Acceptance criteria in D1.1 for allowable porosity?

By adaugherty Date 02-09-2009 21:25

I have a carbon steel stack that has just passed an MT test with only one instance of surface porosity on a lifting lug weld. It measures 1/32" but our customer's inspector insist that it's a safety issue if any porosity is present. I disagree because our engineer has figured a safety factor of 2 for the lifting lugs. My question is, can someone tell me where the reference is in the D1.1 that tells what the allowable acceptance is for surface porosity? I am thinking it's 3/8", but cannot find this ref to back up my arguement. I wish I had my D1.1 in pdf format so I could search for keywords!

Andy Daugherty
Industrial Environmental Systems
www.iesysinc.com
adaugherty@iesysinc.com

By hogan

Date 02-09-2009 21:49

Look at table 6.1. If I were that concerned with a por I would have required PT.

By adaugherty Date 02-09-2009 22:32

Thanks Hogan for the post...exactly what I was looking for. And I agree on the PT. I will use this ref to support my argument and try to get my equipment released to ship. Have a great day.

By CWI555

Date 02-10-2009 00:53

Better read the commentary before pulling that trigger.

Annex K 2006
*piping porosity (general). Elongated porosity whose
major dimension lies in a direction approximately
normal to the weld surface. Frequently referred to
as pin holes when the porosity extends to the weld
surface.

porosity. Cavity-type discontinuities formed by gas entrapment
during solidification or in a thermal spray
deposit.

Commentary Paragraph C-6.10
The code does not include acceptance criteria for liquid
penetrant testing based on bleedout of the dye. When
PT is used, the acceptance of any discontinuity shall be
based on a visual evaluation of the discontinuity after the
removal of the indicating medium.

C-Table 6.1 Item 8--Piping Porosity. Table 6.1 contains
visual acceptance criteria for surface-breaking piping
porosity, since this is visually detectable, and may
significantly reduce the cross-sectional areas of the weld
available to resist applied loads. Other forms of surfacebreaking
porosity do not reduce the cross-sectional area
as significantly (see Annex K for a definition of piping
porosity).

Therefore; unless modified by contract docs, porosity as found in table 6.1 means piping porosity. Not standard porosity also defined in annex K.
It also means it cannot be judged for the size of indication created by MT or PT, but rather by the visual criteria of table 6.1.

As will all codes there is a source of confusion involved in this:

Annex C (Normative)
Weld Quality Requirements for Tension Joints
in Cyclically Loaded Structures

This annex doesn't really specify a difference between porosity types.

5.24 Weld Profiles
All welds meet the visual acceptance criteria of Table
6.1 and shall be free from cracks, overlaps, and the unacceptable
profile discontinuities exhibited in Figure 5.4
except as otherwise allowed in 5.24

I take this statement in 5.24 to refer back to Table 6.1 which utilizes the term piping porosity.
Some have tried to argue that annex C applies. the problem with that is, annex C is directly invoked under para 6.12 which is part of the RT criteria.

To make a long story short, unless your contract docs specifically make a delineation, porosity as found by either MT, PT, or VT is to be judge by table 6.1
If they insist on more without any more backup than opinion, I would suggest back charging them for the work.

Regards,
Gerald

By 803056

Date 02-11-2009 16:25

Piping porosity is the only porosity addressed by D1.1 Table 6.1.

Piping porosity is a particular type of porosity, i.e., it has depth extending down toward the root of the weld. This is in contrast to spherical porosity that is not addressed by D1.1 and is not a basis for rejecting a weld unless it contains slag, in which case it is a slag inclusion. Slag inclusions are rejectable because they indicate incomplete fusion is present.

An isolated pore hole is not a concern, but I believe the presence of uniform porosity, elongated porosity, aligned porosity, cluster porosity is indicative of other problems that should be looked into.

That's my humble opinion on the subject.

Best regards - Al