The purpose of this report is to summarize the background of Code Cases N-122-2 and N-318-5. Case N-122-2 is included in this report as an Appendix. Case N-318-5 is Appendix E of Report 2. Frequent reference will be made in the following text to these Cases. The definitions of symbols used in this report are those of the Cases. Other symbols are defined where used in the text and/or tables.N-122 and N-318 were first published around 1980; some four years after the publication of Welding Research Council Bulletin 198. The motivation of the development of N-122 is described by the following extract from WRC 198.A piping system design requires the specification of a corresponding support system whose function is to transmit forces to the piping system or to limit its deformation. Structural attachments which connect the pipe system with its supporting elements are classified into two general categories, those integral to the piping system and those that are not. Lugs welded to the pipe are examples of integral attachments, whereas roller supports and various types of clamps are examples of nonintegral attachments. Article NB-3645 of Section III of the ASME Boiler and Pressure Vessel Code requires that the effects of attachments in producing thermal stresses, stress concentrations, and restraints on pressure-retaining members shall be taken into account in checking for compliance with design criteria.The preceding quote is directly relevant to N-122 (Class 1 piping); WRC 198 covered only Class 1 piping. However, having a relatively simple method of calculating stresses at lugs, the analogous N-318, for Class 2 and 3 piping, was developed.