Strength calculation of the rectangular opening above the shell cover plate
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The strength calculation of square openings in the shell cover is a concern in heat exchanger design. Square openings are often made in the shell cover to house air coolers, and there is no such calculation model specified in GB150; therefore, it’s unclear how such calculations should be carried out. Additionally, the small tube sheet covers inside the shell are also square in shape – how should their strength be calculated? Sometimes, the side of these covers extends outside the shell and is sealed using compression rings; how should the strength of these rings be determined? These are all questions I have in my work, and I hope to get answers from experts (preferably formulas that do not require analytical methods). Below is the structural diagram
Square holes are made in the housing cover plate: The calculation is based on circular holes, with the hole diameter equal to the length of the diagonal of the square. The rotating cover is calculated based on a cubic container. The tube sheet is calculated based on the hole arrangement of a square-shaped vessel. Ring strength: The specific structure is not clear; if the size and quantity of flanges and studs are involved, refer to the relevant standards and add an appropriate margin. Personal opinion.
1. Regarding the issue of square holes in the cover plate, calculations are done as if they were circular holes, with the hole diameter equal to the diagonal length of the square. This is also how we calculate it now. However, there is a problem: when calculating the strength of the bolts, the requirements cannot be met; it is indicated that either the bolt spacing is too small or the bolt diameter is too small. Since the actual spacing between bolts differs between a square perimeter and a circular perimeter, this issue needs to be resolved； Also, when creating square-shaped holes, it is necessary to round off the edges, as this helps to address the issue of stress concentration. So how is the impact of these rounded edges on strength calculated? ； There is also a formula for the equivalent diameter of square holes in shipbuilding standards; can it be used to calculate this value? After all, using the diagonal length for calculation will definitely result in a more conservative estimate. We have asked external experts to carry out analyses and calculations, and the results showed that the thickness required is about 25% less compared to the value obtained by using the diagonal length. Additionally, the effect of rounding off corners is significant as well. 2. The square-type rotating cover should be calculated based on the principles applicable to square containers; the ratio of the longer sides to the shorter sides indicates that it does not meet the requirements, and the same applies to the ratio of the cylinder length to the long side plates. How can this problem be resolved? 3. The rear tube sheet should belong to the category of square flat covers with perforations. Could you please provide detailed information on the calculation methods for this part? 4. Regarding the strength of the compression ring: there is no compression ring shown in this diagram. The compression ring structure is replaced by a sealing plate at the back, with circular holes in it. Both the small tube sheet and the rotating cover are circular in shape, and the perimeter of the small tube sheet is sealed using O-rings. These O-rings are located between the rear sealing plate and the compression ring. The compression ring has the same structure as a circular butt-welded flange, with a 45-degree bevel on its inner perimeter to hold the O-rings in place
Your shape is square, but your calculations can be done using the structure of a circular blind plate.
I’ve encountered the issue of square holes before as well; back then, I calculated them as circular holes, using the diagonal length of the square hole as the approximate diameter. This method might not be very accurate, but there’s no better way either