1. PRESSURE VESSELS DESIGN PROCEDURES Engr. Butch G. Bataller
ChE 192 Process Equipment Design
September 20, 2011

2. Pressure Vessels
Closed vessel having an internal pressure between 15 psig to 3000 psig
ASME Boiler and Pressure Vessel Code contains rules for the design, fabrication and inspection of boilers and pressure vessels
May include reflux drum, storage tanks, heat exchangers, chemical reactors, distillation columns, absorption tower, stripping columns, etc.

3. PV Design: Shell Thickness
In general, the minimum wall thickness of welded metal plates subject to pressure, excluding corrosion allowances, should not be less than 2.4 mm
a function of the ultimate tensile strength of the metal at operating temperature, operating pressure, vessel diameter and welding joint efficiency

4. PV Design: Shell Thickness
For a cylinder based on Inside diameter
where
tp = shell thickness required (inch) [m]
P = Internal design gauge pressure (psig) [kN/m2]
R = Inside Radius (inch) [m]
S = Allowable stress (psi) [kN/m2]
E = Joint efficiency factor (Table 6-2)
C = Corrosion allowance (inch) [m]

5. PV Design: Shell Thickness
For a cylinder based on Inside diameter
Provided that
tp less than or equal to or
Pressure is less than or equal to SE (Jawad and Farr, 1988)

6. PV Design: Shell Thickness
For a cylinder based on Outside diameter
where
tp = shell thickness required (inch) [m]
P = Internal gauge pressure (psig) [kN/m2]
R = outside Radius (inch) [m]
S = Allowable stress (psi) [kN/m2]
E = Joint efficiency factor (Table 6-2)
C = Corrosion allowance (inch) [m]

7. PV Design: Shell Thickness
Allowance for Vertical PV
For 10>( L/Di)2/ Pd>1.34:
tv = tp[ E( L/Di)2/Pd]
If (L/Di)2/Pd < 1.34, tv=tp

8. PV Design: Shell Thickness
Corrosion Allowance
1/8 inch for noncorrosive conditions
¼ for corrosive environments.
ts = tV + tc

9. PV Design: Shell Thickness
For Vacuum Vessels
where
Pc = Collapsing pressure (psi)
Te = Thickness to withstand external pressure (inch)
Do = Outside diameter (inch)
Em = Material’s modulus of elasticity [Table 6-4]
** Te must be high enough so that Pc is five times greater than the difference between atmospheric pressure and design vacuum pressure

10. PV Design: Shell Thickness
For Vacuum Vessels (alternate)
tE=1.3(PdL/EmDo)4
tEC=L(0.18Di-2.2 )x
tV = tE + tEC
where
Pd = internal design gauge pressure (psi)
Te = Thickness to withstand external pressure (inch)
Do = Outside diameter (inch)
Em = Material’s modulus of elasticity

11. PV Design: Shell Thickness
Spherical Vessels
where
P = internal design gauge pressure (psig)
R = Inside Radius (inch)
tp = Minimum required thickness (inch)
E = Lowest joint efficiency
S = Max allowable stress (psi)

12. Design Temperature
design temperature may be equal to operating temperatue plus 50oF

13. Design Pressure Operating Pressure ,Po (psig)
Design Pressure ,Pd (psig)
0 -5 10
10 – 1,000
P= exp{ [ln Po] [ ln Po ]2 }
1,000 +
1.1Po

14. Material of Construction
Carbon Steel >>> Non-corrosive environment, T= (-20 to 650 OF)
Low Alloy Steel >>> Non-corrosive environment, T= (650 to 900 OF)
Stainless Steel 300 Series >>> can be used up to 1,500 OF

15. Modulus of Elasticity Values
Temperature (ºF)
Psi x 106
Carbon Steel
Low-alloy Steel
-20
30.2
200
29.5
400
28.3
28.6
650
26.0
27.0
700 -
26.6
800
25.7
900
24.5

16. Recommended Stress Values
Joint efficiencies
Recommended stress values
Metal
Temp., ºC
S, kPa
For double-welded butt joints
If fully radiographed = 1.0
If spot-examined = 0.85
If not radiographed = 0.70
In general, for spot examined
If electric resistance weld = 0.85
If lap-welded = 0.80
If single-butt-welded = 0.60
Carbon steel
(SA-285, Gr. C)
Low-alloy steel
for resistance to
H2 and H2S
(SA-387, Gr. 12C1.1)
High-tensile steel
for heavy-wall
vessels
(SA-302, Gr.B)
High-alloy steel
for cladding and
corrosion resistance
Stainless 304
(SA-240)
Stainless 316
Nonferrous metals
Copper (SB-11)
Aluminum(SB-209, )
-29 to 343
399
454
-29 to 427
510
565
649
-29 to 399
538
-29
343
427
345 38
204
94,500
82,700
57,200
75,800
34,500
6,900
137,900
115,800
69,000
42,750
128,900
77,200
72,400
66,900
79,300
73,100
46,200
20,700
15,900

17. Sample Problem
Determine the thickness of a 5 meter inside diameter spherical tank for handling a corrosive liquid at a design pressure and temperature of 300KPa and 27F, respectively. The material of construction is made of carbon steel.

18. Sample Problem
If the height of the tank is 35m, what is the thickness of the tank incorporating earthquake and wind load?
What if the given pressure is an operating pressure?

19. Types of Welded Joints Butt joint Corner joint Edge joint Lap joint

20. Square Butt Joints Used to butt weld light sheet metal
1/16 to 3/16 thick metal.

21. Beveled Butt Joints Used to butt weld heavier pieces of metal together
3/8 to ½ inch metal can welded using a single V or U joint
½ Inch metal and up can be welded using a double V or U joint

22. Beveled Cont.

23. Corner Joints
Used to join to pieces of metal that are approximately right angles to each other
Closed corner joint is used on light sheet metal were strength is not required at the joint
Half open corner joint is used on heavier metal when welding can only be done on one side. Used when load is not severe.

24. Corner Cont.
Open corner joint is used on heavy material. It is the strongest of the corner joints
Corner joints on heavy material are welded on both sides  The outside first then reinforced on the inside

25. Corners Cont.

26. Edge Joints
Used to join two parallel or nearly parallel pieces of metal (0.25 in thick or less). Not very strong.
Used mainly to join edges of sheet metal, reinforce flanges of I beams, and mufflers.

27. Lap Joints Used to join two overlapping pieces of metal
Single lap joint welded from one side
Single lap joint welded from two sides develops full strength
Off set lap joint is used when two pieces of metal need to be joined in the same plain.

28. Lap Joints Cont. A- single lap joint, one weld.
B- single lap joint, two welds.
C- offset lap joint.

29. Tee Joints
Used to join two pieces of metal that are approximately 90 degrees to each other, but the surface of one piece of metal is not in the same plain as the other metal.

30. Tee Joints Cont. A- plain tee B- single beveled C- double beveled
D- single J
E- double J

31. Types of Welds
Fillet weld- basic weld used. Used when joining two pieces of metal without preparing the surface of the metal first.
Groove weld- basic weld, used when preparing the metal before welding it into place.

32. Fillet Welds

33. Groove Welds

35. Weld/Joint Efficiency
Welding – heats the metal surrounding the welding area
- results in warping, shrinking of the welded area
Stress Relieving - required to release locked up localized stress
- annealing or hammering
Radiographing - locate weld defects and other structural trouble
- welded joints are exposed to x-ray to detect excessive porosity, defective fusion and other defects in the welding process

36. Weld/Joint Efficiency
For carbon steels (t ≤ 1.25 in)
requires only 10% x-ray check
E = 85%
For thicker walls
requires 100% x-ray check
E = 100%

37. Weld/Joint Efficiency
Longitudinal joints should be butt- welded
Vessels in lethal application should be butt-welded and fully radiographed
All vessels fabricated on carbon or alloy steel requires post-heat treatment
All welded joints of cryogenic tanks must be butt welded, postweld heat treated and X- ray examined

38. For double butt joint, the following are the corresponding efficiencies
Full radiography 100%
Spot radiography %
No radiography 70 %
** when welded joint efficiency is not known, assume a no spot radiography

39. Welded Joints Categories
Category A – Longitudinal welded joints within main parts (shells, heads, cones, flat plates, nozzles, and the attachment weld of a hemispherical head to a shell)

40. Welded Joints Categories
Catefory B – Circumferential welded joints within the main parts (shell, cone, nozzles and the attachment joint between formed heads (elliptical and torispherical) and shell).

41. Welded Joints Categories
Category C – welded joints connecting flanges, tubesheets, flat heads to main shell, to formed heads, to transition in diameter, to nozzles, or any welded joint connecting one side plate to another side plate of a flat-sided vessel
Welded Joints Categories
Category C – welded joints connecting flanges, tubesheets, flat heads to main shell, formed heads, transition in diameter, nozzles, or any welded joint connecting one side plate to another side plate of a flat-sided vessel

42. Welded Joints Categories
Category C – welded joints connecting flanges, tubesheets, flat heads to main shell, to formed heads, to transition in diameter, to nozzles, or any welded joint connecting one side plate to another side plate of a flat-sided vessel
Welded Joints Categories
Category D – welded joints connecting nozzles to main shells, spheres, formed heads, flat heads, flat-sided vessels.

43. Maximum Allowable Joint Efficiencies for Arc and Gas Welded Joints
Type No.
Joint Description
Limitations
Joint Category
Degree of Radiographic Examination a b c
Full
Spot
None
(1)
Butt joints as attained by double-welding or by other means which will obtain the same quality of deposited weld metal on the inside and outside weld surfaces to agree with the requirements of UW-35; welds using metal backing strips which remain in place are excluded.
A, B, C & D
1.0
0.85
0.70
(2)
Single welded butt joint with backing strip other than those included in (1)
(a) None except as shown in (b) below
0,90
0.80
0.65
(b) Circumferential butt joints with one plate offset, see UW-13(c) and Fig. UW-13.1 (k).
A, B & C
0.90

44. Degree of Radiographic Examination
Type No.
Joint Description
Limitations
Joint Category
Degree of Radiographic Examination a b c
Full
Spot
None
(3)
Single-welded butt joint without use of backing strip
Circumferential butt joints only. Not over 5/8in. thick and not over 24in outside diameter
A, B & C NA
0.60
(4)
Double full fillet lap joint
longitudinal joints not over 3/8in. thick A
0.55
circumferential joints not over 5/8in. thick
B & C

45. Degree of Radiographic Examination
Type No.
Joint Description
Limitations
Joint Category
Degree of Radiographic Examination a b c
Full
Spot
None
(5)
Single full fillet lap joints with plug welds confirming to UW-17
(a) Circumferential joints2 for attachment of heads not over 24in. outside diameter to shells not over 1/2in. thick. B NA
0.50
(b) Circumferential joint for the attachment to shells of jackets not over 5/8in. in nominal thickness where the distance from the center of the plug weld to the edge of the plate is not less than 1-1/2 times the diameter of the hole for the plug. C
(6)
Single full fillet lap joints without plug welds
(a) For the attachment of heads convex to pressure to shells not over 5/8in. required thickness. only with use of fillet weld on
inside of shells, or
(b) For attachment of heads having pressure on either side. To shells not over 24in. inside diameter and not over 1/4in. required thickness with fillet weld on outside of head flange only.
A & B