failure analysis

Please give more details for type of fittings, its material, design conditions, country of origin, methods of fabrication,... etc., because there is something wrong.

Anyway:

1. The material of fittings are to be checked visually by an inspector to show the mode of failure.

2. The material certification are to be checked to assure that its type, grade, thickness, chemical properties, mechanical requirements are within the project specification.

3. Is the hydrotest pressure in accordance with the permitted by the code of fabrication?

1) it's ECC - RED SCH 40-S 4"X3"

spec ASTM A234 Gr. WPB NACE MR0175-2000 ASME SA 234

C-18 Si 18 Mn 56 P24 S19 Cu4 Ni 5 Cr1 Mo4 V3 YS315 TS 460 E%34 HB158 HARDNESS

test pressure was only 6.2 bar

another fitting is a RF Flange and requested contractor to submit MTC

it's look like a tight crack, may be need microscopic exam..

By the information given, it seems there are standard carbon steel fittings. A234 WPB are fittings made usually by hot forming A 106 Gr. B pipe. According to rules, piping fittings should have a bursting pressure higher than the straight pipe, so the fittings you have, provided the pipe is the same material (A 106 Gr. B) and the same schedule, they should not break in hydro-test.

If this is the case the fittings are obviously defective, but MTC doesn't have necessarily to clarify the failure. It will give you information on chemical composition and mechanical tensile properties of original pipe, plus hardness of hot formed fitting.

It doesn't give you any information about integrity. If you want to check for the 20 remaining, I will recommend you, before taking a decision, to perform a surface examination to them by dye penetrant or magnetic particle testing. This would reveal if any open defect are present which grew under pressure load.

Best regards

Good morning (here)

You need to find the reason of failure.

There are many literature regarding failure analysis methodology which use to include visual inspection, micrographic inspection, chemical and/or mechanical testing, etc. to find the root cause of failure.

Only after that thorough investigation you can know why the fittings failed and then take a decision on the remaining 20.

Here you have one example of literature you can easily find in the net.

http://www.plant-maintenance.com/articles/tcr-whitepaper-failure-analysis.pdf

Best regards

The American Society for Materials (ASM) has a book titled "How Components Fail". Its a pretty good starting book on failure analysis. Not too technical, but a good "Failure 101" book.

Is that society ASM (The American Society for Materials) differ from ASTM (American Society for Testing and Material)?

Dear Abdel Halim Galala,

Yes, ASM International is the organisation who issue (among others) the "ASM Handbook" formerly known as "Metals Handbook" and within this ASM Handbook there is a volume (nº 11) dedicated to Failure analysis and prevention.

Here you have a link to the index of ASM Handbook. They have many other more specific handbooks.

http://asmcommunity.asminternational.org/portal/site/ASM/ResearchLibrary/Publications/ASMHandbook/

Best regards

Dear Kwetz,

Thank you very much for your clarification.