Reporte de Ultrasonido PM-1501 Motor de Bomba de

Detecting Rotor Bar Problems in
AC Induction Motors
by Airborne/Structureborne Ultrasound
Mechanical Inspection.
Mechanical Department.
Predictive Maintenance & Reliability
Speaker: Eng. Carlos Hdz. Conti, CMRP
Level II Airborne Ultrasound Certified Analyst. By UESystems
ClearWater Beach, F.L. Mayo 2011 1
Content
• About TLA
• Machine.
• Problem.
• Diagnostic Chart.
• Failure Zone Graph.
• Failure Effect.
• Technique.
• Recommendations & Diagnostics
• Results.
• References.
• Appendix A, MCA Diagnostics &
Severity Chart.
2
TLA ALTAMIRA – WHERE IS IT?
3
ORGANIZATIONAL STRUCTURE & PROCESS
Type
Joint Venture ( Shell-TotalMitsui )
Industry
Oil & Gas
Founded
2004, by Shell-Total-Mitsui
Headquarters Altamira, Tams. MX
Key people
Carlos Barajas (Managing
Director)
Loran Karwacki (Asset manager)
Jair Rojas (Finance Manager)
Carlos Oropeza (Operations
Manger)
Juan M. Hdz (Maintenance
Manager)
Verónica Zavaleta ( HR Manager)
Luis Núñez (Commercial &
Proyects Manager)
Products
Natural Gas
Employees
80 (2010)
Website
http://www.shell.com/
http://www.altamiralng.com.mx
4
LNG Importing Terminal - Assets & Technical Scope.
• Berthing basin, including mooring & unloading facilities for LNG
Carriers (Carrier Capacity 70,000 to 200,000 m3)
• 2 LNG Storage Tanks (net capacity 150,000 m3 each)
• Process equipment for vaporization & gas pressurizing;
• Seawater Supply System with capacity of up to 30,000 m3/hr
• Send Out Facilities into Pemex Pipeline and Altamira V PP
• Buildings (Control Room, Administration Building, Warehouse –
2010 replacing temporary buildings)
• Terminal Capacity (Phase 1): 760 mmscf/d Peak (500mmscfd
base load = 3.75 mtpa)
• Potential for Expansion (Phase 2):1,200 mmscf/d Peak
(1070mmscfd base load = 8 mtpa)
5
Machine: PM-1501
PM-1501 is an electric motor of approximately 450 HP's and runs at 1800 rpm, is coupled to a double
suction bipartite horizontal centrifugal pump, whose function is to provide water for fire fighting, this
machine operates every week about 10 minutes and the route is inspected every 3 months.
6
Safe Maintenance
P-F Curve, Safety and Reliability
Where is safer, reliable and economic doing maintenance?
Source:
PdM Secrets Revealed 4th Ed AlliedcRealiaility
Are You Doing Too Much PM?
7
Problem:
PM1501, Ultrasound Spectrum Analysis shows a typical spectrum of Rotor Loose-Broken Bar Problems
in the engine, note Rotor Bar Pass Frec. @102.7 kcpm and up to 4 harmonics each one with
SideBands @ 2XFl. Bars # = 102700 cpm / 1800 rpm = 57.05 bars
8
Diagnostic Chart:
9
Diagnostic Chart:
A normal AC motor signature ought to include a rotor bar passing frequency
(RBPF) response. This response takes place when each rotor bar passes slight disruptions
within the magnetic field because of the electrical current’s path through the stator/rotor
geometry. An elevated RBPF is created when the rotor bars pass a significant disruption in
these fields produced when the current path is altered or distorted from broken or cracked
rotor bars, loose or defective rotor bar joints, improperly brazed rotor bar joints, porous rotor
bar castings, or electrical arcing across the rotor bar to end ring interfaces.
RBPF is recognized as an integer multiple of rotor speed, and will usually have
sidebands spaced at 2x electrical line frequency (7200 CPM). Rotor eccentricity problems
can be indicated by additional (less dominant) sidebands sets spaced at 1x RPM.
AC motor may have from 35-96 rotor bars, so an FFT spectrum with
sufficient frequency range will be necessary to capture this fault. 1x and 2x RBPF will
be captured by a 360000 CPM with a 1600 FFT line resolution, and will provide enough
resolution to define the 2x LF sidebands.
Severity is usually judged by changes in RBPF amplitudes over time. Amplitude variation
with load is common.
10
Failure
Zone Graph:
11
Failure Effect:
When analyzing the
post mortem
rotor
failure, locate and
identify
points
of
blackened-blue
overheating
areas
Check dye penetrant
crack.
12
Failure Effect:
13
Technique:
The inspection technique used was: Mechanical inspection of bearings, using
magnetic module placed closest to the loading of the bearings, a freq. @ 25 kHz
was settled, the data was saved and downloaded to the DMS for follow-up. This
type of problems typically generate audible “go & back” sound .
14
Recommendation & Diagnostics:
Applying the Theory of Vibration Analysis to Ultrasound Analysis: When dealing
with Problems of Rotor Bar Loose / Broken in electric motors, their
physics is not due to friction or impact, and if not settled a Fmax. suitable
for capturing high frequencies in the FFT, they can go unnoticed, their
severity is dictated by the amount of harmonics, as well as side bands
around them, this is an advantage of using ultrasound in mechanical
inspections. For better results try to apply and combine diagnostics with
at least 2 PdM technologies. ( see appendix A)
Results:
It was proceeded to prepare the respective report, continuing with routine
monitoring, this type of rotor problems are usually related to manufacturing
quality problems, and given that the engine do not operates continuously, its
development has been slow, but by predictive task, this Potential Failure as
intensified so shall be changed with the spare motor, which is already in stock.
15
Appendix A MCA:
MCA results performed on this same engine to confirm the problem, note the
warning notice indicating possible failure of rotor bars.
Motor ID
Database
Building
Location
Date/Time
PM 1501 TLA
WORK 2005
Bba contraincendio
BASEMENT
4/14/2011 01:21:31 PM
Name Plate
450.00
1785
4160
55.0
1.0
1.0
1324.7
98.5
100.0
Hp
RPM
Volts
Amps
pf (pu)
Nema Derating (pu)
Torque (ft-lb)
Efficiency
Percent Load
Test
% Over Voltage
% Unbalance
% Voltage Dist.
% Current
Ef. Service Factor
Rotor Bar (db)
% Op. Point
% Loss Diff.
% Loss Diff.
Tested by
Tested for
Explorer SN#
Test Type
Value
2.43
0.75
0.57
71.33
0.73
-30.87
0.00
0.00
N/A
Status
GOOD
GOOD
GOOD
GOOD
GOOD
WARNING
GOOD
INDET
INDET
333
Electrical
Measured
326.72
1792.6
4261.3
38.6
0.9
1.0
957.7
96.4
72.6
Caution Level
10.0
2.0
7.0
110.0
1.1
-45.0
20.0
25.0
60.0
Warning Level
20.0
3.5
9.0
120.0
1.2
-36.0
30.0
50.0
24.0
16
Appendix A:
MCA
Power Spectrum
Graphics showing
the Rotor Bar
Pass Problem,
which also is
affected in
response to
torque.
Motor ID
Database
Building
Location
Date/Time
PM 1501 TLA
WORK 2005
Bba contraincendio
BASEMENT
4/14/2011 01:21:31 PM
Tested by
Tested for
Explorer SN#
Test Type
333
Electrical
Voltage and Current Waveforms
Phasor Diagram
Rotor Bar
Torque Ripple
17
Appendix A:
MCA
Diagnosis and
Severity Table for
MCA, used to
assess Electric AC
Motors problems.
18
References:
• “A New Version of MachineLibrary Multimedia Training Package is Now Available”, pp. 66-67, or visit the
MachineLibrary™ www.bently.com.
• Technical Associates Of Charlotte, Vibration Analysis Level II & III
Aknowledgements:
• Special thanks to Ing. Alvaro Castillo, BASF of Altamira, for support with the MCA analysis by Baker, all under
the Interplant support of the AISTAC Reliability Committee .
• Special thanks to Ing. Carlos Garza, UESystems Regional Manager for México & LA for the chance to take part in
this Conference.
• Special thanks to all those M&R Practitioners for sharing knowledge and experience at WU VII
Mr. Carlos Hdz. Conti can be reached at :
carloshconti@yahoo.com
C.Hernande@shell.com
19
Detectando Problemas de Rotor
por medio de
Inspección Mecánica de Ultrasonido Estructural
Depto.Mecánico
Mantto. Predictivo y Confiabilidad.
Presenta: Ing. Carlos Hdz. Conti, CMRP
Level II Airborne Ultrasound Certified Analyst. By UESystems
ClearWater Beach, F.L. Mayo 2011 1
Contenido
• Maquina.
• Problema.
• Carta de Diagnóstico.
• Esquema de Zonas de Falla.
• Efectos de Falla.
•Técnica.
•Recomendación Diagnóstico
•Resultado.
•Referencias
•Anexo A, MCA & Carta de Diagnóstico y Severidad.
2
TLA ALTAMIRA – EN DONDE SE UBICA?
3
ESTRUCTURA ORGANIZACIONAL & PROCESO
Type
Joint Venture ( Shell-TotalMitsui )
Industry
Oil & Gas
Founded
2004, by Shell-Total-Mitsui
Headquarters Altamira, Tams. MX
Key people
Carlos Barajas (Managing
Director)
Loran Karwacki (Asset manager)
Jair Rojas (Finance Manager)
Carlos Oropeza (Operations
Manger)
Juan M. Hdz (Maintenance
Manager)
Verónica Zavaleta ( HR Manager)
Luis Núñez (Commercial &
Proyects Manager)
Products
Natural Gas
Employees
80 (2010)
Website
http://sww.shell.com/
4
Terminal de Importación de LNG- Activos & Alcance Técnico.
• Berthing basin, including mooring & unloading facilities for LNG
Carriers (Carrier Capacity 70,000 to 200,000 m3)
• 2 LNG Storage Tanks (net capacity 150,000 m3 each)
• Process equipment for vaporization & gas pressurizing;
• Seawater Supply System with capacity of up to 30,000 m3/hr
• Send Out Facilities into Pemex Pipeline and Altamira V PP
• Buildings (Control Room, Administration Building, Warehouse –
2010 replacing temporary buildings)
• Terminal Capacity (Phase 1): 760 mmscf/d Peak (500mmscfd
base load = 3.75 mtpa)
• Potential for Expansion (Phase 2):1,200 mmscf/d Peak
(1070mmscfd base load = 8 mtpa)
5
Máquina: PM-1501
PM-1501 es un motor eléctrico de aprox 450 HP’s y gira a 1800 rpm, está acoplado a una bomba
centrífuga bipartida de doble succión, cuya función es proveer agua de contra incendio, éste equipo
opera cada semana alrededor de 10 minutos y la ruta se inspecciona cada 3 meses.
6
Problema:
PM1501, El Análisis de Espectros de Ultrasonido muestra espectro típico de Problemas de Barras de
Rotor Flojas/Rotas en el Motor, nótese Frec. Paso de Barras de Rotor @ 102.7 Kcpm y hasta 4
armónicos c/u con Bandas Laterales @ 2XFl. # Barras= 102700 cpm / 1800 rpm = 57.05 barras
7
Carta de Diagnóstico:
8
Carta de Diagnóstico:
Una firma de motor de CA normal debe incluir una respuesta de frecuencia de paso de barra del rotor
(RBPF) . Esta respuesta se produce cuando cada barra del rotor pasa perturbaciones leves en el campo
magnético debido a la trayectoria de la corriente eléctrica a través de la geometría del estator / rotor. Una
RBPF elevada se crea cuando las barras del rotor pasan una interrupción significativa en estos campos
producida cuando la trayectoria actual se ve alterada o distorsionada de las barras de rotor rotas o
agrietadas, juntas de barra del rotor sueltas o defectuosas, mal soldadas, piezas de fundición porosas de
barra del rotor, o arcos eléctricos a través de la barra del rotor a través de las interfaces de anillo.
RBPF se identifica como un múltiplo entero de la velocidad del rotor, y por lo general tienen
bandas laterales espaciadas a 2 veces la frecuencia de línea eléctrica (7200 RPM). Los Problemas de
excentricidad del rotor puede ser indicado por otros (menos dominante) conjuntos de bandas laterales
espaciados a 1 x RPM.
Un Motor de CA puede tener de 35 a 96 barras del rotor, por lo que un espectro de FFT con un
rango de frecuencia suficiente, será necesario para capturar esta falla. 1x y 2x RBPF será capturado con
una Fmax de 360000 kcpm con una resolución de 1600 líneas , y proporcionará suficiente resolución para
definir
las
bandas
laterales
a
2xFL.
La severidad se evalúa considerado los cambios en las amplitudes de RBPF a lo largo del tiempo. La
variación de la amplitud con la carga es común.
9
Esquema
de Zonas DE
de Fallas:
10
Efectos
de Fallas:
Cuando analize la falla
de rotor, busque e
identifique zonas con
puntos de
recalentamiento
ennegrecidasazuladas. Compruebe
fisuras con líquidos
penetrantes.
11
Técnica:
La técnica de inspección usada fue: Inspección mecánica de rodamientos, aplicando el módulo
magnético posicionándolo lo más cerca de la zona de carga de los rodamientos, frec.@ 25 khz, se
salvan los datos y se descargan al DMS para su posterior seguimiento. Éste tipo de problemas
generan un sonido típico audible y oscilante de “vaivén”.
Recomendación Diagnóstico:
Aplicando la Teoría de Análisis de Vibraciones al Análisis de Ultrasonido: En los Problemas de Barras
de Rotor Flojas/Rotas en motores eléctricos, su física no obedece a fricción ó impactos, y si no
se ajusta una Fmáx. adecuada para captar altas frecuencias en el FFT, pueden pasar
desapercibidos, su severidad está dictada por la cantidad de armónicos, así como de bandas
laterales alrededor de éstos, lo anterior es una ventaja del uso del Ultrasonido en Inspecciones
Mecánicas.
Resultado:
Se procedió a elaborar el reporte respectivo, continuándose con monitoreo rutinario, éste tipo de
Problemas de Rotor normalmente están relacionados con problemas de calidad de manufactura, y
dado que no opera continuamente el motor, su evolución ha sido lenta, pero como actividad predictiva,
ésta Falla Potencial en tanto se intensifique se procederá a cambiar el motor el cual ya está en
almacén.
12
Anexo A MCA:
Resultados de MCA practicado a éste mismo motor para corroborar el Problema, nótese el aviso de
advertencia indicando fallas por posibles Barras de Rotor.
Motor ID
Database
Building
Location
Date/Time
PM 1501 TLA
WORK 2005
Bba contraincendio
BASEMENT
4/14/2011 01:21:31 PM
Name Plate
450.00
1785
4160
55.0
1.0
1.0
1324.7
98.5
100.0
Hp
RPM
Volts
Amps
pf (pu)
Nema Derating (pu)
Torque (ft-lb)
Efficiency
Percent Load
Test
% Over Voltage
% Unbalance
% Voltage Dist.
% Current
Ef. Service Factor
Rotor Bar (db)
% Op. Point
% Loss Diff.
% Loss Diff.
Tested by
Tested for
Explorer SN#
Test Type
Value
2.43
0.75
0.57
71.33
0.73
-30.87
0.00
0.00
N/A
Status
GOOD
GOOD
GOOD
GOOD
GOOD
WARNING
GOOD
INDET
INDET
333
Electrical
Measured
326.72
1792.6
4261.3
38.6
0.9
1.0
957.7
96.4
72.6
Caution Level
10.0
2.0
7.0
110.0
1.1
-45.0
20.0
25.0
60.0
Warning Level
20.0
3.5
9.0
120.0
1.2
-36.0
30.0
50.0
24.0
13
Anexo A MCA:
Gráficos de Espectro de
Corriente mostrando el
Problema de Paso de
Barras de Rotor, el cual
también se ve afectado
en respuesta al torque.
Motor ID
Database
Building
Location
Date/Time
PM 1501 TLA
WORK 2005
Bba contraincendio
BASEMENT
4/14/2011 01:21:31 PM
Tested by
Tested for
Explorer SN#
Test Type
333
Electrical
Voltage and Current Waveforms
Phasor Diagram
Rotor Bar
Torque Ripple
14
Anexo A MCA:
Tabla de Diagnóstico y
Severidad para MCA,
usada para evaluar
Problemas
Eléctricos
de Motores de CA
15
Referencias:
• “A New Version of MachineLibrary Multimedia Training Package is Now Available”, pp. 66-67, or visit the
MachineLibrary™ www.bently.com.
• Technical Associates Of Charlotte, Vibration Analysis Level II & III
Mr. Carlos Hdz. Conti can be reached at :
carloshconti@yahoo.com
C.Hernande@shell.com
16