API 579- Brittle Fracture Analysis

[mechmania]

I am analysing the vessels manufactured befor 1990 for Bittle fracture analysis using API 579 section 3.

I read through this standard and I have some doubt.

I would really appreciate if you can give some clarification for my better understanding.

Back ground:

Charpy impect test is performed at -150 F temp on the vessel I am evaluating for all the pressure parts.So as per Level 1 analysis MAT(Minimum allowable temperature) for all the parts is -150 F.

While CET(critical exposure temoperature) for the vessel is -174 F.

So I have to go for Level 2 analysis.

My question is Can I utilize Table 3.2 and Fig 3.5 for API and still reduce the Temperature bellow the Impact test Temperatue?

If yes than How do you detemine reduced MAT (below Impact test temp) for nozzle flanges and reinforing pad?

Thanks a lot.

 

[LSThill]

mechmania (Mechanical)

Are refering to API 579-ASME FF1 JULY 2007?



L S THILL

 

[mechmania]

I am referring to API/PETRO 579 2000.

Is July 2007 version is more updated and clear?

Thanks

 

[LSThill]

Yes! "API 579-ASME FFS1 JULY 2007"


L S THILL

 

[mechmania]

I received latest version of API 579-ASME FFS1 July 2007.

Under the paragraph 3.4.2.1 C step 1.4 it says, MAT for the flanges meeting ASME B16.5 or B16.47 shall be set at -29 C (-20F).

In my case charpy imect test has performed at -150F temperature.So my initial MAT for flanges is -150F.While CET of the vessel is -174 F.

Can anybody please tell me How do I reduced the MAT for flanges below CET of the vessel to pass the level 2 assesment for flanges.

It is easy to do use formulas for shell and head in
Level 2 to assesment for reducing MAT.I am not sure which formula should i use for Flanges and nozzle pad.

Thanks for your time.

Hiren