welding symbols

[holdpt]

We have 1/4" plate lapped onto a C15 and the detail drawings have a typical fillet weld symbol with a 1/4" size. D1.1 calls for a maximum fillet size of 3/16" for a 1/4" plate thickness. However, it also says that if the weld size is detailed as throat thickness equal to the 1/4" plate thickness then that is acceptable. My question is when do you know when symbols dictate throat thickness or leg thickness? I always thought throat thickness was additional information needed in the tail or general notes.

 

[gtaw]

The maximum fillet weld size pertains to lap joints only.

The weld size specified by the fillet weld symbol on the fabrication drawing is the leg dimension, not the throat dimension. The minimum fillet size for 1/4 inch thick material is 1/8 inch, not 3/16 inch. Take another look at table 5.8, you are looking at base material thicknesses greater than 1/4 inch through 1/2 inch.

If you multiply the leg dimension by 0.707 you will get the dimension of the throat if the fillet weld has a convex or flush (face contour) face. However, the welding symbol specifies the minimum leg dimension for an inscribed isoceles right triangle. If the nonbutting member is skewed, annex B should be used to calculate the required weld size needed to maintain the required strength.

Skewed joints are a special case. The fillet weld is applicable when the dihedral angle is no less than 80 degrees, but no more than 100 degrees. If the diheadral angle is less than 80 degrees the design drawing must specify the required throat and the fabrication drawings must specify the leg dimensions that is required to produce the specified throat. If the dihedral angle is less than 60 degrees the fabrication drawings must specify the leg dimension that also factors in the Z-loss.

Best regards - Al

 

[drumsdw]

I agree with GTAW on this one. He hit the nail on the head.

 

[holdpt]

Thanks for clarifying the leg vs. throat, but I did not state minimum size. The max. size is stated in fig. 2.1 from 2.4.2.9.
Although 1/4" weld size was called out, the welders performed a traditional 3/16" seal weld. I was trying to determine if a complete reweld was necessary to meet the size.

 

[gtaw]

What country and what welding standard are you using?


Best regards - Al

 

[holdpt]

USA, D1.1 2010.

 

[gtaw]

It is customary to specify the leg dimension when using AWS welding symbols. Check AWS A2.4.

Best regards - Al