Distance between the welding of pad plates in storage tank as per API 650

[jayadeep C]

Hi,

 Any one please clarify What is the solution if a pad plate crosses over another pad plate in the storage tank shell/roof? Anything mentioned in API 650?

Jayadeep

[Umar]

Hi,

There are two scenarios:

1.       The tank is new construction: it doesn’t seem to be a good practice; it creates complications to make bending on the pad plate, extra stress on the pad plates and also it may result in poor welding advise the designer to combine the two pad plates and make it one.

2.       The tank is in service: if you don’t have any repair on the area of the said plates, just ignore it. If you have repairs on the pad plate area you can switch to scenario one and combine the two pad plates into one pad plate.

 

With best regards,

Firoz Ahmed (Umar), PMP®, MICorr®, Sr Corrosion Technologist

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[Arun Padman]

Dear,

As per API 650

5.8.1.2 When attachments are made to shell courses of material in Group IV, IVA, V, or VI, the movement of the
shell (particularly the movement of the bottom course) under hydrostatic loading shall be considered, and the
attachments shall meet the following requirements:
a) Permanent attachments may be welded directly to the shell with fillet welds having a maximum leg dimension of
13 mm (1/2 in.). The edge of any permanent attachment welds shall be at least 75 mm (3 in.) from the horizontal
joints of the shell and at least 150 mm (6 in.) from the vertical joints, insert-plate joints, thickened insert plate joints,
or reinforcing-plate fillet welds. Permanent attachment welds may cross shell horizontal or vertical butt welds
providing the welds are continuous within these limits and the angle of incidence between the two welds is greater
than or equal to 45 degrees. Additionally, any splice weld in the permanent attachment shall be located a
minimum of 150 mm (6 in.) from any shell weld unless the splice weld is kept from intersecting the shell weld by
acceptable modifications to the attachment.

Please keep in mind the following. 

 5.8.11.4 All non-circular miscellaneous pads shall have rounded corners with a minimum radius of 50 mm (2 in.).

Pads that must cover shell seams shall be provided with a 6 mm (1/4 in.) telltale hole (see 5.7.3.4)

Regards,

Arun Padman Manayil

Inspection Engineer

Tel:+968 93305032 

B Tech in Production Engineering

CSWIP 3.1, ASNT Level II in RT, UT, PT, MT

API-510 Pressure Vessel Inspector

API-653 Aboveground Storage Tank Inspector

API-570 Piping Inspector, API-571 Corrosion and Materials 

Life Associate Member IIW (India )

Member of the American Welding Society (AWS)

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