Speaking of expansion joint design

1. I have seen the calculation methods used by professional manufacturers; their approach to determining the values for the following two parameters is as follows: 1.1. The actual yield strength at the design temperature is taken from Section D – Properties of materials in Part 2 of the ASME standards, where yield strengths of materials at different temperatures can be found. 1.2. The yield strength at room temperature as stated in the quality certificate comes from the quality certificate provided by the manufacturer for the materials purchased; it certainly isn’t data related to the materials to be purchased, but rather data from previous batches’ certificates. 2. Example: 2.1. If Incoloy800 is used as the material, the standard specifies a yield strength of 207 MPa for the annealed state at room temperature, while the design temperature yield strength for the annealed state is given as 153 MPa; the quality certificate indicates a yield strength of 216 MPa. 2.2. Before issuing this response, the material data for 800 as specified in ASME II D was verified, and it matches the standard data used in the calculations conducted by the specialized manufacturer ； It is reasonable for the data in the warranty certificate to be slightly higher than the minimum yield strength specified in the standards.

I wonder what the intention was behind adding this content in this update?

This post was last edited by lupg on 2022-4-12 09:05. These two items are not new; they were already included in the GBT12777-2008 standard.

This post was last edited by lupg on 2022-4-12 09:17. 1 These data are included to determine the yield strength of bellows materials in their formed or heat-treated state at the design temperature. The ratio of the yield strength at room temperature specified in the warranty letter to the yield strength at room temperature specified in the standards acts as a kind of coefficient, as this ratio is a value slightly greater than 1; it takes into account the fact that the actual yield strength is higher than the minimum yield strength specified in the standards. 2 If the data in the warranty certificate are taken as the minimum yield strength specified in the standards, that is, with a ratio of 1, it simply results in a more conservative calculation.

Thank you for the explanation, but I still don’t understand how, during the device design phase, designers can determine these two values If you don’t know, how is an expansion joint calculated, and how is it designed?

1. For specifications regarding data, it is recommended to refer to ASME standards; the specific source has been indicated in the previous response. 2. As for the data related to warranty certificates, it is advisable to consult specialized units that manufacture expansion joints, as they have warranty certificates for materials in stock. 3. If it is necessary to ask, take the minimum value of the standard data. 4. I’m not clear about your design process. As users, our *usual practice is to have the design institute prepare a quotation document for purchased products, and then ask the manufacturing unit to submit a design proposal; this way, the issue of the data source is resolved. Another approach is to obtain a quote based on the drawings provided by the design firm; if there are any suggestions for modifications, have the designers confirm them. 5. As I mentioned in my previous response, using the data from the warranty certificate is equivalent to applying a coefficient slightly greater than 1. If the minimum yield strength specified in the standards is used, it simply results in a thickness that is slightly larger; it is also possible to adjust the wave height, wave spacing, and wave number to meet the stiffness requirements. 6. In fact, it’s easy to imagine that if your drawings are accurate but the properties of the steel plates purchased differ significantly from those you calculated and selected, you won’t know what to make of the bellows that end up being produced The stiffness of the bellows is designed with a margin of safety, and moreover, the values in the standards are not actual values; so how can you determine the actual yield limit? 7. We currently use bellows, with the manufacturing unit being responsible for ensuring performance and quality; the user only needs to clearly state their requirements.