Piping Stress Analysis
STI engineering (Design & Consulting)
Global Design, Consulting, Management and Digital services
Structural integrity and functionality in overstress and overload situations
In piping systems with high forces—common in setups involving high temperatures, pressures, large diameters, or special materials—it's crucial to predict potential overstress or overload situations. Manual analysis falls short in these cases; instead, computerized calculations are necessary.
Neglecting this analysis can lead to severe consequences, including breakage, premature component replacement, and increased maintenance. The primary goal of this analysis is to ensure structural integrity and maintain system functionality throughout its entire service life—both during operation and downtime. Common issues arising from the absence of a dedicated Stress Analysis include:
Piping Stress Analysis is closely tied to the layout of piping systems and the placement and type of supports and constraints. The piping layout must consider stress and bearing requirements, provide sufficient flexibility for thermal expansion, and use appropriate routing to allow for simple and cost-effective supports. Additionally, it must ensure controlled expansion throughout the system.
Solutions are refined through an iterative process following a cost-effective approach. This starts with adjusting the arrangement configurations and progresses to introducing specialized components like elastic supports and expansion compensators.
Analysis Input
The first step in performing a piping stress analysis is to accurately input the characteristics and routing of the lines into the software. Based on the design data, the analyst enters the properties of the piping, fluids, insulation, and the system's environmental conditions. This allows the program to correctly simulate the pipes' behavior under flexural, torsional, and weight loads. The simulation takes into account the geometry and stress intensification factors (SIFs) caused by components such as bends, tees, olets, and valves.
Another crucial step before conducting the actual analysis is identifying and setting up the various load cases affecting the system. The designer separately analyzes and combines the effects of temperature, pressure, and weight, as well as occasional loads from wind and earthquakes. For sizing and design purposes, the most severe case among those considered is then used.
Before conducting the final system verification, it's crucial to properly evaluate the supports and the constraints they exert. The support, regardless of its type, significantly influences the line stress. Therefore, its sizing and placement are essential for proper stress verification. Following design standards, one ensures that all positioning criteria are met (such as maximum span between supports, distance from bends, and distance from equipment spouts).
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Analysis Output
At this stage, the generated calculation reports are extracted and analyzed. Several key values must be checked to ensure successful verification and determine the next steps, if needed:
When these values are not met, action is taken in various ways. To reduce stresses, more flexibility is added to the system by creating additional loops and sections. However, this requires striking the right balance, as excessive flexibility can lead to additional costs, reduced resistance to occasional loads, increased vibration, or pressure drop.
For supports, once the type is defined (shoe, post, dummy leg, etc.), standard collections—generally provided by customers—are consulted. These collections indicate the maximum loads a given support can handle. If these are lower than the calculated loads, the support's size is increased or a special one is designed to accommodate the stresses involved.
A calculation report can only be produced when all parameters, including safety coefficients, are met.
This document includes all input data considered in the calculation, the regulations followed, and the main information about the analyzed lines. It highlights the most stressed points and their stress percentages relative to the allowable stress.
As an annex, we can provide isometric sketches showing the location and type of supports, along with a detailed calculation report. This report contains load and displacement values for each individual node (constraint, curve, fitting) in the system.
STI Engineering, with its multidisciplinary approach, excels in handling complex situations in the Oil & Gas field. The company's design teams are skilled in Piping Stress Analysis, enabling them to tackle even the most challenging projects.