P91 failure in China - 3 fatalities
P91 failure in China - 3 fatalities
(OP)
WE understand that there was a failure of a P91 HP main steam line in China 1 week ago ( circa 4 Dec 06). The plant was a new 300 MWe coal fired plant, less than 1 month operating hours.
Can anyone advise what plant this was and more details?
Can anyone advise what plant this was and more details?





RE: P91 failure in China - 3 fatalities
Yes, I had heard about this incident in an email that made its way around. There was some question as to the heat treatment and number of hand-offs between the mill and supplier.
The folks at EPRI seem to know about this event. Did you see the email from the Chair of Section
VIII, Subgroup on Materials?
RE: P91 failure in China - 3 fatalities
RE: P91 failure in China - 3 fatalities
This may be of intrest.
http://www.psimedia.info/Industry%20Alert.pdf
RE: P91 failure in China - 3 fatalities
Here are some pictures that came with the email;
[IMG]http://i12.tinypic.com/343n5sn.jpg[/IMG]
[IMG]http://i14.tinypic.com/33kx1cz.jpg[/IMG]
This was supposed to be seamless Grade 91 pipe material. However, in looking at the second picture there is no evidence of any ductility in this material. This could imply there was either a seam weld (preferred path of failure) at this location or a pre-existing flaw (hard to tell from the photo) from fabrication.
davefitz let us know what you find. I suspect information will be difficult to obtain because of worker deaths.
RE: P91 failure in China - 3 fatalities
From the above posted pictures, it looks like a thick lipped failure- I'm not a metallurgist, but it looks similar to a brittle fracture ; a pre-exisiting crack ( from fabrication or from hydro test at too low a temperature) may have progressed to failure at full operating temp + press.
RE: P91 failure in China - 3 fatalities
RE: P91 failure in China - 3 fatalities
RE: P91 failure in China - 3 fatalities
I have received the following email, to allert of the consequences of greedy / shonky dealings in the today market. The e-mail is in relation to the 300MW unit at the Datong Power Station Unit 2, the failure of HP main steam line:
"It is very important that we deal with reputable companies and know the origin of the materials we supply.
The material that failed was supplied by a company in Houston TX, called S.M.A.N.T,who certified it as US pipe when it came from questionable sources in China. These details have been confirmed by the Bechtel QA Manager of Power. Bechtel China has also conducted an investigation and the supply chain is ugly due to the extent of how many agents, brokers, and mills are involved. The Chinese Government has stepped in and has called for a formal
investigation. The Chinese Government has also banned Chinese made pipe for use in major power plant critical applications. Thus far there is evidence to support that over 30 plants contain similar or other “fake pipe” all over China."
I wander if anyone did/could read the original Chinese certificates.
Cheers,
gr2vessels
RE: P91 failure in China - 3 fatalities
rmw
RE: P91 failure in China - 3 fatalities
Here is an excerpt of the email below;
RE: P91 failure in China - 3 fatalities
Last year I had an export enquiry for seamless pipes. My rates were high obviously by 20%. I was asked to quote a lower price,and win the bid. Thereafter I was asked to supply good original samples for approval. Thereafter I could supply fake ones just by placing the stamp of original manufacturer. I refused. The Chinese guy accepted and to this day the orders go to him and the business goes there.
RE: P91 failure in China - 3 fatalities
I don't have a contact for you, but in the past I have spoken with the regional power research institute about similar issues. These institures are all around China. It actually makes these guys look good to the Power Supervision Commission when they can 'uncover' cases of this activity.
= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm
RE: P91 failure in China - 3 fatalities
RE: P91 failure in China - 3 fatalities
RE: P91 failure in China - 3 fatalities
RE: P91 failure in China - 3 fatalities
Trust me, this one is getting a lot of play in ASME.
= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm
RE: P91 failure in China - 3 fatalities
If I had to provide an educated guess, it would be a pre-existing flaw on the ID surface of the pipe that was introduced some time during fabrication. If this was carbon steel, the failure would occur from stress rupture and you would expect to see a whole lot more rupture ductility.
RE: P91 failure in China - 3 fatalities
You may be right, but it should be easy to compute. There are correclations for graphitization as a function of temperature and time, and such graphitization would lead to a brittle failure.
Likewise, there are creep correlations for CS also. This could be an opportunity to see if the old HP 42s still works.
RE: P91 failure in China - 3 fatalities
I am always up to the challenge, especially when it comes to Power Plant metallurgy. Ok, assuming a design temperate of 541 deg C, (1006 deg F), and assume we had a 0.9 capacity factor during operation, and we operated lets say 4 months,
0.9 x 4 x 31 days(average)x 24 hours = 2678 operating hours
In checking with the best available resource material in my possession (EPRI Metallurgical Guide Book for Fossil Plant Boilers), spheroidization and graphitization damage mechanisms compete with one another in the temperature range of 850 deg F to 1300 deg F.
In reviewing a semi-log plot of metal temperature versus time for carbon steel, there are two linear curves one for spheroidization and another for graphitization. The curve for spheroidization dominates for carbon steel between 1050 deg F and 1275 deg F. Below 1050 deg F the graphitization curve dominates down to 850 deg F. The intersection between these two curves is about 2,000 hours at 1050 deg F.
Assuming a service temperature of 1006 deg F, (which in my estimation is conservative because the actual temperature is probably lower), the time to graphitization is +5,000 hours. This is a ball park estimate and only serves as an approximation, I would suspect the value should be well above 5,000 operating hours at this temperature.
Keep in mind that prior to reaching the graphitization region, the main steam pipe would be subjected to noticeable swelling and distress from accelerated creep deformation. The allowable stress value for carbon steel at 1006 deg F decreases to only about 2.5 Ksi. So, I stick by my conclusion that the pipe material was probably not carbon steel, given the limited visual evidence.
RE: P91 failure in China - 3 fatalities
RE: P91 failure in China - 3 fatalities
RE: P91 failure in China - 3 fatalities
The general feeling among several of my close metallurgical peers in the Power industry is that the failed main steam pipe was Grade 91 material. The caveat is that this pipe material was not properly heat treated. Here is where I believe the introduction of an axial flaw could have occurred. My best guess is that this material (spool) was either not tempered or was inadequately tempered (high hardness). This high hardness, low toughness, pipe material could set the stage for either an axial crack introduced during a hydrostatic test or stress corrosion crack from exposure to moisture. Both of these damage mechanisms could indeed explain why the pipe ruptured with little to no ductility in service and exhibited a predominantly brittle-looking fracture surface. In reviewing the pictures once again, there was little to no oxide that would be expected if the spool failed from creep rupture (as with CS).
Unfortunately, my colleagues don't believe we will ever get to the bottom of this because the Chinese government confiscated this material.
RE: P91 failure in China - 3 fatalities
RE: P91 failure in China - 3 fatalities
Any additional information and photos would be great.
I especially enjoyed reading "metengr's" analysis of the problem. Good work and great information for future work.
Best regards - Al
RE: P91 failure in China - 3 fatalities
Excellent information..... This is an excellent thread
You state:
"The Chinese Government has also banned Chinese made pipe for use in major power plant critical applications."
Where did you get your information ?
Is there not just a little bit of irony here ???
Will there be a comprehensive report ever ??
-MJC