Old column 1

[PAN]

Please comment for these conditions :-

- The column thickness is lower than retiring thickness (localized corrosion).
- There were patched outside of shell for strength reinforcement.
- High alloy strip lining will be carried out for more corrosion resistance.

Should we decide to fabricate new column?

 

[jcrowe]

Primarily it's a function of cost, you can patch and band-aid about anything, but there's a point where it's more cost effective to just replace the column.

 

[twjag]

I agree with jcrowe comments.
If column is repaired, corroded areas must meet minimum thickness for rated MAWP. If operating conditions allow, the column MAWP could be derate, which may reduce the amount of required repairs. A thorough UT thickness examaination, & internal & external visual examination, of all pressure boundary component are required to evaluate extent of repairs. Also, check with the local jurisdiction to obtain their requirements, & for approvals (where required).

 

[Raydel]

PAN, you need a standard against which to evaluate the remaining life of the unit (if indeed there is any life left). The modern method is to employ a fitness for service code such as API 579 to figure the remaining life or need for repair. There is software available to take the drudge out of this analysis. You could use CodeCalc by
COADE, which has the API 579 analysis built-in.

 

[sadane]

We have corrosion problems localised just in the skirt.
Does anyone help to propose a repair metho.
Thanks

 

[aybee]

Sadane
where is the corrosion ? at the shell/skirt weld / skirt to base ring? How bad/deep?. what extent? what thickness of skirt? material? weight/windload ? any high temperatures involved?...tell us more than "my skirt is corroded what shall I do?

 

[sadane]

In fact ther is several colums with corrosion problems.
Some corrosions are veru extended in the skirt and not in the welds.
Ex:

Column 6201A
Diam :5029 mm
Area 90 m2
Thickness:19.05+ 3.00 mm
Weight empty :115 000 kg
Weight (full of water): 485 000 Kg
Material : A 515 Gr 70
Wind : 70 DaN/m2 severe: 122.5 DaN/m2
Seismic loads: IN=8.8 ALPHA= 1.75


Mesures

North East South West

1 17.5 14.8 19 17.7

2 21 13.7 18.7 17.8

3 19 14.5 19.1 17.6

4 18.8 15.6 17.5 17.5

! !
1--> ! !
2--> ! SKIRT !
3--> ! !
4--> ! !
! !

 

[jay165]

You may want to try Stress Engineering Services,

http://www.stress.com

They do fit for service analysis using API 579. They are extremely knowledgeable and well qualified and no, I don't work for them.