Download SIKO The Safety Design Concept

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SIKO
The Safety Design Concept
Safety Design Concept SIKO
SIKO is ABB Turbocharging’s Safety Design Concept for
enhancing the reliability and safety of ABB turbochargers and
for making their life cycle costs more predictable.
Centrifugal force
97 tons / blade
Tip velocity
480 m /s ~ 1,750 km / h
Revolutions
9,900 rpm
Tu
rb
in
o
ep
we
r1
0
0,0
0k
W
Fig. 1: TPL 91-B rotor – some key figures
Over the past decade the output of diesel and gas engines
has been steadily increased, presenting the turbocharger
manufacturer with the challenge of continually increasing the
compressor pressure ratio. Whereas in the past, turbochargers
could be operated with large design margins, the higher
performance required today calls for design solutions which
lie much closer to the physical limits of the turbochargers.
The load factor for the rotating components in particular has
increased dramatically – turbochargers are turning faster
and faster.
2
At the same time, expectations regarding the reliability and
safe operation of the equipment have grown considerably.
Plus there is also demand within the industry for reduced life
cycle costs and optimized maintenance of the engines and
turbochargers. ABB Turbocharging addresses this issue with
its Safety Design Concept “SIKO”.
SIKO is a calculation tool for determining the speed and
temperature limits of turbocharger rotor components for given
exchange intervals. The program is available for the older
VTR . . 4, VTC . . 4 and RR . . 1 turbocharger families as well as
for today’s TPS, TPL, TPR and A100 series. SIKO is regularly
updated to keep it state-of-the-art and will also be implemented
for coming ABB turbocharger generations.
SIKO modules
Why SIKO?
Turbocharger rotor components are subject to extremely high
loading under operating conditions (Fig. 1). The high rotating
speed, for example, has the effect of producing very high
kinetic energy inside the turbocharger. Failure of a rotor component often leads to total loss of the turbocharger, and thus
costly downtime.
Modules of the Safety Design Concept
SIKO consists of four modules (Fig. 2), designed specifically
to determine
1 Load profiles, i.e. turbocharger operating conditions
2 Material properties
3 Stress and material temperature distributions
4 Speed and temperature limits using a damage
accumulation method.
SIKO was created to increase turbocharger reliability, maximize
safety and make life cycle costs more predictable by adopting
the principle of preventive maintenance instead of “break and
fix”.
Fig. 2: Structure of the Safety Design Concept
Safety Design Concept
1 Load profile
2 Material properties
3 Stress analysis, temperature distribution
t, N
4 Calculation of speed limit
σ
damage
accumulation
method
t, N
ABB Turbo Systems Ltd
Turbocharger
Type
HZTL 428 765 P2
t
n
n
Mmax
HT
1
S
Bmax
t Mmax
t Bmax
°C
kg
Application according to
the Operation Manual
made in Switzerland
3
SIKO modules
1. Turbocharger operating conditions.
Knowledge of how the rotor components be have in operation
is a key element of SIKO. The load profile for a turbocharger –
load versus time and versus the number of load cycles (Fig. 3)
– is not the same, for example, for a container vessel and a
locomotive. Similarly, it is different for a base load power plant
and a hospital emergency unit. Even within marine applications, the load profiles can be completely different.
Load
Load
ABB designed special data loggers, similar to the “black box”
in aircraft, in order to measure and collect real world turbocharger operation data over an extended period of time, typically four to six months and in some cases up to one year.
This measuring device has allowed ABB to determine load
profiles for a wide range of engine applications. Over the
years, the company has built up a huge database and accumulated a wealth of information and knowledge about the
real world operating conditions of turbochargers used in many
different engine applications.
The measurements include the turbocharger speed and the
temperatures at the compressor and turbine inlets. The twopart load profile (Fig. 3) allows an evaluation of the creep and
fatigue loading of the rotor components.
Time
Fig. 3: Load profile
4
Number of cycles
SIKO modules
2. Determination of material properties.
ABB carried out extensive tests to determine the material
properties, i.e. the tensile strength, yield strength, creep
strength and fatigue strength. Fig. 4 shows the effect on the
creep rupture strength of increasing temperature, and Fig. 5
the fatigue strength.
Stress amplitude
Creep rupture strength
The material properties are obtained by means of tests carried
out on laboratory specimens. One important aspect of the
material properties is the statistical scatter. This is clearly seen,
for example, when several specimens with the same geometry
are loaded at the same stress level and at the same temperature. The time until failure will vary strongly. It is usually necessary to repeat a test at the same stress and temperature level
several times in order to obtain statistically significant material
properties. Such tests demand special laboratory resources
and run for a very long time – a 100,000 hour creep test, for
example, lasts all of 11 years.
Increasing temperature
Time
Fig. 4: Creep rupture strength development
Number of cycles
Fig. 5: Fatigue strength curve
5
SIKO modules
3. Stress and material temperature distribution.
Finite element analyses are carried out to obtain the stress
and material temperature distribution in the rotor components.
These analyses identify the critical locations and determine
the local stress and material temperature as a function of the
turbocharger speed and the suction air and exhaust gas temperatures.
Stress distribution in the rotor components of a turbocharger
varies greatly according to the geometry of the part. Finite
element analyses have therefore been carried out for every
design of the compressor wheel and turbine. SIKO also takes
account of the thermal stress caused by temperature distribution in the component and, in the case of compressor wheels
with a center bore, even the prestresses induced by spinning
during manufacture.
Damping wire
Blade at damping
wire hole section
Blade
Fir tree root
of blade
Disk
Turbine disk at
fir tree profile
Backwall
Center of hub
Hub
Fig. 6: Typical critical locations in a TPL compressor wheel
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Fig. 7: Typical critical locations in a TPL turbine
Figs. 6 and 7 show typical critical locations in a compressor
wheel and in a turbine. Figs. 8 and 9 show a finite element
net of a compressor wheel and its stress distribution under
operating conditions.
The material temperature strongly influences the material
properties, and thus the speed limit and exchange interval for
the rotor components. In addition, the temperature distribution induces thermal stress in the components, as already
mentioned. SIKO therefore takes full account of the influence
of temperature. Extensive measurements carried out on
turbochargers provided the basis for the calculation and
calibration of the temperature distributions. The suction air
temperature and exhaust gas temperature at the turbine inlet,
for example, directly influence the temperature level in the
compressor wheel and turbine.
Fig. 8: Finite element model of a compressor wheel
Fig. 9: Stress distribution under operating conditions
7
8
SIKO modules
4. Calculation of speed and temperature limits using the
damage accumulation method.
The turbocharger speed and the inlet temperatures are
the parameters directly responsible for the loading of rotor
components.
1.
T = constant
Stress
When the material properties, the stress distributions and the
material temperature distributions are all known, it is possible
to determine the speed and temperature limits for the required
exchange intervals.
Calculations are performed for every critical location in the
compressor wheel and turbine. SIKO makes use of the linear
damage accumulation method according to Palmgren-Miner
(Fig. 10). An accumulated damage value of 1.0 represents the
time at which the ex change becomes due. The speed limit for
the complete component is determined by the lowest speed
limit at one of the critical locations.
Based on the application and ambient conditions, ABB
recommends speed and exhaust gas temperature limits as
well as exchange intervals for the rotor components, allowing
safe and reliable operation from the beginning. This information is given on the rating plate of every delivered turbocharger. In some applications, e.g. where a higher speed
limit is required or when the load profile features many more
load cycles, certain restrictions may be introduced. These
could require, for example, shorter exchange intervals or the
use of special materials, such as titanium for the compressor
wheel, as a further means of ensuring reliable turbocharger
service and avoiding cost intensive downtime of the equipment.
t Ti
Time
To prevent a creep fracture the following law
has to be observed:
∑ ti ≤ 1
tTi
冢冣
2.
T = constant
Stress
The following parameters strongly influence the speed limit
and exchange intervals of the rotor components:
– Turbocharger speed profile (speed level and speed cycles)
– Suction air temperature
– Exhaust gas temperature at turbine inlet
ti
nk
nfk
Number of cycles
To prevent a fatigue fracture the following
law has to be observed:
∑ nk ≤ 1
nfk
冢 冣
3.
For combined creep and fatigue
loading the following law has to be observed:
∑ ti + ∑ nk
≤1
nfk
tTi
关 冢 冣 冢 冣兴
Fig. 10: Linear damage accumulation according to Palmgren-Miner
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Information on the rating plate
ABB Turbo Systems Ltd
Turbocharger
Type
HZTL 428 765 P2
The results of the SIKO evaluation, i. e. the turbocharger
speed and temperature limits as well as the recommended
exchange intervals, are given on the rating plate (Fig. 11)
of every delivered turbocharger. Operating the turbocharger
beyond the specified exchange interval increases the risk of
failure. Timely replacement of the rotor components according
to the rating plate is a major factor in trouble free turbocharger operation and can prevent costly downtime.
n
n
Mmax
Bmax
HT
1
S
t Mmax
t Bmax
°C
kg
Application according to
the Operation Manual
made in Switzerland
Turbocharger operational limits at engine overload (110 %)
in test rig operation only
Turbocharger operational limits in service
Recommended exchange interval for the compressor wheel
Recommended exchange interval for the turbine
Fig. 11: Turbocharger rating plate
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SIKO benefits for the customer
ABB turbochargers are designed to perform efficiently and
reliably in all operating environments. SIKO was developed
to ensure that this performance is maintained over every
turbocharger’s operating life. Systematically applied by the
global ABB Turbocharging Service network and product
support organization, SIKO provides customers with a highly
useful tool for optimizing maintenance and minimizing
unplanned downtime of equipment. SIKO is an excellent tool
for the proactive planning of overhauls, thereby helping to
prevent avoidable serious breakdown which could affect the
profitability and reputation of a customer’s company.
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CHTUS-1150-1208-5000-EN
© 2012 ABB Turbo Systems Ltd, Baden / Switzerland
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ABB Turbo Systems Ltd
Bruggerstrasse 71 a
CH-5401 Baden / Switzerland
Phone: +41 58 585 7777
Fax:
+41 58 585 5144
E-mail: [email protected]
www.abb.com/turbocharging