-standard fittings will need registering for pressure vessel use. 

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

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

We made up a diagram to help illustrate:

The attached piping system and vessel are under identical operating conditions. The red items need registration, the green items do not. The non-standard elliptical manway cover always needs registering – on vessels or piping. The standard flanges, elbows and couplings need registration for use on the piping system but not the vessel.

Some fittings are always exempt in some provinces (latest here: Fittings).

Design Code used in Alterations

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

Design Code used in Alterations

Last Updated: Jan 16 2014, SMM/LRB


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.

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. Not all files can be found.

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 often reduces it to 1.3x at time of test.

Registering B16.9 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. ASME Standard B16.9 does not specify wall thicknesses leaving it up to the manufacturer to design. PRINT EXPAND SHRINK LINK

Registering B16.9 Fittings

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:

  • a properly completed statutory declaration form for the registration of fittings clearly identifying the applicable nationally recognized Standard; –
  • the manufacturer’s scope within the Standard; and
  • the manufacturer’s identification marking(s). (B51-09 4.2.6(a))

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:

  • a properly completed statutory declaration form for the registration of fittings;
  • the designation of the Code or Standard;
  • material specifications;
  • identification markings;
  • dimensions; and
  • detailed calculations and/or copies of proof test results witnessed by an inspector or an authorized inspector and acceptable to the regulatory authority
  • (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 Manitoba, Saskatchewan or British Columbia (more here: Fittings).

Will I Need to Renew My CRN?

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. PRINT EXPAND SHRINK LINK

Will I Need to Renew My CRN?

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


Even though fitting registrations expire after 10 years, and the CRN is no longer valid for repair work, alterations or new construction, users may keep using the same fittings in error.

If a fitting is registered in one province 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 in all provinces at the 10th anniversary of the registration in the first province.

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 values 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 continued 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 1.5 cuft for the whole piping system). If so, you can avoid having to register each item sold. Many duplicate designs 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

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. Alberta has created a registration process for mobile piping (Mobile Piping). 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.

We Don’t (Usually) Register Actuators

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. Each province has its own piping rules, but most do not require registration of small diameter air piping systems and the actuators that are attached. PRINT EXPAND SHRINK LINK

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…


A typical pneumatic actuator

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, but if it was designed to code rules, the flanges (and other components) would weigh much more.

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 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:

Most actuators on valves are not part of the piping system for the fluid that the valve is regulating. Instead they are 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.

ABSA – Impact Test Information on the Drawing

ABSA requires impact test information to be put on fabrication drawings whenever impact testing is a requirement of the design. PRINT EXPAND SHRINK LINK

ABSA – Impact Test Information on the Drawing

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

Impact test information 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.

Info from ABSA:

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.

These are not new code requirement. The difference is that this information which usually ends up on the Manufacturer’s Data Report also must be put on the drawing so that it is available to the reviewer, shop floor workers and inspectors and the National Board inspector. 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,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!

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. And it is acceptable to ABSA.

Registering Steam Heated Molds

Steam heated platens and steam heated cavity molds need CRNs in Ontario. Tire molds with steam cavities are registered in Quebec. PRINT EXPAND SHRINK LINK

Registering Steam Heated Molds

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

In some provinces, heated molds need to have CRN registration. For example, steam heated platens and steam heated cavity molds need registration 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.

We 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:

  • The mold is usually registered as a fitting based on the inside volume of the passages being less than 1.5 cuft. As a fitting, a statutory declaration must be filled out and declared by someone with an appropriate quality control program for manufacturing a pressurized fitting – which can be hard to find for a mold manufacturer. This is even more difficult for a mold that is in service with uncertain lineage.
  • Usually a mold is not built to ASME code rules, so the materials may not be ASME listed. As a fitting, the material can be adopted if the tensile and yield properties are known or can be determined by testing. See Unlisted Materials for more information.
  • Applying code rules can be interesting. Typically a platen or mold will have a number of gun drilled heating passages. These passages will have intersecting passages to connect and direct the flow of steam and condensate. The passages are surrounded by material that could be considered to be the wall of a pipe. The intersecting passages could also be considered to be a header to branch pipe intersection. The mold ends up being calculated as a piping system!

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.

Code Cases and Interpretations in Alberta

Alberta does not automatically accept either ASME code cases or Interpretations. Interpretations and code cases are not part of the code, and are not automatically adopted for use in Alberta. PRINT EXPAND SHRINK LINK

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-516 Rev 11 2016-01-08 page 25:

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 accepted for limited use in Alberta  see Bulletin IB13-008

Interpretations for all ASME code can be found at

Registration of Plastic Fittings

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? PRINT EXPAND SHRINK LINK

Registration of Plastic Fittings

PVE-5246, Last Updated: Mar 22 2018, By: LRB

Plastic pipe can be calculated and registered in Canada under the code rules found in B31.1 or B31.3. But a registered piping plastic piping system also needs registered plastic fittings. Burst testing or Calculations with FEA are two methods of justifying fittings for registration.

Burst Testing:

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):

  • 4x – for all materials not listed below
  • 6x – cast iron
  • 10x – glass
  • 10x – non-metallic, non-automated fabrication process

Although molded plastic parts are made with automated processes justifying a 4x factor, we are sometimes required to use a 10x factor. These factors are for Ontario only, other provinces do not have guidelines. 

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 too conservative or expensive. Read more about burst testing on our website


B31.3 provides allowed stress levels for calculating plastic fittings. B31.3 Table B-1 and B31.1 table III-3.2.1 provide Hydrostatic Design Stress (HDS) allowed stress levels for many common plastics. The Plastics Piping Institute (PPI) has a larger list of HDS values here. Where the B31.1/31.3/PPI listings overlap, identical HDS values are provided.

With an allowed HDS, the fitting can be calculated either by using standard code rules or as shown in the illustration below, by FEA (or by a combination of both). FEA provides detailed insight into the failure mechanism of a plastic fitting which usually results in a higher allowable operating pressure than achievable when burst testing is used. When more than one grade of plastic is used, only the weakest has to be analyzed.

This plastic pressure retaining fitting is analyzed by FEA.


Moving or Changing Your Company Name?

PVE-4045, Last Updated: Mar 22 2018, By: LRB

Q – VESSELS – If your company changes their name or address, do you need to update the registration?

A – No, but the jurisdictions need to be notified.

A letter of explanation outlining the name change and listing all of the affected CRN numbers has to be sent to all the jurisdictions. (See additional ABSA info below.)

Q – FITTINGS – If your company changes their name or address, do you need to update the registration?

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 discussed below.

The following is required to update the CRN applications:

  • A cover letter explaining that your corporate name has changed or that your company has moved and that you are updating your registered products as a result.
  • A copy of the updated QC certificate issued in your new company name or new address (this is the plaque that hangs on your wall). Most QC certificates list the physical address which needs to be updated.
  • A copy of the original proof of registration (the original statutory declaration returned by the jurisdiction with the CRN number on it, or the letter of registration – whatever was returned by the Jurisdiction when the fitting was originally registered).
  • The correct number of revised statutory declarations covering the same scope as the original statutory declaration.
  • In Alberta and Ontario, renewals can be treated as new submissions at the reviewers discretion. If this happens, the entire original drawing and calculation package must be re-submitted for re-review.


  1. Get the original jurisdiction that did the first registration on the original CRN to update the CRN using the above listed materials.
  2. include 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?

  • Fittings Name Change – A separate submission for each CRN consisting of a new AB-31 application form, a new QC certificate, two new Stat Decs and a cover letter explaining the name change. No drawings or calculations are required as they are already on file at ABSA.
  • Fittings Add a Factory – A separate submission for each CRN consisting of a new AB-31 application form, a new QC certificate, two new Stat Decs and a cover letter explaining the new manufacturing location. Please note that the supporting documents referenced by the original statutory declaration must remain identical for the new manufacturing location.
  • Vessels Name Change- A letter of explanation outlining the name change and listing all of the affected CRN numbers is all that is required.

2. Can a company own a CRN on a fitting or vessel and have multiple fabricators manufacturer it for them? Assuming valid QC documentation and Statutory Declarations (if it is a fitting) for each fabricator.

  • Fittings – No. A different CRN number is required for each manufacturer. Each manufacturer must submit their own complete application package (drawings, calculations, statutory declarations, proof tests, and all other required supporting documents).
  • Vessels – Yes. However, if a different drawing number is used by different fabricators, they must all reference the original drawing that the CRN covers. The data report needs to show the original drawing number and any other fabricator drawing number should be shown in the remarks section only.

3. Can ownership of a CRN be transferred between companies?

  • Fittings – This will result in a new CRN being issued to the purchasing company due to the fact that new Stat Decs need to be submitted with a different manufacturing address or company name. See question 2 above.
  • Vessels – This would work the same as a name change. A letter of explanation outlining the name change and listing all of the affected CRN numbers is all that is required. Although Company A may purchase the registered vessel designs from Company B, please note that Company A is not just purchasing the design, they also accept full responsibility and liability of the designs including vessels that were previously built by Company B.

Costing and Timeline:

For a typical case where the brand name to be affixed to a fitting needed to be updated, the re-registration process takes about the same amount of time as the first submission with design review – 8 weeks for Canada wide. The renewal fees are around 70-85% of the original registration cost. The product was registered Canada wide both times, except for BC and Saskatchewan where it was exempt from registration based on its fitting category.

CRN Registration at PVEng

We are Canada’s largest independent registrar of fittings, vessels and piping under the CRN program registering for more than a thousand customers. We are experts in the specialized field of pressure equipment design and registration.

  • Integrated design, review and registration services
  • Extensive knowledge of registration requirements, including what needs registering and what is exempt province by province
  • We work to many ASME codes – VIII-1, VIII-2, I, IV, B31.1, B31.3, B31.5 and others
  • Design validation by burst test to many codes

Other Services

ASME Code DesignWe work to many ASME standards to design and validate pressure vessels, boiler, fittings and piping systems.

Finite Element Analysis (FEA)We use FEA to design and validate fittings and vessels that cannot be designed by rule-based codes like VIII-1 or B31.3.

Pipe Stress Analysis Pipe stress analysis is mandatory for British Columbia registration and it is recommended practice for many other systems.

About Us

Pressure Vessel Engineering has twenty years of successful experience in the pressure vessel field working for more than a thousand customers.

  • Six Professional Engineers on staff licensed to stamp and sign off on designs for use in all Canadian jurisdictions.
  • Fast and professional assistance from our team.

Need help? Our contact information is to the right.