Forged Crosses and ASME B31.3 2

[Ben A]

Hi,

We've been asked to forge some crosses for a customer and they've also requested design calculations in line with ASME B31.3.

B31.3 makes passing reference to crosses, however it's not explicitly stated whether the branch reinforcement calculations can be applied to a cross. Is it simply a case of applying the reinforcement calculations to both branches in the same way as one would for a forged tee? Is there any reason not to do that?

Thanks in advance.

 

[1503-44]

Do branch reinforcement calculations even apply to forgings?

 

[LittleInch]

Crosses are included in ASME B 16.9

Why are you trying to redo something?

In B 31.3 I think you can use the same re-iforcement either side of the main run pipe centreline.

note also though section 320.1 where it says crosses are not specifically identified.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Ben A]

Re: -fifty_three
Our tees are pretty analogous to an extruded outlet (we start with seamless pipe and then forge and extrude) and we typically use the replacement area calculations for those as design justification when clients require it.


Re: LittleInch
B16.9 requires verification of the design either by proof burst test (we don't have any for crosses), FEA, BPVC stress analysis, or by calculation to a recognised code such as B31.3/4/8 etc.

We don't have the time or budget in this job to go with a proof test or FEA, and BPVC analysis would need SIFs and flexibilty factors which we don't have, leaving code calculation as the option requested by the client.

 

[LittleInch]

We've looked at this before.

Basically your SIF for the piping analysis is where you run into trouble.

https://www.eng-tips.com/viewthread.cfm?qid=206895

https://www.eng-tips.com/viewthread.cfm?qid=379970

I don't like the wording "We don't have the time or budget in this job"

Then you might need to walk away. By supplying something you take some responsibility. If it fails in service then you could be on the hook.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

Analogous <> =
Better to refer to the proper spec.

 

[Ben A]

>>I don't like the wording "We don't have the time or budget in this job"

Me either, and that's why I am asking the question rather than blindly agreeing. I've made it clear internally that I'm going to need to do burst tests before my name goes anywhere near it, however whilst the wheels of industry slowly turn thought it would be worth seeing if anyone had experience of designing them by calculation.

 

[MJCronin]

I agree with LittleInch .... The SIF representation in a detailed stress analysis is where the problem occurs

Neither B31.1 nor B31.3 has any proper guidance on crosses.

There is no process reason to have them !!!

Have the piper substitute two "tees" instead

MJCronin
Sr. Process Engineer

 

[Ben A]

Wish I had the ability to do that, but I'm far too low down the food-chain. I'm not even actually sure who the end client is in this case!

 

[saplanti]

Here are some examples how engineers derive the SIF for crosses;

http://www.jandbengineers.com/deter...ication-factor-sif-non-standard-pipe-fitting/

 

[Ben A]

Thanks saplanti, that's a really interesting and useful link.

 

[1503-44]

I think saplanti deserves at least one well earned star.

 

[LittleInch]

-fortyeight,

I know this isn't on subject, but why do you keep changing your handle??

Are you the same poster as ax1e?, -five, -sixtyfive, -sixty, etc??

It's quite odd to do this and I'm wondering why.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

I see you're on to me.

 

[LittleInch]

Indeed I am. Still don't know why though.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Compositepro]

It is pretty obvious in some other threads where you are the op and then you respond to questions under a different handle.

 

[1503-44]

No. No. I don't engage in solo conversations or arguements, or otherwise obfuscate handles. Each time I change handle, all threads I have participated in prior to are immediately updated automatically by the site's server to reflect my new name, so what you say I think is not possible, at least to my limited knowledge. Maybe that is simply honest confusion on my part that you are seeing? Click on my handle and you can see that there are not enough threads that I have started to be doing any of that. I don't know how many threads I have started, but it must be somewhere between 0 and 10, I think. And I don't think I have ever answered such threads, if indeed there are any where answers to the OP were given. I think I am simply protecting my privacy from Web crawlers that archive these kinds of things forever. Would not multiple handle changes throw those off track? Besides, where's the value in making it even more difficult to collect LPS. They aren't worth so much anyway.

However I am sorry about any confusion created amongst all the humans here. That was not intended. And the diversion of this thread's topic. I trust any mystery will reveal itself soon enough

 

[MJCronin]

However I am sorry about any confusion created amongst all the humans here.

???????

Are there other species participating in these fora that I am not aware of ???!!!

MJCronin
Sr. Process Engineer

 

[1503-44]

Are some not bots? You know the ones.

And that one is very human-like... I'd include him(?)

 

[LittleInch]

The only thing it throws off track is regulars who get used to certain posters and over time get to know whether they are talking rubbish or not.

As it happened "ax1e" I was starting to recognise as being someone who had good experience, talked a lot of sense and who I generally agreed with.

Then the daily /weekly handle changes started happening and I got confused.
No one else does it.

Occasionally people seem to have two or three different accounts and then answer their own question, but they usually get found out pretty fast.

I trust any mystery will reveal itself soon enough

I can't wait!

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.