SECTION 3—DESIGN
3.7 SHELL OPENINGS .1 General
3.7.3 Spacing of Welds Around Connections See Figure 3-22 for spacing requirements listed in .1
through 3.7.3.4.
Note: Additional weld spacing requirements exist in this standard.
Other paragraphs and tables dealing with nozzles and manholes may increase the minimum spacing.
Note: Whenever stress relief or thermal stress relief is used in this standard, it shall mean post-weld heat treatment.
3.7.3.1 For nonstress-relieved welds on shell plates over 12.5 mm (1/2 in.) thick, the minimum spacing between pene- tration connections and adjacent shell-plate joints shall be governed by the following:
a. The outer edge or toe of fillet around a penetration, around the periphery of a thickened insert plate, or around the periph- ery of a reinforcing plate shall be spaced at least the greater of eight times the weld size or 250 mm (10 in.) from the center- line of any butt-welded shell joints.
b. The welds around the periphery of a thickened insert plate, around a reinforcing insert plate, or around a reinforcing plate shall be spaced at least the greater of eight times the larger weld size or 150 mm (6 in.) from each other.
3.7.3.2 Where stress-relieving of the periphery weld has been performed prior to welding of the adjacent shell joint or where a nonstress-relieved weld is on a shell plate less than or equal to 12.5 mm (1/2 in.) thick, the spacing may be reduced to 150 mm (6 in.) from vertical joints or to the greater of 75 mm (3 in.) or 21/2 times the shell thickness from horizontal joints. The spacing between the welds around the periphery of a thickened insert plate or around a reinforcing plate shall be the greater of 75 mm (3 in.) or 21/2 times the shell thickness.
Table 3-5—Dimensions for Bolt Circle Diameter Db and Cover Plate Diameter Dc for Shell Manholes
Column 1 Column 2 Column 3
Manhole Diameter mm (in.)
Bolt Circle Diameter Db mm (in.)
Cover Plate Diameter Dc mm (in.) 500 (20) 656 (261/4) 720 (283/4) 600 (24) 756 (301/4) 820 (323/4) 750 (30) 906 (361/4) 970 (383/4) 900 (36) 1056 (421/4) 1120 (443/4) Note: See Figure 3-4A.
00
Figure 3-4A—Shell Manhole
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500 mm (20") manhole: 635 mm (253/8") OD × 500 mm (20") ID × 3 mm (1/8") thickness 600 mm (24") manhole: 735 mm (293/8") OD × 600 mm (24") ID × 3 mm (1/8") thickness 750 mm (30") manhole: 885 mm (353/8") OD × 750 mm (30") ID × 3 mm (1/8") thickness 900 mm (36") manhole: 1035 mm (413/8") OD × 900 mm (36") ID × 3 mm (1/8") thickness Gasket (see Note 1):
Reinforcing pad shall be shaped to suit tank curvature
Rounded corners
(150 mm [6"] minimum radius)
Arc dimension = W/2 500 mm (20") and 600 mm (24") manhole: 750 mm (30") 750 mm (30") manhole: 900 mm (36") 900 mm (36") manhole: 1050 mm (42") (Increase as necessary for clearance)
t T
See details
125 mm (5") minimum 32 mm (11/4")
500 mm (20") and 600 mm (24") shell manholes: twenty-eight 20 mm-diameter (3/4") bolts in 24 mm (7/8") holes 750 mm (30") and 900 mm (36") shell manholes: forty-two 20 mm-diameter (3/4") bolts in 24 mm (7/8") holes (Bolt holes shall straddle the flange vertical centerline.)
(See Figure 3-4B)
Alternative circular shape (see Note 8)
1 1
230 mm (9")
10 mm-diameter (3/8") rod
75 mm (3")
150 mm (6")
ID
DO/2 (see Note 8)
CL CL
Db Dp
Dc
6 mm (1/4") C L
One 6 mm (1/4") telltale hole in reinforcing plate, on horizontal centerline
L
Symmetrical about
DR/2 (see Note 8) L
See Figure 3-4B
(See Note 7)
See Note 2
(see Note 4) Rounded
corner Manhole ID Uniform, smooth surface
tn
6 mm (1/4")
Detail a
See Note 2
tn (see Note 4)
tf (see Note 3) Manhole ID Rounded
corners
See Note 5
Detail b tf (see Note 3)
tc
tf
tn
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(see Note 8)
Notes:
1. Gasket material shall be specified by the purchaser. See 3.7.5.4.
2. The gasketed face shall be machine finished to provide a mini- mum gasket-bearing width of 20 mm (3/4 in.).
3. See Table 3-3.
4. See Table 3-4.
5. The size of the weld shall equal the thickness of the thinner member joined.
6. The shell nozzles shown in Table 3-6 may be substituted for man- holes.
7. When the shell nozzles shown in Figure 3-5 are used, the mini- mum centerline heights above the tank bottom given in Table 3-6 are acceptable.
8. For dimensions for Do, DR, L, and W, see Table 3-6, Columns 4, 5, and 6.
01 ●
D (min) O
L and W or D
O
(see Table 3-6)
OD of insert plate
(See Note 2)
C L
JJNeck bevel should be about 10 degrees Round and grind corner (See Table 3-7)(See Tables 3-6 and 3-7)
C L
T + t (min) Shell
(See Note 2) D (min) O
(See Note 3)A
t (min) 45°
1/3 (T + t) min
(See Note 2)
1/3 (t +T) min (See Table 3-7) T + t (min)A Bottom
45° [10 mm (3/8") maximum][10 mm (3/8") maximum] Radiograph (see 6.1.2.2, Item d)
T + t (min) 1:4 bevel
Alternative bevel Radiograph (see 6.1.2.2, Item d)
45°
C L C L
INSERT-TYPE REINFORCEMENT FOR MANHOLES AND NOZZLES
A Radiograph (see 6.1.2.2, Item d)
tt
1.5 mm (1/16")1.5 mm (1/16") t1:4 bevel
1:4 bevel
(See Tables 3-6 and 3-7)
(See Note 1) Manufacturer’s standard (15 degrees minimum, 35 degrees maximum)
Tt
A Round corner if weld <T
(See Table 3-7)(See Table 3-7) A [10 mm (3/8") maximum] NOZZLE
JJ
(See Note 1) Manufacturer’s standard
(15 degrees minimum, 35 degrees maximum)
L and W (Table 3-6) or D
O
Tt
T or t [40 mm (11/2") maximum]
A
1.5 mm (1/16") T or t [40 mm (11/2") maximum]
1.5 mm (1/16") Round corner if weld <T
(See Tables 3-6 and 3-7)
Round and grind
Neck bevel should be about 10 degrees (See Table 3-7) MANHOLE OR NOZZLE Alternative neck detail
tn tn
tn 1.5 mm (1/16") Notes: 1.See Table 3-7, Column 3, for the shell cutout, which shall not be less than the outside diameter of the neck plus 13 mm (1/2) inch. 2.Refer to 3.7.3 for minimum spacing of welds at opening connections. 3.The weld size shall be either A (from Table 3-7, based on t ) or tn (mini- mum neck thickness from Tables 3-4, 3-6, and 3-7), whichever is greater.
4.Other permissible insert details are shown in Figure 3-8 of API Standard 620. The reinforcement area shall conform to 3.7.2. 5.Dimensions and weld sizes that are not shown are the same as those given in Figure 3-4A and Tables 3-4 through 3-8. 6.Details of welding bevels may vary from those shown if agreed to by the purchaser.● Figure3-4B—Details of Shell Manholes and Nozzles
00
01
Figure 3-5—Shell Nozzles (See Tables 3-6, 3-7, and 3-8)
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REINFORCING PLATE
REGULAR-TYPE FLANGED NOZZLES, NPS 3 OR LARGER (Bolt holes shall straddle flange centerlines)
Diamond Circular
Single Flange Special Flange
Detail b One 6 mm (1/4") telltale hole
in reinforcing plate, on horizontal centerline Bend reinforcing plate to
radius of tank shell Alternative shape for low-type nozzles See Detail a or b for
bottom edge
(See Figure 3-4B) (See Figure 3-4B) (See Figure 3-4B)
(See Figure 3-4B) Arc distance 1
1
Tank bottom
Victaulic groove or threads
(See Note 1) (See Note 1)
(See Note 1)
(See Note 5) 60°
t / 2 [6 mm (1/4") minimum]
C Chip
DO DP
DR DR
W
L DP
DR/ 2
DR/ 2
J J
t T Q
OD
B B HN
OD
J J
t T
Q Q
J t
T Q
OD
B
Nozzle CL
Double Flange
T T
t t
L
Detail a
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LOW-TYPE FLANGED NOZZLES, NPS 3 OR LARGER (Bolt holes shall straddle flange centerlines) Notes:
1. See 3.1.5.7 for information on the size of welds.
2. See 3.8.8 for information on the couplings used in shell nozzles.
3. Nozzles NPS 3 or larger require reinforcement.
4. Details of welding bevels may vary from those shown if agreed to by the purchaser.
5. Shop weld not attached to bottom plate.
●
3.7.3.3 The rules in 3.7.3.1 and 3.7.3.2 shall also apply to the bottom-to-shell joint unless, as an alternative, the insert plate or reinforcing plate extends to the bottom-to-shell joint and intersects it at approximately 90 degrees. A minimum distance of 75 mm (3 in.) shall be maintained between the toe of a weld around a nonreinforced penetration (see 3.7.2.1) and the toe of the shell-to-bottom weld.
3.7.3.4 By agreement between the purchaser and the man- ufacturer, circular shell openings and reinforcing plates (if used) may be located in a horizontal or vertical butt-welded shell joint provided that minimum spacing dimensions are met and a radiographic examination of the welded shell joint is conducted (see Figure 3-6, Details a, c, and e). The welded shell joint shall be 100% radiographed for a length equal to three times the diameter of the opening, but weld seam being removed need not be radiographed. Radiographic examina- tion shall be in accordance with 6.1.3 through 6.1.8.