Pipe Stress Analysis
Piping TechEng provides a complete package of pipe stress analysis. We look into all the required aspects of the piping system to ensure that the piping system and connected equipment will provide a safe operation for the defined life span.
Software Packages
Piping TechEng uses CAESAR II and Autopipe and their complementary tools for pipe stress analysis.
Pipe Stress Model
Pipe stress analysis starts with a piping system that has been already designed. If piping model is available, we transfer the model by pcf or other methods to ensure accuracy and to save on modeling time. We have developed multiple macro scripts that facilitates the process of model transfer. If the piping model is not available, the modeling tools of stress analysis software is used.
Process Properties
We work closely with process team to apply the process properties of each system such as design and operating temperature and pressure, specific gravity, etc. An accurate pipe stress analysis requires an accurate input of information.
Load Cases
By taking in to account all the loads and sources of stress, pipe stress analysis is intended to ensure that stresses on the piping system is lower than the limit defined by relevant code. Beside that, it is essential to keep the load on the connecting equipment within the allowable limit. Piping TechEng performs a comprehensive analysis so that all essential components are captured to meet the mentioned requirements. We define load cases and perform both static and dynamic stress analysis for all applicable sustained, displacement, and occasional loads. If the piping system experiences multiple thermal scenarios, we make sure to capture the worst case scenario as the basis of the analysis. Beside static loads, dynamic loads from sources such as relief device, vibration, pulsation, slug flow are some other items that are considered in load cases as required.
Piping System Supports
In the next step, supports such as weight supports, guides, anchors, and hangers are added to the stress model by following client’s standard or the industry best practices for maximum support spans. This step requires strong experience to achieve the optimum supporting in terms of the location and type. The goal is to apply sufficient support on the sustained loads such as weight and pressure while keeping enough flexibility for piping system to accommodate thermal displacements without experiencing overstress.
Code Compliance and Load Check
Once the stress analysis is complete, we perform a comprehensive check on the results such as code stresses, restrain force and moments, displacements, and loads on equipment connection nodes. Piping TechEng compares the results of stresses with the applicable code limits. ASME B31.1 for power piping and ASME B31.3 for process piping are two major codes with the most applications in the industry. In addition, we compare the loads on equipment such as pumps, compressors, and vessels with the recommended values from manufacturers, or relevant standards such as API 520 for pumps or the procedures such as WRC 107/297 for vessels.
Design Modifications
During comprehensive check of the results some overstress or overloads may be observed. In this step we make sure to address each and every one of them. The preference is to lowering loads and stresses by modifying the supports. If this does not works, we look at modifying pipe routing. Adding expansion loops, rerouting some portions of the piping system, or adding spring hangers are some examples of the changes that may apply in this step. Any routing modifications will be a part of information provided in pipe stress report.
Pipe Stress Report
Piping TechEng provides a complete pipe stress report that reflects all the items checked and their results. Typically the report consists of two parts.
Analysis and Results report
First part of the report provides information regarding the performed analysis and the results. This report includes information such as:
Supports and Piping Modifications Report
The second part of stress report includes the type and location of piping supports and the re-routing of piping system. This can be provided by multiple ways as per client’s preference. One typical method is to generate iso stress drawings that most of stress software packages such as CAESAR II and Autopipe provide them. If the piping system has a complex routing, the iso stress drawings may be difficult to follow. Piping TechEng provides the option to provide re-routing on a 3d model that is readable with client’s modeling software. This model also include supports with the symbology similar to what most pipe stress packages use. Each support is tagged by a node number. Piping contractor can refer to that node number in pdf report for forces and displacements on that supports. Our experience show that clients and contractors prefer this 3d model to iso stress drawings.