There is no specific dimensional tolerance for weld root drape-thru (excessive root penetration) in B31.1. Refer to 127.4.2 (girth butt welds), C5 this section pertains to the condition of a weld root where an abrupt density change on an RT (radiographic test) film is not acceptable. Thus, if you have drape-thru or even concavity (suck back) and the RT of the weld root shows an abrupt density change, this condition must be corrected. If the weld does not require RT per B31.1, I would allow no more than a 1/32" drape-thru based on only a visual examination of the root.
ASME B31.1 provides acceptance criteria for a visual examination and for radiography in 136.4.2 and 136.4.5, respectively.
Yes, it is a tight restriction. However, I should have mentioned that this is our own internal requirements for weld roots in high fluid flow applications or in high pressure boiler tubing or piping applications. Excessive drape-thru can result in local flow disturbances downstream of a butt weld. For piping or tubing that falls under ASME Section I, VIII, B31.1 we mandate GTAW roots.
Regarding C5, the second sentence refers to the "internal condition" of the root surface of a butt weld, which implies to me any possible condition like concavity, drape thru or sharp transitions that could cause an abrupt density change in an RT. The concavity issue is spelled out in the first sentence because this could lead to a reduction in wall thickness beyond the minimum allowed by Code.
I read C5 differently. I'll have to look thru the interpretations. Thanks for the info. Sec I handles the internal reinforcement issue as internalbeing equal to the external. Therefore a .250" wall tube is allowed 5/32" internal reinforcement. A far cry from 1/32".
I'm sure there are occasions when the code should be exceeded for engineering reasons and I don't have the education to understand those. I've cut out many waterwall and superheater tubes and have seen a few variations on root contours.
Thanks metengr and pipewelder1999 for your contributions. But I still have doubt. I cannot get the clear picture from where I should find specifically that subject. Because in my case I should to present a good evidence to my subcontractor that shows clearly written that excess root penetration is acceptable or not...
The internal reinforcement that is referenced in the ASME B&PV code, Section I PW 35.1 applies to full penetration butt welds where the weld face reinforcement mentioned on the internal surface is treated the same as the weld face on the OD surface. The weld face is not, in my opinion, the weld root.
Regarding weld root penetration. The Code is very clear on this - there shall be FULL penetration. My opinion anything beyond full penetration at the weld root provides NO benefit, and could be harmful in certain applications. Keeping this in mind, one could make the case that ANY amount of excessive root penetration is NOT acceptable going above and beyond code requirements.
As I stated in my previous post, one has to take into consideration the specific application.
I agree that there is nothing gained from reinforcement internally or externally.
Am I reading your statement that the allowabe reinforcement on the inside of a complete penetration butt weld welded from one side is NOT the same as allowed for the outside. If so what is the allowable internal reinforcement per code. I have not looked at a current section I for a few years but I remember the note quite clearly.
We are talking about two ides on t his subject. One os what the code says and the other which is specific to a given design. As far as the code goes both Section I and B31.1 nothing has been given that limits the amount of reinforcement at the root other than limiting to the same amount at the cap.
Someone straighten me out on the code. I have a B31.1 but may be mistaken on the Sec I. If the code text is handy I would appreciate it as I have been mistaken for years regarding the Sec I requirements.
SecI has limits. PW-35.1 Inside same as outside. There could be arguments about this of course.
B31.1 Dont think the Code is really silent on this. If I had a problem,would go to the following.
1.Forward
2.127.4.2(C.5) General note(b) in the table does apply,however this is not a good reason for poor welding.
3.136.4 esp.Table 136.4.1
This should start a good argument in anycase. The end result would be that it would take less time to perform good work then argue about bad. Been here once or twice.
Notch effects from excess internal reinforcemnt? This would not benefit anyone. So what reason would there be not to follow SecI and SecVIII on this? The AI may ask you to justify another result.
pipewelder1999
By me pipewelder99,
I am in qualituy control and learning
by arguing with the best AIs in the industry,
believe me, I do not always win (more loses than winnings),
Whats the best weld out there: NO reinforsing at all inside or outside period. Of course, you are allowed a little in Sec VIII-1 and in Sec I as well, Sec I is more strict.
GB
pipewelder1999 and et al
Some additional information that I was able to locate regarding excessive weld root penetration;
Acceptance
The criteria which sets the level of acceptable penetration depends primarily on the application code or specification.
BS 2971 requires that the 'penetration bead shall not exceed 3mm for pipes up to and including 150mm bore or 6mm for pipes over 150mm bore'.
BS 2633 gives specific limits for smaller diameters pipes, e.g. for pipe size 25-50mm the maximum allowed bore penetration is 2.5mm.
ASME B31.3 bases acceptability on the nominal thickness of the weld, for instance, allowing for a thickness range of 13-25mm up to 4mm of protrusion. However, ASME notes that 'more stringent criteria may be specified in the engineering design'.
BS EN 25817 relates the acceptable protrusion to the width of the under-bead as follows:
Severity of service Moderate, D Stringent, B
Limit (up to maximum) h 1mm + 1.2 b h 1mm + 0.3 b
Maximum 10 mm 3 mm
Where: h = height of excess & b = width of bead (see Fig.1)
Avoidance
It is important to ensure that joint fit-up is as specified in the welding procedure. If welder technique is the problem then re training is required.
Thanks metengr for the code references. The one with the width to height ratio seems to make the most sense as that would typically change the angle that the toe of the weld enters the base metal.
Any of you know of any books on weld related failures I could read up on this?
I'm sure between all here we could write a volume or two on code compliance vs fitness for service vs industry practice vs what the inspector wants.
Genb, forgive me for my response above regarding the acceptance criteria for your acceptance criteria. It appears it may have been taken wrong.
Hey guys.... we are talking here is ASME B31.1. In which paragraph of this standard we can find the tolerance of root excess penetration? We cannot just go through different standards. We have rules to follow and every standard have their own applicability.
carlomaderazo;
The answer is there is no specific requirement limiting excessive root penetration in B31.1. The owner can specify excessive root penetration above and beyond B31.1 requirements... and yes, you can use specific requirements from other standards if they don't conflict with the requirements in the original standard.
