Shortcut Method for "L" and "Z" Pipe Bend Sizing

2021 ◽  
Author(s):  
Nikola Jacimovic ◽  
Milos Ivosevic
Keyword(s):  
Stress Analysis ◽  
Engineering Practice ◽  
Piping System ◽  
Pipe Bend ◽  
Rule Of Thumb ◽  
Early Stages ◽  
Present Procedure ◽  
Piping Systems ◽  
Shortcut Method ◽  
Material Requirements

Abstract In the engineering practice it may often prove necessary to provide quick and relatively accurate estimates of piping routing and material requirements in very early stages of a project. In these cases there is typically no time to perform detailed pipe stress analysis in order to obtain accurate routing which allows for sufficient piping system flexibility and the designer is constrained to the use of rule of thumb approach and good engineering judgment. This approach, although often used, may prove challenging in many situations, one of which is establishing sufficient pipe loop dimensions. Method proposed by the authors in [1] provides a procedure for quick estimation of U loops while the present procedure aims to provide additional procedures for estimation of L and Z bends, thus completing the circle of shortcut methods for quick estimation of expansion requirements of piping systems.

Shortcut Method for Pipe Expansion Loop Sizing

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Nikola Jaćimović ◽  
Miloš Ivošević
Keyword(s):  
Distribution Systems ◽  
Worked Examples ◽  
Engineering Practice ◽  
Piping System ◽  
Comprehensive Overview ◽  
Approximate Methods ◽  
Proposed Model ◽  
Piping Systems ◽  
Early Phases ◽  
Shortcut Method

Abstract In the engineering practice, it is often necessary to define supporting scheme and expansion loop requirements for piping distribution systems in very early phases of a project. While placing pipe supports is a relatively easy and straightforward task, providing accurate loop locations and dimensions for hot piping systems can often be challenging. In the early phases of any project, it is impractical, costly and time consuming to perform detailed stress analysis of a piping system to provide expansion loop dimensions, and therefore approximate methods are often used. Comprehensive overview of these existing procedures most commonly used in the engineering practice is given in this article. However, the fact is that most of the existing methods are based on the inconvenient charts and tables with scarce background data. Procedure proposed in this article is based on over 150 expansion loop models and provides a simple and accurate analytical method to size and verify piping loops. Two fully worked examples show the simplicity and accuracy of the proposed model and its advantages over the methods typically used in the engineering practice.

Influence of Local Wall Thinning and Support Stiffness in Piping Systems on Safety Assessments for Dynamic Loading

2014 ◽  
Author(s):  
Klaus Kerkhof ◽  
Fabian Dwenger ◽  
Gereon Hinz ◽  
Siegfried Schmauder
Keyword(s):  
Stress Analysis ◽  
Response Spectrum ◽  
System Response ◽  
Piping System ◽  
Load Bearing ◽  
Wall Thinning ◽  
Safety Margins ◽  
Piping Systems ◽  
Bearing Behavior ◽  
Local Wall Thinning

The load bearing behavior of piping systems depends considerably on support distances and stiffness as well as cross section characteristics. Stiffness of supports can often be defined only with difficulty by applying simplified procedures or guidelines based on assumptions. Load cases can be estimated quite well, but the safety assessment of a piping system can only be as reliable as the system model can realistically describe the present support stiffness or imperfections e.g. local wall thinning. As a consequence, the prediction of the system response may be poor. It is likely that calculated frequencies differ from natural frequencies determined experimentally. These frequency shifts lead to unrealistic predictions of stress analysis. Examples for overestimations and underestimations of stress analysis are given regarding the load case earthquake, depending on whether the frequency shift runs into or out of the plateau of the applied floor response spectrum. The influence of local wall thinning on modal characteristics is investigated. Conservative estimations of the influence on the load bearing behavior regarding severe local wall thinning are given. For fatigue checks the linear response of an experimental piping system is calculated and safety margins are demonstrated by comparing calculated with experimental results.

Brittle Fracture Assessments on Offshore Piping Systems

2013 ◽  
Author(s):  
Kannan Subramanian ◽  
Jorge Penso ◽  
Graham McVinnie ◽  
Greg Garic
Keyword(s):  
Low Temperature ◽  
Brittle Fracture ◽  
Stress Analysis ◽  
Pressure Vessels ◽  
Piping System ◽  
Piping Systems ◽  
Assessment Approach ◽  
Section Viii ◽  
System Information ◽  
Safe Operating

Offshore piping systems may be subject to low temperatures due to operation related scenarios and are cause for brittle fracture concern. The analyses included in this work consider probable events leading to low temperature conditions such as auto-refrigeration. In such circumstances, brittle fracture assessments of piping are typically carried out using API 579-1/ASME FFS-1, latest referred as API 579, procedures. The assessment of piping systems are in many cases very involved, requiring extended piping system information followed by stress analysis and MAT calculations depending on the material type, thickness of the piping analyzed, and stress levels. In addition, the component-by-component assessment approach recommended in API 579 leads to tedious calculations. In this paper, approaches used for static and dynamic low temperature scenarios are presented. Static cases involve constant pressures and temperatures. Dynamic cases involve varying pressures and temperatures as the low temperature events unfold (e.g., blowdown of a valve or a vessel). Dynamic cases warrant the requirement of a safe operating envelope or MAT curve similar to those developed for pressure vessels. Case studies involving the influence of the extent of the system analyzed and the restraint conditions on the results are also presented. In addition, the importance of separately assessing the rated components such as flanges and valves away from the stress analysis is discussed. Based on the assessments carried out, a discussion on the toughness rules defined in ASME Section VIII Divisions 1, 2, and the original piping code of construction is provided.

Computer Piping Analysis, ASME B31.3 Appendix S: Example S3 — Moment Reversal

2007 ◽  
Author(s):  
Don R. Edwards
Keyword(s):  
Stress Analysis ◽  
Petroleum Refinery ◽  
Axial Stress ◽  
Piping System ◽  
Stress Range ◽  
Analysis Software ◽  
Process Piping ◽  
Piping Systems ◽  
Operating Stress ◽  
The Impact

The American Standards Association (ASA) B31.3-1959 Petroleum Refinery Piping Code [1] grew out of an ASA document that addressed all manner of fluid conveying piping systems. ASA B31.3 was created long before widespread engineering use of computer “mainframes” or even before the inception of piping stress analysis software. From its inception until recent times, the B31.3 Process Piping Code [2] (hereafter referred to as the “Code”) has remained ambiguous in several areas. This paper describes some of these subtle concepts that are included in the Code 2006 Edition for Appendix S Example S3. This paper discusses: • the effect of moment reversal in determining the largest Displacement Stress Range, • the impact of the average axial stress caused by displacement strains on the Example S3 piping system and the augmenting of the Code Eq. (17) thereto, • a brief comparison of Example S3 results to that of the operating stress range evaluated in accordance with the 2006 Code Appendix P Alternative Requirements.

Flexibility Analysis of Piping Systems With Discontinuities in Displacement

2016 ◽  
Author(s):  
Birendra N. Choudhury
Keyword(s):  
Thermal Expansion ◽  
Ambient Temperature ◽  
Stress Analysis ◽  
Elastic Deformation ◽  
The Other ◽  
Piping System ◽  
Current Stress ◽  
Flexibility Analysis ◽  
Other Hand ◽  
Piping Systems

The class of piping flexibility analysis problems discussed in this paper arises when a new piping system at ambient temperature is connected to a piping system that is in operation. At the time of tie-in, the new piping has no thermal expansion and no elastic deformation. Therefore, displacement at the tie-points in the new piping system is zero. On the other hand, the operating piping systems would have undergone some displacements at this point before the tie-in. So there is a discontinuity in displacement at the tie point. This paper discusses how the equations for piping flexibility analysis can be modified to accurately obtain the redundant restraint forces for such cases and their use with current stress analysis programs for some piping configurations.

scholarly journals Stress and stability analysis of steel piping systems in the petroleum industry

2020 ◽  
Author(s):  
◽  
Justin Pillay
Keyword(s):  
Stress Analysis ◽  
Failure Modes ◽  
Petroleum Industry ◽  
Piping System ◽  
Increased Risk ◽  
Piping Systems ◽  
The Many ◽  
The Impact ◽  
Dimensional Specification ◽  
Petroleum Plant

This study aims to reach a level of proficiency on the available technical theories to assess steel pressure piping systems and the identification of potential risks of failure. The research focuses mainly on piping systems in the petroleum industry. The importance of this study is based on the risk reduction of petroleum plant downtime and the harming of life as a result of piping failures. The apparent need for piping systems stress analysis was a result of the many failures that occurred at Indy Oil’s petroleum plant. The recent acquisition of the petroleum plant under the GUD Holdings group brought along minimum engineering experience with regards to piping systems. GUD’s inhouse engineering teams executed the many plant expansion and upgrade projects. A common industry perception is that piping systems are basic and do not require much attention. These misconceptions are a result of many piping failures in the industry. The failures that occurred called for a thorough investigation of all equipment setups and piping installations at Indy Oil. Specific failure identifications at the petroleum plant were done. The research and analysis of piping systems stress analysis were performed to aid in understanding the cause of these failures. Fluid dynamics, as a major contributor to stress and strain state in pipes, is the object of much attention. The dimensional specification and layout optimization of a piping system is highly dependent on the internal piping pressure. Studies, developments, and prediction analysis on the impact of sustained and thermal loads are reviewed to understand the numerical and analytical techniques available which enables the analysis of various piping systems. A risk- informed approach is applied that incorporates various design criteria, as well as, failure contributors in piping systems. At first, each component and failure mode is determined separately. Thereafter, the instances of simultaneous loading and increased risk of failure in piping systems have been determined. The available literature is used to source necessary data, as well as, compare the obtained results with those available in the literature. Government statutory requirements are used as a basis in the design process. Material specifications and engineering quality is controlled by these governing standards. The application of this study is done by the design and analysis of a piping system for Indy Oil’s Tank Farm. Piping systems failures as a result of improper design raised importance for a thorough stress analysis at the Petrochemical site. The calculations of stress-strain contributions are done using theoretical methods, as well as, computer software programs. The piping system is analysed on various conditions according to the process requirements of the Plant. Various load cases were developed to account for simultaneous loadings. The expected result of the system is for stress contributions to not exceed the maximum allowable stresses. CAESAR II software is selected as the most suitable for the analysis. The simulation is done on each pipe element and demonstrates a three-dimensional analysis. The results of the study were used to determine the failure modes of previously installed piping systems and to create a design guide for all future piping systems projects.

Non-Linear Design Verification of Nuclear Power Piping According to ASME III NB/NC

2008 ◽  
Author(s):  
Lingfu Zeng ◽  
Lennart G. Jansson
Keyword(s):  
Nuclear Power ◽  
Design Evaluation ◽  
Piping System ◽  
Design Verification ◽  
Intensive Study ◽  
Non Linear ◽  
Piping Systems ◽  
Design Requirements

A nuclear piping system which is found to be disqualified, i.e. overstressed, in design evaluation in accordance with ASME III, can still be qualified if further non-linear design requirements can be satisfied in refined non-linear analyses in which material plasticity and other non-linear conditions are taken into account. This paper attempts first to categorize the design verification according to ASME III into the linear design and non-linear design verifications. Thereafter, the corresponding design requirements, in particular, those non-linear design requirements, are reviewed and examined in detail. The emphasis is placed on our view on several formulations and design requirements in ASME III when applied to nuclear power piping systems that are currently under intensive study in Sweden.

Comparison of Failure Modes of Piping Systems With Wall Thinning Subjected to In-Plane, Out-of-Plane, and Mixed Mode Bending Under Seismic Load: An Experimental Approach

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Izumi Nakamura ◽  
Akihito Otani ◽  
Masaki Shiratori
Keyword(s):  
Dynamic Behavior ◽  
Failure Modes ◽  
Seismic Load ◽  
Piping System ◽  
Shake Table ◽  
Shake Table Tests ◽  
Wall Thinning ◽  
Piping Systems ◽  
Out Of Plane ◽  
Plane Bending

Pressurized piping systems used for an extended period may develop degradations such as wall thinning or cracks due to aging. It is important to estimate the effects of degradation on the dynamic behavior and to ascertain the failure modes and remaining strength of the piping systems with degradation through experiments and analyses to ensure the seismic safety of degraded piping systems under destructive seismic events. In order to investigate the influence of degradation on the dynamic behavior and failure modes of piping systems with local wall thinning, shake table tests using 3D piping system models were conducted. About 50% full circumferential wall thinning at elbows was considered in the test. Three types of models were used in the shake table tests. The difference of the models was the applied bending direction to the thinned-wall elbow. The bending direction considered in the tests was either of the in-plane bending, out-of-plane bending, or mixed bending of the in-plane and out-of-plane. These models were excited under the same input acceleration until failure occurred. Through these tests, the vibration characteristic and failure modes of the piping models with wall thinning under seismic load were obtained. The test results showed that the out-of-plane bending is not significant for a sound elbow, but should be considered for a thinned-wall elbow, because the life of the piping models with wall thinning subjected to out-of-plane bending may reduce significantly.

The Influence of Support Hardware and Piping System Seismic Response on Snubber Support Damping

1997 ◽  
Vol 119 (4) ◽  
pp. 451-456 ◽  
Author(s):  
C. Lay ◽  
O. A. Abu-Yasein ◽  
M. A. Pickett ◽  
J. Madia ◽  
S. K. Sinha
Keyword(s):  
Seismic Response ◽  
Fundamental Frequency ◽  
Damping Ratio ◽  
Damping Coefficient ◽  
Piping System ◽  
Nodal Displacement ◽  
Damping Coefficients ◽  
Fundamental Frequencies ◽  
Piping Systems

The damping coefficients and ratios of piping system snubber supports were found to vary logarithmically with pipe support nodal displacement. For piping systems with fundamental frequencies in the range of 0.6 to 6.6 Hz, the support damping ratio for snubber supports was found to increase with increasing fundamental frequency. For 3-kip snubbers, damping coefficient and damping ratio decreased logarithmically with nodal displacement, indicating that the 3-kip snubbers studied behaved essentially as coulomb dampers; while for the 10-kip snubbers studied, damping coefficient and damping ratio increased logarithmically with nodal displacement.

Computer Based Process Piping Stress Analysis: ASME B31.3 Appendix S — Example S2

2006 ◽  
Author(s):  
Don R. Edwards
Keyword(s):  
Stress Analysis ◽  
Operating Temperature ◽  
Stress Range ◽  
Explicit Equation ◽  
The Past ◽  
Process Piping ◽  
Piping Systems ◽  
Sustained Loads ◽  
Computer Based ◽  
Temperature And Pressure

The American Standards Association (ASA) B31.3-1959 Petroleum Refinery Piping Code [1] grew out of an ASA document that addressed all manner of fluid conveying piping systems. ASA B31.3 was created long before widespread engineering use of computer “mainframes” or even before the inception of piping stress analysis software. Also as B31.3 continued to pass thru standards organizations from ASA, ANSI, to ASME, the B31.3 Process Piping Code [2] (hereafter referred to as the “Code”) has remained ambiguous over the past few decades in several areas. The displacement stress range, SE, has always been explicitly defined by both verbiage and equation. Yet, the sustained condition(s) stress, SL, is mentioned not with an explicit equation but with a statement that the sustained stress shall be limited by the allowable stress at the corresponding operating temperature, Sh. Also one might infer from the vague verbiage in the Code that there is only one sustained condition; this would also be an incorrect inference. Also, assumptions would then have to be made as to which supports are allowed to be included in a sustained analysis based on whether the piping “lifts-off” any of the pipe supports during the corresponding operating condition. This paper describes the subtle yet possibly radical concepts that are included in the (recently approved for inclusion into) ASME B31.3-2006 Appendix S Example S2. This paper discusses: • when and in what manner the most severe set of operating temperature and pressure is to be used; • the concept of “sustained condition” and multiple “anticipated” sustained conditions; • determining the support scenario(s) for each anticipated sustained condition; • establishing the most severe sustained condition to evaluate and determine the stress due to sustained loads, SL; • utilizing an equation with sustained stress indices to evaluate SL; • establishing the least severe sustained condition and its effect in determining the largest displacement stress range, SE.

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