American Welding Society Forum
How would you measure fillet weld size on coped tube intersections?
For instance/example a perpendicular tube intersection with 1.5" OD round tubing. Tube intersecting is coped to match 1.5" OD of other tube. Fillet weld size .125", continuous weld around joint.
How can you quantify/measure the size of the weld nondestructively. Or is the welding symbol lacking info?
How can it be a fillet weld all around?
At two locations around the joint, it represents a t-joint momentarily and engineers have a tendency from what I have seem to identify using a fillet weld symbol.
The joint configuration changes as you move around the joint. The strength of the fillet weld is based on the shortest failure path through the weld, i.e. the theoretical throat. It is the shortest failure path through the weld that is of concern.
The Engineer is delegating the responsibility for the joint detail to contractor. The contractor is tasked with coming up with the geometry that provides a weld that meets the load capacity required to transmit the load from one member to the next. The engineer is telling the contractor indirectly what dimension is needed to provide the strength required.
Understandably we need to work together to achieve what the customer is asking for. If they are lacking specific requirements it is up to them to give us that I believe. For instance if they reject a weld like I've mentioned. On what basis could they reject it. I think it is probably just a lack of specific details, probably because it would inccurr more work and clutter drawings.
This sounds the same as a pipe branch/saddle joint. I used to work as QC of an US welding shop and practically the drawings always give detailed sectional views of such joint other than using standardized AWS A2.4 welding symbols.
My case was for pressure retaining so the branch pipe was also beveled with changing degrees. For your case if it is structual purpose maybe there is no bevel required. It is like a weld gradually changes from fillet (or G+F combination) to pure groove with depth of the branch tube wall thickness.
What I did was measuring the two fillet positions using standard fillet gage according to drawing details. The remaining part I just verify and make sure no underfill, i.e. weld metal are not below branch pipe surface. For this purpose a flash moving around with light parallel to the branch pipe surface will give you quick judgement.
Yeah most of the time I see joint geometry like this with fillet welds it all very small comparatively. Most of the welding is d17.1 in smaller diameters of tubing .250 OD to 1.5" OD. Also mostly fillet welds only.
I'm just trying to cover my bases overall and this scenario is one still in question. Our customers hold our feet to the fire over any differences they may find, understandably. More often than not, it is for issues that are hard to measure or quantify. So I'm just looking for a way to prove nondestructively fillet weld size. It's worse than pulling teeth trying to get DOD customers to change or update prints even when they are deficient without proper logical cause.
By Jovi Zhu
I have to confess that D17.1 is an uncharted area for me. Curious about the welding process, is it manual GTAW? since you mentioned fillet welds for small OD tubes, it excludes the possibility of using other processes in my head~
The tube wall thk is normmally up to the calculated weld throat, i.e. 0.088", roughly based on my understanding of what the engineer do. As per the "shortest failure path" already pointed out by Al, a tranditional GTAW process can give a penetration more than the required fillet weld size. For your case I'm afraid that you might need to worry about the burn-through more that the fillet weld size.
A cross-section macro coupon may give you confidence showing to your customer and with that workmanship sample the two "fillet" positions are merely to provide a smooth rounding avoiding sharp corners. You may have a chance to get yourself out of that small corner and no one will ask you to do any measurement beyond a visual inspection.
Just some thoughts~
Yes its Manuel GTAW. The melt through and burn through are a concern but falls well when the requirements of d17.1 when it has happened before. We have cross sectioned other joint geometries to identify throat and leg size when the geometry is abnormal. We use these as workmanship samples like you've mentioned. This was derived from our facility to help identify weld size.
With coped tubing how can establish a weld size when the joint geometry is always changing around the tube. It would need to be identified by the customer in my mind. If your engineering a weldment to achieve certain results, how do you prove that you have achieved the correct size of weld?
Workmanship samples, mock-ups, they can be your friend.
By Jovi Zhu
Back to the deffinition of fillet weld by AWS A3.0:
"A weld of approximately triangular cross section joining two surfaces approximately at right angles to each other in a lap joint, T-joint, or corner joint."
For your case there will be two ways to prepare the tube ends:
A. Tube ends are shaped to suit the curve tube surface but the exposed cutting face at a single point is always vertical to the coped tube axial;
B. Tube ends are shaped with the cutting face suiting the curve tube surface perfectly;
When a close look is taken,
For Case A the root face gradually opens and becomes a groove face with angle from 0(fillet position) until 90(a lap joint is formed);
For Case B the root face never opens and always suits the tube curve. Most welded areas are like "scarf groove" joints within the definition of groove welds other than fillet.
I assume for your tubes of that small OD, B is probably your case as it can be achieved by easier machining or grinding.
As mensioned in my earlier post, we know when inspecting groove welds we do not measure the size. If we do not see any underfill, the size is there.
Hope all the above can defend yourself from being asked how to measure and evaluate all around the joint, as it is per se not an all-around fillet weld.
Thanks for your help and input.
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