Process Equipment Design 2nd

7/24/2019 Process Equipment Design 2nd

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Process Equipment Design



Head or Cover

End caps on a cylindrically shaped pressure vessel

Can be attached to shell by welded, riveted or bolted

construction

Must be capable of withstanding the working pressure

Common types:

(a) Flat Plate: mainly used for horizontal vessel at atm

pressure

(b) Flanged & dished head: Used for low P vessels

(i !lared " dished head

(ii #hallow dished head



(iii) Torispherical head: used for pressure range between ($%$&

kg'cm

(iv Elliptical head: used for pressure over $& kg'cm

(v Hemispherical head: strongest formed head, e)pensive,used only in a few cases

(vi Conical head: widely used as bottom head where removal or

draining of material is facilitated*



Shallow dished & torispherical head

dished radius or crown radiusc R →

c i R D≤

$+ knuckle radius or corner

-ransition between the cylinder " dish is called .nuckle/

01 of i

R

D=



Head thicness

!: fatigue factor

nominal stress for typically bend andintersection components

$

(

$2

3

ch

c

pRW t fJ

RW

R

=

= + ÷ ÷

$

internal design pressure

crown radius

stress intensification factor

knuckle radius

c

p

R

W

R

→→

→→



• "o##les:

Provide certain re4uirements such as inlet or outlet

connections, manholes, vent, drain etc

Circular or elliptical

• Flange $oints:

5hen heads, nozzles, pipes are to be of the detachable '

removable, they must be provided with flanges with bolt*

Consists of a pair of flanges

6 gasket (narrow gasket " e)tended gasket is interposed

between the two ad7oining flange faces*



materials of gasket8 paper, cloth, rubber, asbestos etc*

prevent leakage

%aset : 9*& to 2 mm thickness

: 9 mm width

-he sizing of gasket & no. & dia. of bolts necessary to create the

tightening action, it is essential to evaluate the forces due to

gasket reaction, both under atm. Condition & also underoperating pressure conditions*



Types o lange $oints

5elding ;eck !lange

#lip <n !lange

#ocket 5eld !lange =ap >oint !lange

-hreaded !lange

?lind !lange

'aterials or Flanges: stainless steel, cast iron, aluminium,

brass, bronze, plastic etc*



Flange $oint



PCD pitch circle dia.

OD outer dia.of flange



nder atm Condition:

(i) Under atm. Condition:

Bolt load due to gasket reaction,

9 9

area of gasket under compression

effective gasket contact surface width (taken from table'literature

dia* of gasket load reaction

gasket seating stress*& , basic g

a g a a m

g

a

W A Y bGY W

A

b

G

Y b b b

π = × = =

→

→

→

→

= →

9

asket seating width (from table

, ;+width of gasket

N b =



*perating condition:

(ii) Operating condition:

Te !olt load eiter "ill create a tensilestress in te #$section o% !olt.

( 3

p m g p nW W A Y A b Gm G π

π = = × + = +

@asket factor

design pressure

m

→→

$ orm mW W

$

$

"

m

m

a

m

m

b

W

A f

W A

f

=

=

$ " )%sectional area of bolt

permissible tensile stress in

bolts under atm*

permissible stress in bolts under

operating condition

m m

a

b

A A

f

f

→

→

→



&arger area ( ) sould !e considered

'o. o% !olts sould !e multiple o%

Calculate !olt dia. *

&et us !olt speci+cation -

'o" pitc dia. #/ mm

inor dia. #0 mm

1Pitch: measure distance !et"een te tread2

$ or

m m A A

$ or ;o* of boltsm m m

A A A= ×

mean dia* of gasket (cm ;o* of bolt +

*&





'o",

3ctual !olt area,

$

no* of bolts3 $99

+ %%%%% cm

m

! ! A

π += × ×

, width of gasketa

b

a

Y GN A N

f

π = →

for satisfying bolt areab m A A>



Pitch of bolts + (2*& to & A B& (for this case B& + dia* of bolt*/

Pitch circle dia* ( + outside dia* of gasket D ) dia* of bolt D $

mm

<utside dia* of flange + pitch circle dia* D ) dia* of bolt

0( mm

9*&

bolt dia*

thickness

f

b b

b

f

t d

m

d t

= +

+

=

=



Flange thicness

permissible stress for flange

design pressure

corrosion allowance

$

$*&9*2

f

m a

t G ckf

f

c

k W h

"G

= +

→

→→

= +



Flange thickness …..

total bolt load (already calculated

E+3

m

a

W

G

# Gh

π

→

− = ÷

dia* of gasket load reaction

? P*C*F

G

→→



S+pports or vessel

-his is e)ternal part of vessel design

-ype of support depends on the height " dia* <f vessel,

available floor space, location, operating temperature "

material of construction

#hould withstand all stresses created due to operating

pressure

S+pport or vertical vessel:

(a) Skirt support:

Gesting on a reinforced concrete foundation



suitable for tall vessel

forces sub7ected to dead weight, wind load, seismic load

(b ,+g or bracet s+pport:

rest on leg or beam

welded to vessel wall

-dvantage:

% ine)pensive

% can absorb e)pansion

%eccentricity

%compressive, tensile (wind,

shear stresses are induced in

the vessel wall*



Saddle s+pport

• Hori#ontal vessel: #addle support

% placed at two positions

% behave as beam

9

(9*3 9*& distance from tangent line/

9*

$9 total included angle

E Eead of vessel0

total load per saddle (lb

A R

$

D "

%

θ

→ −<

≥ → → = ÷

→

4



Saddle s+pport



Forces

a =ongitudinal bending moment

b =ongitudinal stress (a)ial

c Circumferential stress (tangential

d #hear stress

(i .ending moment at the s+pport:

( )

$

$$

3$

2

R " A $ A$ & %A

"

$

−− + = − +



(ii) ?ending moment at the centre8

Stress:

– =ongitudinal stress at support*

Hf the shell does not retain its round shape under load, a portion of the upper part of its )%section is ineffective

against bending*

( )

$ 3

33$

2

R " %$ A $ &

" $

$

−+ = − +



(a)at topmost o% 5$section:

(!) at !ottom most o% 5$sections:

$$

$

, shell thickness &

f t ' R t π

= →

$( (

(

&

f ' R t π

= $

9

$

9

9

9

Hf 9*& , $*9

Hf 9*& , 9*$9B, $9

+ 9*$0$, +$&9 9*$I, $9

+ 9*BI, +$&9

#hear stress is generall

A R ' '

A R '

'

θ

θ

θ

θ

< = =

> = =

= =

y of a small magnitude*



6tress at mid span:

• Design condition:

2

circumferential stress p

f R t

f

π

=

→

( ) ( )$ 2" permissible stress p p f f f f + + <



!lared " dished head

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Process Equipment Design 2nd