Piping force, moment, stress

Acceptable comprehensive methods of analysis are analytical, model-test, and chart methods, which evaluate for the entire piping system under consideration the forces, moments, and stresses caused by bending and torsion from a simultaneous consideration of terminal and intermediate restraints to thermal expansion and include all external movements transmitted under thermal change to the piping by its terminal and intermediate attachments. Correction factors, as provided by the details of these rules, must be applied for the stress intensification of curved pipe and branch connections and may be applied for the increased flexibihty of such component parts. 

Example 11.17. A 12-in. NPS Schedule 160 branch and run pipe are attached to one another. The design pressure is 2200 psi. The allowable stress at ambient temperature is = 17,5 ksi and at design temperature is S = 12.0 ksi. In addition to the internal pressure, the branch is subjected to externally applied forces and moments from thermal expansion of connecting piping. These moments and force are M = 600,000 in.-lb Mg = 900,000 in.-Ib M, = 750,000 in.-lb and Fma = 90,000 lb. The nozzle is designed for 20,000 cycles. Using the design procedure of the ASME-ANSI B31.1 Code, what is the total applied stress and what is the allowable stress ... 

The Stress-Rang e Concept. The solution of the problem of the rigid system is based on the linear relationship between stress and strain. This relationship allows the superposition of the effects of many iadividual forces and moments. If the relationship between stress and strain is nonlinear, an elementary problem, such as a siagle-plane two-member system, can be solved but only with considerable difficulty. Most practical piping systems do, ia fact, have stresses that are initially ia the nonlinear range. Using linear analysis ia an apparendy nonlinear problem is justified by the stress-range concept... 

Increasing pipe-wall thickness will not remedy overstress as it would in the usual fixed-load static problem in fact this tends to increase the forces and moments at the ends [see Eq. (9-8)], Undesirable thermal stress conditions can only be relieved by proper flexibility design. 

Forces and moments on the piping resulting from thrust developed by full opening of the relief valve(s) are determined in the stress analysis. Dynamic amplification load factors are considered in the determination of the... 

---