An Analysis of Creep Phenomena in the Power Boiler Superheaters
Abstract
:1. Introduction
2. Basic Formulations
3. Analysis of Creep Phenomena
- maximum stresses are limited to allowable values for the initial time.
- maximum stresses are limited to allowable values for the time of 200,000 h under creep conditions (if a design lifetime is not specified), and creep strain should be less than 1% at 100,000 h (if design lifetimes is shorted than 100,000 h).
3.1. Calculation Based on European Standards
3.2. Verification of Calculated Temperature Values Based on a Detailed Analysis of the Creep Phenomenon
4. Numerical Example
4.1. Calculation Based on European Standards
4.2. Verification of the Final Solution Based on a Detailed Analysis of the Creep Phenomenon
5. Conclusions
Author Contributions
Funding
Conflicts of Interest
Nomenclature
A | the highest creep strain at the end of the first stage of creep, - |
cp | specific heat capacity, J/(kg·K) |
c1 | experimental constant, ln(h) |
c2 | experimental constant, ln(h)/ln(MPa2) |
c3 | directional factor for the second stage of creep, (ln(1/h))/MPa |
c4 | coordinate of the t-intercept for the second stage of creep, ln(1/h) |
do | pipe outer diameter, mm |
en | pipe thickness, mm |
fR, fCR | allowable stresses, MPa |
G | Lame constant, MPa |
i | stress intensification factor, - |
k | thermal conductivity, W/(m·K) |
K, M | coefficients describing the destruction process intensity, - |
MA | moment caused by weight and other sustained loads, Nm |
MC | moment caused by thermal expansion, Nm |
P | pressure, MPa |
t | time, h |
tII | time marking the beginning of the second stage of creep, h |
T | temperature, °C |
Tm | the material melting point, °C |
u | displacement vector, m |
x,y,z | Cartesian coordinates, m |
Z | the pipe section modulus, mm3 |
β | thermal expansion coefficient, 1/K |
εc(t) | actual normal creep strain, - |
ε | strain tensor, - |
λ | Lame constant, MPa |
ν | Poisson’s ratio, - |
ρ | density, kg/m3 |
σ | normal stress, MPa |
σ | stress tensor, MPa |
n | time step (subscripts) |
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Chemical Composition (%)—ASME Code Case 2328-1 | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
C | Si | Mn | P | S | Cu | Cr | Ni | Nb | B | N | Al |
0.07–0.13 | Max 0.30 | Max 1.00 | Max 0.0040 | Max 0.0010 | 2.50 3.50 | 17.0 19.0 | 7.5 10.5 | 0.30 0.60 | 0.0001 0.0010 | 0.05 0.12 | 0.0003 0.0030 |
Temperature (°C) | Stress σ (MPa) | Stress σC (MPa) | Yield Strength (MPa) | Allowable Stress (MPa) (See Section 3.1) | ||
---|---|---|---|---|---|---|
fR | fCR | σC/fCR | ||||
650 | 158 | 90 | 172 | 319.0 | 105.3 | 0.85 |
700 | 167 | 92 | 160 | 252.5 | 58.3 | 1.58 |
665 | 160 | 90 | 160 | 296.5 | 91.2 | 0.99 |
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Duda, P.; Felkowski, Ł.; Duda, A. An Analysis of Creep Phenomena in the Power Boiler Superheaters. Metals 2018, 8, 892. https://doi.org/10.3390/met8110892
Duda P, Felkowski Ł, Duda A. An Analysis of Creep Phenomena in the Power Boiler Superheaters. Metals. 2018; 8(11):892. https://doi.org/10.3390/met8110892
Chicago/Turabian StyleDuda, Piotr, Łukasz Felkowski, and Andrzej Duda. 2018. "An Analysis of Creep Phenomena in the Power Boiler Superheaters" Metals 8, no. 11: 892. https://doi.org/10.3390/met8110892