Question:

I receive a tailing lug deficiency message that states "The local stresses for the lug have not been calculated."  What does this mean and why is it presented?

Answer:

COMPRESS provides two methods to determine local stresses in the skirt or shell at the tailing lug attachment (1) Welding Research Council bulletin 107 (WRC-107) and (2) the EN 13445 (European pressure vessel code) method.

The WRC-107 method is applied only when the tailing lug is attached to the vessel shell. The method of this bulletin is not applicable when the lug is adjacent to a base ring on the skirt; the close proximity of the base ring provides additional stiffness that is not accounted for in the WRC-107 bulletin. Use of this method would provide overly conservative results. Consequently, COMPRESS does not perform the WRC-107 analysis when the tailing lug is on the skirt.

To obtain local stress analysis for case of tailing lug attached to skirt, select the EN 13445 method shown on the tailing lug design dialog.

Further discussion of the line load analysis used in the European pressure vessel code (EN 13445) can be found in EN 13445 "Unfired Pressure Vessels" Background to the rules in Part 3 Design.