This paper present a predictive test to monitor and ensure the extension of the lifecycle of Kaplan runner based on theoretical tests performed using finite elements, the dynamic tests carried out by sensors installed on rotating parts and the calculation of remaining lifecycle of internal components of the Kaplan runner.

1. July 19-22, 2011 ~ Sacramento Convention Center ~ Sacramento, CA USA
Kaplan Runners, discussing a case of internal mechanism fracture and proposal for
predictive monitoring
By Carlos Alberto Dias Costa, Duke Energy International, Brazil;
Renato J. Baccili Castilho, Duke Energy International, Brazil;
Wilson Takao, Alstom Power, Brazil and
Wanderley Silva, Alstom Power, Brazil
1. ABSTRACT
In 2007, a problem was identified on the Kaplan runner at one of the generating unit at Rosana
Power Plant.
The generating unit was approximately 15 years old with around 157,000 hours of operation.
The metallurgical analysis of the fractured parts (pins and spacers of the blade links) indicated
that the crack was caused by rupture due to fatigue on the pins of the blade links installed in the
Kaplan runner.
Before reassembling the machine, evaluations were made regarding the force applied on the
internal components of the drive mechanism of the Kaplan blades through finite element
simulations aiming to identify improvements in design of materials.
This paper will show the ratings listed in the preceding paragraph, the investigations undertaken
to identify the source of the problem after the breakdown of the generating unit, the verification
of static and dynamic behavior of structural parts of the drive mechanism of the Kaplan runner
with the unit in operation and the result of measurements taken to ensure operational reliability
after equipment returned to operation.
The authors will also present a predictive test to monitor and ensure the extension of the lifecycle
of Kaplan runner based on theoretical tests performed using finite elements, the dynamic tests
carried out by sensors installed on rotating parts and the calculation of remaining lifecycle of
internal components of the Kaplan runner.
The predictive test proposed can be performed with the generating unit in operation, with defined
periodicity and is supported by the theoretical and practical results of the analysis.
The proposed predictive monitoring can be expanded to several generating units in operation
with low initial investment.

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2. INTRODUCTION
In January 2007, generating unit 01 at Rosana Power Plant was being put back into operation
when, after tests on the voltage regulator and reaching 15 MW power, abnormal noise and
vibration was detected and shutdown necessary.
Tests were conducted on command and control systems and verifications were performed on the
clearances of the bearings. As no abnormalities were identified, an inspection on the hydraulic
turbine was initiated.
During inspection, after drainage of the generating unit, one of the blades wasn’t responding to
the drive mechanism of the blades (open command) which resulted in the withdrawal of the
runner cap for more detailed verification.
After inspection with the runner cap lowered, the following abnormalities were observed:
Components of the drive mechanism of the blades were found in the runner cap: two
blade link spacers and part of the blade link pin that was torn out;
Drag of material on the internal surface of the runner hub due to probable contact between
the external blade links and runner hub;
Contact between blades and runner strap with no material tear;
Blade 01 had marks on the suction side of the blade due to the blows received from blade
05 (pressure side of the blade);
Blade 5 didn’t respond to opening and closing commands from the drive mechanism of
the blades.
Abnormalities mentioned above are shown in the following photos:
Figure 1-photo of drag of
material in the rotor hub
Figure 2-photo of contact
between blades and runner
strap
Figure 3-photo of marks left
on Blade 01 (suction side of
the blade) by blow received
from blade 05

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In view of the complexity of the recovery services required and particulars of the project beyond
the difficulty to access the location (confined space), the best option was to perform a complete
disassembly of the rotating parts in order to carry out necessary repairs.
After complete disassembly of the rotating parts and Kaplan runner, the following additional
abnormalities were identified:
Two blade link pins were broken;
Two blade link pins were cracked;
Flange of the servomotor cylinder presented cracks at the fixation holes of eyebolts 4 and
5;
Spade lever 05 cracked.
Metallurgical analysis on the blade link pins (fractured components) indicated that the cause of
the incident was rupture due to fatigue. Accordingly and to investigate the source of the problem
and the possible occurrence on other generating units, the following investigations were held:
Metallurgical Analysis;
Modeling of the internal components of the Kaplan runner through finite element
method;
Measurement of dynamic behavior obtaining axis oscillation signals, electric power,
rotation, opening of distributor and runner blades, force applied on internal components
of the Kaplan runner, command signal for the rotor valve, upstream and downstream
level.
3. METALLURGICAL ANALYSIS
The two ruptured pins present similar metallurgical characteristics, manufactured in medium
carbon steel, type AISI/SAE 1040, without evidence of metallurgical problems that could
compromise their performance.
Conclusion was that both blade link pins ruptured due to FATIGUE. Rupture began at the radius
of resistant sections between the largest and the smallest diameter, and subcritical propagation
through practically the entire resistant section, indicating low load.

4. July 19-22, 2011 ~ Sacramento Convention Center ~ Sacramento, CA USA
Figure 4 – Aspect of the ruptured
blade link pins
Figure 5 – Macroscopic and
Macrographic aspect of
ruptured Blade Link PIN #01. *
* The rupture started at the strain concentration point, which corresponds to the radius between
the smallest and largest diameters.
4. MODELLING THE INTERNAL COMPONENTS OF THE KAPLAN RUNNER
THROUGH FINITE ELEMENT METHOD
In order to load the finite element model, the stress verified on internal components of the
Kaplan runner is a result of the operation pressure when opening and closing the runner blades.
4.1. Calculations
4.1.1.Calculation Method
The calculations were made through finite element method - EF using ANSYS v10.0
software. The model was designed with Solid Type Elements (SOLID95). Existing
contacts in the mechanism were modeled by contact elements (CONTACT 174).
4.1.2.Load conditions and limits
Blade link, blade link pins and blade link spacers
Restrictions were imposed at the middle section of the blade link pin limiting axial
displacement.
The blade link restrictions were imposed on the mid longitudinal section limiting
transverse displacement (normal to the longitudinal section). The restrictions regarding
model offset towards the load were imposed on the blade link pin, spade lever side.

5. July 19-22, 2011 ~ Sacramento Convention Center ~ Sacramento, CA USA
The load model, resulting from operation pressures in each case considered, was applied
on the blade link pin (eyebolt side) in the form of distributed load – normal pressure;
having equal value and resultant force from the initial load. The interface blade link and
the blade link pins and blade link spacers were developed through contact elements with a
0.17 static friction coefficient.
Figure 6 – Model of the
blade link, blade link pins
and blade link spacers
Figure 7 – Model of the
blade link pins
4.1.3.Load
Force applied on the mechanism results from the operation pressure of the servomotor
that actuates the runner and is defined by the relation:
Where:
FT- total force applied on servomotors
- operation pressure on the opening chamber
- operation pressure on the closing chamber
- projected area of the piston on the opening chamber side.
- projected area of the piston on the closing chamber side.
Dep - external diameter of the piston
- internal diameter of the piston on the opening chamber side.
- internal diameter of the piston on the closing chamber side.
The operation pressure on the opening and closing chamber was obtained through tests
using pressure sensors installed in existing pressure taps on the Kaplan head.
The values obtained during tests were used to feed the finite element model.

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The tests to measure the pressure on the opening and closing chamber of the runner servo
motor were performed on generating unit 02. The highest pressure differential between
the chambers was chosen as operational condition, resulting in a greater load to be applied
on the model. In the case of generating unit 02, the operational condition chosen
comprises a power range of 80-88 MW for opening and 93-80 MW for closing, with the
values below:
Blades opening:
o Closing pressure =14.1 bar
o Opening pressure =36.0 bar
Blades closing:
o Closing pressure =30.6 bar
o Opening pressure =20.3 bar
4.1.4.Force on Mechanism:
The servomotor force was obtained by using the pressure data:
The force applied on each mechanism was obtained on the basis of total force developed
by servo motor and the number of runner blades. In this case, the force on each
mechanism corresponds to 1/5 of total force. Therefore:
F = 1,222 KN (blades opening)
F = 4,67 KN (blades closing)

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4.2. Results
The following results were obtained after feeding the finite element model with the
results from the opening and closing chamber pressure metering tests:
Table 1 – Pressure and Frequency Values from the tests on GU02 used to input
(feed) FEA
Opening Chamber Closing Chamber ∆p
Opening 36.0 14.1 21.9
Closing 20.3 30.6 -10.3
Period Approximately every 2 minutes
Frequency 26.8 cycles/hour
Table 2 – Von Misses Stress σ [Mpa] – FEA (GU02)
Component Condition FEA (UG02)
Blade link Opening 19.6 (4.9)
Closing -7.6 (9.9)
Obs:
1- The values were obtained at the same points where the strain gauge was installed
(described on item 4.0);
2 – On the components that present more than one metering point, an average between
the values obtained was reached. The standard deviation is shown in parentheses.
Figure 8 – Blade link
Longitudinal Stress – Opening
Figure 9 - Blade link
Longitudinal Stress – Closing

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5. DYNAMIC BEHAVIOR MEASUREMENTS ON GENERATING UNIT
Measurements were performed with sensors installed on stationary and rotating parts. Static and
dynamic deformations were measured on the following four sets of servomotor cylinder
actuators: blade link, eyebolts, spade levers, blade link spacers and flanges of the cylinder.
The deformations on space levers, blade link spacers and eyebolts was measured using
unidirectional strain gauges, in other words, in a specific given direction. As for the spade levers
and the flange, the deformations were measured by three-directional strain gauge (strain rosettes),
in other words, in three directions on the surface plane.
Figure 10 - strain gauges
installed at the blade link
Deformation was also measured on the guide bearing support cone in order to obtain vertical
load. The pressure was measured in both chambers of the servo motor, spiral case, draft tube and
on the turbine head cover. Axis oscillation was measured by proximity sensors on the turbine and
generator guide bearing. Signs related to electric power, rotation, opening of distributor blades
and runner blades, command signal for the rotor valve, upstream and downstream levels were
measured concurrently with other signals.

9. July 19-22, 2011 ~ Sacramento Convention Center ~ Sacramento, CA USA
5.1. Charts representing the pressure measurements of the chambers and blade link stress
The charts below were obtained after eight hours of operation with the generating unit at
80MW Power:
Figure 11 – Power and pressure of the opening and closing chambers
Figure 12 – Stress on Blade link 4

10. July 19-22, 2011 ~ Sacramento Convention Center ~ Sacramento, CA USA
Figures 11 and 12 demonstrate that the stress on components is directly related to the
difference between the pressures of the opening and closing chambers.
With GU 01 under stable operating conditions (80MW), the pressure graphs clearly
demonstrated the presence of cycles with inversion of pressures in the chambers (opening
and closing) of the runner servomotor. There are 12 cycles in a 7 hours period.
5.2. Results
The following values were obtained during testing performed after returning Generating
Unit 01 to service:
Table 3 – Pressure Values and Frequency of Testing on GU01
Opening Chamber Closing Chamber ∆p
Opening 38.0 12.0 26.0
Closing 15.0 35.0 -20.0
Period Aproximately every 35 minutes
Frequency 1.71 cycles/hour
Table 4 - Von Misses stress σ [Mpa] – IPT (UG01)
Component Condition IPT (UG01)
Blade link Opening 26.4 (6.1)
Closing -10.0 (5.5)
Obs:
1 – For each type of component an average of all the values measured was calculated.
This is the value presented on the table. In parentheses is the standard deviation value.
6. BLADE LINK PIN USEFUL LIFE
Using the measurements taken on Unit 1, verification was performed to validate the lifecycle of
GU01 blade link pins by using the same finite element model.
The load on the blade link, blade link pins and equipment was set based on the medium stress
measured on the blade link as in table 4.

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Based on the average value of stress and the cross-sectional area of the blade link, we can
determine the force acting on components, assuming that the average stress is constant
throughout this surface.
F = σ ⋅ A Transversal section area is:
Therefore, the force on the blade link pin is:
Opening: Fop = 26.4 *57,682 = 1,522,805N
Closing: Fclos = −10.0 *57,682 = −576,820N
Figure 13 – Von Mises stress
calculated - Opening
Figure 14 – Von Mises stress
calculated - Closing
Taking into account the load above, we can determine, by means of finite element model, the
matrix of the tensor of stress for the opening and closing conditions. Based on the difference
between the tensors, alternating stress is obtained (Salt). The remaining lifecycle of the blade link
pins under fatigue is then determined in accordance with the ASME code sec. VIII div. 2.
The points were analyzed with high intensity stress, and the maximum stress obtained was 174
MPa. Correcting this value for the modulus of elasticity:
The current material of blade link pins is ABNT 4340 steel, which is a high-alloy steel. From this
information, you can determine the number of cycles of the component using the Fig. 5-110.2.2
m –Curve design for fatigue on high alloy steels, ASME code sec. VIII div. 2, Appendix 5.

12. July 19-22, 2011 ~ Sacramento Convention Center ~ Sacramento, CA USA
Figure 15 – extracted from the ASME sec. VIII, div. 2, appendix 5.
Using curve A in the figure above, it is possible to determine that at an alternating stress of 162
MPa the result is: N > 1,011 cycles or an Infinite lifecycle for the blade link pins from the Kaplan
runner analyzed.
7. CONCLUSIONS
Stress in the internal components of the Kaplan runner have direct relation to the difference
between the pressures of the opening and closing chambers of the servo motors that actuate the
runner, as well as their alternation.
From the pressure data, the force developed by servo motors can be obtained.
The force applied at each mechanism is obtained in function of total force developed by servo
motors and the number of blades on the runner.
The number of cycles (inversions of the opening and closing chamber pressures) and the pressure
difference between chambers (∆ p) is inversely proportional to the useful life of internal
components of the Kaplan runner.
In this way and based on the results of investigations above, the authors of this paper recommend
periodic monitoring of the pressure behavior of the opening and closing chambers of the Kaplan
runner servo motors, while maintaining generating unit on a fixed power for a minimum period

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of eight hours, according to graph from Figure 11, to proceed with corrective actions on oil-
hydraulic power system in a anticipated manner in the case of deviations.
8. BIBLIOGRAPHICAL REFERENCES
[1] ZANUTO, J.C., RELATÓRIO TÉCNICO IPT N° 97 976-205 MEDIÇÕES DINÂMICAS
NO ROTOR KAPLAN DA UNIDADE GERADORA 01, DA UHE ROSANA
[2] ALSTOM RKV5168032 003-01 – Modelamento em elementos finitos: biela, pino e
distanciadores
[3] ALSTOM RKV5168032 004-01 – Modelamento em elementos finitos: alavanca, cilindro e
olhal
[4] ALSTOM RKV5168032 006-00 – Roda Kaplan – Análise do Mecanismo da Roda
[5] DUKE ENERGY Technical Report RT-ENG-050-07 – R2 – Análise da ocorrência na UG01
da usina Rosana
[6] TECMETAL Technical Report RT 335/2007 Rev.02 – Análise Metalúrgica de pinos da biela
da roda Kaplan. (Tecmetal)
[7] ALSTOM Relatório técnico Alstom RKV5168032-007-00 – Análise do mecanismo da roda
após ensaio embarcado
9. AUTHORS
Carlos Alberto Dias Costa was born in Casa Branca, São Paulo state, Brazil, on August 4, 1958.
He received his Electrical Engineering degree from Mackenzie University in 1984 and his MBA
degree from Fundação Dom Cabral. Currently he is the Operations Director for Duke Energy
International, Geração Paranapanema in Brazil. He is responsible for the operation and
maintenance of eight power plants with 2,307 MW installed capacity.
Renato José Baccili Castilho, was born in Ourinhos, São Paulo state, Brazil on February 13,
1971. He received his Electrical Engineering degree from Marilia University in 1997; his
Masters degree on Project Management from Fundação Getulio Vargas in 2004 and his MBA
degree from Fundação Dom Cabral in 2007. Currently he is Manager of Electromechanical
Maintenance Engineering at Duke Energy International in Brazil, responsible for maintenance of
eight power plants with 2,307MW installed capacity.

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Wanderley Silva, was born in Araras, São Paulo state, Brazil, in 1953. He received his
Mechanical Engineering degree from the Universidade de Taubaté in 1981 and his
Specialization Degree from Alstom Technological Center in France in 1995. Currently he is
responsible for Alstom projects in Brazil and has 25 years of experience projecting hydro
turbines.
Wilson Takao, was born in Taubaté, São Paulo state, Brazil, in 1954. He received his
Mechanical Engineering degree from UNESP in 1977, has post-graduated from ITA-Aerospace
Technology and his Specialization degree on equipment from Petrobras. Currently he works as
an Alstom Specialist responsible for Santo Antonio Power Plant project.