The specific requirements for the straight edge length of ASME head are as follows:
When the thickness of the head is greater than the thickness of the cylinder, the ASME standard stipulates that the minimum length of the straight edge of the head should be three times the thickness of the cylinder, but not exceeding 38mm. For example:
If the thickness of the cylinder is 10mm and the thickness of the head after considering the thinning amount during forming is 12mm (the difference in thickness between the cylinder and the head is less than 3mm), then the straight edge should be at least 36mm.
If the thickness of the cylinder is 20mm and the thickness of the head after considering the thinning amount during forming is 22mm (the difference in thickness between the cylinder and the head is less than 3mm), then the straight edge should be at least 38mm.
If the thickness of the cylinder is 40mm and the thickness of the head after considering the thinning amount during forming is 45mm (the difference in thickness between the cylinder and the head is greater than 3mm), then the straight edge should be at least 38mm.
In addition, the straight edge section of the head needs to be calculated, and its calculation formula is the same as that of the cylinder. When the minimum thickness of the head is much smaller than the minimum calculated thickness of the cylinder, it is necessary to calculate the straight edge of the head to avoid excessive primary membrane stress on the straight edge.