Pressure Vessels

LOGO

HESSE AND RUSHTON METHOD

Pressure Vessels

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LOGOSHELL THICKNESS

wheretp = 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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CPSe

PDt p

2

LOGOSHELL THICKNESS

Applicable if:1. tp < 0.10D2. tp > tmin

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CPSe

PDt p

2

1000100

min

Dt

LOGOAllowable Stress Estimation

S = Su x Fm x Fs x Fr x Fa

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WhereSu = Minimum Specified Tensile Strength

Fm = Material FactorFm = 1 for Grade A materialFm = 0.97 for Grade B material Fm = 0.92 for Grade C material

Fs = Temperature Factor (Use Table 6-7)

Fr = Stress Relief (SR) FactorFr = 1.06 When SR is applied

Fa = Radiographing FactorFa = 1.12 when Radiographing is applied and

subsequent repair of defects

LOGOMinimum Specified Tensile Strength1 9 8 5

SpecifiedASME Minimum Allowable Unit Tensile Stress, Thousands psiCode Tensile at Various Temperatures, °FSpec. Material Data Strength - 20No. and Description Grade 1000 psi to

650700 750 800 850 900 950 1000

S-2 Steel plates - flange and A 45 9.0 8.8 8.4 6.9 5.7 4.4 2.6firebox quality B 50 10.0 9.6 9.0 7.5 6.0 4.4 2.6

S-1 Carbon steel for boilers 11.0 10.4 9.5 8.0 6.3 4.4 2.5Carbon-silicon steel, A 55 11.0 10.4 9.5 8.5 7.2 5.6 3.8 2.0

S-42 ordinary strength range B 60 12.0 11.4 10.4 9.1 7.4 5.6 3.8 2.0S-44 Molybdenum steel A 13.0 13.0 13.0 12.5 11.5 10.0 8.0 5.0S-43 Low-carbon nickel steel AS-55 Carbon-silicon steel, high 65

strength range, 4-1/2” A 13.0 12.3 11.1 9.4 7.6 5.6 3.8 2.0plates and under

S-44 B 14.0 14.0 14.0 13.5 12.0 10.2 8.0 5.0S-43 B 70 14.0 13.3 11.9 10.0 7.8 5.6 3.8 2.0S-55 B 14.0 13.3 11.9 10.0 7.8 5.6 3.8 2.0S-44 C 15.0 15.0 15.0 14.4 12.7 10.4 8.0 5.0S-43 C 75S-28 Chrome-manganese-

siliconA 15.0 14.1 12.4 10.1 7.8 5.6 3.8 2.0

alloy steel B 85

LOGOTemperature Factor1 9 8 5

Metal Temperature, Plate and Forged°F Steel, % Cast Steel, %

Up to 650 25.0 16.7700 23.7 16.4750 21.0 14.7800 18.0 12.9850 15.0 11.1900 12.0 9.3950 9.0 7.5

1000 6.2 5.7

LOGOWeld/Joint Efficiency1 9 8 5

EFFICIENCY CRITERIA

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%

tp < ⅝”tp < ⅝”tp > ⅝”

tp < ⅝”tp < 1¼”tp > 1¼”tp > 1¼”

LOGOStress Relief Factor1 9 8 5

Stress relieving is mandatory for: 

1. tp > 1¼”

2. (For thinner plates)

where D has a minimum value of 20 inches

3. ASTM A – 150

4. ASTM A – 149 (under certain conditions)

12050

Dt p

LOGORadiographing Factor1 9 8 5

Radiographing is mandatory for:

1. ASTM A – 150

2. ASTM A – 149 (under certain conditions)

3. Lethal gases application

4. Nuclear Reactor applications

LOGOSample 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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LOGOSample 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 250ºF, what is the shell thickness of the vessel? (Use minimum corrosion allowance and Hesse and Rushton method).

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LOGOHEAD 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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LOGOHEAD 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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LOGOHEAD 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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LOGOHEAD 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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LOGOHEAD Configurations

Cones for Pressure Vessels The maximum internal apex angle for cones =120O

The I.K.R = 6% of the inside diameter of the vessel The S.F =10mm and 30mm

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LOGOHEAD 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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LOGOHEAD 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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LOGOHEAD THICKNESS

Standard Ellipsoidal

Hemispherical

Standard Dished

whereL = crown radius in inches = Do – 6Kr = knuckle radius = 0.06 Do

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SE2PDt

SE4PDt

SE2PLWt

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Standard Dished Values for W or dished heads 

Kr/L W

0.06 1.80.07 1.70.08 1.650.09 1.60.10 1.550.11 1.500.12 1.470.13 1.440.14 1.41

LOGOHEAD THICKNESS1 9 8 5

Standard Dished Values for W or dished heads 

Kr/L W

0.15 1.400.16 1.380.17 1.370.18 1.350.19 1.320.20 1.300.25 1.250.50 1.121.0 1.0

LOGOHEAD THICKNESS

Flat Heads*Lap Welded w/ or w/o Plug Welds:

*Single or Double V Butt Welded

*Cut from Solid PlateStandard Dished

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SP3.0dt

SP25.0dt

SP5.0dt