What is Piping stress analysis – In simple words and why is it important
What is Piping stress analysis – In simple words and why is it important Home / Learning An introduction to stress analysis and its importance Introduction to pipe stress analysis: Pipe stress analysis is the study of stresses in a piping system. It is a term applied to calculations, which addresses the static and dynamic loads such as deadweight (self-weight of the pipe including fluid, fittings and its associated components), internal and external pressure, thermal loads (due to change in temperature), seismic loads, wind loads, vibration, water hammer, steam hammer, slug force, PSV reaction force, etc. Not all the type of loads are applicable in every system e.g. if the system temperature is expected to stay at ambient conditions, thermal loads will not apply. The applicable loads derive from the design basis. We will cover separately an article on the “Design Basis†(both for nuclear and non-nuclear applications). The objective of the stress analysis is to calculate these loads and strategically design the layout which allows required flexibility (e.g. expansion loops or change in the direction of pipe) and provide the constraints (directional and rotational) using piping supports, anchors, and hangers. The type of supports can be rigid, spring, snubbers, etc based on the stresses and forces in the piping system. Why Stress Analysis is so important: We have practically seen many failures where the stress analysis is not performed properly and/or the required supporting system is not installed in the field as per the design. Some of our personal experiences are: 1. Steam Pipe header: Complete block of the foundation shifted. You can imagine the amount of forces generated in the pipe header due to thermal expansion which shifted the complete concrete block. In this case, the importance of stress analysis was completely ignored. 2. All loads from the design basis not considered during the analysis. 3. Earthquake anchor movement for Seismic loads response spectrum not properly analyzed. 4. Cold pull suggested by design based on the analysis not properly implemented. (Note: sometimes the cold pull of pipe is needed due to higher expansion expected because of high temperature and a long run of pipe. In those situations a cold pull is recommended to accommodate the full expansion when the pipe is heated and expands). 5. The travel stop pin from the spring hanger is not taken out. 6. Missing nuts and bolts in the hangers. A very common problem in a running station and ignored. 7. Allowable forces at the equipment nozzle exceed the allowable provided by the manufacturer of equipment such as Pumps, compressors, heat exchangers, vessels. This is a very common situation for a stress engineer when it is not practically possible to limit the forces at the equipment nozzle provided by the equipment manufacturer. A solution to this is to work together with the equipment manufacturer engineer as they generally have more margins than defined in their standard specifications. I have faced and resolved this type of issue on many occasions. Objectives of Piping Stress Analysis: The main purpose and objective of piping stress analysis is to ensure structural integrity and to maintain system operability. It can be elaborated as below: • To ensure adequate flexibility in the piping system for absorbing the thermal expansion of the pipe. • To ensure that the stresses in the piping components are within the allowable limits with respect to applicable codes and standards. • To keep the piping connected equipment nozzle loads within specified allowable limits with respect to relevant standards (e.g. NEMA SM 23, API 610, API 661, API 667, ASME sec III, etc.) and Vendor allowable. • To select the correct type of pipe support based on piping stress calculation. • To check and ensure pipe displacements at maximum and minimum temperatures for clash-free routing. • To calculate and ensure loads and moments on the supporting structures are in the acceptable range with respect to civil requirements. • To solve dynamic problems in piping, such as those due to seismic loads, mechanical vibration, acoustic vibration, fluid hammer, pulsation, transient flow, relief valve discharge. • To ensure leakage proof flange joints. • To find out unintentional disengagement of pipe from support. One of the prerequisites for satisfactorily performing piping stress analysis is to become familiar with the principles of strength of materials. Below is a brief understanding of pipe material behavior under stresses in a piping system. Stress-strain behavior of material: Typical stress-strain behavior of a ductile material under tensile loading is shown in the famous stress-strain curve below, taking A 53 Gr B – a commonly used CS material. The various terms associated with the stress-strain curve of material is briefly discussed below and same is shown at different stages of the curve: • Stress: – The resistance developed in the material per unit area against the applied force is the stress in the material. It can be simply specified as force per unit area of the material. Stress (s) = Force / Cross-sectional area • Strain: – A component subjected to load undergoes deformation. The deformation is quantified by strain defined as the change in length per unit length of the material. Strain (e) = dl / L (Lateral strain) • Modulus of elasticity (E): – Up to a certain limit of loading known as the proportional limit, the strain developed in the material is in direct proportion to the stress. This law is called Hooke’s law and the constant of proportionality, E, is the modulus of elasticity or Young’s modulus, which is a definite property of the material. Mathematically: E = s / e> • Yield strength: The point at which the specimen or material under tension or compression generates a large deformation without the addition of any load is called the yield point. The corresponding stress is called the yield stress, or yield strength, Sy. The yield point is easy to recognize for materials with a stress-strain curve similar to that shown in the above figure. • Ultimate Tensile Strength: The maximum
Key Considerations for Optimal Steam Piping Design
Key Considerations for Optimal Steam Piping Design Home / Learning Steam piping design is a paramount consideration engineers and designers working in industries such as Power, Oil and Gas, Petrochemicals, refineries, and other process industry. Steam piping serves as the vital system that transports steam from steam generators, commonly known as boilers, to different points of usage.Depending on the specific application, the steam can be either saturated or superheated, operating under extremely high temperatures and pressures. To ensure both the safety and efficiency of steam piping systems, strict adherence to industry codes and standards is imperative. In this comprehensive article, we will explore the key aspects of steam piping design, including code requirements. Code Requirements for Steam Piping Design The two most common codes for the design and construction of steam piping systems are ASME B31.1 – Power Piping and ASME B31.3 – Process Piping. B31.1 applies to steam piping systems in power plants, while B31.3 covers piping in chemical, petroleum, pharmaceutical, and other process industries. These codes outline the minimum requirements for material selection, design, fabrication, inspection, and testing to ensure safety and reliability. Selecting the Right Piping Materials Choosing the appropriate materials for steam piping is crucial due to the extreme conditions that steam systems operate under. The most common materials used are carbon steel, stainless steel, and alloy steel. These materials offer excellent resistance to high temperatures and pressure. For higher-temperature applications, consider materials such as chrome-molybdenum alloys. Factors Influencing Material Selection: Temperature and Pressure: Steam piping systems can operate at varying temperatures and pressures. Material selection should consider the maximum and minimum temperatures the system will experience, as well as the pressure levels it will handle. Strength and Toughness: The material must possess sufficient mechanical strength to handle the stresses generated by high pressures and temperature differentials. Toughness is important to prevent brittle fractures under sudden temperature changes.Thermal Expansion: Steam piping materials should have compatible thermal expansion properties to prevent issues related to differential expansion and contraction.Also Read: A comprehensive guide to pressure vessel design: Ensuring Safety and Reliability Common Piping Materials for Steam Piping Design Carbon Steel (ASTM A106/A53): Carbon steel is widely used in steam piping due to its affordability, high strength, and thermal conductivity. It’s suitable for lower temperature and pressure applications. However, it’s susceptible to corrosion in the presence of moisture and aggressive substances in the steam.Stainless Steel (ASTM A312/A358): Stainless steel offers excellent corrosion resistance and strength, making it suitable for a wide range of steam applications. Types 304 and 316 are commonly used in steam piping systems.Alloy Steel (ASTM A335): Alloy steels, such as chrome-molybdenum alloys (e.g., P11, P22), offer enhanced resistance to high-temperature and high-pressure conditions. They are commonly used in superheated steam applications.Duplex and Super Duplex Stainless Steel: These materials combine high corrosion resistance with strength, making them suitable for aggressive environments or applications with both high pressure and temperature.Nickel Alloys: Nickel-based alloys, like Inconel and Monel, are used in extreme conditions involving high temperatures and aggressive media. They’re suitable for specialized applications in industries like petrochemicals. Applicable Codes for Material Selection: When selecting piping materials, it’s important to consult industry codes and standards that provide guidance on material specifications, properties, and limitations. For instance:ASME B31.1 and ASME B31.3 codes provide guidelines for material selection based on factors like temperature and pressure ratings and ASTM standards provide detailed specifications for various piping materials, helping engineers choose suitable materials based on the application’s requirements. Sizing and Layout of Steam Piping Design Sizing and layout are critical aspects of steam piping design that directly impact the efficiency, performance, and safety of the entire system. Properly sizing the pipes and arranging them in an optimal layout ensures efficient steam distribution, minimizes pressure drop, and reduces the risk of operational issues such as water hammer, condensate accumulation, excessive pressure drop, steam trapping, steam quality, and leakage of steam. The optimum design also helps in the following important points related to sizing and layout: Sizing of Steam Piping: Steam Flow Rate: Determining the steam flow rate is the first step in sizing steam pipes. This involves understanding the amount of steam required for the process and accounting for any potential variations. Pressure Requirements: Consider the desired pressure at the point of use. Pipe sizing should accommodate the pressure drop due to friction and elevation changes, ensuring that the required pressure is maintained.Velocity: Steam velocity within the pipes should be maintained within acceptable limits. Very high velocities can lead to erosion, while low velocities may cause condensation and reduced efficiency.Pipe Diameter: The calculated steam flow rate and pressure drop help determine the appropriate pipe diameter. Smaller pipes can result in excessive pressure drop, while oversized pipes lead to condensation and reduced efficiency.Sizing Standards: Industry codes and standards, such as ASME B31.1 and B31.3, provide guidelines for pipe sizing based on factors like flow rate, pressure, and material. The layout of Steam Piping design: Routing and Accessibility: The layout should allow for easy access for maintenance and repairs. Proper routing prevents obstruction and minimizes the need for complex maneuvers around the piping. Pressure Drop Minimization: Arrange pipes to minimize pressure drop, especially in long runs. Consider gradual inclines and declines to prevent pockets where condensate can accumulate. Expansion and Flexibility: Account for thermal expansion and contraction. Properly placed expansion joints and loops accommodate these movements without stressing the piping or causing misalignments. Drainage: Incorporate proper drainage points to allow condensate to be efficiently removed from the system. Improper drainage can lead to reduced heat transfer and potential water hammer issues. Branching and Manifolds: Design branching and manifold systems that ensure uniform steam distribution to different points of use. Avoid abrupt changes in pipe diameter that can cause turbulence. Supports and Hangers: Install supports and hangers at appropriate intervals to prevent excessive stress on the pipes. This maintains the integrity of the system and prevents sagging. Isolation and Valves: Include isolation valves for maintenance purposes, allowing sections of the system to be shut off without
6 Most Popular Piping Stress Analysis Software Packages Used In The Industry
6 Most Popular Piping Stress Analysis Software Packages Used In The Industry Home / Learning Introduction: Piping stress analysis constitutes a major portion of engineering work in most of the industries e.g. Power, Oil and Gas, Petrochemicals, Refineries, pulp and paper, chemicals, and process industry. The current trend in the EPC and owner sector is integrated systems of management, design, manufacturing, and construction. There are various software for stress analysis, some of them developed and used by big corporations for their own use particularly in the Nuclear industry. In this article, we will cover the 6 most commonly used piping stress analysis software. Piping Stress Analysis Software Tools: 1. CAESAR II, by Hexagon 2. Autopipe, by Bentley 3. CAEPIPE, by SST USA 4. Rohr2, by Sigma, Germany 5. PEPS, by DST Engineering 6. PASS/STRAT-PROF Now let’s take a brief look on all this software one by one, 1. CAESAR II, by Hexagon: Caesar II by Hexagon (Previously Intergraph) is arguably the most popular 3D tool for piping stress analysis. It enjoys the largest market share as a pipe stress package. Caesar II works on beam element method. It is used in the piping industry to understand and evaluate working piping models. Caesar II works on a color-coded system in the output report, which helps to understand the areas of concern in the piping system. The software can be easily integrated with other Hexagon 3D model software. CII is user-friendly and has a large database consisting of over 35 international and local codes (such as ASME B31.3, B31.4, B31.1, B31.8, European codes, and many more) making it much easier for the user to analyze a piping model in question. Benefits and features of Caesar II(source: Hexagon PPM site_Caesar II features PDF): Time required for modeling gets reduced as the software has a large database of all types of standard models. Most of these works with a single click. The graphics involved in the modeling is highly optimized which helps to keep bigger models also smooth. It has an advanced analysis and stress reporting system. The use of recommended load cases option is very handy to import all the important cases in one click. Caesar II gives the user access of 3rd party Finite element analysis tool for FEA related checks. Advanced analysis features such as the use of ASME B31J. Interfacing with most of the CAD-based software is robust. 2. Autopipe, by Bentley AutoPIPE is one of the most popular piping stress package in the EPC industry. The software is developed by Bentley Systems, a US based organization. Autopipe’s cost-effective solution to design any plant piping including nuclear units makes it highly efficient and popular. It increases productivity and improves quality with special piping stress features such as both static and dynamic analysis, wave loading, fluid transients available. The software can be easily integrated with all other Bentley and 3rd party applications such as Smart Plant, Aveva E3D, Autodesk Plant 3D, PDS, CAESAR II etc. (Source: Few of the points taken from Bentley.com_Autopipe section) For Nuclear applications, the software has AutoPIPE Nuclear. AutoPIPE Nuclear(Source: Bentley.com_Autopipe section): The software allows to analyze critical nuclear systems adhering to ASME Class 1, 2, or 3 standards. It gives the productive graphical CAD interface as well as a graphical view of results. AutoPIPE Nuclear conforms with ASME NQA-1, ISO 9001, CSA N286.7-99, ASME N45.2, and 10CFR50 standards backed by several independent audits by the Nuclear Regulatory Commission (NRC) customers and the Nuclear Procurement Issues Committee (NUPIC). Benefits and features of Autopipe (Source: Points taken from Bentley.com_Autopipe feature section): Unique graphical user interface. All major international and local codes (total 25) are included in the stress package. Quality assurance as per 10CFR Part 50 Appendix B, 10CFR Part 21, and ASME NQA-1. Advanced analysis features including the latest ASME B31J requirements, Stress intensification factors, fluid transient analysis 3. CAEPIPE, by SST Systems: Caepipe is developed by SST Systems USA. It performs both linear and non-linear, static and dynamic piping stress calculations. It is used in EPC and client-based industries for e.g., oil and gas, power, nuclear, fertilizers, petrochemicals etc. Benefits and feature of Caepipe (Source: points taken from sstusa.com_caepipe section): Multiple windows of the model can be opened for the visual and textual detailing of the system. System updates in a single-window gets updated in all the windows giving a dynamic real-time effect. Advanced analysis features including the latest ASME B31J requirements. Advanced Microsoft windows installation for better operation. 4. Rohr2, by SIGMA Ingenieurgesellschaft mbH Rohr2 is a leading piping stress software mainly used in Europe. This package is developed by SIGMA Ingenieurgesellschaft mbH The main tasks of ROHR2 are component analysis, construction, and structural analysis of complex piping systems and associated steel structures. ROHR2win is the pre- and postprocessor of ROHR2. All inputs can be made using ROHR2win. A wide range of control functions enables the user to check the input data easily. The software can be integrated with 3rd party applications such as Smart Plant, Aveva PDMS/ E3D, CAESAR II, Caepipe etc. Benefits and features of Rohr2 (Source: Points taken from rohr2.com basics and feature section): ROHR2 includes optional modules as ROHR2fesu (used for detail FEA analysis of branch connections, Trunnions, Junction stress checks, etc.) and ROHR2flange (Used for flange check evaluation). ROHR2 consists of a good database of all international and European codes and standards such as, ASME B31.1, B31.3, B31.4, B31.8, CODETI, EN codes etc. It offers transfer data with all major CAD and CAE systems. Both dynamic and static analysis can be performed in Rohr2. 5. PEPS, by DST Computers PEPS is developed by DST engineering of Switzerland. The software package contains PIPESTRESS, the stress analysis package and Editpipe, it’s pre and post processor. The package is claimed being used by more than 400 engineering organizations used in 30 countries. The PEPS program is used for stress analysis of piping systems falling under nuclear Class 1, 2 & 3 and non-nuclear codes. It is being used as the main piping
6 most popular Piping Design tools used in the industry
6 most popular Piping Design tools used in the industry Home / Learning Introduction: 3d piping design software is a major portion of engineering work in most of the industries e.g. Power, Oil and Gas, Petrochemicals, Refineries, pulp and paper, chemicals, and process industry. There are close to 50 plant or piping design software used by various engineering companies throughout the world. There are pros and cons with every software including the price point. The current trend in the EPC and owner sector is towards integrated systems of management, design, manufacturing, and construction. In today’s plant engineering practices, organizations try to develop a detailed 3D model of the plant for optimized design, construction, material management, planning, and safety. In this article, we will cover the 6 most popular software for piping design. 3d Piping Design Software Tools: Smart® 3D – developed by Hexagon PPM (Previously Intergraph) PDMS – Plant Design & Management software developed by AVEVA PLANT PDS – Plant Design software developed by Hexagon CADWorx – developed by Hexagon AutoPLANT – developed by BENTLEY AutoCAD Plant 3D – by Autodesk Now let’s take a brief look on all this software one by one, 1. Smart® 3D – developed by Hexagon PPM (Previously Intergraph): Smart® 3D is a next-generation, data-centric, rule-driven solution specifically designed to deliver mission-critical requirements. Smart 3D provides all capabilities needed to design plant, marine, and materials handling facilities and then maintain their 3D “as-built” representations, which offers a competitive edge to EPCs and owner-operators. Smart plant 3D can integrate easily with other Hexagon products such as Smart Plant Instrumentation and Smart Plant P&ID. Smart® 3D also can integrate with 3rd party AVEVA Plant™ products & applications making the software very worthy. (Source: Points taken from Hexagon PPM site_SP3D section) Benefits and features of Smart® 3D: (Source: Points taken from Hexagon PPM site_SP3D product features sheet) Real-time Concurrent Design Automated Deliverables Intelligent Rules and Relationships Interoperability Task-based Modeling Undo function available Offers 3D visualization tools for creating models 2. PDMS – Plant design & Management software developed by AVEVA PLANT: PDMS (Plant Design Management System) as it is known in the 3D CAD industry, is a customizable, multi-user and multi-discipline, engineer controlled design software package for engineering, design, and construction projects in offshore and onshore’. PDMS software is a very popular software for piping design developed by AVEVA. It’s customizable and multi user characteristics make PDMS as one of the most demanding piping software in the EPC and Owner sector. AVEVA PDMS is gradually being phased out and will be removed from the market by 2024. It will be migrated to the AVEVA E3D Design package subsequently. (Source: Points taken from Aveva.com site PDMS section_and wikipedia) Benefits and features of AVEVA PDMS: (Source: Some Points taken from Aveva.com , PDMS feature section ) Reuses designs from incorporated components Offers visual highlighting through Status Management Smooth integration with 2D AutoCAD Easier modification of existing models Handles higher job sizes efficiently User-defined commands can be created Online clash detection available 3. PDS- Plant design software developed by Hexagon: PDS or Plant Design System is a comprehensive, intelligent computer-aided design/engineering application. PDS is one of the most popular 3D model piping program used by various Engineering companies throughout the world since 1980. PDS is developed by Intergraph (Currently Hexagon). PDS runs on Microsoft windows and are much compatible with most of the 3rd party modules and hexagon software. The software is comprehensively used in sectors like refinery, offshore facilities, power plants, petrochemical plants, chemical, etc. (Source: Points taken from Hexagon PPM site_PDS section) Benefits and feature of PDS: Dynamic walkthrough for operations and maintenance personnel Interference checking by developing clash-free systems Accurate material take-offs Specification-driven design and phased reviews Integration with complementary applications 4. CADWorx developed by Hexagon: CADWorx Plant Professional runs on AutoCAD or BricsCAD platform and includes BricsCAD® Pro, providing a complete package with powerful and adaptive tools that enable quick and easy creation of fully intelligent 3D plant models. CADWorx enables efficient plant design for various packages including oil and gas, green field and brownfield refinery, petrochemicals, fertilizers and many more. (Source: Points taken from Hexagon PPM site_CADWorx section) Additional modules that are included with CADWorx Plant Professional: CADWorx Design Review CADWorx Equipment CADWorx HVAC CADWorx Structure CADWorx P&ID Basic, BricsCAD Pro Benefits and features of CADWorx® (Source: Points taken from Hexagon PPM site_CADWorx features) Accurate piping design with over 60,000 parametrically driven components Automatic isometrics from layouts, databases, or Isogen® Clash/collision detection in current or referenced models Real-time design status and BOM creation in various formats Intelligent 3D Piping Design Equipment Library Administration As-builts from Point Clouds 5. Auto PLANT developed by BENTLEY: Bentley Auto PLANT Design is an object-based 3D piping design and modeling application that runs on AutoCAD. The system is built on powerful object-oriented technology, yet it is easy to use and customize. Piping models can be easily created and developed in the 3D environment of Auto PLANT. It provides state of the art 3D modelling previously unavailable in any AutoCAD-based package. Auto PLANT provides interactive routing for various industries in the oil and gas, petrochemicals, refinery, water treatment, power generation, chemical sectors. (Source: Points taken from Bentley.com site_AutoPlant modeller section) Additional modules that are included in Auto PLANT: AutoPLANT Piping AutoPLANT Equipment AutoPLANT I&W AutoPLANT P&ID AutoPLANT AutoIsogen Benefits and features of Auto PLANT: (Source: Points taken from Bentley.com site_AutoPlant modeller feature sheet) Automatic Piping Isometrics with OpenPlant Isometrics Manager Integration with Bentley plant design for data mobility Access over 100 component catalogs Save IT time with scripting for AutoPLANT install Create user-defined equipment for vendor accuracy High information mobility 6. AutoCAD Plant-3D by Autodesk: AutoCAD Plant 3D adds 3D models, including piping, equipment, support structures, generation of isometric, and orthographic drawings. Additionally, integrated AutoCAD P&ID functionality and quick generation of isometric increase productivity, accuracy, and coordination. Benefits and features of AutoCAD Plant 3D: (Source: Points taken from autodesk.com site_AutoCAD plant 3D section) Solid mesh modeling characteristics Modern 3D navigation tools
