Section 4 Dished ends subject to internal pressure
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Naval Ships, January 2023 - Volume 2 Machinery and Engineering Systems - Part 8 Pressure Plant - Chapter 2 Other Pressure Vessels - Section 4 Dished ends subject to internal pressure

Section 4 Dished ends subject to internal pressure

Parent topic: Chapter 2 Other Pressure Vessels

4.1 Minimum thickness

4.1.1 The thickness, t, of semi-ellipsoidal, and hemispherical unstayed ends, and the knuckle section of torispherical ends dished from plate, having pressure on the concave side and satisfying the conditions listed below, is to be determined by the following formula:

where t, p, Do, c σ and J are as defined in Vol 2, Pt 8, Ch 2, 1.2 Definition of symbols

4.1.2 For semi-ellipsoidal ends:

  1. the external height, H ≥ 0,18Do

where

D o = the external diameter of the parallel portion of the end, in mm.

4.1.3 For torispherical ends:

  1. the internal radius, R i ≤ D o

    the internal knuckle radius, r i ≥ 0,1D o

    the internal knuckle radius, r i ≥ 3t

    the external height, H ≥ 0,18D o, and is determined as follows:

4.1.4 In addition to the formula in Vol 2, Pt 8, Ch 2, 4.1 Minimum thickness 4.1.1 the thickness, t, of a torispherical head made from more than one plate, in the crown section, is to be not less than that determined by the following formula:

where t, p, Ri, c σ, and J are as defined in Vol 2, Pt 8, Ch 2, 1.2 Definition of symbols

4.1.5 The thickness required by Vol 2, Pt 8, Ch 2, 4.1 Minimum thickness 4.1.1 for the knuckle section of a torispherical head is to extend past the common tangent point of the knuckle and crown radii into the crown section for a distance not less than mm, before reducing to the crown thickness permitted by Vol 2, Pt 8, Ch 2, 4.1 Minimum thickness 4.1.4 where t = the required thickness from Vol 2, Pt 8, Ch 2, 4.1 Minimum thickness 4.1.1

4.1.6  In all cases, H is to be measured from the commencement of curvature (shown in Figure 1.4.2 Typical dished ends).

4.1.7 The minimum thickness of the head, t, is in no case to be less than mm, where D i is as defined in Vol 2, Pt 8, Ch 2, 1.2 Definition of symbols. The minimum thickness permitted for vessels manufactured in corrosion resistant steels will be the subject of special consideration.

4.1.8 For ends which are butt welded to the drum shell, see Vol 2, Pt 8, Ch 2, 1.9 Joint factors, the thickness of the edge of the flange for connection to the shell is to be not less than the thickness of an unpierced seamless or welded shell, whichever is applicable, of the same diameter and material and determined by Vol 2, Pt 8, Ch 2, 2.1 Minimum thickness

4.2 CROSS-REFERENCES

4.2.1 For shape factors dished ends, see Vol 2, Pt 8, Ch 1, 4.2 Shape factors for dished ends
For dished ends with unreinforced openings, see Vol 2, Pt 8, Ch 1, 4.3 Dished ends with unreinforced openings
For flanged openings in dished ends, see Vol 2, Pt 8, Ch 1, 4.4 Flanged openings in dished ends.
For location of unreinforced and flanged openings in dished ends, see Vol 2, Pt 8, Ch 1, 4.5 Location of unreinforced and flanged openings in dished ends.
For dished ends with reinforced openings, see Vol 2, Pt 8, Ch 1, 4.6 Dished ends with reinforced openings

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