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.