Issues regarding the calculation of deformation rate in Appendix F of HGT20584-2020
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Guys, does anyone know whether, in Appendix F of HG/T20584-2020 regarding the calculation of the fiber deformation rate during cold bending of steel pipes, the calculated values from those two formulas need to be multiplied by 100%? Today, we encountered a problem. The supervisor casually decided to cancel the solution treatment following the cold bending of stainless steel U-shaped heat exchange tubes. We checked the relevant standard; according to Section 6.2.1, Part 3 of HGT20584-2020, for calculating the cold bending deformation rate of steel pipes: the pipe has a diameter of φ10, and its bending radius is R20. Using Equation (F.3) in Appendix F, we get 5/20 = 0.25. However, the supervisor insisted that the calculated result should be 0.25%, rather than 0.25 × 100% = 25%. Have you ever encountered this situation, bro? There’s something that feels off about this, isn’t there? But with the notation like in formula (F.3), what the leader says seems reasonable as well; from a mathematical perspective, if it’s to be expressed as a percentage, it should probably be written as “×100%”. Which one is correct?
Isn’t the formula quite clear? Why X that 100?
6.2.1 The requirement is that the deformation rate calculated should be more than half of the elongation after fracture specified in the standards for steel pipes; heat treatment is necessary. For stainless steel heat exchange tubes, type 13296 is used, with an elongation of 35%, so half of that is 17.5%. What type of tube can achieve a bending deformation rate higher than this value? So, does this standard still make any sense?
This post was last edited by zjq1962 on 2021-12-31 at 13:53. GB151 does not have such a requirement, but it specifies a minimum bending radius
If the execution is different, don’t discuss it together
I think there’s an issue with the standard formatting; *100% is the correct value. Your manager is being irresponsible towards their own company – they don’t care about the standards when there are problems with the products.
Personally, I feel the same way; leaders just want to cut costs. Then another problem arises. Bro, tell me: on normal drawings, usually only a few main standards like the Pressure Equipment Regulation and 151 are specified. The design requirements and technical manuals provided by the client are quite simple; they don’t list all the applicable standards in detail, but only mention a few key ones. So, if you were to do this design, would you follow standard 20584 in such a situation? From my experience in various companies, it’s common for the experienced technicians to request that this be included. Some managers then ask whether it can be removed, while others agree to include it. I wonder what you guys usually do in such situations?
Since HG20584 isn’t specified in the contract, we definitely won’t design it according to the requirements of HG20584； But I still hold the same view: the standards represent the minimum requirements. It’s up to you manufacturers to ensure that the quality is good; the standards aren’t meant to be followed by you. This might seem like common sense, but design is really difficult. If everyone simply followed the standards, there would be no need to go to college or take entrance exams for graduate school. Even an elementary school student who can read and memorize the standards has a much better memory than us old folks.
The expression of the formula 20584 is ambiguous. . . Refer to GB/T20801 EN13445 EN13480 50D/R 50*10/20 %=25%
Ah, it’s hard to put into words – it’s too tough. I’m 33 now, and I don’t want to work in design anymore. Although I have an MBA degree, I lack management experience. Plus, due to the pandemic, companies are under a lot of pressure, so I haven’t been able to find a suitable management position. Even for project management roles, I haven’t found anything suitable. Working in technology is extremely difficult; it’s really not easy to hold onto one’s principles...