Further reinforcement of weldolet 2

[GeorgeDV]

Hi, We have a scenario, where the stress exceeds at the 20"X10" weldolet. Is there any means to reinforce a weldolet, though weldolet itself is a integrally reinforced branch fitting.

 

[mk3223]

How about to consider a branch connection with a saddle or split tee design?

 

[XL83NL]

Which stress is exceeded? What’s the design code? Answers to such questions matter, as were otherwise guessing here. My first idea was to use something like a weldolet, which has (far) less welding and reinforcement, and may be less susceptible to fatigue damage. But that’s just a guess.

 

[LittleInch]

Not directly no.

If you need more reinforcement try bracing it or some other sort of support.

A different type of branch fitting might be better. Weldolet is a fixed type of reinforcement.

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

 

[AGazo]

You need to use reinforcing pad by weld seams

 

[GeorgeDV]

Thanks for the responses.

This project is a replacement of existing facility, where we have a constraint, that we have to go with the like to like replacement. But unfortunately stress analysis is been asked to done, and we find the stresses exceeds at many location, where we could managed at all except this one. In spite of our suggestion to change the branch connection type, we were insisted to go with the Weldolet. Now we are stuck up with excessive stress at the branch during the stress range and pure expansion case in ceasar. My stress engineer needs more reinforcement and I have no idea how to reinforce the Weldolet. The code is 31.3.

Dear Little inch,

I was out for a meeting, so couldn't respond immediately, sorry about it.

Dear Break Boy,

Could you share some drawing of RPAD for weldolets. I need it to illustrate.

 

[XL83NL]

I dont understand why one wouldever reinforce a weldolet. These fittings have vast amounts of weld metal (and thus reinforcement) as per their design & fab requirements. Adding more weld metal means creating more stress risers and thus a lower design life, from a fatigue point of view. Also, the increased stiffness will most likely result in a decrease in flexibility and thus increase in the thermal displacement stress range.

Furthermore, you mention

excessive stress at the branch during the stress range and pure expansion case

This tells me you're talking about the thermal displacement stress range, thus secondary stresses

My stress engineer needs more reinforcement

If one requires more reinforcement my first guess would the design doesnt meet B31.3 para 304.3.3, so the primary stress would most likely be the issue. Either you or your stress engineer didnt get it.

Could you share some drawing of RPAD for weldolets. I need it to illustrate.

With all due respect but if you need pictures for such details you're not the right the person for this job.

 

[GeorgeDV]

Dear XL83NL,

Thanks for you remark, but I believe you didn't understand either the project requirement or my need. I have asked the picture for something I have never done and couldn't imagine of i.e. Rpad for weldolet. But please let me know if there is any possibility to strengthen the weldolet further with RPAD.

 

[LittleInch]

So basically the client is asking you not to do any real design work, just "give me back what I already have", but then gets a stress analysis undertaken which presumably wasn't done before or only using some simple analysis and now the answer isn't what he wanted wants you to somehow fix everything without changing it??

In this case you either need to reduce your stresses and forces by some other means, add a larger weldolet and then reduce down ( 12", 16" whatever), replace the weldolet with a branch and re-inforcement pad or pads ( which is all that a weldolet does, it just does it as a single element) or just accept the overstress on the basis that the existing pipework didn't break after ?? years service. If you're not changing anything, including the service conditions then you could argue that the stress analysis is just being conservative.

B31.3 gives the owner a large amount of leeway in terms of what they can accept.

Reinforcing a weldolet is not, IMHO, an option open to you as it would invalidate the acceptance of a weldolet as an integrally reinforced fitting and without going to an FEA model, I don't know how something like Caesar could actually accurately model it.



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

 

[GeorgeDV]

thank you very much for your advise, option of using a larger weldolet might resolve this. let me try that.

 

[MJCronin]

As always, XL83NL and LittleInch give solid and accurate advice .... I support them

I suspect that this is some type of "unbalanced" system.... Some configuration that would not normally occur following normal and customary piping practices.

Could it be that a relatively large diameter piping branch is tied into a large diameter run pipe with an undersized weldolet ?

This would cause a perceived overstress at the weldolet by an inexperienced stress analyst.

Since the OP is so reluctant to tell us details of his situation, we may never know ...

MJCronin
Sr. Process Engineer

 

[pennpiper]

GeorgeDV,
Sometimes the Stress Analysis goes off the rails when the Pipe Stress Engineer(PSE) uses the wrong Temperature in the evaluation.
There are normally four potential Temperatures for possible consideration:
- Design Temp
- High (product) Operating Temp
- Low (product) Operating Temp (Cryogenic)
- Environmental (High/Low) Temp.

Which temperature did your PSE use for these calcs?

Sometimes its possible to do all the right things and still get bad results