Section 5 Conical ends subject to internal pressure
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Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Ships, July 2022 - Part 5 Main and Auxiliary Machinery - Chapter 10 Steam Raising Plant and Associated Pressure Vessels - Section 5 Conical ends subject to internal pressure

Section 5 Conical ends subject to internal pressure

Parent topic: Chapter 10 Steam Raising Plant and Associated Pressure Vessels

5.1 General

5.1.1 Conical ends and conical reducing sections, as shown in Figure 10.5.1 Conical ends and conical reducing sections, are to be designed in accordance with the equations given in Pt 5, Ch 10, 5.2 Minimum thickness.

5.1.2 Connections between cylindrical shell and conical sections and ends should preferably be by means of a knuckle transition radius. Typical permitted details are shown in Figure 10.5.1 Conical ends and conical reducing sections. Alternatively, conical sections and ends may be butt welded to cylinders without a knuckle radius where the change in angle of slope, ψ, between the two sections under consideration does not exceed 30°.

5.1.3 Conical ends may be constructed of several ring sections of decreasing thickness, as determined by the corresponding decreasing diameter.

5.2 Minimum thickness

5.2.1 The minimum thickness, t, of cylinder, knuckle and conical section at the junction and within the distance, L, from the junction is to be determined by the following formula:

where

t, p, c, σ and J are as defined in Pt 5, Ch 10, 1.2 Definition of symbols,

K = a factor, taking into account the stress in the knuckle, see Table 10.5.1 Values of K as a function of ψ and ri/Do.
D o = outside diameter, in mm, of the conical section or end, see Figure 10.5.1 Conical ends and conical reducing sections.

5.2.2 If the distance of a circumferential seam from the knuckle or junction is not to be less than L, then J is to be taken as 1,0; otherwise J is to be taken as the weld joint factor appropriate to the circumferential seam,

where
L = distance, in mm, from the knuckle or junction within which meridional stresses determine the required thickness, see Figure 10.5.1 Conical ends and conical reducing sections
=
r i = inside radius of transition knuckle, in mm, which is to be taken as 0,01D c in the case of conical sections without knuckle transition.
ψ = difference between angle of slope of two adjoining conical sections, see Figure 10.5.1 Conical ends and conical reducing sections.

Figure 10.5.1 Conical ends and conical reducing sections

Table 10.5.1 Values of K as a function of ψ and r i/D o

  Values of K for r i/D o ratios of
ψ 0,01 0,02 0,03 0,04 0,06 0,08 0,10 0,15 0,20 0,30 0,40 0,50
10° 0,70 0,65 0,60 0,60 0,55 0,55 0,55 0,55 0,55 0,55 0,55 0,55
20° 1,00 0,90 0,85 0,80 0,70 0,65 0,60 0,55 0,55 0,55 0,55 0,55
30° 1,35 1,20 1,10 1,00 0,90 0,85 0,80 0,70 0,65 0,55 0,55 0,55
45° 2,05 1,85 1,65 1,50 1,30 1,20 1,10 0,95 0,90 0,70 0,55 0,55
60° 3,20 2,85 2,55 2,35 2,00 1,75 1,60 1,40 1,25 1,00 0,70 0,55
75° 6,80 5,85 5,35 4,75 3,85 3,50 3,15 2,70 2,40 1,55 1,00 0,55

5.2.3 The minimum thickness, t, of those parts of conical sections not less than a distance, L, from the junction with a cylinder or other conical section is to be determined by the following formula:

where
D c = inside diameter, in mm of conical section or end at the position under consideration, see Figure 10.5.1 Conical ends and conical reducing sections
α, α1, α2 = angle of slope of conical section (at the point under consideration) to the vessel axis, see Figure 10.5.1 Conical ends and conical reducing sections

c is defined in Pt 5, Ch 10, 1.2 Definition of symbols

5.2.4 The greater of the two thicknesses determined by the formulae in Pt 5, Ch 10, 5.2 Minimum thickness 5.2.1 and Pt 5, Ch 10, 5.2 Minimum thickness 5.2.3 is to apply at the junction or knuckle and within the limits of reinforcement.

5.2.5 The thickness of conical sections having an angle of inclination to the vessel axis of more than 75° is to be determined as for a flat plate.

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