How to roughly estimate the thrust exerted on a fixed bracket?
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Without using software for detailed stress analysis, how can one roughly estimate the amount of thrust exerted on a fixed bracket? How is such a calculation carried out? . Pipe specifications and material are known ； The configurations between the fixing frames are L-shaped, Z-shaped, square, and space-compensated, with the lengths of each section known ； Ignore the friction of the pipe rack, and assume an ideal condition for the guide supports.
Based on the experience gained in estimating pipe thrust, this simplified method can be tried: first calculate the thermal expansion amount ΔL = α·L·ΔT (where α is the linear expansion coefficient of the material), and then use the elastic force formula F = EAΔL/L to estimate the thrust (where E is the elastic modulus and A is the cross-sectional area). For L/Z-shaped compensation sections, it is recommended to treat the elbow as a rigid node and perform calculations by superimposing straight sections. However, this simplified calculation ignores secondary stresses; it is actually recommended to leave a 30% margin. The specific parameters can be found in Appendix D of GB/T 20801 or ASME B31.3.
The thrust exerted by a fixed support can be estimated using simplified formulas, and it is primarily composed of pipeline friction force, the elastic force of the compensator, and the forces resulting from pressure imbalances. The following are common methods for estimation: 1. Thrust generated by the friction force at the movable support (the most common case). This is one of the main horizontal forces acting on a fixed support. The calculation formula is as follows: P₁ = μ × q × L, where μ is the friction coefficient (0.3 for steel-to-steel contacts, and 0.1 for PTFE sliding supports); q represents the weight per unit length of the pipeline, plus the weight of the fluid and the insulation layer (in N/m); L is the distance between fixed supports (in meters). Example: For a DN150 steel pipe, q ≈ 600 N/m, L = 4.2 m, μ = 0.3 → P₁ = 0.3 × 600 × 4.2 ≈ 756 N
Elastic force is the dominant force, and it is also the part that is difficult to calculate. Friction accounts for only a small portion.
After reviewing some literature, there are several simplified models for calculating the thermal expansion force. 1. The Grinnell method, for example, the thermal expansion force in the X direction is Fx=0.01*Kx*C*I/L². 2. Guided cantilever method (simply supported beam method). 3. Elastic center method. Those who are interested can search for the specific details on their own.