Why don’t the flanges selected according to standards pass the SW6-98 calculations?
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Why don’t the flanges selected according to standards pass the SW6-98 calculation? At this point, the nominal pressure of the flange is higher than the design pressure. What should I do in this situation?
Standard flanges do not require calculation; they can be selected directly.
Back to Floor 2: “Standard flanges do not require calculation; they can be selected directly.” Selecting standard flanges directly is conditional. When the material changes or when the maximum allowable operating pressure of the flange is lower than the design pressure, it cannot be selected directly; calculations must be performed instead.
This post was last edited by GUANGWEI8.26 on 2009-5-13 at 17:23. The fundamental reason is that the data in the current JB4700~4707 standards still largely uses the old data from earlier versions; the flange calculation models from back then were different from those specified in GB150 today! It is recommended not to perform strength calculations for standard flanges!
When selecting standard flanges, the maximum allowable operating pressure must be higher than the design pressure; therefore, standard flanges can be used directly, and there should be no issues with this.
I mentioned this issue in my post; one of the participants during the training also asked the training expert the same question. The expert said that those flanges had been tested and were fine, haha. We even joked about that expert at the time
Standard flanges may not meet the requirements when calculated according to GB150 or SW. This is normal, as long as the flange equivalent design pressure does not exceed the flange’s maximum shock-free pressure. The dimensions of standard flanges are not calculated like those in Gb150; some are determined through actual use or testing. It cannot be said that just because the calculation based on Sw or GB150 fails, it cannot be used.
Is it a problem with the material of the fasteners and gaskets used? Choose a softer material.
Sometimes, it may be impossible to proceed with the use of standard flanges due to calculation issues; it’s probably a problem with the SW6 software. When selecting standard flanges, the maximum allowable operating pressure must certainly be higher than their design pressure; in cases like this, our usual approach is to simply choose those flanges.
For standard flanges, we simply choose them without any calculations
Choose according to the requirements of GB150.