Structural Analysis of a Corroded Chimney

Structural Analysis of a Corroded
Chimney
Hervandil Morosini Sant’Anna
Murilo Fonseca Leal
Petrobras – Abastecimento – Refino
PRESENTATION TOPICS
•
•
•
•
Brief Company Overview (where we are in Petrobras);
Problem Description;
Methodology;
Conclusions and recommendations.
Company Overview: Where we are?
An integrated energy company!
Company Overview: Where we are?
Company Overview: What do we do?
• We perform technical assistances to the company downstream
concerning inspection techniques, corrosion and structural
integrity of static equipments.
Problem Description
• Assess whether a corroded chimney of a hydrotreating unity
unit can operate safely or must be repaired;
• Linear and non-linear Finite Element Method were used for
stress and stability analysis.
F-211302
Gás Residual
Vaso de topo
Bomba
da retificadora
Retificadora
de nafta
Problem Description: The Chimney
Problem Description: Corrosion and Pitting
Methodology: Performed Analsys
• Corroded structure
• Corroded structure with guy cables
• Structure with rings 19 to 22 repaired
• Linear elastic analysis
• Stability (non-linear) analysis
REMEMBERING THE GOAL
Define if the structure can operate
safely in this situation different from the
original design
Methodology: Loads
• Self-weight
• Mean temperature
• Wind pressure
Methodology: Materials
Carbon steel SA-285 gr. C (Mean temperature: 187°C)
• Young’s modulus: 192000 MPa
• Poisson ratio: 0,3
• Tensile strength: 379 MPa
• Yield strength: 176 MPa
Ramberg-Osgood Model


K 
E
E
 elastic
Multi-linear
isotropic hardening
 
 plastic
n
Methodology: Allowable Stresses
LINEAR ANALYSIS:
• Allowable stress: Sm = 108 MPa
•  Pl  Pb   1,5Sm  162MPa
NON-LINEAR ANALYSIS:
• Carregamento  2, 4  peso  2,6  vento
 Sim  Estrutura Estável
• Carregamento  Análise Converge?  Não  Estrutura Instável

Methodology: Finite Element Model
• SHELL281
• LINK10 (cable option)
Results: Linear Elastic Von Mises Stresses
Limit: 162 MPa
New Plates
Corroded
Guy Cables
Results: Stability Analysis (corroded)
Evolução do Carregamento
120
0,835
Tensão de Von Mises [MPa]
100
80
0,575
0,7
0,825
0,35
60
0,7625
40
20
0
0%
0,2
0,1
10%
20%
30%
40%
50%
% Carga Total
60%
70%
80%
90%
Results: Stability Analysis (new plates)
Evolução do Carregamento
80
Tensão de Von Mises [MPa]
70
0,85258
1
60
0,60258
50
40
0,43172
30
0,31781
0,24188
0,19125
20
10
0,1
0
0%
10%
20%
30%
40%
50%
% Carga Total
60%
70%
80%
90%
100%
Conclusions
• A repair is necessary!
• Two kind of repair were suggested: guy cables are easier to
implement but new plates reach to lower stresses.
Thank You!!
• Contacts:
• Hervandil Sant’Anna – (21)3224-3148 –
[email protected]
• Murilo Fonseca Leal – (21)3224-1680 –
[email protected]