How is the length of the straight edge section of a concave pressure-rated head determined?
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As the title suggests, also, is it possible to avoid using straight edge segments?
Generally, standard elliptical heads have straight edge sections; otherwise, the calculations for the ring seams will not be valid. The length of these straight edges varies depending on the size of the head and can be 25, 50, 100, 150, 200, etc.; however, too long a length is also meaningless. Spherical heads are commonly used in thick-walled vessels; they are generally a spherical segment.
For standard elliptical and butterfly heads, the height of the straight edges is generally 25 mm when it is less than or equal to 2000 mm, and 40 mm when it is greater than 2000 mm. Detailed regulations are provided in JB/T4746-2002; it seems that straight edge sections are necessary.
As mentioned above, the head standards specify standard lengths; the straight edge on the head is intended to keep the area where stress is most concentrated away from the circumferential joint between the head and the cylinder, thereby preventing the accumulation of welding stress and structural stress – it is therefore necessary to have such a straight edge
We don’t look at it from a standard perspective; as a head manufacturing factory, when it comes to heads, there is manufacturing with straight edges and manufacturing without straight edges – having straight edges makes it easier to control dimensions and simplifies the manufacturing process； Without straight edges, it is difficult to control the dimensions, and the shape is prone to becoming oval. According to the standards, straight edges are required; this is not just a casual requirement but is based on certain principles. It is done so that the welding stress and membrane stress at the seam between the head and the cylinder, where the peak stress is most concentrated, can be combined
We don’t look at it from a standard perspective; as a head manufacturing factory, when it comes to heads, there is manufacturing with straight edges and manufacturing without straight edges – having straight edges makes it easier to control dimensions and simplifies the manufacturing process； Without straight edges, it is difficult to control the dimensions, and the shape is prone to becoming oval. According to the standards, straight edges are required; this isn’t just a casual requirement but is based on certain principles. It is necessary so that the welding stress and film stress at the seam where the head meets the cylinder, where the peak stress is most concentrated, can be combined. Therefore, having straight edges is indeed beneficial
This post was last edited by wkj522 on 2009-12-19 at 11:27. There are no specific regulations; the generally recommended values are 25mmHE and 40mm, which are also the most commonly used. It’s not possible to use sections without straight edges.
The straight edges on the end caps are present, mainly due to considerations related to the stress conditions involved.
Thank you all for your answers; they were very helpful