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HESSE AND RUSHTON METHOD

Pressure Vessels

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SHELL THICKNESS

t p

 2

PD Se



P



C

where

t p P D S e C

= shell thickness

(inch)

= Max allowable working pressure

(psi)

= Inside diameter (inch) = Max allowable tensile stress

(psi)

(Table 6-6) = Efficiency of welded joint (Table 6-7) = 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

Where

S u F m F s F r F a

=

S = S u x F m x F s x F r x F a

= Minimum Specified Tensile Strength = Material Factor

F m

= 1 for Grade A material

F m

= 0.97 for Grade B material

F m

= 0.92 for Grade C material = Temperature Factor (Use Table 6-7) = Stress Relief (SR) Factor

F r

= 1.06 When SR is applied 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 S-1 S-42 S-44 S-43 S-55 Steel plates - flange and firebox quality Carbon steel for boilers Carbon-silicon steel, ordinary strength range Molybdenum steel Low-carbon nickel steel 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-manganese silicon alloy steel A B A B A A A B B B C C A B Grade Specified Minimum Tensile Strength 1000 psi - 20 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

10.0

11.0

11.0

12.0

13.0

8.8

9.6

10.4

10.4

11.4

13.0

8.4

9.0

9.5

9.5

10.4

13.0

6.9

7.5

8.0

8.5

9.1

12.5

5.7

6.0

6.3

7.2

7.4

11.5

4.4

4.4

4.4

5.6

5.6

10.0

2.6

2.6

2.5

3.8

3.8

8.0

2.0

2.0

5.0

65 70 75 85 13.0

14.0

14.0

14.0

15.0

15.0

12.3

11.1

14.0

13.3

13.3

15.0

14.0

11.9

11.9

15.0

14.1

12.4

9.4

10.1

7.6

13.5

10.0

10.0

14.4

12.0

7.8

7.8

12.7

7.8

5.6

10.2

5.6

5.6

10.4

5.6

3.8

8.0

3.8

3.8

8.0

3.8

2.0

5.0

2.0

2.0

5.0

2.0

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Temperature Factor

Metal Temperature, ° F Up to 650 700 750 800 850 900 950 1000 Plate and Forged Steel, % 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 t p t p < ⅝” < 1¼” t p p > 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 allowance.

method.

Assume zero corrosion

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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 diameter and customer requirements) (depending on the  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

t  PD 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