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Occasional stress is “The sum of longitudinal stresses produced by internal pressure, live and dead loads, and those produced by occasional loads,” according to ASME B31.1, paragraph 102.3.3(A). Occasional stresses can exceed the allowable code stress by a given percentage depending on frequency and duration of the load; for ASME piping codes, this is typically 15% or 20%. For example, wind loads can only exceed the allowable code stress by 15% due to their frequency, but seismic loads can exceed by 20% due to the relative infrequency of the loads.

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Pressure design basics

As a pipe stress analyst, it is critical to understand how wall thickness is determined. If the pipe wall is too thin, it will not matter how the pipe is supported; it will fail. Typically, the engineer designing the system also will determine the wall thickness; however, the wall thickness is also verified during the pipe stress analysis. Most engineers are more concerned with mass flow and pressure drop, therefore the effects of pipe size and wall thickness may be lost on them. Going to a thicker pipe wall or a larger pipe size may be worth the material costs, versus facing design issues and added pipe-support costs in labor and materials.

⬆️ cold box installation

Basic of Caesar 2 API610 analysis ⬇️

Module 2, Pulsations and Other Forces in a Reciprocating Compressor ⬇️⬇️

Caesar II: input basics 1

Caesar II:input basics 2

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Buried Piping/Pipelines Stress Analysis with PASS/Start-Prof Tutorial

Controlling Piping System Vibration ⬇️⬇️⬇️⬇️

The method used to solve a particular vibration problem depends on the type of vibration and the type of piping system. For example, adding restraints to a piping system will not solve a vibration problem caused by high acoustic energy.

It is not always possible to eliminate or isolate the source of vibration in many piping systems. Therefore, other means must be used to control vibration. Some common methods for doing this are briefly described below.

Bracing ⬇️

One way to control piping vibration is by adding bracing (i.e., restraints) to the system. This increases the mechanical natural frequency of the piping, thus ensuring that resonance due to low frequency excitation will not occur. It also limits large deflections that could be caused by slug flow, water hammer, etc.

When bracing addition is being considered, it must be confirmed that this will not adversely affect the thermal flexibility of the piping system. Adding restraints increases the system stiffness and can cause higher pipe thermal stresses and end-point reaction loads. New thermal flexibility calculations may be required to confirm that the design is acceptable after adding the restraints.