Tank Settlement Survey

[Whin]

Is it necessary to perform a routine soil settlement survey for in-service tanks that are supported by concrete ring wall, or is this requirement applicable only to tanks that rest on an earthen foundation (without ring wall)? Could someone provide a relevant reference standard for this requirement? Thanks in advance...

 

[HTURKAK]

Refer to API 653 , Appendix B which is normative.
Evaluation of Tank Bottom Settlement
...
B.1.1 ...... During operations, settlement measurements should be taken at a planned frequency, based on an assessment of soil settlement predictions. For existing tanks that do not have initial settlement data, a program of settlement monitoring should be based on prior service history.
...
The monthly routine in-service inspection shall also include a visual inspection of signs of settlement.

 

[LittleInch]

"Necessary "? Not really, but depends on what the ground situation is and whether there are any visual clues that settlement has occurred.

And foundation can settle or subside given poor ground conditions or undermining by e g. water flow

 

[Whin]

Refer to API 653 , Appendix B which is normative.
Evaluation of Tank Bottom Settlement
...
B.1.1 ...... During operations, settlement measurements should be taken at a planned frequency, based on an assessment of soil settlement predictions. For existing tanks that do not have initial settlement data, a program of settlement monitoring should be based on prior service history.
...
The monthly routine in-service inspection shall also include a visual inspection of signs of settlement.

Settlement survey was taken during hydrostatic test after tank construction, subsequent external visual inspection (5yrs of service) doesn't shows any signs of settlement. Is it mandatory to have another set of settlement survey as planned frequency?

 

[LittleInch]

"Mandatory" implies legislation so no, but would seem to be a good thing to do a 5 or 10 yearly basis. Really doesn't cost that much.