API 650/653

[unclebensrice]

dear all,

we have a tank with the following 2 problems:

1. huge gap between bottom plate and the tank foundation

2. nozzle misalignment

does anyone have any experience with this??

also what is the tolerance for bottom plate slope as per api code??

 

[Dhurjati Sen]

Need to repair both. If it is a new tank still not taken into service, follow API 650 else go as per API 653.

Bottom slope varies with service.

DHURJATI SEN

 

[HTURKAK]

Regarding the first problem; is this buckling of bottom plates due to weld distortion? did the you observe after the hydrotest ?

 

[Carlos F Molina]

Hi unclebensrice

1. PROJECTION OF THE BOTTOM

An inspector should always review the inspection/construction/maintenance records.

Has the tank been operating this way without problems during some time? Repairs not always needed. Compare to the Annex B of API 653 to check if repairs are recommended by the standard.

Buckling of bottom plates in the perimeter of the tank can be due to weld distorion as HTURKAK says or due to overpressure in the tank. The roof of the tank is gas-tight?

If it is weld distortion, there isn´t much trouble but water accumulation. Can you fill with something without sealing the bottom-foundation gap? But if you really don´t want problems, you should repair that. It implies removing the weld and rewelding using stiffeners to avoid deformation of the projection.

2. NOZZLE MISALIGNMENT

This is a big problem. If you say this, I get it that the tank is new.

Do you need to realign the neck? Remove the former shell-neck without damaging the shell, this is important, then weld a new assembly making any NDT you can and feel comfortable with. Depending on nozzle size, a test that serves as a proxy for an hydrostatic test will be needed. Build a rig to hydrostatically test only the nozzle including the neck.

Do you need to realign the flange? Remove the flange-neck weld and weld a new nozzle making any NDT you can and feel comfortable with. Build a rig to hydrostatically test only the nozzle.

Thanks
Carlos Molina
apiexam



apiexam.com

 

[LittleInch]

Really needs more data/ photos.

Define "huge gap". 5mm, 50mm, 500mm???

Do you mean for plays out the ring beam?

How big is the tank?

Has it been tested?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.