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Lack of Fusion vs Lack of Penetration B31.5
2

Lack of Fusion vs Lack of Penetration B31.5

Lack of Fusion vs Lack of Penetration B31.5

(OP)
Hey All,

I am having a hard time understanding the following code section:
B31.5 - Refrigeration piping
Section - 527.3.2(d)(4)(5) Butt Welds
(d) The welding shall be such as to assure that the following requirements are met:
(4)Incomplete Penetration. The total joint penetration shall not be less than the thinner of the two components being joined, except to the extent that incomplete root penetration is permitted for girth welds only. The depth of incomplete root penetration at the weld root of girth welds shall not exceed 1/32 in. (0.8mm) or one half the thickness of the weld reinforcement, whichever is smaller. The total length of such incomplete root penetration or at the root shall not exceed 1 1/2 in. (38mm) in and 6 in. (152 mm) of weld length.
(5) Lack of Fusion. None Permitted.

The part I am struggling with is where it allows for Incomplete root penetration of 1.5" in 6" of weld, yet in the next sentence say Lack of fusion, None Permitted.
If the root is not tied into one or both sides of a typical pipe "V" groove joint, that is lack of fusion of the root. So how are you allowed up to 1.5" of Lack of Penetration of the root? If the root is not penetrated its not fused??? What am I missing here?

Thanks in advance?

RE: Lack of Fusion vs Lack of Penetration B31.5

GMEHL,
I do not have a copy of B31.5 but it sounds exactly the same as B31.3.
If you have a copy of B31.3 have a look at Figure 341.3.2
I have been fighting this same battle for years (and I am on the code committee).
Cheers,
Shane

RE: Lack of Fusion vs Lack of Penetration B31.5

(OP)
Shane,

Thanks for the response, it makes a little more sense now after reviewing the charts and visuals on pages 83 to 86 in B31.3, and how it applies to acceptance criteria for Normal, "M", Cyclic, and "D".

With that said, I am still struggling with the difference between Incomplete Penetration and Lack of Fusion.... LOL, to me its one and the same!

Gene

RE: Lack of Fusion vs Lack of Penetration B31.5

Best explanation in AWS A3.0 13th Edition, Standard Welding Terms and Definitions.

In B31.3 lack of fusion is allowed WITH TOLERANCES as incomplete penetration tolerances.

Regards

RE: Lack of Fusion vs Lack of Penetration B31.5

There currently is some work under way in both B31.3 and B31.5 to address some inconsistencies about IF and IP. Not sure when it will hit the code books (for B31.3 its still in ballot), but this may be addressed better in the near future.

If the item is still too unclear, I suggest you provide the relevant Code committee with an interpretation request or request a code change.

Huub
- You never get what you expect, you only get what you inspect.

RE: Lack of Fusion vs Lack of Penetration B31.5

1)LACK OF FUSION
Detect by VT during welding, and in finished weld by RT, UT and Acoustic Emission Examination during pressure test.

2)INCOMPLETE PENETRATION
Detect by VT, RT, UT and Acoustic Emission Examination during pressure test.

a) IP acts as a crack and increase risk in low temperatura service
b) affects fatigue
c) fluid turbulence increases
d) local corrosion

Regards

RE: Lack of Fusion vs Lack of Penetration B31.5


Greetings Hubert,
I have tried getting this looked at previously by the committee to no avail.
I always struggle with Question 2 below,
Cheers,
Shane


Interpretation: 13ยท16
Subject: ASME B31.3-1993 Edition, Chapter VI Inspection, Examination, and Testing
Date Issued: November 21, 1994
File: B31-94-o59
Question (1): In accordance with ASME B31.3-1993 Edition, Addenda a, if a weld has not
penetrated to the inside corner of the root face on one side of the joint and the remainder of the
weld is sound, does ASME B31.3 classify this defect as lack of fusion?
Reply (1): No, refer to Fig. 341.3.2 sketch (c).
Question (2): Can lack of fusion occur at the root of a groove weld joint?
Reply (2): Yes.

RE: Lack of Fusion vs Lack of Penetration B31.5

The definitions are clear to me.
Inspectors and NDE personnel have not problem to detect and is not question of IP or IF naming these imperfections when they detect them.
IMHO the Committee does not need to change.

Regards

RE: Lack of Fusion vs Lack of Penetration B31.5

Think of it this way, in the case of a butt joint, complete penetration means the weld melts all the way through the joint so one can see weld has penetrated all the way through to the root surface.

Complete fusion means that the weld has melted the base metal and "fused" to the member. Likewise with each weld bead, complete fusion means there are no voids between adjacent weld beads or between weld beads and the adjoining base metal.

Incomplete joint penetration means the weld did not penetrate the full thickness of the weld joint. So, there may be edges of the root face that are still visible.

One can have complete joint penetration, but have incomplete fusion where the weld didn't properly fuse to one side or the other, i.e., the root face is still visible on one of the two members, but is fully fused to one other side of the root.

AWS A3.0 most likely will provide a better definition and sketches to show the difference. You will however need to use proper AWS terminology. Incomplete fusion, not lack of fusion. Incomplete joint penetration, not lack of penetration.

Best regards - Al

RE: Lack of Fusion vs Lack of Penetration B31.5

Thanks DD. it seems it can be very challenging in moving the code committees to some sort of consensus that works for all smile

Huub
- You never get what you expect, you only get what you inspect.

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