Spring hangers may be variable or constant spring hangers. Springs are engineered hardware, which permit movement of the pipe (by providing less than rigid restraint) and apply an upward force to the pipe. Variable springs are modeled as a combination of a vertical, two-way restraint with a stiffness equal to that of the spring constant, and an external force (equal to the spring preload) acting in the +Y direction. Constant springs are modeled as only an external force (equal to the spring pre-load) acting in the +Y direction, since the spring constant is effectively zero. Modeling of spring hangers are extensively discussed in Section 2.4 (Hanger Design) of these pipe stress analysis notes, so they are not discussed further here.
2.4.1 Variable Spring Hanger Design Basics 2.4.2 Load Variation 2.4.3 Hanger Selection Table 2.4.4 Hanger Design Process — Restrained Weight, Free Thermal, and More.. 2.4.5 Restraint Placement Using Distance to First Rigid Criteria 2.4.6 Notes on Hanger Design 2.4.7 CAESAR II Hanger Design Control and Options
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