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EJMA Standards 10th Edition: A Comprehensive Guide for Metallic Bellows Expansion Joints
The Expansion Joint Manufacturers Association (EJMA) is a global organization that provides authoritative guidance on the proper selection and application of metallic bellows type expansion joints for safe and reliable piping and vessel installation. The EJMA Standards are recognized throughout the world as the reference document for this purpose.
The 10th Edition of the EJMA Standards was published in 2019 and incorporates significant changes and improvements from the previous editions. Some of the main features of the 10th Edition are:
A new approach for the design of reinforced bellows, resulting in a modified set of equations for some stress components and for the spring rates.
A simplified method for the calculation of fatigue cycles for both unreinforced and reinforced bellows.
A revised 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.
A distinction of thin versus thick bellows and their respective design criteria.
A modification of the benchmark table inputs and outputs, with material class and correction factor.
A revision of the single bellows axial vibration constants.
A clarification of the definitions in the nomenclature section.
An inclusion of both English and Metric units of measure, with standard conversions and constants.
The 10th Edition of the EJMA Standards is available in printed or e-reader format from the EJMA website[^1^] [^2^]. Each printed copy comes with a practical guide to expansion joints, a pocket size primer based on the EJMA Standards. The e-book version can be downloaded to your PC, laptop or tablet for easy access.
If you are involved in the design, installation, maintenance or operation of metallic bellows type expansion joints, you will benefit from having a copy of the 10th Edition of the EJMA Standards. It is an invaluable resource that combines the knowledge and experience of the leading manufacturers of expansion joints into a comprehensive guide.
In this article, we will review some of the key concepts and terms related to metallic bellows expansion joints and the EJMA Standards. We will also provide some examples of how to use the 10th Edition of the EJMA Standards to design and evaluate expansion joints for different applications.
What are metallic bellows expansion joints
Metallic bellows expansion joints are flexible connectors that are used to accommodate thermal expansion, contraction, vibration and misalignment in piping and vessel systems. They consist of one or more metal convolutions that are formed by hydraulic or mechanical means from a thin-walled tube. The convolutions allow the expansion joint to deform in axial, lateral and angular directions, depending on the configuration and loading conditions.
Metallic bellows expansion joints can be classified into different types based on their geometry and function. Some of the common types are:
Single bellows: A single bellows element with end connections. It can absorb axial movement and some lateral and angular movement.
Universal bellows: Two single bellows elements connected by a center spool piece with end connections. It can absorb large lateral movement and some axial and angular movement.
Hinged bellows: A single or universal bellows element with hinge hardware that allows angular rotation in a single plane. It can absorb angular movement and some axial movement.
Gimbal bellows: A single or universal bellows element with gimbal hardware that allows angular rotation in any plane. It can absorb angular movement and some axial movement.
Pressure balanced bellows: A single or universal bellows element with additional balancing bellows that are subjected to the same internal pressure as the main bellows. It can absorb axial or lateral movement without creating pressure thrust forces on the system.
Tied bellows: A single or universal bellows element with tie rods or bars that limit the axial movement and prevent squirming or instability. It can absorb lateral and angular movement.
What are the EJMA Standards
The EJMA Standards are a set of guidelines and recommendations for the design, manufacture, testing and installation of metallic bellows expansion joints. They are developed by the Expansion Joint Manufacturers Association (EJMA), which is a non-profit organization composed of leading manufacturers of expansion joints in North America. The EJMA Standards are based on the collective experience and knowledge of the members, as well as on extensive research and testing conducted by EJMA and other organizations.
The EJMA Standards cover various aspects of metallic bellows expansion joints, such as:
Nomenclature and definitions
Design criteria and equations
Materials and fabrication
Quality control and inspection
Installation and maintenance
Performance data and ratings
The EJMA Standards are intended to provide users with a reliable basis for selecting and applying metallic bellows expansion joints for various piping and vessel systems. They are also intended to promote uniformity and consistency among manufacturers and suppliers of expansion joints. However, the EJMA Standards are not mandatory or legally binding, and they do not supersede any applicable codes, regulations or specifications that may govern a particular project or application. aa16f39245