Internal pressure elbow calculation
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Chapter 21 of HG/T20582-2011 deals with the calculation of pressure-rated elbows; there are two formulas for calculating the C value, but the standard does not specify under what conditions each formula should be used. So how should we choose the appropriate formula when calculating elbows?
The estimation is made based on the bending degree R/Dw value
Either of these two formulas works; the first formula is likely a simplified version of the second one, applicable when the value in A1 is very small. To be more accurate, the second formula is generally used.
Following HG/T20582-2011 is a compilation note; the formulas are based on those in GB9222. According to the explanations in GB9222, the first formula applies to elbows formed by bending straight pipes, while the second formula applies to cast elbows.
Both formulas must be satisfied simultaneously. . . That is, to satisfy Equation 2. . .