[Weekly Topic] Considerations for Using Q235-B in Pressure Vessels (2011.06.13-06.19)
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This post was last edited by SuperFree2316 on 2011-6-14 08:26. In accordance with the requirements of TSG R0004, the specifications for fixed capacity, the P and S content in the materials used for pressure vessels must be controlled. Therefore, if Q235B is used, it is necessary to retest whether the PS content meets the requirements. Some time ago, when I was reviewing the draft of the new GB150 standards, I noticed that the allowable stress values for various materials did not include those for material Q235B. The appendix lists various requirements. Assuming that the new GB150 standard is issued, does that mean that restrictions on Q235B will become even stricter? Discussion: What factors are being considered this time to impose stricter controls on 235?
Appendix to the revised material section of GB150 includes Q235-B, with specific application conditions and allowable stresses. It can be checked to see if it is permissible for use; only the operating conditions change, and the allowable stress also changes.
Article 4.1.13 of the material section of GB150.2 (draft for review): The requirements for the use of Q235 series steel plates (Q235B and Q235C) are specified in Appendix D. Appendix D sets out requirements regarding sulfur and phosphorus content, impact energy, cold bending tests, design pressure, operating temperature range, thickness requirements for the steel plates, as well as the allowable stress values and allowable negative deviations in thickness. I am not sure whether the draft held by the moderator is used as a teaching material for training courses; my version was the training material provided by the High-Tech Education Working Committee last October, taught by Zhang Xiaohu from Hefei General Machinery
Furthermore, there is a statement in the preamble to the material section that reads: \"Appendices A and D of this standard are normative appendices\"”
Although the sulfur and phosphorus content needs to be restricted, this can simply be specified in the purchase contract; the exact amount is indicated in the material warranty sheet, so no retesting is required, right?
For pressure vessels whose sulfur and phosphorus content exceeds the requirements specified in the Code for Fixed Pressure Vessels, I believe they are not subject to the inspection regulations of that code; however, they are designed, manufactured, inspected, and accepted in accordance with the 150 standard. Such situations are quite common. For example, in the simplest case of a water storage tank without any gas space, materials like Q235B and Q235C can be used, as they meet the 150 standard requirements while also being exempt from the controls outlined in the Code for Fixed Pressure Vessels
Reply to 5# Wen Bing: Doesn’t the fixed capacity specification require the manufacturer to be responsible for the materials?
Our company generally uses it as the outer shell for double-layer containers; it can withstand a negative pressure of -0.1 MPa, and no component analysis or testing is required
Reply to 8# quzhaoming: The pressure tests still need to be carried out; it’s mainly the test plates that won’t be used, as mentioned earlier
It is indeed a problem, but in terms of price, the difference between Q235B and Q245R is probably not very large anymore. I’m not sure if anyone with experience in procurement can give a definite answer on this. However, in terms of performance and quality, container steel plates (the latter) are more reliable and stringent. We have been using Q235B for vacuum steam pipes, and I am considering switching to Q245R; I’m not sure if there are any economic benefits to doing so.
As long as the S and P contents meet the requirements, the quality certificates must be provided one per sheet, regardless of the material. With the release of the new GB150 standards, the Q235 series may no longer be usable for components subject to primary compressive stresses; the minimum grade that can be used is Q245R.