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What are Ejma Standards and why are they important?




If you are involved in the design, installation, or maintenance of piping or vessel systems that use metallic bellows type expansion joints, you may have heard of Ejma Standards. But what are they and why are they important?




Ejma Standards Pdf Free 16



Ejma Standards are the standards of the Expansion Joint Manufacturers Association, Inc., a trade association that was founded in 1955 by a group of companies experienced in the application, design, and fabrication of expansion joints. The Ejma Standards are recognized throughout the world as the authority on the proper selection and application of metallic bellows type expansion joints for safe and reliable piping and vessel installation.


Metallic bellows type expansion joints are devices that consist of one or more metal convolutions that can flex under pressure, temperature, or other external forces. They are used to accommodate thermal expansion and contraction, vibration, movement, or misalignment in a piping or vessel system. They can also reduce stress, noise, vibration, and leakage in a piping or vessel system, as well as extend its service life and performance.


However, metallic bellows type expansion joints also require proper design, selection, installation, and maintenance to ensure safety and reliability. They can be affected by corrosion, erosion, fatigue, abrasion, or other environmental factors. They can also be subject to pressure thrust forces that need to be restrained by adequate hardware. Therefore, it is essential to follow the best practices and guidelines provided by Ejma Standards when using metallic bellows type expansion joints.


In this article, we will explain how Ejma Standards are developed and updated, what are the main features and changes of the 10th Edition of Ejma Standards, and how to access and order Ejma Standards. We will also answer some frequently asked questions about metallic bellows type expansion joints and Ejma Standards.


By the end of this article, you will have a better understanding of what Ejma Standards are and why they are important for your expansion joint needs.


How are Ejma Standards developed and updated?




Ejma Standards have a long history of providing reliable and comprehensive information on metallic bellows type expansion joints. Since 1986, when the first edition was published, Ejma Standards have been revised and expanded by the cooperative effort of its association members through research and testing.


The association members of Ejma are companies that manufacture metallic bellows type expansion joints or supply related products or services. They have extensive knowledge and experience in the application, design, and fabrication of expansion joints. They also have access to state-of-the-art testing facilities and equipment to conduct experiments and simulations on expansion joint performance and behavior.


The association members form the Technical Committee of Ejma, which is dedicated to continuously improving the quality and technical content of the Standards. The Technical Committee collects and analyzes data from research and testing results, as well as feedback from industry users and experts. The Technical Committee then revises and updates the Standards based on the latest findings and best practices.


The Technical Committee also responds to technical inquiries from users who have questions or issues regarding the application or design of expansion joints. The Technical Committee provides guidance and recommendations based on the Ejma Standards and their own expertise.


By using Ejma Standards, users can benefit from the collective wisdom and experience of the leading manufacturers of expansion joints in the world. Users can also be assured that the Ejma Standards are based on sound engineering principles and rigorous testing methods. Users can also access the Technical Committee for further assistance or clarification.


What are the main features and changes of the 10th Edition of Ejma Standards?




The 10th Edition of Ejma Standards is the latest version of the Standards, published in 2016. It is available in printed or e-book format. It contains over 200 pages of information on metallic bellows type expansion joints, covering topics such as:


  • Nomenclature



  • Design criteria



  • Materials



  • Fabrication



  • Installation



  • Maintenance



  • Testing



  • Analysis



  • Examples



  • Benchmark tables



  • Fatigue curves



  • Vibration constants



  • Spring rates



  • Allowable stresses



  • Conversion factors



The 10th Edition of Ejma Standards has several significant changes from the previous editions, such as:


A new approach for the design of reinforced bellows




approach results in a modified set of equations for some stress components and for the spring rates. The main and most important result is that the calculated bending stress due to deflection can be considerably reduced. This means that the reinforced bellows can have a longer fatigue life and a higher allowable movement.


Enhanced and simplified fatigue life calculations




The 10th Edition also enhances and simplifies the fatigue life calculations for metallic bellows type expansion joints. The fatigue life is the number of cycles that an expansion joint can withstand before failure due to fatigue. The 10th Edition uses a new set of fatigue curves that are based on more accurate and consistent data from testing and analysis. The new fatigue curves are applicable for both unreinforced and reinforced bellows, as well as for toroidal bellows, which are bellows with a circular cross-section. The 10th Edition also provides a simplified method for calculating the fatigue life based on the maximum stress range and the number of cycles.


A modified equation for the axial movement per convolution of universal type expansion joints




The 10th Edition modifies the equation for the axial movement per convolution of universal type expansion joints, which are expansion joints with two bellows separated by a center spool. The modified equation takes into account the effect of pressure on the axial stiffness of the bellows, which was previously neglected. The modified equation results in a more accurate prediction of the axial movement per convolution, which affects the design and performance of the expansion joint.


An acceptable radial gap between equalizing/reinforcing rings and the root of convolution/bellows tangent




The 10th Edition introduces an acceptable radial gap between equalizing/reinforcing rings and the root of convolution/bellows tangent, which is the point where the bellows curve meets the straight section of the pipe or spool. The radial gap is the distance between the inner diameter of the ring and the outer diameter of the pipe or spool at that point. The radial gap allows for some clearance between the ring and the pipe or spool to accommodate manufacturing tolerances and thermal expansion. The 10th Edition specifies an acceptable range for the radial gap based on empirical data and analysis.


The inclusion of both English and Metric units of measure




The 10th Edition includes both English and Metric units of measure for all parameters and equations in the Standards. This allows for easier conversion and comparison between different units of measure. The 10th Edition also provides standard conversions and constants used in calculations.


The consideration of tightness of bellows, bands, and rings due to dissimilar material growth rates




The 10th Edition considers the tightness of bellows, bands, and rings due to dissimilar material growth rates, which is the difference in thermal expansion between different materials used in an expansion joint. For example, if a stainless steel bellows is attached to a carbon steel pipe or spool, the stainless steel will expand more than the carbon steel when heated. This can cause stress and deformation in the expansion joint components. The 10th Edition provides guidance on how to account for dissimilar material growth rates in the design and fabrication of expansion joints.


The distinction of thin versus thick bellows




The 10th Edition distinguishes between thin and thick bellows based on their thickness-to-diameter ratio. Thin bellows have a thickness-to-diameter ratio less than or equal to 0.015, while thick bellows have a ratio greater than 0.015. Thin bellows are more flexible and less resistant to pressure than thick bellows. Thick bellows are more rigid and more resistant to pressure than thin bellows. The distinction of thin versus thick bellows affects some parameters and equations in the Standards, such as allowable stresses, spring rates, and fatigue curves.


Revised single bellows axial vibration constants




the single bellows axial vibration constants, which are factors that relate the natural frequency of a single bellows to its geometry and material properties. The revised constants are based on more accurate and consistent data from testing and analysis. The revised constants result in a more accurate prediction of the natural frequency of a single bellows, which affects the vibration behavior and performance of the expansion joint.


Clarified definitions in the nomenclature section




The 10th Edition clarifies some definitions in the nomenclature section, which is the section that defines and explains the terms and symbols used in the Standards. The clarified definitions provide more consistency and precision in the use and interpretation of the terms and symbols. Some examples of clarified definitions are:


  • Convolution: A single annular fold or corrugation in a bellows.



  • Effective Area: The cross-sectional area of a bellows convolution subjected to internal pressure.



  • Pressure Thrust: The axial force exerted by internal pressure on an unrestrained expansion joint.



  • Squirm: A lateral or angular instability of a bellows due to excessive internal pressure or insufficient lateral restraint.



  • Universal Expansion Joint: An expansion joint consisting of two bellows connected by a center spool with tie rods or other hardware to restrain the pressure thrust.



Examples




The 10th Edition provides some examples of how to use the Ejma Standards for expansion joint design and application. The examples illustrate how to calculate some parameters and equations in the Standards, such as:


  • The effective area of a bellows



  • The pressure thrust of an expansion joint



  • The spring rate of an expansion joint



  • The allowable stress of a bellows



  • The fatigue life of an expansion joint



  • The natural frequency of a single bellows



The examples also show how to use the benchmark tables, fatigue curves, vibration constants, spring rates, allowable stresses, and conversion factors provided in the Standards. The examples are intended to help users understand and apply the Ejma Standards correctly and effectively.


How to access and order Ejma Standards?




If you are interested in using Ejma Standards for your expansion joint needs, you have several options for accessing and ordering them. You can choose from:


Printed copy




You can order a printed copy of the 10th Edition of Ejma Standards from the Ejma website. The printed copy comes with a pocket size primer called EJMA's Practical Guide to Expansion Joints, which is based on the Ejma Standards. The primer provides users with a basic understanding of expansion joints and how to communicate design requirements to the manufacturers and to properly install and maintain the expansion joint in service. The printed copy costs $225 for non-members and $175 for members.


E-book version




You can also order an e-book version of the 10th Edition of Ejma Standards from the Ejma website. The e-book version can be downloaded to your PC, laptop, or tablet. The e-book version also comes with the pocket size primer. The e-book version costs $200 for non-members and $150 for members.


Online subscription




You can also subscribe to an online version of the 10th Edition of Ejma Standards from the Ejma website. The online version allows you to access the Standards from any device with an internet connection. The online version also includes interactive features such as calculators, graphs, animations, and videos. The online subscription costs $300 per year for non-members and $250 per year for members.


Contact information




To order or subscribe to Ejma Standards, you can visit the Ejma website at www.ejma.org. You can also contact Ejma by email at ejma@ejma.org, by phone at (914) 332-0040, or by mail at 25 North Broadway, Tarrytown, NY 10591.


Conclusion




the proper selection and application of metallic bellows type expansion joints for safe and reliable piping and vessel installation.


Ejma Standards are developed and updated by the cooperative effort of its association members, who are experienced and knowledgeable manufacturers of expansion joints. Ejma Standards are based on sound engineering principles and rigorous testing methods. Ejma Standards also provide guidance and recommendations to users who have technical inquiries regarding expansion joint design and application.


The 10th Edition of Ejma Standards is the latest version of the Standards, published in 2016. It contains over 200 pages of information on metallic bellows type expansion joints, covering topics such as nomenclature, design criteria, materials, fabrication, installation, maintenance, testing, analysis, examples, benchmark tables, fatigue curves, vibration constants, spring rates, allowable stresses, and conversion factors. The 10th Edition also introduces several significant changes from the previous editions, such as a new approach for the design of reinforced bellows, enhanced and simplified fatigue life calculations, a modified equation for the axial movement per convolution of universal type expansion joints, an acceptable radial gap between equalizing/reinforcing rings and the root of convolution/bellows tangent, the inclusion of both English and Metric units of measure, the consideration of tightness of bellows, bands, and rings due to dissimilar material growth rates, the distinction of thin versus thick bellows, revised single bellows axial vibration constants, and clarified definitions in the nomenclature section.


Users can access and order Ejma Standards from the Ejma website in different formats, such as printed copy, e-book version, or online subscription. Users can also contact Ejma by email, phone, or mail for more information or assistance.


We hope that this article has helped you understand what Ejma Standards are and why they are important for your expansion joint needs. We encourage you to use Ejma Standards for your expansion joint design and application and to contact Ejma for any questions or issues you may have. Thank you for reading.


FAQs




Q1: What is an expansion joint?




A1: An expansion joint is a device that allows for thermal expansion and contraction, vibration, movement, or misalignment in a piping or vessel system.


Q2: What is a metallic bellows type expansion joint?




A2: A metallic bellows type expansion joint is an expansion joint that consists of one or more metal convolutions that can flex under pressure, temperature, or other external forces.


Q3: What are some applications of metallic bellows type expansion joints?




A3: Some applications of metallic bellows type expansion joints are:


  • Power generation



  • Chemical and petrochemical processing



  • Oil and gas transportation



  • HVAC systems



  • Aerospace and defense



Q4: What are some benefits of using metallic bellows type expansion joints?




A4: Some benefits of using metallic bellows type expansion joints are:


  • They can accommodate large movements in a compact space



and leakage in a piping or vessel system


  • They can extend the service life and performance of a piping or vessel system



  • They can reduce maintenance costs and downtime



Q5: What are some challenges or limitations of using metallic bellows type expansion joints?




A5: Some challenges or limitations of using metallic bellows type expansion joints are:


  • They require proper design, selection, installation, and maintenance to ensure safety and reliability



  • They can be affected by corrosion, erosion, fatigue, abrasion, or other environmental factors



  • They can be subject to pressure thrust forces that need to be restrained by adequate hardware



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