Dear Wahab,
-- As you are constructing tank as per API 650 you have to follow the 650 tolerances.
SA 6 or 20 doesn't say about plumbness as the scope states it gives a general requirement for certain plates / shapes.
While in 7.5.2 it clearly states that plumbness allowed is 1/200 for the total height and the waviness or flatness on one single course (i.e in one single plate) shall not exceed the values in SA 6 / 20 this is the case for local deviations. For local deviations in one shell course follow SA 6 /20 for tank plumbness follow 1/200.
Peaking and banding talks about local deviations in vertical and horizantal weld joints, and it clearley states that peaking and banding shall not exceed 13mm, so upto and including 13mm is accepted.
Below are the scope of SA 20 & it states
"This general requirements specification covers a group of common requirements that, unless otherwise specified
in the applicable product specification, apply to rolled steel plates for pressure vessels covered by each of the
following product specifications issued by ASTM"
As you see the scope of SA 6 it states
This general requirements specification covers a group of common requirements that, unless otherwise specified
in the applicable product specification, apply to rolled structural steel bars, plates, shapes, and sheet piling covered
by each of the following product specifications issued by ASTM"
Cheers
MM
On Sat, Feb 26, 2011 at 11:44 AM, Abdul Wahab <awengineer@gmail.com> wrote:
Dear All,
I am Abdul Wahab working in KSA as QA/QC Inspector, I have an issue
which is confusioning me. Below there is copy of Paragraph of API 650.
Plumbness, peaking, banding & flat spot discussed in this & tolerances
are provided but along with tolerance of API 650, also refering to
ASTM standards, those standards have tolerances aproximately a double
values as compared to API 650 Tolerances. Do we need to follow those
as ASTM is not a tank construction code but provide guidance about
matrial manufacturing,testing & handling etc.
We have Banding Value for 6 mm Plate of 13 mm max, can we consider a
dent as a banding problem in tank shell.
Please see below & advice.
7.5.2 Plumbness
a. 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 20M/A 20, or ASTM A 480M/A 480,
whichever is applicable.
7.5.4 Local Deviations
c. Flat spots measured in the vertical plane shall not exceed the
appropriate plate flatness and waviness requirements given in
7.5.2.
If there is any confusion to understand, please ask.
Abdul Wahab
Mechanical Inspector
KSA
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