GOT THIS IN EMAIL TODAY 4

[vesselfab]

A un-verified account of failure during hydrotest of vessel in China. Folks, please be aware of material and workmanship problems in China and other countries as well.

Again, this is un-verified, but from a pretty reliable source.

 

[doct9960]

vesselfab,

Where's the attachment?

Are you talking about the article on the attached file?

 

[vesselfab]

YES IT IS

Thank you

I don't know what happened on my attachment

 

[MJCronin]

vessel....

These are the same people that are starting up a brand-new supercritical new coal fired power plant every week..... is that right ??

There have been many warnings on the threads of various forums about a "buyer beware" attitude that might be adopted...

 

[vesselfab]

I don't really know if they are starting up a new plant every week or not. I just saw pictures of a vessel with a blow up and some pretty nasty looking welding. I do not know the complete validity of it...AS STATED....and don't know anything about the company. I thought if some had not seen the article or were not aware of it, there may be some interest. Obviously you have your ear a little closer to the ground than I do and are more aware of happenings around the world. This little ol' country boy here found it interesting and thought others may as well

 

[tlcos]

While I am not really big on the idea of Chinese production (materials or finished products), the lack of information provided with the impressive set of pictures begs a lot questions concerning the failure depicted.

Such as: What is the metallugy? Thickness? Is it a Cr-Mo steel clad with a SS? (I am guessing 1.25 Cr plate, but could be anything including CS, 2.25 Cr, 5Cr, etc.) Was it properly preheated and PWHT'd? Was the vessel correctly designed per the appropriate code? While the welds were not pretty (we call those Gorilla Welds), were the acceptable and per code. I didn't see the undercuts mentioned, but then again, I am not a weld inspector.

So all we really see is a fractured thick shell in a transition section about a reinforced opening. Or maybe that isn't a transition section, but a deformation of the cylinder. I just can't tell. It looks to have an internal lining. Is it clad or overlay of camera flash?

Where does the fault lie? With the designer, the E&C, the material supplier, the fabricator, inspection, somewhere else, or a combination of factors.

Without more information, I hesitate to totally condemn Chinese materials and production. For all we know, the plate may have come from the good ole USA and those pictures could be from the shop of a quite reputable fabricator (the letter could even be a hoax).

Please if someone has details of this failure, I would like to know.

I have witnessed a similar hydro failure in a US shop due to improperly heat treated heads from a reputable US fabricator.

The only conclusion I draw from this is that we should continue to be critical of material sources and equipment suppliers and only buy from reputable sources. Does this rule out Chinese sources? Not necessarily, but we do need to be diligent in our qualification of new vendors.

 

[vesselfab]

well, if one of my vessels made it to hydro with welds that looked like that and clean up that look like that, I would really have to launch an internal investigation as to how such crap made it through both production and QC first being made to look like that and then without being fixed.

as far as being properly PWHT? still poor fabrication

as far as proper design and code & hydro...still poor fabrication

just a sad situation.

 

[SnTMan]

wonder how bad they missed it.

 

[gr2vessels]

Years ago, my maths teacher told me that nothing replaces the pen and the paper, for manual calculations. I still use the pen to calculate the Hydro test pressure. The only thing the mongrel did not tell me, which MAWP to select from the PV Elite print-out...Probably they had a similar teacher...
cheers,
gr2vessels

 

[roca]

gr2vessels,
you state "which MAWP to select from the PV Elite print-out". What does this mean?
Surely on a vessel there is only one MAWP (New and cold)?
Each component can have its own MAWP value.

 

[dig1]

This is the vessel that was fabricated at Nanjing Yuchuang Petrochemical Engineering. The base material was 16MnR w/ a 410 SS clad.

My understanding of the failure is that the required hydrotest pressure was 3.15 MPa but the failure occured at <2 MPa. The material only had a an impact energy of 7-8 J even though the material certs had significantly higher values (31 J). What I have read on this is that there was an improper heat treatment after the clad bonding and that lead to a brittle material. The hydrotest temperature was about 12C.

Based on this and another project I am aware of in China, the material cetificates must be looked at very critically. I know of some end-users that are no requiring 3rd party testing witnessed by an end-user rep of material.

 

[DIRTYDAVE]

Nil ductility? How cold was it during the hydro?
In one picture it looked like there might be snow on the ground & the man was wearing heavy clothing. dig1's post indicated the temperature was 12C.
This is 53.6F
I dug some old instructions for hydrostatic testing of boilers & external piping out of my files.
"The water used to fill the components shall not be at a temperature less than 70F to avoid the danger of brittle facture failures."
This is my first post so I hope I clicked on the right things

 

[vesselguy]

dig1,
Can you confirm where you got your information from please? I just want to know if it is authentic.

I didn't know what 16MnR is so I found a thread that talked about it.

http://www.eng-tips.com/viewthread.cfm?qid=148531&page=11

Looks like the material is low cs with high yield strength. The cost of high strength is lower toughness like the P91. If the material property stated in the thread is true then perhaps the engineers in charge did not check the ductile to brittle transition temperature before they spec out the hydrotest. Maybe they've been asking questions on web sites like this to do their job, but didn't get the proper answers.

 

[dig1]

I spoke w/ someone who spoke directly with the shop & local authorities.

 

[gr2vessels]

Found this one:
"16MnR (BS1501-223) whose yield stress is 378.0 MPa and ultimate tensile strength is 513.6 MPa"
It is also an acceptable equivalent to AS 1548-7-460, in Australian pressure vessel fabrication. These days, most of the carbon steel dished heads are being imported in Australia from China as 16MnR anyway, but nobody seems to give a proverbial for the certificates signature (the gate guard, his uncle or someone else..).
More later...
cheers,
gr2vessels

 

[athomas236]

Gentlemen,

If you are interested in horror stories, here is one for the books. The moral here seems to be that placing a contract with a major company is no guarantee of quality.

I have recently become involved in a project where the contract for 4 HRSGs was placed with one of the US's major boiler makers who had the HRSGs manufactured in their own factory in Asia. Defects have been found in the shop welds of the superheater outlet header, the main steam pipe and all integral piping.

The outlet header and main steam pipe are made from P91 with P22 branches and nozzles.

Brief details of the header and pipe problems on the first HRSG are shown below.

1. Main steam pipe

a) Shop weld defects such as inadequate root penetration of 2-3mm, excessive root penetration up to 5mm into the pipe bore. In addition, high weld hardness's have been measured.
b) Parent metal of pipe spools between shop welds have low hardness's.

The contractors initial proposal was to repair the shop welds on site and put the pipe into service for 2-3 years while replacement pipe was manufactured. A brief life time analysis was carried based on the assumption that the creep properties of incorrectly heat treated P91 are the same as P22. The predicted life was 6000hours at design conditions and the actual pressure stresses in the pipe were 85% higher than the allowable stress for P22.

The contractor has now revised his proposals and proposing that the pipe is removed from site, N&T and the shop welds remade.

2. Outlet steam header

a) Nozzle to header welds have various defects including
- lack of root fusion/penetration up to approximately 2mm and over-penetration
- defects on the external weld surfaces such as undercutting of 2.5mm
- welding rods protruding through the roots of six welds

b) Deep circumferential and longitudinal grooves on the bores of nozzles that are not associated with welding

c) Low hardness values on the header.

The contractor's initial proposals were not to replace this headers but to undertake the following:

a) Nozzle to header welds - headers to be removed from the boilers, the nozzles cut-off, the headers N&T and the nozzles re-welded.

b) Circumferential and longitudinal grooves - still under investigation.

c) Low hardness values on at least one header - still under investigation.

The initial proposals are still current.

Inspections of the remaining three HRSGs are in progress.

Regards,

athomas236

 

[gr2vessels]

athomas236,
Please confirm that the contract was for a plant built outside USA.
gr2vessels

 

[athomas236]

g2vessels,
I confirm that the contract was for a plant built outside the USA.

Does this make the problems any less?

Regards,

athomas236

 

[MJCronin]

What.......You people are surprised ???!!!! This type of fraud has been going on for decades !!!

Ummmm... like you guys didn't see this coming ????

This has been a long, long festering problem from Asia.

"Buyer beware" has been the manefesto in these countries for millenia..... and if you cant see it (like, say the heat treatment of weldments, charge the customer .... but.... um you don't have to really do it)

Try this thread:

http://www.eng-tips.com/viewthread.cfm?qid=194913

Any response from anyone else..!???

-MJC

 

[stanweld]

MJCronin:
I hate to say this but with regard to P91, it really doesn't matter where the materal is manufactured or equipment fabricated. From extensive BAD experience, I have seen the same problems described by athomas236 from manufacturers/fabricators in the USA, Europe, South America and Asia. They shold all be considered guilty until proven innocent!!!

Extensive testing of all materials and welded fabrications are required by the Owner/Engineer/Contractor to "hopefully" insure appropriate quality.