Material Failure / P91

I think you will have to keep to a rigorous regime with regards to purchase and certificate verification. If you buy cheap as your budget does not allow the good stuff, you must expect problems. Chinese will even issue false certificates I have heard (and experienced myself with stainless steel) so you cannot trust that either.

It could of course also be "an accident", if so you need to consider that that could happen here as well with even the best of materials. The problem in China is that it is common place and those "accidents" are a fact of life for most people.

They have to regularly cut of peoples water supplies for days or weeks as ther has been another "accident" and tons of heavy pollution has been dumped in some river.

Hi,

I've read the link and it seems the problem was a brittle fracture due to improper material/manufacturing process.

It's not strange to find this type of fraud. If you cannot buy enough quantity of material, you must do it through some dealers and not to purchase it from the pipe manufacturer.

Unfortunately, there are some "tricky" suppliers.

To avoid this type of problem you need to be sure of your suppliers and made your purchasing only to qualified ones.

Furthermore it's convenient to perform a good receiving inspection, and for critical applications I would recommend to make some random checks to assure the material is really what you asked for. There are some non destructive inspections which can help: Portable spectrometers to check main alloy elements, eddy current sorting techniques, metallographic replicas, etc. Of course you can perform random destructive tests too.

We've used P91 for long time in many steam piping on combined cycle power plants and never had this problem.

But let me tell you an old experience I live some years ago with one of this "tricky" dealers: We were purchasing 304L type stainless steel and we just made a visual inspection and an administrative officer checked the mill certificates. He wasn't specialist on materials, just check the certificate against the ASME standard. He found one certificate in which the Cr content wasn`t included and ask the dealer.

The dealer supply a new copy of the certificate with the Cr content. When I further check both certificates I was really surprised: The first one hasn`t Cr content but under the column "Mo" it appears 18.3. The second one keep the Mo content but a Cr content of 19,2 had been added!!!

I ordered to compile all certificates coming from that dealer whose piping components came from the same japanese steel maker and found just placing them in couples and looking with a negatoscope light and... all signatures were absolutely coincident even crossing the form lines in the same places.

Obviously, the dealer had taken one certificate, erase the figures and use it as a "master" certificate which he filled according to his wants.

Of course, we delete the dealer from our suppliers list and have to check all material supplied.

Based on the issue, it seems problem isn't caused by Chinese manufacturer only but the Dealers. This happened even the material could have been supplied from a recognized dealer / trader in USA; who has import the material from China, re-print it in USA as Made in USA and sell it as USA product (if he is responsible; he should have incur inspection, testing and control in the mill while manufacturing). Note: it doesn't mean all product from USA is defectless or product from China is bad but the issue is a cheating / criminal act; losses of sincerity and honesty of human due to selfish and commercial benefits.

From the above, apart of performing receiving inspection, random PMI (positive material identification), purchase material with 3.1B or 3.2 type of certificate, and / or random sampling for destructive mechanical testing, a reliable supplier / trader. We still will be exposing to certain risks as we are not possible in follow through / trace the material from its origin to trader and to our store; anything can be made fake during the supply chain by copying / change of certificate, change of material, re-print identification on material etc. However the higher level of inspections applies may be the best approaches at least lower down the exposure risks, plus a hydrotesting / proof testing at the end of installation / erection.

Any other new technique can be utilise?

I agree with you in which there are many intermediate parts involved and it's difficult to control all of them, so the most reliable method is to thoroughly inspect the materials with all the technique available (when there is really a risk in case of failure).

I don´t completely agree in the hydrostatic testing issue. A piping system can withstand the test and fail in service, because the service conditions (fluid, temperature, etc) affect in a different form to different material grades. This test is a requirement but by itself do not assure that materials and manufacturing has been made according to the specified rules.

Cheers

Agreed as commented; the hydrotest is one way to ensure and validate the installation fit for the design purpose and mitigate or prevent some safety hazard and putting out some unforeseen fabrication and manufacturing errors.

Our AIS told me a story related with many explosions happened at power stations located at many states at USA. They found that the cause was due to piping flanges. They imported these flanges from China in accordance with ASME A105 & ASME B16.5, in which its specs. state that the flanges must be produced by forging, i.e one piece then machined.

They found that the cracking was noticed at portion between neck and flange, and by investigation they discovered that the flanges were produced from two pieces, and welded together and good machined, i.e not in accordance to the standard.

This problem happened I think at power plants at 1990, and was named as China Gate.

HAZ...HAZ...HAZ... Not EPRI ask Alstom and Oak Ridge. If not extruded then seamed...HAZ...HAZ...HAZ..................................................