D1.1 VT Acceptance Criteria for Porosity

By kpauley (*)

Date 08-01-2001 14:11

[deleted]

By pipewelder_1999 (****)

Date 08-01-2001 14:30

This section applies to Radiography not visual.

Is there a statement somewhere in the code that indicates acceptance criteria for RT can be used for visual?

Thanks for your response

Gerald Austin
http://www.weldinginspectionsvcs.com/

By - Date 08-01-2001 17:01

Hi Pipewelder_1999
You may have a clue right there in 6.12.1.1. The size of rounded discontinuities that are allowed for radiographic examination, possibly reflects why only "piping" porosity is considered relavent with visual! In my former company's specs, we didn't allow any surface porosity for corrosion and cosmetic reasons.
People, such as myself who work in the ASME's the majority of the time, have always thumbed through the D1.1 a couple of times before applying AWS, VT acceptance criteria involving surface porosity.

Have a great day,

By pipewelder_1999 (****)

Date 08-01-2001 17:58

Notice that paragraph 5.26.1.3 "Fabrication" indicates that excessive porosity is to be removed. Not excessive piping porosity.

Anyone from AWS or on a D1.1 code committe feel free to jump in any time!

Gerald Austin

http://www.weldinginspectionsvcs.com/

By gibster Date 08-02-2001 12:11

AWS official interpretation 1D1-91-010-09 for code edition D1.1-90 answers the inquiry "is surface porosity a requirement for visual inspection?" by responding "the Code has no requirement for surface porosity relative to visual inspection." The second part of the inquiry asks "is surface porosity acceptable?" The response states that "If surface is of concern to the Engineer, the limit of porosity shall be established by agreement between the owner and contractor."

By pipewelder_1999 (****)

Date 08-02-2001 19:27

I am looking for acceptance criteria for porosity other than piping. "Surface Porosity" could be "Piping Porosity" if the porosity extends to the surface could it not?

The only way to tell from the surface is to grind.

I am looking for acceptance criteria for visually round indications in which the only dimension available is the diameter of the "Pore". Surface porosity is not in the terms and definitions of d1.1. Piping porosity would have to be elongated in one direction at a ratio of 3 to 1 using the interpretation of "elongated" in D1.1 for radiography.

If I have a butt weld in 1/4" material with 1/16" reinforcement and drill a hole in it with a 1/8" drill bit 3/16" deep then interpret this as porosity it is acceptable by the above criteria. Or all the way through for that matter.

Any rounded discontinuity visual to the surface regardless of size is acceptable per AWS D1.1? Yet when found by radiography they become rejectable?

Which one is better, the accepted visual weld or the rejected weld that was repaired. Would you want the item that was correct the first time or had to be repaired.

Thanks for your response regarding surface porosity. Is "Surface Porosity" mentioned in the D1.1 code? Other than the reference to the interpretation.

Have a joyous Day

Gerald Austin

By G.S.Crisi (****)

Date 08-03-2001 16:11

Trying to be of help to Pipewelder 1999 I've gone through the following Codes and Standards:
ASME Code, Section VIII: Unfired Pressure Vessels
API Std. 510: Welded Steel Tanks for Oil Storage at Atmospheric Pressure
API Std. 5L: Specification for Line Pipe.
If someone doesn't know who ASME and API are, ASME is the American Society of Mechanical Engineers in New York City (www.asme.org) and API is the American Petroleum Institute in Washington DC (www.api.org).
I must confess that the results of my research are not brilliant.
ASME VIII. On Part UW (vessels made by welding) of the Code, the paragraph related to Repair of Welded Defects, says that the defects which are OPEN TO THE EXTERNAL SURFACE, such as cracks, EXCESSIVE POROSITY, lack of fusion ...............shall be removed by mechanical means.......... and the removed portion shall be rewelded. I couldn't find what the Code means by "excessive porosity".
API 510. The paragraph related to Inspection of Welds refers to the two types of welds which are present in a storage tank: butt (side of the tank) and fillet (often, bottom and roof).
For butt welds, it says that if the VISUAL INSPECTION of the weld is NOT SATISFACTORY, its acceptance or rejection shall be based on one of the following criteria: a) RT of the weld under consideration, b) sectioning of the weld and destructive test of the specimen.
For fillet welds, the Std. says that they shall be always subjected to visual inspection (of course, you can't RT a fillet weld), and that if it is NOT SATISFACTORY, the acceptance or rejection shall be based on sectioning of the weld and destructive test of the specimen.
I couldn't find in the Std. when and why the visual inspection is "not satisfactory".
API 5L. The paragraphs related to Visual Inspection, not only of the weld but of the entire pipe, under the title of OTHER DEFECTS, say that any imperfection (I understand that porosity is included) having a depth greater than 12,5 per cent of the specified wall thickness, measured from the surface of the pipe, shall be removed by any of the following methods: etc. etc.
Frankly I doubt these results will be of any help, but if they are, I'll feel quite happy.
Giovanni S. Crisi
Sao Paulo - Brazil

By Ronalb

Date 08-03-2001 16:43

In Table 6.1 (Visual Inspection Acceptance Criteria) of D1.1-1998 & 2000. Note 8 (A), (B), & (C) give you the criteria.

It addresses piping porosity which according to Jefferson's Welding Encyclopedia is "A form of porosity having a length greater than its width that lies approximately perpendicular to the weld face."

Any porosity that is deeper than it is wide is considered piping porosity.

If it is open to the surface then it falls into the Acceptance Criteria of Table 6.1. If it is not open to the surface, then it is covered under 6.12.2.1 & 6.12.3.1.

I hope this helps because it is al there is and it is correct.
Ronald B.

By pipewelder_1999 (****)

Date 08-03-2001 19:18

Jeffersons welding encyclopedia is not referenced by any AWS standards I am aware of.

D1.1 does refer to piping porosity as being elongated porosity.
Elongated is described in D1.1 Para 6.12 (Reference to radiography) ".. an elongated discontinuity is one in which its length exceeds three times its width."

A ratio of length to width must be established. Rounded is not round. A round item would have the same radius and center throught its circumference. Depending upon the amount of precision used during measurement, round could always be argued. Rounded would need to be separated from elongated by some measurable dimension. Usually a ratio of major dimension to minor dimension is used in describing a discontinuity.

Elongated, linear discontinuities are "usually" described as above using the 3/1 ratio.

This may or may not be correct but is an accurate representation of my opinion based on facts gained by various experiences that have somehow become part of my memory.

Thanks for your information Mr. B.

Gerald Austin
http://www.weldinginspectionsvcs.com/

By pipewelder_1999 (****)

Date 08-03-2001 17:45

Thanks to you all for your information. I have had a few questions answered here.

Based on the discussion here think what time could be saved in the field if this were a little clearer.

Thank you all

Gerald Austin
http://www.weldinginspectionsvcs.com/