Calculating Stress for High-Temperature Piping

Stresses arises in a piping systems are not only depend on pressure and/or temperature. It mainly depends on :

a. Fluid Temperature.

b. Change in atmospheric Temperature (e.g. day & light).

c. Pressure.

d. The piping configuration (isometric).

e. Number of elbows and piping system flexibility.

f. Number & type of pipe supports.

g. Piping material.

h. Expansion and stresses arises from the equipment in which the piping connected.

i. Wind load & Earthquke.

j. Type of equipment (rotatory or static) and vibration transmitted to piping system.

The need for formal stress analysis should be determined by designers with extensive flexibility experience. Hot piping connecting to strain-sensitive equipment such as pumps, compressors and turbines shall be closely reviewed for possible full analysis.

For other systems full stress analysis is required when the following criteria is not satisfied :

D E / (L-U)² ≤ 0.03 [ASME B31.1]

Where,

D = Nominal pipe size, in inches.

E = Expansion to be absorbed, in inches (E = U e)

L = Developed length of line axis, in feet

U = Anchor distance, in feet = Length of straight line joining the anchors

e = Coefficient of expansion.

I recommend using a computerized piping design and stress analysis software for steam turbine such as AutoPIPE or Ceaser.

AutoPIPE or Ceaser is a stand alone computer aided engineering (CAE) program for the analysis and design of piping systems.

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