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1.0 INTRODUCTION
A kiln is basically an industrial oven, and although the term is generic, several quite distinctive designs
have been used over the years, such a kiln in PT. Semen Baturaja made about 1,200.000 tonnes of
clinker per year. The Company was first established under the name of PT. Semen Baturaja Persero on
November 14, 1974. The Company specifically engages in clinker production business with its
production center located in Baturaja, South Sumatera, while the cement grinding and
packing process are operated in Baturaja Plant, Palembang Plant and Panjang Plant to be distributed
to the Company’s marketing areas. The Company, in its effort for business development, endeavors to
improve the existing equipment in order to achieve the target of installed capacity amounting to 50,000
tons cement per year and to improve its installed capacity.
Rotary kiln shell is a large-scale welded structure with 4.5 m in diameter and 75 m in length and produced by
welding thin cylindrical steel plate one by one. The shell of the kiln is made of mild steel plate. Mild steel is
the only viable material for the purpose, but presents the problem that the maximum temperature of the
feed inside the kiln is over 1400°C, while the gas temperatures reach 1900°C. The melting point of mild
steel is around 1300°C, and it starts to weaken at 480°C, so considerable effort is required to protect the
shell from overheating FLSmidth.
Padded plates are directly soldered to the shell in the supporting rollers places to reduce their
concentrated stress. Crack are often initiated at these welded joints, and the over long circumferential
crack are prevailing at welded joints near the supporting rollers. However, Kikuchi et.al. 2010 has
predicted of two interacting surface cracks of dissimilar sizes by finite element analysis. The
simulations were performed for fatigue crack growth experiments and the method validity was shown on
this research. It was shown that the offset distance and the relative size were both important parameters
to determine the interaction between two surfaces of crack; the smaller crack stopped growing when the
difference in size was large. It was possible to judge whether the effect of interaction should be considered
based on the correlation between the relative spacing and relative size. In 2014, Fatigue crack growth
simulation in a heterogeneous material using finite element method has generated by Kikuchi et.al.
Kikuchi has developed a fully automatic fatigue crack growth simulation system using FEM and applied it to
three-dimensional surface crack problems, in order to evaluate the interaction of multiple surface cracks,
and the crack closure effects of surface cracks. The system is modified to manage residual stress field
problems, and the stress corrosion cracking process is simulated.
To prediction of crack propagation under thermal, residual stress fields using S-Version FEM S-FEM, Kikuchi
was employed to solve a crack growth problem by combining with the auto-meshing technique, this re-
meshing process of the local mesh becomes very simple, and modeling of three-dimensional crack
shape becomes computationally easy. On the other hand, in 2004, Irsyadi has developed visualization of
finite element analysis in 3D C, C++, under LinuxFedora, with this system, analysis for extra
large problems such as fatigue life predictions becomes easy and fast. Irsyadi, Kikuchi, and Kanto
employed numerical analysis of 3-D Surface Crack in 2006, and then, Irsyadi and Kikuchi was developed a
numerical analysis in the low carbon steel by finite element method and experimental method under
fatigue loading. In this research, they were predicted fatigue live of material under stresses.
Fatigue, or metal fatigue, is the failure of a component as a result of cyclic stress. The failure
occurs in three phases: crack initiation, crack propagation, and catastrophic overload failure. The
duration of each of these three phases depends on many factors including fundamental raw material
characteristics, magnitude and orientation of applied stresses, processing history, etc. Fatigue failures often
result from applied stress levels significantly below those necessary to cause static failure.
The prediction of fatigue life of rotary cement kiln welded shell is not completely understood and
fascinating, therefore it should be investigated. For rotary kiln shell, cracks can grow with a complex
overloading conditions for over thousands of tons, and then results in premature shell failure. The affecting
conditions crack growth include material characteristics, initial crack size, service stresses, and
stress concentration due to overheated in hot spot area, all these conditions are random. The fatigue life
of the welded shell during crack growth need to be predicted numerically by using finite element analysis
and experimentally. T he fatigue life analysis attempts to provide the answers to general questions, which
remain unclear on the evolution of the crack growth and its impacts on failure in rotary cement kiln system.
In addition, the research is intended to bring our knowledge of the simulation and experimental of the
fatigue life analysis in the welded joints of a rotary cement kiln in PT. Semen Baturaja. The primary
objective of this study is to investigate the fatigue life of the crack growth analysis in the welded joints of a
rotary cement kiln in PT. Semen Baturaja. We approach the goal through a combined analysis of
fatigue growth observational data and numerical model simulation.
2.0 METHODOLOGY
Some materials, such as steel, show an endurance limit stress below which the fatigue life is essentially
infinite. Other materials may not show such behavior
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but an effective endurance limit may be specified at some large number of cycles. the important
parameters to characterize a given cyclic loading history are :
Stress range : σ = σ
max
- σ
min
Stress amplitude: σ
a
= 0.5 σ
max -
σ
min
Mean stress : σ
m
= 0.5 σ
max
+ σ
min
Load ratio : R = σ
max
σ
min
The total fatigue life of a component can be considered to have two parts, the initiatio n life and the
p ro p a g a tio n life
. The stress-life approach just
described is applicable for situations involving primarily elastic deformation. Under these conditions
the component is expected to have a long lifetime. For situations involving high stresses, high
temperatures, or stress concentrations such as notches, where significant plasticity can be involved,
the approach is not appropriate.
The main geometrical characteristics of the rotary kiln shell are shown in Table 1.
Table 1: The main geometrical characteristics of the
rotary kiln
Magnitude Value
Units
Cold real length Inner diameter
Number of tires Slope in direction to outlet
Maximum speed 75
4.5 3
3.5 3.5
meters meters
-- rpm
The thicknesses of the shells along the different sections of the rotary kiln are given in Table 2 and
Figure 1. In Table 2 zero is placed in the upper end of the rotary kiln, called ‘inlet-I’. The distances
between supports, in millimeters, are given in Table 3 where ‘III-outlet’ denotes the lower end of the rotary
kiln.
Table 2: Thicknesses of the shells along the different
sections of the rotary kiln
Section mm
Thickness mm
Section mm
Thickness mm
0 – 1,800 1,800 – 2,500
2,500 – 5,500 5,500 – 8,100
8,100 – 9,700 9,700 – 9,900
9,900 – 11,855 11,855 – 14,190
14,190 – 16,525 16,525 – 18,860
18,860 – 21,195 21,195 – 23,530
23,530 – 25,865 25,865 – 28,200
28,200 – 30,000 30,000 – 32,200
32,200 – 34,000 34,000 – 35,260
60 60
90 70
40 28
28 28
28 28
28 28
28 28
40 60
40 28
35,260 – 37,595 37,595 – 39,930
39,930 – 42,265 42,265 – 44,100
44,100 – 46,435 46,435 – 48,770
48,770 – 51,105 51,105 – 53,440
53,440 – 55,400 55,400 – 56,900
56,900 – 59,400 59,400 – 61,000
61,000 – 63,200 63,200 – 64,800
64,800 – 68,100 68,100 – 71,400
71,400 – 73,650 73,650 – 75,000
28 28
28 28
28 28
28 28
28 40
40 40
60 40
25 25
25 25
Figure 1. Diameter, length, and thickness variation of
rotary kiln
Table 3: Distances between supports Supports
Distance mm
Inlet – I I – Girth Gear
I – II II – III
III – Outlet
13,000 4,200
31,000 27,000
4,000 Tables 2, 3, Figure 1 and 2 is the rotary kiln 1 along
with the structural elements to rotate the kilns 3, 10, 7, and 11 around its longitudinal axis. The kiln 1
includes an elongated, cylindrical, rotating shell 2 which has a feed end 8, an opposite discharge end
5. The kiln 1 is erected so that the discharge end 5 is at a lower level then the feed end 8 in order
to cause the material being processed. It travels through the open processing zone to the discharge
end 5. The kiln shell 2 is supported by riding rings or tires 3 that engage steel rollers 10 which are
supported on concrete piers 4 and steel frames 6.
Figure 2. Rotary kiln configuration
Materials used for the kiln are shown in Table 4. These materials are used to build the kiln components. The
shell, tire, roller and pinion are the main components in the kiln. However, the material has been modeled
as isotropic and linear, elastic temperature dependent, according to the elastic properties of the
steel used in Table 4. The kiln shell is welded circumferentially and longitudinally.
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Table 4: Materials are used for the kiln Component
Material
Shells Tires
Rollers Pinion
ASTM A.36 Low alloy steel casting
Low alloy steel casting 30 Cr Ni Mo 8 ISO R 638 =
II-68 Type 3 As mentioned earlier there are mainly four
methods to predict fatigue of welded components:
Nominal Stress
Structural Stress
Effective Notch Stress
Linear Elastic Fracture Mechanics LEFM The effects of welding residual stresses, R-ratio, wall
thickness and improvement techniques are included in this research. In case of variable amplitude loading,
Palmgren- Miner´s linear damage rule is used when the design methods nominal, structural and effective
notch stress are applied.
3.0 RESULTS AND DISCUSSION
