ASME B16.9 fittings in EN-13480 design code

NAGROEN · May 2, 2025

Hello everybody, I have a question that keeps me busy for a while. I hope there are people here that can give me some advice / experiences for this matter in how to handle with this.

I'm a piping (stress) engineer from The Netherlands and for most clients we use the design code EN-13480 for the calculation and fabrication of piping systems.
Currently I'm working on a project with piping diameters up to and including DN900 (36"). The system is calculated according to the EN-13480.

Due to the delivery time and/or costs of some large bore fittings (in this example DN900 equal Tee type B1) we are currently looking for alternative ASME fittings. I know it's possible to use ASME fittings in Europe, as long as we make a Particular Material Appraisal for this component and make a strength calculation.
And here is where the problems comes. How to calculate an ASME fitting as the wall thicknesses are not defined in the ASME B16.9?

When using an ASME design code like the B31.1 or 31.3, this is no problem, because the B16.9 says that the fittings of a certain schedule are at least just as strong as the corresponding pipe. So a 36" pipe with schedule XS can handle the same pressure as a 36" equal tee schedule XS. The fabricator probably knows how thick the tee needs to be in order to comply to the B16.9.

But this will not work when using a B16.9 fitting in combination with the EN-13480. Because this code says you need to calculate it to verify that it will be strong enough.
How is it possible to calculate it without having the wall thickness? And it's not possible to get a measurement report, because the tee will only be fabricated after ordering.

So in my example the supplier offers a B16.9 A234WPB / P265GH 36" tee schedule XS. According to the B16.9 this tee should be at least as strong as a P265GH 36" pipe schedule XS.
Now I calculated that a P265GH 36" pipe schedule XS can handle 32 bar(g). That means that the corresponding tee should also be able to handle 32 bar(g), according to the B16.9. The fabricator needs to make sure the tee will be fabricated accordingly.

But within the EN-13480 I stilll need to verify this with a calculation. Is it possible to make a calculation before the tee is actually fabricated?

My system is only 19 bar(g) so based on the B16.9 this tee should be strong enough. But I just can't verify it with a calculation as required for the EN-13480. Kinda frustrating.....

It's a long story, sorry for that. Maybe someone can tell me their experiences with a similiar case?

KevinNZ · May 9, 2025

However the B16.9 fitting manufacture determines the fitting thickness (2.2.1) they will have minimum thickness distribution to apply to all fittings.
They are required to provide records of the design/test (2.2.3) to the purchaser.

Agnul93 · May 9, 2025

Could be an option to consider type A Tee with an increased wall thickness to comply with the code?

GD2 · May 9, 2025

OP,
What best you can have other than a Proof Test? Ask for a copy of the proof test from the Supplier/Manufacturer when they qualified the fitting design. Note the acceptable size range that qualifies with a proof test (read B16.9 Para 9.4.1).
A production test is not required by B16.9. However, you can ask for a compliance certificate from the manufacturer stating that there will be no leakage or impairment of serviceability when the fitting is hydrotested as per the piping Code.

nikolastrojman · May 11, 2025

Maybe you can turn the whole thing in your favor by making an internal pressure calculation based on the parameters you have acc. to EN 10253-2 for Type B tee´s and then request from the manufacturer to confirm required thickness and crotch radius you´ve calculated yourself.
Other option would be to speak with the NOBO to see how they treated this kind of issues in the past.

XL83NL · May 14, 2025

Interesting question. (Im Dutch as well and we also often stumble on some of the nasty quirks and shortcomings of working with EN 13480). Apart from the previous advices given, what you could also is show that the 'B31.3' equivalent strength (or call it pressure rating) meets the EN 13480 standard. So, just regards it as a B31.3 component. Doing so will result in rating xyz per 302.2.2/304.1.2. Then, outline any possible differences between B31.3 and EN 13480 (or even better, per PED or Annex ZA of EN 13480-3) and indicate how those differences may affect the overall theoretical rating. Where necessary, take a conservative deduction on the pressure rating for those differences. Set up a draft, provide this to the NoBo for acceptance, and work this out in detail when the draft is approved.

LittleInch · May 14, 2025

I'm just curious here, but how would this work if you were buying a tee to 13480?

Does this specify a min thickness in the tee?
Or as you're buying it to some linked spec it is part of the vendors design?

And how did you get 32 bar? Seems very low for an XS thickness of pipe.

XL83NL · May 14, 2025

For fittings, EN 13480 relies on EN 10253. That standard has two types of design for each fitting; type A and B. Type A has a pressure resting that’s less than an equivalent sized seamless pipe rating. The derating is quite complex, or at least not straight forward. Type B has the same rating as equivalent sized seamless pipe, but can be (much) thicker. EN 10253 is just a wast of time and money. If someone can explain the real benefit I’d love to hear so. As an example, we once had a PN100 1.4404 pipe spec. A two inch tee was required, but not available in the required thickness (say 5 mm) acc type B. We ended up getting a machined block with a branch that had 15 mm wall and and internal (what later appeared to be) restricted orifice effect. Sometimes type B may actually be a lot thicker. You find out once you receive the item.

Sometimes you make a spec and you find out type A or type B isn’t available actually. So for the specific grade you first need to determine if what you need is actually something you can buy (not on your national, but the European market!…). EN 10253 is a 150 page standard (!). There are hundreds of formulae in there to design all sorts of fittings. The update cycle of the standard currently is around 14 years. There are more reasons why EN 10253 doesn’t work very well.

Unless you have a VERY simple system in a very common material (say P265GH in PN10), EN 13480 piping design is - at best - just crazy at times, due to standards like EN 10253.

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

ASME B16.9 fittings in EN-13480 design code

NAGROEN

Mechanical

Recommended for you

KevinNZ

Mechanical

Agnul93

Industrial

GD2

Mechanical

nikolastrojman

Industrial

XL83NL

Mechanical

LittleInch

Petroleum

XL83NL

Mechanical

Similar threads

Part and Inventory Search

Sponsor