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EJMA Standards: The Authority on Expansion Joints
EJMA stands for Expansion Joint Manufacturers Association, Inc., an organization of established manufacturers of metal bellows type expansion joints. EJMA publishes standards that 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. The latest edition of the EJMA Standards is the 10th Edition, which was released in 2016.
The EJMA Standards cover the design, fabrication, testing, and installation of expansion joints, as well as providing definitions, nomenclature, symbols, and units of measure. The Standards also include practical guides, examples, benchmarks, and appendices for reference. The Standards are intended to provide users with a basic understanding of expansion joints, as well as to assist them in communicating design requirements to the manufacturers and to properly install and maintain the expansion joint in service.
The EJMA Standards are available in printed or e-reader format. They can be ordered from the EJMA website or from other online sources. The EJMA Standards are not a manufacturing standard or a quality assurance document. They do not limit or dictate the manufacturing process to be used for construction of expansion joints, nor do they establish specific engineering requirements deemed necessary for the safe application, design, and manufacture of expansion joints. If there is a strong preference for a certain type of manufacturing process, the user should provide this information.
The EJMA Standards are a valuable resource for anyone involved in the design, selection, application, or maintenance of expansion joints. They combine the knowledge and experience of the leading manufacturers of expansion joints into an invaluable reference document.
Some of the significant changes in the 10th Edition of the EJMA Standards are:
- A new approach was developed for the design of reinforced bellows, resulting in a modified set of equations for some stress components and for the spring rates. The main and most important result was that the calculated bending stress due to deflection could be considerably reduced. The number of fatigue cycles can now be calculated from the same set of fatigue curves which are relevant for the unreinforced bellows and for the toroidal bellows. Fatigue life calculations were greatly enhanced and simplified.
- The calculation of universal type expansion joints has been simplified by a modified equation for the axial movement per convolution. An acceptable radial gap between equalizing/reinforcing rings and the root of convolution/bellows tangent is introduced to section 6.
- The 10th Edition has been modified to include English & Metric units of measure. This includes standard conversions in addition to constants used in calculations. Tightness of bellows, bands, and rings due to dissimilar material growth rates is considered. The distinction of thin versus thick bellows has been added.
- Benchmark table inputs and outputs have been revised, with material class and correction factor. Single bellows axial vibration constants were revised. Definitions in the nomenclature section 1.3 have been clarified.
Expansion joints are used in a variety of applications that involve thermal expansion, vibration, or pressure fluctuations. Some examples are:
- Piping systems that transport steam, hot water, gas, oil, or chemicals.
- Power generation plants that use boilers, turbines, generators, or heat exchangers.
- Chemical and petrochemical plants that process or refine various substances.
- Metallic structures that are exposed to temperature changes or dynamic loads.
- Aerospace and marine vehicles that experience high temperatures and pressures.
The EJMA Standards are updated periodically to reflect the latest developments and innovations in the field of expansion joints. The Technical Committee of EJMA reviews and revises the Standards based on feedback from users, manufacturers, testing laboratories, and research institutions. The last update was in 2016, when the 10th Edition was released. The next update is expected to be in 2021.
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