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AALBORG INDUSTRIES
Impact of Internal Pressure
to D-type Boiler Panel Wall
and Buckstay Catur Indra Pratisto
10/13/2008
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
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 as panel 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 Beamax was 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 Workbench’s thermal analysis.
Introduction
Panel wall used in D-type boiler is subjected to internal pressure of 500mm 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
Analysis – Panel Wall
Manual Calculation Results
In order to simplify the calculation, one
section of the panel wall is extracted for
analysis. 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.
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 = 250°°°°C (approximation)
Yield Strength at 250°°°°C, σyield@250°C = 165 MPa (approximation)
σ max = (M max * y) / I total
= 8.69e+07
Pa
= 86.94 MPa
Thus, σmax < σyield@250°C
86.94 MPa < 165 MPa
Finite Element Analysis Results
From FEA Simulation:
σ 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 = 250°°°°C (approximation)
Yield Strength at 250°°°°C, σyield@250°C = 165 MPa (approximation)
Thus, σmax < σyield@250°C
93.68 MPa < 165 MPa
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
H-beam 200 x 200
I H-beam = 57e+06
mm4
Material = St 52.0
Temperature of saturated steam at 40 barg = 250°°°°C (approximation)
Yield Strength at 250°°°°C, σyield@250°C = 225 MPa (approximation)
y = 100 mm
σ max = (M max * y) / I total
= 2.05e+08
Pa
= 205.34 MPa
Thus, σmax < σyield@250°C
205.34 MPa < 225 MPa
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:
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:
σ max = 2.08e+08
Pa
= 207.78 MPa
H-beam 200 x 200
Material = St 52.0
Temperature of saturated steam at 40 barg = 250°°°°C (approximation)
Yield Strength at 250°°°°C, σyield@250°C = 225 MPa (approximation)
Thus, σmax < σyield@250°C
207.78 MPa < 225 MPa
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:
σmax < σyield@250°C
86.94 MPa < 165 MPa
Maximum stress in panel wall is lower than yield stress
- Result of from FEA simulation:
σmax < σyield@250°C
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 simplify
the calculation.
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:
σmax < σyield@250°C
205.34 MPa < 225 MPa
Maximum stress in H-beam ‘buck stay’ is lower than yield stress
- Result of from FEA simulation:
σmax < σyield@250°C
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 simplify
the calculation.
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