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HESSE AND RUSHTON METHOD

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SHELL THICKNESS t p

2
PD
Se

P

C where t p
= shell thickness (inch)
P = Max allowable working pressure (psi)
D = Inside diameter (inch)
S = Max allowable tensile stress (psi) (Table 6-6) e = Efficiency of welded joint (Table 6-7)
C = Corrosion allowance

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SHELL THICKNESS t p

2
PD
Se

P

C
Applicable if:
1. t p
< 0.10D
2. t p
> t min t min

D

100
1000

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Allowable Stress Estimation
S = S u x F m x F s x F r x F a
Where
S
F u m
= Minimum Specified Tensile Strength
= Material Factor
F m
F m
F m
= 1 for Grade A material
= 0.97 for Grade B material
= 0.92 for Grade C material
= Temperature Factor (Use Table 6-7) F s
F r
= Stress Relief (SR) Factor
F r
= 1.06 When SR is applied
F a
= Radiographing Factor
F a
= 1.12 when Radiographing is applied and subsequent repair of defects

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Minimum Specified Tensile Strength
ASME
Code
Spec.
No.
Material Data and Description
S-2 Steel plates - flange and firebox quality
S-1 Carbon steel for boilers
Carbon-silicon steel,
S-42 ordinary strength range
S-44 Molybdenum steel
S-43 Low-carbon nickel steel
S-55 Carbon-silicon steel, high strength range, 4-1/2” plates and under
S-44
S-43
S-55
S-44
S-43
S-28 Chrome-manganesesilicon alloy steel
A
B
A
A
A
B
A
Specified
Minimum
Tensile
Strength - 20
Grade 1000 psi to
650
Allowable Unit Tensile Stress, Thousands psi at Various Temperatures, ° F
700 750 800 850 900 950 1000
45
50
55
60
9.0
8.8
8.4
6.9
5.7
4.4
2.6
10.0
9.6
9.0
7.5
6.0
4.4
2.6
11.0
10.4
9.5
8.0
6.3
4.4
2.5
11.0
10.4
9.5
8.5
7.2
5.6
3.8
2.0
12.0
11.4
10.4
9.1
7.4
5.6
3.8
2.0
13.0
13.0
13.0
12.5
11.5
10.0
8.0
5.0
65
13.0
12.3
11.1
9.4
7.6
5.6
3.8
2.0
B
C
C
B
B
A
B
70
75
85
14.0
14.0
14.0
13.5
12.0
10.2
8.0
5.0
14.0
13.3
11.9
10.0
7.8
5.6
3.8
2.0
14.0
13.3
11.9
10.0
7.8
5.6
3.8
2.0
15.0
15.0
15.0
14.1
15.0
12.4
14.4
10.1
12.7
7.8
10.4
5.6
8.0
3.8
5.0
2.0

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Temperature Factor
Metal Temperature, Plate and Forged
° F Steel, %
Up to 650
700
750
800
850
900
950
1000
25.0
23.7
21.0
18.0
15.0
12.0
9.0
6.2
Cast Steel, %
16.7
16.4
14.7
12.9
11.1
9.3
7.5
5.7

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Weld/Joint Efficiency
EFFICIENCY
LAP WELD (For circumferential Joint)
Single Lap
Single Lap with plug weld
Double Lap
BUTT WELD (For circumferential and longitudinal joints)
Single Butt
Single Butt with Back-up Strip
Double Butt
Double Butt with reinforce at center
55%
65%
65%
70%
80%
80%
90%
CRITERIA t p t p t p
< ⅝”
< ⅝”
> ⅝” t p t p t t p p
< ⅝”
< 1¼”
> 1¼”
> 1¼”

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Stress Relief Factor
Stress relieving is mandatory for:
1. t p
2. t p
> 1 ¼”

D

120
50
(For thinner plates) where D has a minimum value of 20 inches
3. ASTM A – 150
4. ASTM A – 149
(under certain conditions)

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Radiographing Factor
Radiographing is mandatory for:
1. ASTM A – 150
2. ASTM A – 149 (under certain conditions)
3. Lethal gases application
4. Nuclear Reactor applications

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Sample Problem 1
A 12 in diameter S-2 Grade A steel has a working pressure and temperature of 500 psi and 300F respectively. Determine the type of weld to be used and plate thickness using Hesse and
Rushton method.
Assume zero corrosion allowance.

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Sample Problem 2
Grade A S2 steel, butt welded pressured vessel for lethal gas application has an inside diameter of 20 inches. If the working pressure is 900 psi and the working temperature is 250 ºF, what is the shell thickness of the vessel?
(Use minimum corrosion allowance and Hesse and
Rushton method).

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HEAD Configurations
 Torispherical
 most common type of head used and usually the most economical to form
 The I.C.R = I.D of the head or less
• between 90% to 95% of the I.D of the head
 The I.K.R = 6% and 10% of the I.C.R of the head
 The S.F = 10mm and 30mm

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HEAD Configurations
 2:1 Semi-Ellipsoidal
 deeper and stronger than a torispherical head
 more expensive to form than a torispherical head,
• but may allow a reduction in material thickness as the strength is greater
 The I.C.R is 0.8 of the O.D of the head
 The I.K.R is 0.154 of the O.D of the head
 The S.F =10mm and 30mm

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HEAD Configurations
 Hemispherical
 allow more pressure than any other head
 most expensive to form
 The depth of the head is half of the diameter.

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HEAD Configurations
 Shallow Head
 commonly used atmospheric tanks
 not suitable for pressure vessels
 I.C.R =1.5 to 2.0 times the I.D of the head
 I.K.R = 32mm, 51mm or 76mm (depending on the diameter and customer requirements)
 The S.F =10mm and 30mm

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HEAD Configurations
 Cones for Pressure Vessels
 The maximum internal apex angle for cones =120 O
 The I.K.R = 6% of the inside diameter of the vessel
 The S.F =10mm and 30mm

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HEAD Configurations
 Flat.
 A flat end with a knuckled outer edge
 used as bases on vertical atmospheric tanks and lids for smaller tanks
 The I.K.R =25mm, 32mm and 51mm
 The S.F. = 10mm and 30mm

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HEAD Configurations
 Dish.
 used for atmospheric tanks and vessels and for bulk heads or baffles inside horizontal tanks or tankers
 Typically the I.C.R is equal to the diameter

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HEAD THICKNESS
Standard Ellipsoidal t

PD
2 SE
Hemispherical
PD t

4 SE
Standard Dished where t

PLW
2 SE
L = crown radius in inches = D o
– 6
K r
= knuckle radius = 0.06 D o

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HEAD THICKNESS
Standard Dished
 Values for W or dished heads
Kr/L
0.06
0.07
0.08
0.09
0.10
0.11
0.12
0.13
0.14
W
1.8
1.7
1.65
1.6
1.55
1.50
1.47
1.44
1.41

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HEAD THICKNESS
Standard Dished
 Values for W or dished heads
Kr/L
0.15
0.16
0.17
0.18
0.19
0.20
0.25
0.50
1.0
W
1.40
1.38
1.37
1.35
1.32
1.30
1.25
1.12
1.0

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HEAD THICKNESS
Flat Heads
*Lap Welded w/ or w/o Plug Welds: t
 d
0 .
3 P
S
*Single or Double V Butt Welded t
 d
0 .
25 P
S
*Cut from Solid PlateStandard Dished t
 d
0 .
5 P
S