API 579 FFS-1 general / local metal thinning case study

[mariolucas75]

Dear All,

Can you advise me any resource link for learning API 579 FFS-1 general / local metal thinning case study... with some basic examples / calculations....

Thks

 

[IdanPV]

ASME PTB-14 is a good place to start.

 

[HTURKAK]

Have a look to API 579-2 / ASME FFS-2 ( Fitness-For-Service Example Problem Manual )
.
There are worked examples for metal thinning.

 

[mariolucas75]

It says that variation of thicknesses (Coefficient of Variation) in general metal loss assessment in API 579-2 / ASME FFS-2 part-4 should not be more than 10% of neighboring locations. Therefore can we define a general metal loss within an area of grid - it is an area where the neighboring thicknesses do not vary by more than 10% ? Otherwise my corroded location will be characterized as local metal loss ?

During localized metal loss evaluation it is needed to have CTP - critical thickness profile - obtained by grid measurement - min 15 readings at intersection of grid lines), during general metal loss it is it is needed just PTR - point thickness readings min 15 readings (not specifying the grid) ... so where are these 15 PTRs obtained ? Is it also on grid ? Why it is not specified then in 579?

 

[GD2]

It says that variation of thicknesses (Coefficient of Variation) in general metal loss assessment in API 579-2 / ASME FFS-2 part-4 should not be more than 10% of neighboring locations. Therefore can we define a general metal loss within an area of grid - it is an area where the neighboring thicknesses do not vary by more than 10% ? Otherwise my corroded location will be characterized as local metal loss ?

During localized metal loss evaluation it is needed to have CTP - critical thickness profile - obtained by grid measurement - min 15 readings at intersection of grid lines), during general metal loss it is it is needed just PTR - point thickness readings min 15 readings (not specifying the grid) ... so where are these 15 PTRs obtained ? Is it also on grid ? Why it is not specified then in 579?

Grid option is preferable for both because if the PTR produces COV >10%, grid is required anyway.