Help with welding symbols required 3

[CobusvanJ]

Hi,

Please see the attached pdf and the clouded weld symbols. Curently we are having a disagreement internally about the proper symbols to use, on the top weld I drew in my take on the weld symbol (fillet far side, flush weld near side)as I don't think the double fillet symbol is correct.

On the bottom weld it shows a 45deg weld prep symbol, however there is no preparation involved, the plates are just simply welded together at an angle with a 'filler' weld. Even though I disagree with the current symbol, I am at a loss as to what the correct symbol should be. Thus far I think it should just be a line underneath the arrow line to show 'flush weld', is that correct?

 

[GRoberts]

I think the bottom symbol is fine. The top symbol should be a single bevel groove weld on the near side, and a fillet on the back side. It doesn't matter how you get to the joint configuration (i.e. you say you don't do any weld preparation to the end of the member) as far as the weld symbol is concerned, just what you end up with in the end. Since they have the weld-all-around symbol, these joints are circular, correct?

 

[Ron]

GRoberts.....the weld all around symbol does not only refer to round configurations. It means "the perimeter". I agree with your opinion on the symbols.

 

[GRoberts]

Ron,
You are correct. I was just trying to make sure that the "all-around" symbol wasn't mean to refer to welding both sides of the joint since it was already a double weld symbol.

 

[DVWE]

Cobusvanj,

If you want to be technically correct about this, what you have in both instances is a skewed joint. AWS A2.4 (standard for welding symbols) has a section dealing with these. You might want to get a copy of 2.4.

I have attached the sections which talk about skewed joints and how to detail them.

 

[gtaw]

I would fall back on a definition of the fillet weld and the groove weld:

A fillet weld goes on the joint.
A groove weld goes into the joint.

As mentiones, both welds shown are skewed joints and are neither a true fillet weld nor a true groove weld. AWS D1.1 calls them a skewed T-joint and does not call the welds either a fillet or groove weld.

There are also considerations that must be given to the dihederal angle between the members, the position in which the welds are made, and the welding process. The is a high probability there will be incomplete fusion in the root of the welds depicted. AWS D1.1 addresses that condition with their "Z-loss" factor.

A standard welding symbol leads to confusion with the skewed T-joint configuration. One recommended approach is to use the reference line with the arrow pointing to the appropriate joint and listing a detail in the tail of the welding symbol. The detail should show the weld cross section (as you do in your attachment), but also indicate the "Z-loss" in the root and the critical dimensions. AWS D1.1 does a good job of defining what dimensions are required to be included by the engineer and those to be included on the shop drawings that are used by the welder and inspector.

Best regards - Al

 

[gtaw]

I just looked at the attachment included by DVWE.

AWS A2.4 has been revised. The current edition is 2007.

It should be noted that the examples in A2.4 may or may not be "good" examples of proper joint designs. The function of the standard is to show different types of welds using standard AWS welding symbols. It does not address design nor workmanship requirements. Those issues are addressed in the appliable "construction" code, i.e., D1.1, D1.5, etc.

The examples taken from AWS A2.4 by DVWE do not take into considerations those issues required by AWS D1.1 and many other AWS welding standards, it simply isn't part of A2.4's mandate.

Best regards - Al

 

[GRoberts]

I would still maintain that they are both groove welds since AWS D1.1 even permits pre-qualified groove weld T-joints to skew up to 45 degrees. (see the notes at the beginning of figure 3.3/3.4) Even going beyond 45 degrees does not mean that they are not a groove weld, but only that they are no-longer pre-qualified.

Also note D1.1 figure 3.8, which calls what are basically T-joints (in the form of T-, Y-, & K- joints) that are skewed from 15-180 degrees, groove welds.

 

[DVWE]

GRoberts,

I wouldn't consider these groove welds just by definition as mentioned by gtaw, a groove weld penetrates partially or completely into both members. That is not the case here.

gtaw,

Regardless of what is or is not mandated by 2.4, welding symbols are universal to all AWS standards - and for that matter, adopted by many other standards including ASME. The most correct way to detail this joint in particular is per 2.4. Although the attachments I provided are from an earlier version, I don't believe that skewed joints were changed in the 2007 version. As far as workmanship and other issues are concerned, yes, those must be mandated by the code of construction.

 

[gtaw]

I have no argument with your choice of weld details extracted from A2.4. I just wanted to make the point that AWS construction codes, D1.1 as an example, have design requirements that must be considered separately from those examples included in A2.4.

While the welding symbols included in A2.4 are adequate to address most welds, there are situations where a separate detail is a better means of providing the information needed by a welder.

AWS D1.1 does not require exclusive use of welding symbols. Clause 2.2.5 contains the following text: "Shop drawings shall clearly indicate by welding symbols or sketches the details of the groove welded joint and preparation of base metal required to make them."

Skewed T-joints are a special case that falls in between a fillet weld and a groove weld. Depending on the dihedral angle between the two members, the weld at the end of the nonbutting member can be considered to be a groove weld or a fillet weld. The joint penetration can be a partial joint penetration when the Z-loss is considered (again depending on the dihedral angle). The weld on the opposite side isn't really a fillet weld if the dihedral angle is such that Z-loss has to be considered and incomplete fusion to the root is expected. Many people will agree that one major premise for properly sizing fillet welds is that fusion to the root is a prerequisite. That may or may not be the case with dihedral angles less than 60 degrees depending on the angle, process, and position of the welding.

Z-loss can be as much as 3/8 inch in joints having an angle of less than 45 degrees. Z-loss is not addressed by all fabrication codes and is not considered by some designers, but it certainly should be considered regardless of what fabrication standard or code is used for design.

Annex B of AWS D1.1 lists the factors to be used when sizing fillet welds in Skewed T-joints when the dihedral angle is 95 degrees down to 60 degrees. The welder should be able to meet the "fusion to the root" requirement. However, when the dihedral angle is less than 60 degrees, the joint more closely resembles the conditions of a partial joint penetration groove weld where fusion to the root is not necessarily expected, hence the Z-loss must be accounted for.

These skewed T-joints make for some lively discussions.

Best regards - Al

 

[DVWE]

While the welding symbols included in A2.4 are adequate to address most welds, there are situations where a separate detail is a better means of providing the information needed by a welder.

AWS D1.1 does not require exclusive use of welding symbols. Clause 2.2.5 contains the following text: "Shop drawings shall clearly indicate by welding symbols or sketches the details of the groove welded joint and preparation of base metal required to make them."

gtaw,

I think you hit on some very, very key points there. After all is said and done, the welder (or fitter) must be able to build what is communicated to him/her on the drawing. The information contained in the drawing must be adequate/sufficient to clearly detail what is required. I can't tell you how many arguments I've ended with that very statement.

These skewed T-joints make for some lively discussions.

Indeed!

 

[GRoberts]

DVWE,
A groove weld need not "penetrate" both members. Otherwise you could never have a groove joint in a T configuration. Obviously that is not the case as it is common to weld t-joints with groove welds.

 

[DVWE]

GRoberts,

I guess I was typing before really thinking about that...

Thank you.

 

[gtaw]

It's difficult at best to think of every possible permutation of every answer to every question posted.

Everyone has differents experience and look at the same problems from different prospectives. That's what makes these forums so valuable. Different view points based on different experiences provides the best conclusions when considered in aggregate.

Best regards - Al

 

[jovizhu]

Dear all,
Maybe we don't need to trap ourselves.
My understanding is that the weld symbol is not must.
We can refer to AWS A2.4 Para. 6.13, 7.7 and Fig. 31 for skewed joints.
For some un-regular and complicated welded joints, detailed dimensions can be shown on the drawing in lieu of the welding/weld symbols.

 

[unclesyd]

I've always been able to convey extra information by making a bend in symbol arrow. By doing this you can add lines with additional symbols parallel to the base line.

 

[gtaw]

I hate to recount how many times I've seen engineers and designers try to "force" a standard welding symbol to define a weld that simply couldn't be described by a standard welding symbol. Invaribly they say, "You know what I want, just weld the darn thing."

When a standard welding symbol doesn't work, don't force it to define something it can't. Sketch it and show the welder what is needed. Just remember, a 45 degree groove will not provide sufficient access to provide a weld that is equal to the depth of preparation. The weld will usually be something less than the depth of the bevel. A weld size equal to the depth of bevel minus 1/8 inch is conservative, but safe.

A fillet weld in a skewed joint where the the dihedral angle is 45 degrees is no different. As a matter of fact, the structural welding code no longer refers to fillet welds in a skewed joint. They are simply welded skewed joints. Once again, there will not be fusion to the root when the dihedral angle is less than 60 degrees for most cases. Refer to AWS D1.1 for the Z-loss factor when the dihedral angle is less than 60 degrees.

Best regards - Al

Best regards - Al