API 650 : Tank - Out of Plumbness tolerence. Kindly help me in this!
API 650 : Tank - Out of Plumbness tolerence. Kindly help me in this!
(OP)
When we go for inspection of tank, plumbness check. We had the readings like 0° +3, 45° +6, 90° +20, 135° +15, 180°+7, 225° +2, 270° -3, 315° -22. Below is the API 650 code states that height/200. eg:7000mm/200 = 35mm. Now the confusion is, is it +/- 35mm or altogether 35mm. Kindly advice.
API 650 code:
Plumbness
The maximum out-of-plumbness of the top of the shell relative
to the bottom of the shell shall not exceed 1/200 of the
total tank height. The out-of-plumbness in one shell course
shall not exceed the permissible variations for flatness and
waviness as specified in ASTM A 6M/A 6, ASTM A 2QMl
A 20, or ASTM A 480MlA 480, whichever is applicable.
The 1/200 criteria shall also apply to fixed roof columns. For
tanks with internal floating roofs, apply the criteria of this
section or Appendix H, whichever is more stringent.
API 650 code:
Plumbness
The maximum out-of-plumbness of the top of the shell relative
to the bottom of the shell shall not exceed 1/200 of the
total tank height. The out-of-plumbness in one shell course
shall not exceed the permissible variations for flatness and
waviness as specified in ASTM A 6M/A 6, ASTM A 2QMl
A 20, or ASTM A 480MlA 480, whichever is applicable.
The 1/200 criteria shall also apply to fixed roof columns. For
tanks with internal floating roofs, apply the criteria of this
section or Appendix H, whichever is more stringent.





RE: API 650 : Tank - Out of Plumbness tolerence. Kindly help me in this!
What i dont get is this...
for a new tank, you're allowed 1/200, however once the tank is in service, you're only allowed 1/100. HMM.... Can anyone clarify this?
From API-653:
10.5.2 Plumbness
10.5.2.1 The maximum out-of-plumbness of the top of the
shell relative to the bottom of the shell shall not exceed 1/100 of the total tank height, with a maximum of 5 in. The 1/100 criteria, with a maximum of 5 in., shall also apply to fixed roof columns. For tanks with internal floating roofs, apply the criteria of this section or API Std 650, Appendix H, whichever is more stringent.
RE: API 650 : Tank - Out of Plumbness tolerence. Kindly help me in this!
RE: API 650 : Tank - Out of Plumbness tolerence. Kindly help me in this!
RE: API 650 : Tank - Out of Plumbness tolerence. Kindly help me in this!
Think about it like this. If you're +20 on one side, and your circumference is consistant throughout, then you should expect to be -20 on the other side. it's as if someone took the top of your tank and pushed it 20mm over.
RE: API 650 : Tank - Out of Plumbness tolerence. Kindly help me in this!
L/100 is twice as big as L/200.
RE: API 650 : Tank - Out of Plumbness tolerence. Kindly help me in this!
Thanks.
RE: API 650 : Tank - Out of Plumbness tolerence. Kindly help me in this!
RE: API 650 : Tank - Out of Plumbness tolerence. Kindly help me in this!
RE: API 650 : Tank - Out of Plumbness tolerence. Kindly help me in this!
with limiting the 'Out of Plumpness' and 'Out of Roundness' values is nothing but Presumably to ensure the uniformity of Tanks constructed/erected
to provide satisfactory service life and least maintenance and ensuring MI(Mechanical Integrity)during operation.
Experts Please correct if I'm wrong.
Now when this comes to localized 'out of plumpness' and 'out of roundness'; I consider that this should be the AHJ or End User
to check and permit acceptance or otherwise.
Since even localized inward bulging may severely impact any EFR's or IFR's if these are to employed subsequently
Thereby hampering the satisfactory sustainable operation in service is a big question mark.
Hope this is somewhat helpful.
Best Regards
Qalander(Chem)
RE: API 650 : Tank - Out of Plumbness tolerence. Kindly help me in this!
Thereby the satisfactory sustainable operation in service is a big question mark.
Best Regards
Qalander(Chem)
RE: API 650 : Tank - Out of Plumbness tolerence. Kindly help me in this!