Can anybody explain this?

Date 02-20-2010 09:48

One of our code (ISO 13847 ) says the following.

"The total area, when projected radially through the weld, shall not exceed 2% of the projected weld area in the radiograph. The area shall be the length the weld affected by the porosity (with a minimum length of 150 mm ) times the maximum width of the weld."

The above criterion is in order to evaluate porosity. Now I've a Cluster porosity of 14 mm dia. The total length of the weld is 192 cm (24i inch OD, pipeline )Can anybody explain me (if possible with a sketch) how to proceed with it?

Regards,

By GRoberts (***)

Date 02-24-2010 00:30

In other words, the porosity area shall not exceed 2% of the projected weld area. The projected area of the weld affected by the porosity shall be the length (150mm min) x the width.

The length of your weld is 192 * Pi cm. Multiply that by the weld width. Multiply that by .02. That is the maximum porosity area permitted.

By ssbn727 (*****)

Date 02-24-2010 01:59

Hi GRoberts!

"The length of your weld is 192 * Pi cm. Multiply that by the weld width. Multiply that by .02. That is the maximum porosity area permitted."

Not for nothing but, does "192 cm * Pi cm." mean that the total length of of weld is the result of multiplying 192 cm times Pi? Or is that scientific notation on your part? Because 192 centimeters (Which is more than likely rounded up, or down to the nearest tenth of a centimeter), already is the circumference of the pipe based on the "nominal" size OD (24inch OD pipe X 2.54 = 60.96 cm X 3.14 = 191.4144 cm), but we all know that the circumference is going to be slightly larger than 191.4144 because after all, 24" OD is a nominal size, and the actual OD is slightly larger than the nominal size listed and Pi is usually as many more decimal places to the right as one wants to use for the sake of accuracy! ;) So, if you meant that the total weld length is 192 centimeters, then please disregard my question. ;)

In other words, multiply the rounded off circumference, or not (for accuracy's sake! ;) ) to the weld width, then multiply that sum by .02 as GRoberts mentioned which will then give one the maximum porosity area permitted....

So the only value that's missing here is the weld width which is to be multiplied by 192 cm (Or a more accurate value instead ;) ), and the sum of that to be multiplied by .02 which will then give you the maximum porosity area permitted. ;) However, if one wants to be really accurate, then one must use actual values as opposed to
"nominal or rounded off or up" values in their calculations because they may very well make the difference between what is truly acceptable and what is unacceptable IMHO. ;) Especially if there are no tolerances to work with when one performs the calculations. ;)

Respectfully,
Henry

By GRoberts (***)

Date 02-24-2010 22:17

Sorry, I misread the post, and though that 192cm was the diameter since the post had 24" diameter shortly following it. I assumed it was a metric conversion without checking. Thanks for the catch. 61cm should be used instead of 192cm for 24" diameter pipe.

By ssbn727 (*****)

Date 02-24-2010 22:20

You're "Weldcome!"
Thank you for the clarification. ;) And I hope all is well with you! :) :) :)

Respectfully,
Henry

By nantong (**)

Date 02-25-2010 00:40

First thing you must do is measure the length of weld containing the porosity (nothing to do with the total weld length). If the length of weld containing the porosity is less than 150mm then you must still use 150mm in your calculation. For example if the porosity is in a weld length of 50mm multiply 150mm by the width of the weld, for example say 10mm wide. You then take 2% of this (150x10x0.02)=3mm2.
Calculate the total area of the pores and add them together. If is less than 3mm2 then it is acceptable.