Section 5 Conical ends subject to internal pressure
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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 1 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 1 Steam Raising Plant and Associated Pressure Vessels

5.1 General

5.1.1 Conical ends and conical reducing sections, as shown in Figure 1.5.1 Conical ends and conical reducing sections, are to be designed in accordance with the equations given in Vol 2, Pt 8, Ch 1, 5.2 Minimum thickness

Figure 1.5.1 Conical ends and conical reducing sections

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 1.5.1 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 30º.

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, σ, c and J are as defined in Vol 2, Pt 8, Ch 1, 1.2 Definition of symbols

K = a factor, taking into account the stress in the knuckle, see Table 1.5.1 Values of K as a function of ψ and r i / D o .
D o = outside diameter, in mm, of the conical section or end, see Figure 1.5.1 Conical ends and conical reducing sections.

Table 1.5.1 Values of K as a function of ψ and r i / D o

ψ Values of K for r i/D o ratios of
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

5.2.2 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 1.5.1 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 1.5.1 Conical ends and conical reducing sections

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

Dc = inside diameter, in mm of conical section or end at the position under consideration, see Figure 1.5.1 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 1.5.1 Conical ends and conical reducing sections

c is as defined in Vol 2, Pt 8, Ch 1, 1.2 Definition of symbols

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

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