Hello Stressers!!!

Just want to know if crotch radius rx (minimum and maximum values) is shown in ASME B16.9 as part of the dimensional requirement? or it is only shown in ASME B31.3 2016 Section 304.3.4(d)?

Since this crotch radius rx is very sensitive to the SIF's, does tee manufacturers follow the minimum and maximum limitation values shown in ASME B31.3 2016 Section 304.3.4(d)or ASME B16.9 (in case it's shown there).

Many Thanks for your help.

Cheers!!!

Sorry for the reverse statement "I mean SIF's for Tees is sensitive to crotch radius rx".

Many Thanks,

I think we all share the same dilemma on this issue.

Cheers!!!

Borzki,

I've only seen B16.9 specified for fittings on the manufacturer or purchaser side, though this code does not specify crotch radius from what I can see. B16.9 only provides fixed positions for the ends and centerlines (per paragraph 6.1).

I will note that B16.9 Paragraph 2.1, 2.2 invokes ASME B31, and ASME B31.3 in turn invokes B16.9 on occasion.

I, however, do not see a smoking gun that says that manufacturers are specifically targeting the dimensions specified in B31.3.

Manufacturers are required to maintain testing data for their design, should that be of any consolation.

Hi Michael,

Thanks for your opinion. Just curious, on how tee manufacturer's perform their work and what are the things they consider in terms of quality control.

As a stress engineer, our main concern is the stress concentration on the crotch discontinuity of tee which is highly dependent on crotch radius.

Anyway, the ASME B31.3 new editions consider now as a default the more conservative SIF using 3.1*Tbar/r2 as the flexibility characteristic h, so the crotch radius will not be an issue anymore.

Many Thanks,

Hi Michael,

Just curious if fatigue test is also part of the testing data from manufacturer or burst test only?

Many Thanks,

Borzki,

Not for listed components, which are already based in historical data. However, for unlisted components, there should be varying degrees of fatigue testing data available.

Thanks Michael.

Cheers!!!

Borzki
I work more on EN Standard but time to time I must checked the ASME Fittings.
We always have a problem because in EN Standard we have also information about a WT or crotch radius, so we can calculate it simple.
In ASME we must always gets the certificate with this value to check the calculation. But the best is the record:
The allowable pressure ratings for fittings designed in accordance with this Standard may be calculated as for straight seamless pipe.
This is not true becasue always the tee will has less strength than straight pipe through opening.
So this is a problem becasue we don't have a WT near the opening in ASME B16.9

Adrian,

You statement "This is not true because always the tee will have less strength than straight pipe through opening" is not true in case you refer to "strength" as "allowable pressure".
The proof is by one of European Standard, EN 10253-2 which defines two types of fittings : Type A fittings have the same wall thickness at the welding ends and at the body of the fitting than a pipe having the same specified wall thickness. Their resistance to internal pressure is, in general, less than that of a straight pipe with the same dimensions. Type B fittings showing increased wall thickness at the body of the fitting are designed to resist the same internal pressure as a straight pipe with same dimensions. These two types of fittings are intended to be used in applications covered by the EU PED Directive.

You may accept that a manufacturer of a tee under ASME B16.9 may have the same technical knowledge than one manufacturing a tee fitting Type B under EN 10253-2 and consequently is able to comply with the requirement that the allowable pressure rating for tee-fitting designed is the same as for straight seamless pipe.

Dear Mario
You have right it is my fault.
Of course I write strength but I think about max allowable pressure.
I think that all information wrote about manufacturer is true.
I want only said that in EN Standard we had a tables with the WT of ends for type A - and for this maximum allowable pressure is less than for the same straight seamless pipe . You have coeficient X.
But type B has in addition to the thickness of the walls at the ends also wrote the WT near the opening Ts and Tb and in this case we have X=100%.
I only want to write that in ASME 16.9 is lack of this information about Ts and Tb but information is that the maximum allowable pressure is the same like for straight seamless pipe. But how prove it ??? If we don't have enough information.

ADRIAN

B16.9 provides two alternatives to qualify the tee- fittings.
One is by math analysis and needs the details you are referring to, other is by a proof test. i.e. based on experimental approach. Of course would be a combination of them, but it is enough the proof test record as formal document.
In this case the user has no information about the tee geometry.

See chapter 2.2 Design of Fittings of B16.9.

"The design of fittings shall be established by mathematical
analyses (e.g.,ASMEB16.49 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 fitting 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."

Mario
thanks for Your answer.
All that You wrote is true.
But In many cases in my job I received a documentation where I have a information about the WT of ends and a material.
And a certificate of 3.1 acc. to EN 10204 that this material is for preesure bearing parts of cat. II, III, IV.
But I don't received any documents about a calculation or proof test.
So when I checked this fittings I only can do this by math analysis.
So this is the problem that the documentation is not delivered.
We had a problem because a lot of this type of fittings are delivered from China so the traceability when You have a lack of part documentation is very dificult.