For design temperatures above 300°C, can Q235 material be used for the baffle plates?
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This post was last edited by yu05210 on 2018-7-6 at 10:57. Dear colleagues, we currently have a fixed-tube-sheet type heat exchanger for soda production. The design temperature on the shell side is 350°C, and the baffle plates are made of Q235B material. During the inspection process, the pressure vessel inspection agency raised an issue, stating that according to Appendix D of the material section of GB/T150.2, materials from the Q235 series are not compliant with the requirements specified in GB/T150.2 when used at temperatures above 300°C, and therefore cannot be used. However, our understanding of the standard is that when Q235 series materials are used as pressure-bearing components, they should comply with the requirements outlined in Appendix D of GB/T150.2. There is a difference in interpretation between the two parties regarding Appendix D, which has led to this situation. The pressure vessel inspection agency considers the material provisions of GB/T150.2 to apply to all materials, whether they are under pressure or not. Let’s share our opinions.
Considering the impact of Q235B at temperatures above 300°C as a non-compressed component on the equipment separately, I think there is no problem; this is even more true for baffle plates, which have no welding points to the equipment； Many of the jackets in this design use heat transfer oil at a temperature of 350°C, and the guide plates are made of Q235B. However, the standard does not explicitly state that it is intended for stressed components; this includes the sentence referencing Appendix D: “4.1.13 – The usage requirements for Q235 series steel plates (Q235B and Q235C) are specified in Appendix D.” ”, but in Appendix D, \"D.1-f) is for shell thicknesses not exceeding 16 mm\" ； It should not exceed so much so much for other compressed components. "Unstressed members were not mentioned. Judging by the standards, one can only rely on their own understanding; one person might think it means one thing, yet it’s hard to explain clearly:Q
What’s the use of discussing it? I’m most afraid of running into those dogmatic so-called quality control officers; anyway, there’s no way to persuade them. I think this method can be used when there’s definitely no problem, but it doesn’t work; unless you can get some authoritative answer, there’s nothing you can do. In fact, you might even be asked to send a letter to the General Administration for Quality Supervision:lol:lol:lol
The competence of special inspectors also varies; there is a concern that they might abuse their power by pretending to know things they don’t
So, according to the boiler inspection agency, when the design pressure is greater than 1.6 MPa, can’t Q235 series materials be used even for non-pressure components? Are all kinds of angle steel supports, connection plates, as well as bolts, washers, and other components no longer usable?
This is what is stated in the GB150 specifications regarding the requirements for Q235B when used as a compressive element. . . . . Let’s see if we can persuade them
Of course it can be used; it’s not meant to function as a cylinder. People ask questions and you just need to provide explanations. Unless there is a mandatory requirement to replace the material, there’s no need to argue with the boiler inspection agency
This post was last edited by wanlirn on 2018-7-6 at 17:52. For you inspectors, looking at this GB150 P40 standard has led us down a dead end; I’m truly impressed
I truly despise the behavior of organizations like boiler inspection agencies that insist that only their own understanding of the standards is correct and refuse to listen to any explanations
The materials specified in GB/T150.2 are intended for pressure-bearing components; for non-pressure-bearing components that are welded to pressure-bearing components, only materials with good weldability are required. For inspection personnel, one can only present evidence to persuade them.