Methods for simplifying the calculation of secondary stresses at construction sites

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Simplified method: The piping system in the judgment formula must satisfy the following assumptions: (1) Both ends of the piping system are fixed points； ⑵The diameter, wall thickness, and material of the pipes within the piping system are all consistent ； ⑶Piping system without branches and supports ； ⑷The number of thermal cycles during the service life of the piping system is less than 7,000. The judgment formula is: DN × Δ / (L–U)² ≤ 228.3. Here, DN refers to the nominal diameter in mm; Δ represents the total deformation of the pipe system in mm; the expansion length per meter of pipe for every 100 degrees is 1.2 mm; L is the extended length of the pipe system between its fixed ends in meters; U is the straight-line distance between the fixed ends of the pipe system in meters. This formula is not applicable to the following pipes: (1) pipes with a number of cycles greater than 7000, which are at risk of fatigue; (2) pipes in which the additional displacement at the ends accounts for the majority of the total displacement; (3) pipes with unequal-leg U-shaped bends where L/U > 2.5, or zigzag-shaped pipes that are approximately straight.