How should the values for pore bridges in TⅠ and I tube bundles be determined in GB/T151-2026, and how should the technical requirements be specified?
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After drilling the tube sheet, the width of allowable pore bridges must be ≥5.74 mm for ≥96% of the holes; the minimum allowable pore bridge width (for ≤4% of the holes) is 4.05 mm. How should this technical requirement be written according to the new standards for tubes TⅠ and Ⅰ?
*Article number for the requirements regarding the classification of tube sheet hole bridge widths and allowable tolerances: 9.4.5 (2014 edition: 8.4.5) *Changes made: The specifications for the classification of tube sheet hole bridge widths and allowable tolerances have been revised; no specific values are given for TI and I grade hole bridge widths, only the allowable tolerances are specified； The allowable and minimum bridge width for grade II steel tube bundles is determined using formulas or tables ； Non-ferrous metals of Grade II are controlled according to the deviations of Grade I.
The standard was released in a hurry; wait for further updates. However, the new standard has not yet been implemented; we are still using the old one for now
I don’t yet have time to review the new standards. Based on the information provided by the original poster, under the new version (assuming heat exchange tubes with a diameter of 25, a tube center distance of 32, and a nominal width of the hole bridges of 7 mm), it should be stated that the allowable deviation for the width of the hole bridges is ±0.4/±0.6. It’s completely different from the previous version
That’s what we discussed as well, but well, we still don’t know how to write it in an authoritative manner~~~
For heat exchange tubes of diameter 25, the tube hole diameter varies depending on the grade, and is slightly larger than 25; the nominal hole bridge width must be calculated by referring to the table in section 7.5.1
Calculate the nominal span width of the bridge; the notation ±0.4/±0.6 is correct
I’m asking how to write it, not how to calculate the positive and negative deviations.