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7/28/2019 Buckstay 1
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AALBORG INDUSTRIES
Impact of Internal Pressure
to D-type Boiler Panel Walland BuckstayCatur Indra Pratisto
10/13/2008
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Table of Contents
Abstract............................................................................................................................................................ 3
Introduction ..................................................................................................................................................... 4
Analysis Panel Wall ....................................................................................................................................... 5
Manual Calculation Results.......................................................................................................................... 5
Finite Element Analysis Results.................................................................................................................... 7
Analysis H-beam / Buckstay .......................................................................................................................... 8
Manual Calculation Results.......................................................................................................................... 8
Finite Element Analysis Results.................................................................................................................. 10
Results Summary and Conclusions ................................................................................................................ 12
Panel Wall .................................................................................................................................................. 12
H-Beam/Buckstay....................................................................................................................................... 13
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Abstract
During operation, boiler is constantly subjected to certain value of internal pressure. In D-type boiler, this
pressure is directly applied to assembly of tube and flat bar commonly referred to aspanel wall. In addition
to panel wall, H-beams are normally added and used as buck stay/support belt to reduce the impact of
internal pressure to the panel wall.
In this paper, simplified model of panel was created using Autodesk Inventor. This model was then imported
to ANSYS Workbench to be analyzed.
As a comparison, manual calculation was carried out using simple Mechanics of Materials principles.
Simplifications and assumptions were made to ease the process of manual calculation. Free structural beam
analysis software called Beamaxwas utilized to create force diagram, bending moment, and displacement
curve to aid manual calculation.
The stress and deformation results from both manual calculation and simulation software were then
compared and analyzed. Stress and deformation values for panel wall as well as buckstay showed that
results from ANSYS Workbench do not vary significantly compared to those of manual calculation.
It is recommended to further develop application of ANSYS Workbench to analyze other areas of boiler
application, for instance: optimization of boiler tube fin design using Workbenchs thermal analysis.
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Introduction
Panel wall used in D-type boiler is subjected to internal pressure of500mm H2O (approximately 5,000 Pa).
An H-beams is used as buck stay/support belt to reduce the impact of internal pressure in the panel wall.
H-beam buck stay
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Analysis Panel Wall
Manual Calculation Results
In order to simplify the calculation, one
section of the panel wall is extracted foranalysis. Section length is approximately
7,900 mm.
Tube dimensions:
Outer diameter, D = 63.5 mm
Thickness, t = 4 mm
Inner diameter, d = D 2t
= 55.5 mm
Flat bar dimensions:
L = 26.5 mm
t = 6 mm
I total = I O-beam + I flat bar
=
= 332,684 mm4
= 3.33e-7 m4
y = D / 2
= 31.75 mm
For simplification, assume pressure is
applied only to total length of extracted
section perpendicular to pressure direction.
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Tube outer diameter, D = 63.5 mm
Flat bar length, L = 26.5 mm
Section Length for Applied Pressure
LA = D + L
= 90 mm
Pressure, P = 5,000 Pa
Distributed Load = P * LA
= 450 N/m
Load and Bending Moment Diagrams
M max = 911 Nm
Panel Wall Tube 63.5 x 4mm thk + Flat bar 26.5 mm x 6 mm
I Total = 3.33e+05 mm4
Material = RSt 35.8
Temperature of saturated steam at 40 barg = 250C (approximation)
Yield Strength at 250C, yield@250C = 165 MPa (approximation)
max = (M max * y) / I total
= 8.69e+07 Pa
= 86.94 MPa
Thus, max < yield@250C
86.94 MPa < 165 MPa
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Finite Element Analysis Results
From FEA Simulation:
max = 9.37e+07 Pa
= 93.68 MPa
Panel Wall Tube 63.5 x 4mm thk + Flat bar 26.5 mm x 6 mm
Material = RSt 35.8
Temperature of saturated steam at 40 barg = 250C (approximation)
Yield Strength at 250C, yield@250C = 165 MPa (approximation)
Thus, max < yield@250C
93.68 MPa < 165 MPa
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Analysis H-beam / Buckstay
Manual Calculation Results
From previous analysis, take the maximum load for worst case scenario analysis:
Load, F = 2,250 N
For simplification, assume pressure is
applied only to total length of extracted
section perpendicular to pressure direction.
Tube outer diameter, D = 63.5 mm
Flat bar length, L = 26.5 mm
Section Length for Applied Pressure
LA = D + L
= 90 mm
Distributed Load, w = F / LA
= 25,000 N/m
Load and Bending Moment Diagrams
M max = 117,045 Nm
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H-beam 200 x 200
I H-beam = 57e+06
mm4
Material = St 52.0
Temperature of saturated steam at 40 barg = 250C (approximation)
Yield Strength at 250C, yield@250C = 225 MPa (approximation)
y = 100 mm
max = (M max * y) / I total
= 2.05e+08 Pa
= 205.34 MPa
Thus, max < yield@250C
205.34 MPa < 225 MPa
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Finite Element Analysis Results
From previous analysis, take the maximum load for worst case scenario analysis:
Load, F = 2,250 N
This load is applied only to length of
extracted section perpendicular to pressure
direction.
Tube outer diameter, D = 63.5 mm
Flat bar length, L = 26.5 mm
Section Length for Applied Load
LA = D + L
= 90 mm
H-beam length 1, LB1 = 6120 mm
H-beam length 2, LB2 = 5630 mm
Total load applied to the whole H-beam length:
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Load at H-beam 1, FB1 = F * LB1 / LA
= 153,000 N
Load at H-beam 2, FB2 = F * LB2 / LA
= 140,750 N
Take the highest load (= FB1) for worst case scenario analysis and apply it to the model:
From FEA Simulation:
max = 2.08e+08 Pa
= 207.78 MPa
H-beam 200 x 200
Material = St 52.0
Temperature of saturated steam at 40 barg = 250C (approximation)
Yield Strength at 250C, yield@250C = 225 MPa (approximation)
Thus, max < yield@250C
207.78 MPa < 225 MPa
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Results Summary and Conclusions
Panel Wall
Max. Bending Stress: 86.94 MPa Max. Bending Stress: 93.68 MPa
Max. Deflection: 16.75 mm Max. Deflection: 12.18 mm
- Result of from calculation:max < yield@250C
86.94 MPa < 165 MPa
Maximum stress in panel wall is lower than yield stress
- Result of from FEA simulation:max < yield@250C
93.68 MPa < 165 MPa
Maximum stress in panel wall is lower than yield stress
- The result from FEA is higher than calculated result due to the assumptions made to simplifythe calculation.
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H-Beam/Buckstay
Max. Bending Stress: 205.34 MPa Max. Bending Stress: 207.78 MPa
Max. Deflection: 38.15 mm Max. Deflection: 40.99 mm
- Result of from calculation:max < yield@250C
205.34 MPa < 225 MPa
Maximum stress in H-beam buck stay is lower than yield stress
- Result of from FEA simulation:max < yield@250C
207.78 MPa < 225 MPa
Maximum stress in H-beam buck stay is lower than yield stress
- The result from FEA is higher than calculated result due to the assumptions made to simplifythe calculation.