[Discussion Thread 10] Can material Q235B be used for flanges with a PN16 pressure rating?
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This post was last edited by kareale88 on 2019-1-21 at 13:07: bg4.png【Discussion Thread 10】Can material Q235B be used for flanges with a PN16 pressure rating? Appendix D of GB150.2 states: (see image)
d) The design pressure for the container is 1.6 MPa. If the design pressure is 1.0 MPa, then Q235B pipe flanges of PN16 grade can be used.
In other words, as long as the design pressure of the container is less than 1.6 MPa, the flange chosen meets the maximum allowable operating pressure at the working temperature, and the wall thickness does not exceed the value specified in factor f, then it’s suitable, right?
Do you agree with this view? In other words, as long as the design pressure of the container is less than 1.6 MPa, the flange chosen meets the maximum allowable operating pressure at the working temperature, and the wall thickness does not exceed the value specified in factor f, then it’s suitable, right?
From what I’ve found online, in Baidu Baike and various other articles, the allowable conditions for Q235b are ① the design pressure of the container p≤1.6MPa； ② The operating temperature for the steel plate is 0～350℃ ； ③ When used for the housing, the steel plate thickness shall not exceed 20 mm. There are differences from GB150, and the sources indicated are all from GB/T 700-2006. Upon checking GB/T 700, I found that it only specifies grades A, B, C, and D, without clearly defining the nominal pressure for Q235b. According to Baidu, as long as it’s not greater than that value, it can be used.
This depends on GB150; in addition, special attention should be paid to the sulfur and phosphorus content, as well as the temperature for the hydraulic test. The technical requirements specified in the diagram usually include: 1. The medium used for hydraulic testing must be clean water, with a temperature of no less than 20°C; for specific requirements, refer to clause 11.4.9 of GB/T150.4-2011. 2. The phosphorus and sulfur content in the Q235-B steel plates must meet the standards of P≤0.035% and S≤0.035%, as well as the relevant requirements outlined in Appendix D of GB150.2-2011.
This post was last edited by zjq1962 on 2019-1-21 at 15:22. Yes, GB/T150.2 is used to determine the design pressure. For example, if the design pressure is 0.2, a PN16 PL flange should be selected (the pressure rating of the flange must be at least equal to the design pressure). As long as the thickness is within the specified range, Q235B material can be used.
By extension: The flange is selected to meet the maximum allowable operating pressure at the operating temperature; first of all, this maximum allowable operating pressure should be compared with the design pressure, right? Can this maximum allowable operating pressure be determined by comparing it with the operating pressure in use? Especially for stainless steel flanges, it is a key factor in cost savings.
Which flange should be chosen to meet the maximum allowable operating pressure at the operating temperature? Should the table be referred to based on the equipment’s operating pressure or its design pressure?
The previous sentence is the exact wording from the book; a chief engineer said that the maximum allowable operating pressure is the design pressure, or the maximum allowable operating pressure specified on the design drawings. I think this operating temperature is more reasonable as a design temperature.