P91 failure in China - 3 fatalities 9

[davefitz]

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?

 

[davefitz]

Thanks , Meteng. Would this calc be affected by an incorrect heat reatment of CS in the fabrication phase, ie, woule graphitization/ sheroidation have been accelerated if a CS pipe had undergone a P91 style N+T under zero stress ?

 

[metengr]

No.

 

[metengr]

While I am on the topic of creep rupture in Power Piping from my previous post, I can provide some insight from "those" individuals that are close to the situation;

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.

 

[davefitz]

Sounds like the failures that occurred in the US in the 1950's blamed on " temper embrittlement"- excess trace amounts of phosphorus , sulphur , etc.- .

 

[gtaw]

Great thread fellas.

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

 

[MJCronin]

gr2..

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