First, the counting thing is just my signature (because I like it so much)
Let me describe it this way......
First let me assume this is an ASME Section VIII Division 1 design. If it is not,.....never mind....
Dimpled or Embossed Assemblies, which consist of a dimpled (embossed) plate welded to another like or plain plate (un-dimpled) and for which the welded attachment is made by fillet welds around holes or slots, shall be constructed in accordance with the requirements of UW-19(c). The rules of Appendix 17 are similar but are applicable only to “weld through” processes. UW-19 (c) utilizes the following for calculating the thickness of plates of “fillet welded” embossed assemblies.:
1. Dimple-to-Dimple Plate thickness, per UW-19(c)(2), established in accordance with UG-101 [Proof Test]
2. Plain-to-Plain Plate thickness, per UW-19(c)(3), established in accordance with UG-47 (a) [Braced and Stayed Surfaces]
3. Dimple to Plain Plate thickness, where the dimpled plate (external jacket) is established per UW-19(c)(2) and the Plain Plate (inner shell) established per UG-47 (a). Of course this is in addition to the UG-27 calculations which may govern. Many variables and configurations exist.
Depending on the configuration you may want to perform UG-28 calculations. When calculating the inner shell thickness for either a negative pressure or for differential pressure, such as may occur during operation of the vessel when the jacket has a higher pressure than the vessel, you may take credit for the stiffening resulting from the jacket welds (plain or dimple). This is accomplished through U-2 (g) and may need to be invoked to address the loadings specified in UG-19 (a) and UG-22 thus complying with the requirements of UG-28 and UG-29. Dimple jacket external pressure design is described in UG-101 (p)
There are three kinds of people in this world; those who can count and those who can't.