DOC. No. :
MECHANICAL CALCULATION NOTE
0
Design calculation for baffle
(everything in SI units , Length in mm)
(As per Procedure 4-6 of Pressure Vessel Design Manual by Dennis Moss
& Roark's Formulas :Table 11.4 Case 2d)
Inputs
units
symbol
values
Design Temperature
Kelvin
Td
363.15
Yeild Stress at design Temperature
Pascal
Ys
2.03E+08
Ultimate Strength at design Temperature
Pascal
Us
corrosion allowance
mm
c.a.
height of baffle
mm
a
4.14E+08
=3+3
6
4600
width of baffle
mm
b
5800
Density of liquid
kg/m3
Sg
1023.3
modulus of elasticity
Pascal
E
2.00E+11
Baffle Design without stiffeners
Calculations
Case : Three edges simply supported one edge free , load uniformly decreasing along the length
a/b
0.25
0.5
0.75
1
1.5
2
2.5
3
3.5
4
PARAMETER
β
0.05
0.11
0.16
0.2
0.28
0.32
0.35
0.36
0.37
0.37
symbol
γ
0.013
0.026
0.033
0.04
0.05
0.058
0.064
0.067
0.069
0.07
Formula
Value
(in SI )
Assumed corrded Thickness
ta
-
19
Allowable bending stress
σ
min[0.66*Ys,0.285*Us]
117899655
liquid pressure loads
p
Sg*g*a
46130.364
height width ratio
k
a/b
0.793
flat plate constant
β
interpolation
0.167
γ
interpolation
0.034
baffle thickness
t
((βpb2)/σ)0.5
46.869
Total baffle thickness
t+c.a.
t+c.a.
52.869
Deflection of Baffle(corroded)
δ
(pγb4)/(Et3)
4067.812
Maximum Allowable Deflection
δa
min(t/2, b/360)
16.111
1.BAFFLE THICKNESS IS NOT SUFFICIENT (EITHER INCREASE THICKNESS OR PROVIDE ADEQUATE STIFFNERS)
2.DEFLECTION IS NOT WITHIN PERMISSIBLE LIMIT
DOC. No. :
MECHANICAL CALCULATION NOTE
0
BAFFLE DESIGN WITH STIFFENERS
HORIZONTAL DISTANCE IS WITH RESPECT TO LEFT MOST AXIS OF PANEL IN INCREMENTAL SENSE
VERTICAL DISTANCE IS WITH RESPECT TO TOPMOST AXIS OF PANEL IN INCREMENTAL SENSE
8
INPUTS
PARAMETER
Symbol
DISTANCE(IN MM)
POSITION OF HORIZONTAL STIFFENER 1
a1
900
POSITION OF HORIZONTAL STIFFENER 2
a2
900
POSITION OF HORIZONTAL STIFFENER 3
a3
900
POSITION OF HORIZONTAL STIFFENER 4
a4
900
POSITION OF VERTICAL STIFFENER 1
b1
1160
POSITION OF VERTICAL STIFFENER 2
b2
1160
POSITION OF VERTICAL STIFFENER 3
b3
1160
POSITION OF VERTICAL STIFFENER 4
b4
1160
put distance as zero if you don’t want to put any particular stiffener
Calculations
Case:
25 panels formed and each corresponds to case of simply supported flat plate with load uniformly decreasing along length
calculations are done for each panel and panel with maximum stress is selected
all calculations related to stress and deflection and flat plate coefficients for each panel are on the second sheet of this document
according to inputs, calculations on second sheet gives a panel with max stresses which is our panel under consideration
parameters of panel under consideration
parameter
symbol
formula
value
a/b
assumed correded thickness
k
tb
0.862068966
19
Allowable Stresses
σmax
a/b
assumption
min[0.66*Ys,0.285*Us]
Calculated thickness
((βuniqunib2)/σ)0.5+((βincqincb2)/σ)0.5
14.16371903
Total calculated thickness
t
tt
T+c.a.
20.16371903
Allowable Deflection
δa
min(t/2, b/360)
(quniαunib )/(ETt3)+(qincαincb4)/(ETt3)
3.222222222
Calculated Deflection
δ
4
(corresponding to assumed thickness)
1.BAFFLE THICKNESS IS NOT SUFFICIENT (EITHER INCREASE THICKNESS OR PROVIDE ADEQUATE STIFFNERS)
2.DEFLECTION IS WITHIN PERMISSIBLE LIMIT
117899655
2.025248739
DOC. No. :
MECHANICAL CALCULATION NOTE
0
Designing for Horizontal stiffeners
inputs
symbol
Units
value
Correded thickness of stiffner
width of stiffner
yeild strength
young's modulus
ultimate strength
ts
mm
mm
pascal
pascal
pascal
8
150
2.03E+08
2.00E+11
4.14E+08
h
Ys
E
Us
critical case of horizontal stiffners are lowermost horizontal stiffeners as maximum moment is acting on them because of maximum pressure
Since lowermost stiffener has been divided into 5 parts , we check for part with maximum moment acting on it
Case: both ends fixed , load uniformly distributed
parameter
symbol
max moment
(acts on end)
Mh
formula
value
(q*tsl2)/12
32385.92233
(in Nmm)
where l is length of stiffener part
calculation for moment of inertia of composite system of stiffner with baffle for lowermost horizontal stiffner
parameter
symbol
formula
unit
value
length of baffle that works with stiffner
l1
min(32tb,a4)
area of baffle working with stiffner
Ap
tbl1
mm
mm2
11552
608
area of stiffner
As
tsl1
mm2
4864
moment of inertia of stiffner
Is
(tsh3)/12
mm4
2250000
Distance of neutral axis from baffle centre
distance from centroid of composite
section to panel
distance from centroid of composite
section to stiffner
moment of inertia of composite
y
(As(h+tb)/(2*(As+Ap))
mm
25.03703704
Cp
((Asy)/(As+Ap)) +tb/2
mm
16.91838134
Cs
Ih
(h+tb)-Cp
I s +(Aptb2)/12 +(AsApy2)/(As+Ap)
mm
mm4
152.0816187
4743125.167
calculation of stress and strain on horizontal stiffner
parameter
symbol
formula
unit
value
calculated stress on stiffner
σ
δh
MhCs/I h
pascal
1038408.922
calculated deflection on stiffner
(q*ts*l4)/(384*E*I)
mm
3.83E-01
allowable stress in stiffner
σa
min(0.66*Ys,0.285*Us)
pascal
1.18E+08
allowable deflection in stiffner
δa
min(ts/2,h/360)
mm
0.416666667
1.STIFFENER THICKNESS AND WIDTH ARE SUFFICIENT
2.DEFLECTION IS WITHIN PERMISSIBLE LIMIT
DOC. No. :
MECHANICAL CALCULATION NOTE
0
Designing of vertical stiffeners
Case: both ends fixed, uniformly varying load
calculation for moment of inertia of composite system of stiffner with baffle for vertical stiffner
length of baffle that works with stiffner
l1
min(32tb,min b)
area of baffle working with stiffner
Ap
tbl1
mm
mm2
2
608
11552
area of stiffner
As
tsl1
mm
4864
moment of inertia of stiffner
Is
(tsh3)/12
mm4
2250000
Distance of neutral axis from baffle centre
distance from centroid of composite
section to panel
distance from centroid of composite
section to stiffner
moment of inertia of composite
y
(As(h+tb)/(2*(As+Ap))
mm
25.03703704
Cp
((Asy)/(As+Ap)) +tb/2
mm
16.91838134
Cs
Iv
(h+tb)-Cp
I s +(Aptb2)/12 +(AsApy2)/(As+Ap)
mm
mm4
152.0816187
4743125.167
we consider vertical stiffener with maximum stress and deflection acting on it
calculations and formula used for selecting max stress stiffener and for calculating its stress and deflection are on second sheet of this document
(0.155*qincreasing*ts*l2)+((quniform*ts*l2)/12)
Moment (Mv)
stress(σv)
MCs/I v
deflection
((0.13*0.001*qincreasing*ts*l4)/EI)+((quniform*ts*l4)/(384EI))
calculation of stress and strain on vertical stiffner
calculated max stress on vertical stiffners
σv
formula stated above
pascal
calculated max deflection on vertical stiffners
δv
formula stated above
mm
3.08E-04
allowable stress in stiffner
σa
min(0.66*Ys,0.285*Us)
pascal
1.18E+08
allowable deflection in stiffner
δa
min(ts/2,h/360)
mm
0.416666667
591642.0233
1.STIFFENER THICKNESS AND WIDTH ARE SUFFICIENT
2.DEFLECTION IS WITHIN PERMISSIBLE LIMIT
Thermal Expansion check for baffle
inputs
symbol
Units
value
mean radius of vessel
thickness of vessel
vessel internal pressure
Rm
t
P
αt
mm
mm
pascal
2918
18
1150000
per degree celcius
4.00E-06
symbol
formula
unit
differential temperature
ΔT
342.04
ΔRp
design temp- 21.11
(0.85*P*Rm)/(t*E)
celcius
vessel radial expansion due to pressure
mm
7.93E-04
coefficient of thermal expansion
Calculations for checking thermal expansion
parameter
value
vessel radial expansion due to temp.
ΔRt
Rm*αt*ΔT
mm
3.99E+00
thermal expansion of baffle
ΔRb
0.5*b*αt*ΔT
mm
3.97E+00
differntial expansion
ΔR
ΔRp +ΔRt - ΔRb
mm
2.54E-02
BAFFLE WILL NOT FAIL DUE TO THERMAL EXPANSION
0
