API 653 Plumbness Criteria

[soundfun]

In API 653, plumbness criteria is "not exceeding 1/100 of tank height, with max of 5 inch." in 10.5.2

I think that criteria is for reconstructed tank case. Because that criteria in under "Section 10. Dismantling and Reconstruction". And 10.5.1 said "The tolerances given in this section have been established to produce a reconstructed tank of acceptable appearance and structural integrity and to permit proper functioning of floating roofs and seals"

So, that criteria is only for reconstructed tank, not for all other tanks in service.

Am i Right ??

In My country, local law forced us to use that criteria for all tanks in service. And i cannot agree with that. You guys have seen that kind of local law??



Please HELP !!!

 

[786392]

Do You cosider this too strict and want more tolerances;

Actually this is for in-service tanks repaired for any reasons and others may correct if wrong here?.

For new tanks API 650 having 1/200 tolerance consideration and if a tank is reconstructed as if totally built new then I will go for applying API650 indeed.

Best Regards
Qalander(Chem)

 

[soundfun]

Thank you for responding.

And to conclusion,

In your opinion, If tank is repaired by any reason (Bottom Patching, Accessory Replacement, etc), API653 1/100 & 5inch. criteria for plumbness should be applied ??

 

[JStephen]

The section you refer to is just for reconstructed tanks. You wouldn't normally start checking plumbness of in-service tanks. The main cause of problems in that case is going to be foundation movement, and there are tolerances for foundation levelness to address that.

 

[KiwiTanks]

You are right that it only refers to reconstructed tanks.

We regularly assess tanks to the tilt clause that you are referring to, just to see how they stack up. (along with a floor plate projection settlement survey)

If we find the tank is beyond this limit, we have performed calculations to see at what angle the tilt will become detrimental to the integrity of the tank. In most cases the tank has to rotate (ie tilt or sink in to the foundation) by more than 3 degrees.

By using this clause as a go - no-go gauge, it allows you to determine if something is happening to the foundation which may need further investigation.

 

[KiwiTanks]

You are right that it only refers to reconstructed tanks.

We regularly assess tanks to the tilt clause that you are referring to, just to see how they stack up. (along with a floor plate projection settlement survey)

If we find the tank is beyond this limit, we have performed calculations to see at what angle the tilt will become detrimental to the integrity of the tank. In most cases the tank has to rotate (ie tilt or sink in to the foundation) by more than 3 degrees. (which is an aweful lot)

By using this clause as a "go - no-go gauge", it allows you to determine if something is happening to the foundation which may need further investigation.