Hello to all.
I and three other Inspectors are having a difference of opinion regarding AWS D17.1 2001 Ed. Here is the scenario:
We have a 0.500” thick piece of aluminum (square butt-joint) with a full penetration Electron Beam Weld. Radiography was performed and it showed some porosity. According to Table 6.1 (Class A welds) and Clause 6.5.1. would the following scenarios be acceptable or rejectable?
Table 6.1 Class A welds states:
Maximum size-0.33T or 0.060”, whichever is less
Spacing minimum- 4 times the size of the larger imperfection
Clause 6.5.1 states- “The dimension of any discontinuity shall be defined by its largest dimension. Two or more discontinuities shall be treated as one when the spacing between them is less than the dimension of the larger discontinuity".
Scenario A- 0.030” pore, 0.010” space, 0.020” pore
Scenario B- 0.030” pore, 0.040” space, 0.020”pore
Scenario C- 0.030” pore, 0.210” space, 0.050” pore
Thanks in advance, for thanks clarification.

A similar type question was asked of me several years ago, see the following:

Gve me your 2 cents in regards to D17.1:

1)  Ref. paragraph 6.5.1 (page 27), sentence #2

2)  Ref. Table 6.1 (page 28), Class A column, word "spacing"

Do these 2 items appear to conflict or does "spacing" in table 6.1 refer to something else not related to what's spoken of in paragraph 6.5.1 ?

If they are related, why do you think they conflict?  Or am I reading this code completely wrong

My Respose:

I think the spacing requirements para. 6.5.1 and table 6.1 are different but related.

I believe that para 6.5.1 is a "Maximum Individual Discontinuities" only related issue. If you have two acceptable (undersize discontinuities) too close together, you have to count them as one and they may exceed the maximum allowed. I think that this is the basic intent.

Of course, the Spacing from Table 6.1 is how close the discontinuities can be to each other.

So if para 6.5.1 applies to the discontinuities, then they are considered one discontinuity and it's not an issue with "Spacing" in Table 6.1.

I believe that all three of your discontinuity situations are Acceptable per D17.1.

Well I was hoping more people would have chimed in on this subject. I was holding back my interpretation on this as to not skew other people’s opinion. Anyways here it goes.
Original Post
Scenario A- This would be acceptable. Due to 6.5.1, the two pores would be counted as one (0.050).
Scenario B - This would be rejectable. Due to Table 6.1, the minimum spacing requirements. Spacing would have to be a minimum of 0.160”.
Scenario C- This would be acceptable. Due to Table 6.1, it meets the minimum spacing requirements. 
My feeling is that the spacing requirement was put in place in the thought that if a crack was to propagate from one pore to the next it would either be contained to a small area such as in Scenario A (0.050” crack). Whereas, in Scenario B the crack would be 0.090”. For  Scenario C, due to the fact that there is 0.210” spacing it would be “less likely” for propagation to occur through sound material.
Mike QC1
To answer your question, assuming the same parameters as was originally used:
Scenario A – Rejected, is over the 0.060” because it would be counted as one, 6.5.1
Scenario B – Rejected, cannot be counted as one and does not meet the spacing requirements.
Scenario C – Rejected for the same reasoning as Scenario A.