Repair of HP steam pipeline - Welding procedure 6

[MechEngCCGT]

Dear All,
I have this issue in a combined cycle power plant (CCGT) that I am currently working on where the HP steam pipeline has to be rectified - repaired.

Welding will be used, so I was wondering if someone can provide some info on the relevant procedure, applicable codes - standards etc so I can overlook the process.

Main issues, lessons learned etc are also of importance if someone wants to share them with us.
Thanks in advance

 

[Duwe6]

ASME B31.1 should be your repair Code.

Two biggest problems are;
1st -- maintaining adequate preheat -- use a stress-relief/PWHT company to provide any preheats above 225°F [repair will probably require PWHT anyway.

2nd -- Low quality welder. You need a 'repair welder', someone experienced in taking the radiograph, marking out the repair area, excavating the defect [typically using carbon-arc gouging], and then rewelding the excavation. You are already paying a *large* amount of money to fix this problem. Paying $80-150/hour for a welding subcontractor is a warranted expense if you want your defect fixed fairly fast, and without further defects.

 

[MechEngCCGT]

Duwe6,
thank you for your help.
Can you refer me to the approx. paragraph of B31.1 for this process? (if there is one of course cc to your experience)

Do you have or you are aware of a welding description for this so I can have a look at?
Thanks

 

[MechEngCCGT]

Also do you thinkthis procedure is acceptable:
1. Preheat at 300 degC
2. Tack welding
3. Preheat 800 degC
4. Complete welding
5. Visual inspection acc. to ASME sect. V
Any comments on the prolonged?

 

[SectionIX]

You will need a WPS appropriate for the material.

You will want to check the preheat values...way too high...

 

[metengr]

There is not enough information to provide any meaningful response regarding suggested parameters for welding. You need to know the material being repaired. The second preheat listed should most likely be post weld heat treatment at 800 deg C. Where are the NDT requirements as part of the repair - pre and post welding? You will need more than a VI.

 

[MechEngCCGT]

Metengr, can you please provide me with those items that you think are missing from this general procedure description. For example material to be welded.

When you say NDT? Can you please be more specific as this is not my area of expertise.

Why do you say more than VI where do you base your thoughs, in a particular paragraph of a certain code perhaps?

 

[DekDee]

redbayron,
HP stands for High Pressure - very dangerous if something goes wrong.

How can you "overlook" the process when you don't have a clue what is going on.

Gaining an "education" via an internet forum is not the way to go about it.

Strongly suggest you or your company get someone involved with the required knowledge / experience,

Regards,
DD

 

[MechEngCCGT]

Thank you DekDee for your answer,
if you pay a closer attention you will see that I wrote the HP abbreviation so I dont understand your comment really.
Overlook was a way of speaking.
I am not trying to gain education I am trying to aquire targeted knowledge from people with experience in this topic. I believe this is the reason that this site exist in the first place.
Thank you for your suggestion but it was irrelevant, pointless and out of line. Of course if you want to share something usefull with us Ill be glad to hear it.
Regards

 

[DekDee]

redbayron,
What you have posted is quite frightening and I hope your CCGT Power Plant is not anywhere near where I live.

Also do you think this procedure is acceptable:
1. Preheat at 300 degC
2. Tack welding
3. Preheat 800 degC ???????
4. Complete welding
5. Visual inspection acc. to ASME sect. V ???????
Any comments on the prolonged?

Regards,
DD

 

[MechEngCCGT]

DekDee,
it seems that you have time to waste my friend and I really do not.
So if you want to help a bit do it if you dont please be on your way.

To answer by the way to your last comment, this was in a nutshell lines from the WPS not written by me but by a company dealing only with weldings that probably has more knowledge than a petroleum engineer.
The second temperature was the PWHT which acc. to B31.1 its between 600 - 820 degC
I dont get the ?????? on the visual inspection line. This is the ASME Section V – Non-destructive examination, in case you are not aware of.

So please I kindly request to leave this topic alone as I dont wish to waste more time on your comments.

Thank you

 

[gtaw]

My friend DekDee is trying to make a point. While you may not appreciate his sense of humor, his points are valid.

You are asking for advice about welding without providing the minimum basic information required to provide you with any useful information. You haven't even mentioned what country you are in. That will certainly influence our advice because different countries have different codes that govern the type of repair you are undertaking.

You have not told us the material that is to be welded, the thickness, the welding process, etc. DekDee is trying to tell you may well be in over your head based on the absence of information you are providing. It indicates you are asking questions about a subject that is beyond your current capabilities and you should be searching for someone with the expertise to help you. It would appear that you do not have the expertise or the experience to undertake this type of work on your own.

As a professional, one must know their limitations. When one is short on both knowledge and experience, the services of a professional with the experience and knowledge to do the job correctly is well advised.

No one can know everything. I would not attempt to walk a tightrope stretched across the Grand Canyon. I do not have the experience to do so. I would hire someone that has that ability. I might not like the idea of admitting my limitations, but it is better than being a red splat on the canyon floor.

None of this is intended to insult you or your sensibilities. It is reasonable advice based on the lack of information you have provided.



Best regards - Al

 

[MechEngCCGT]

gtaw,
your comments are welcomed. Regarding them:

Nobody ask anything, everyone was limited to "you cant do this" "dont do that" etc etc Hell yea I can do that in a forum! Telling everyone else that dont know what they are asking for in the first place.... where is the reason in this?

I really will not go deeper into this and I believe that you should either. If dekdee fancy jokes can do them elsewhere.

Do you have perhaps some questions, instead of spending our time once more? (in case of course you want to provide some help on this)

Regards

 

[pradipgoswami]

Hello,
MechEngCCGT (Mechanical) (OP),

What is the material of construction? What's the design code-- B-31.1 or something else. CCGT HP steam lines are frequently fabricated from Grade -91 steel or Grade -22 steel or there could be other low/high alloy grades also.
It could be as close as 2" or 3" in wall thickness or more. Based on the OEM design, welding of such high alloyed steels are extremely tricky. You need a competant welding engineer to write and engineer the repair guidelines.Such piping would involve , correct welding consumable selection, welding practices, PWHT, NDE and more......

Thanks


Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
Ontario, Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299

 

[Duwe6]

what pradip said.

And to echo some other comments, the proposed preheats are way too high, for any 'normal' power-plant material. Reducing them to one-forth these values may still be too hot. Your 2 best options are the Welding Eng, or hire a well-experienced Boiler & Steam company.

 

[MJCronin]

This thread is a waste of time.....

The original poster is being coy and does not want to tell us what the piping material is, or his location.

If he is asking us what NDT means, he has no experience with this type of work.....

MJCronin
Sr. Process Engineer