Overview
The LM6000 Gas Turbine
The LM6000 is a modern aeroderivative gas turbine from General Electric, and is used extensively for marine propulsion and power generation applications. It is a twin spool Gas Turbine Generator (GG) with a High Pressure (HP) spool and a Low Pressure (LP) spool.
Depending on the configuration, the load is directly coupled to either the cold end or the hot end of the Low Pressure spool, eliminating the need for a conventional power turbine.
The engine has a power output of approximately 50 MW, and a LM6000- DLE version was introduced to meet the demands for reduced NOx and CO emissions.
LM6000 Monitoring
The basic monitoring requirements for the LM6000 are defined by GE in the Installation Design Manual (IDM).
The LM6000 is commonly equipped with accelerometer sensors and a basic suite of analog vibration monitor instruments. However, as electrical products age, monitoring system reliability and obsolescence becomes an issue, and enhancement of the monitoring system, to modern digital technology, becomes a technical and economic necessity.
New Generation LM6000 Monitoring
SKF DYMAC and Vibro-Meter’s new generation of sensors and monitoring systems provide a complete solution for the LM6000, for increased monitoring reliability and capability:
• High Temperature Accelerometers – Two (2) per engine
The proven vibration sensor of choice for gas turbines, the latest CA-series piezo-electric accelerometers offer increased reliability and improved immunity to transference vibration from the gas stream and structure.
• Dynamic Pressure Sensors – Two (2) per DLE Engine
Piezo-electric technology is employed in the CPseries sensor to provide a direct measurement of harmful pressure pulsations within the combustion chamber.
• Industrial accelerometers – Two (2) per Gearbox
When a reduction gearbox is required, for a 50 Hz power generation application for example, the use of accelerometers is recommended to capture the high frequency vibrations generated by gear wheels.
• Displacement Probes – Four (4) per Alternator
For journal bearing monitoring, the newest design CMSS-series “proximity” probes offer improved maintainability and reliability over earlier generations.
• Digital Monitoring System
The VM600 monitor system provides a compact and programmable solution. An single monitor card type, the MPC-4, is used for protection of the entire machine train, see Figure 1. Designed for gas turbine use, the MPC-4 permits the consolidation of vibration and combustion protection into a single monitoring system.
In particular, the programmability of the VM600 allows tracking of specific problems such as “Oil in Rotor”, as well as improved vibration analysis and cross tracking of unbalance components.
• Integrated Condition Monitoring
A single
CMC-16 data acquisition interface, Figure 1, provides high performance monitoring, trending and analysis tools integrated in same rack system for increased reliability.
This application note will now discuss in detail the recommended installation for protection and condition monitoring of the LM6000, while remaining fully compliant to the needs of General Electric’s IDM.
LM6000 uses two high temperature piezo-electric dynamic pressure sensors to measure “pressure pulsation” in the annular combustion chamber.
The consequences of excessive pulsations can be catastrophic, buckling of the combustion chamber and leaks reduce efficiency, and subsequent component failure can wreck the hot gas path components downstream. Hence the ability to measure, warn, and protect against these pressures is of vital importance.
The CP-series employs piezo-electric technology to provide a direct measurement of pressure within the high temperature environment of the combustion chamber itself. This offers a superior solution to indirect measurements utilizing industrial grade pressure sensors, which need to use bleed gas, or water-cooling assemblies.
The GE-approved models for mounting on the LM6000 is now the model CP106 from Vibro-Meter, and can withstand temperatures up to 650°C (1202°F). With a dynamic pressure signal, a current modulated output is once again preferred, owing to the low amplitude of the generated signals. This is converted to a mV/bar signal by the transfer function of the optional
GSI-127 galvanic separator.
Gearbox Vibration
On an LM6000 package the temperature environment at the reduction gearbox (if present) is much less demanding than that at the gas generator (engine). Nevertheless, surface temperatures may still rise well above the 120C (248F) rating of general purpose industrial accelerometers.
The Vibro-Meter model CE136 offers a good compromise between high temperature capability, cost, and the frequency response (3 Hz to 7 kHz) needed to capture the high vibration frequencies generated by the teeth meshes within the gearbox.
The charge amplification electronics, rated to 100C (212F), of the CE136 are built into the local sensor cable assembly and hence mounted only a few metres away from the sensor itself. This minimizes degradation of the charge output and removes the need for a separate signal conditioner (required with the higher temperature models in the gas generator). Once again, a current modulated output signal is used, with conversion to mV/g at the separator.
Relative Shaft Vibration
The vibration of the driven component is usually measured by means of non-contacting sensors, known as “eddy current probes” or “proximity probes”. These sensors provide a direct measurement of shaft radial displacement.
These are typically mounted through the bearing cap and targeted directly onto the shaft. The sensor system consists of a probe, cable and an oscillator/demodulator (known as a “driver” or “proximitor”).
A suitable model is the CMSS 68 series from SKF DYMAC.
The probes have a linear frequency range from DC to 10 kHz. The RYTON™ tip material allows the probe to withstand temperatures up to 177C (350F), and differential pressures to 414 Kpa (60 psi).
The voltage output of 8mV/mm is used owing to the relatively short cable run from the engine to the control package. This is passed through an optional MTL5031 galvanic separator at 1V/V transfer function.
Speed Sensors
Magnetic speed sensors would be provided by the OEM on both the High Pressure and Low Pressure shafts. The High Pressure and Low Pressure probes are targeted on 45 and 48 tooth wheels respectively.
Machine Protection – LM6000
A GE IDM compliant machine protection monitor system for the LM6000 is the VM600.
The system uses a single MPC- 4 universal, digital protection module. This module was specifically designed for gas turbine use, from transducer input, through signal conditioning and processing, to shutdown relay contact closure.
Figure 1 illustrates a system. The entire LM6000 driven train may be protected by three or four identical MPC-4 cards.
Optional redundant power supplies are employed for the highest integrity, and a CPU-M display unit also provides dual serial and/or Ethernet connections to a TCS/DCS/ PLC.
Machine Condition Monitoring – LM6000 Fleet
The VM600 permits addition of parallel data acquisition for condition monitoring in the same monitor chassis as that provided for protection - hence ensuring high system integrity without compromising the machine safeguarding function. Any number of 16-channel CMC-16 cards may be placed in any of the 12 available slots, see Figure 1.
Each channel can process and monitor up to 10 spectral bands. The philosophy of condition monitoring of these critical machines is Multi-Parameter Monitoring. That is, the same input signal is processed in different ways in parallel, in order to determine different characteristic vibration parameters. Each parameter may reveal something different about deteriorating engine condition over time.
The CMS-1 software, Figure 28, is particularly suited to monitoring multiple racks that could be only a few meters apart, or located at remote sites hundreds of kilometers away. The bandwidth typically available on an existing
LAN or WAN is sufficient for operation of a centralized server computer, Figure 27.
During transient conditions, the FFT and bands would be monitored closely in order to identify phenomena including:
• High vibration amplitudes
• Combustion Chamber resonance
• External equipment stress/fretting
• Spool nX harmonics
• Bearing defect frequencies
During normal running conditions, the FFT and bands would be monitored periodically to watch for fluctuations in vibration levels, which can occur during low-, part-, or variable-load conditions.
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Item
|
Qty
|
Model
|
Product Number
|
Description
|
|
|
|
|
SENSORS
|
FWD and AFT Accelerometer Chain
|
|
1
|
1
|
CA 303
|
144-303-000-311
|
FWD Accelerometer, -54°C to +455°C (+850°F), 50 pC/g,
1.22m
(48") integral MI cable with stainless steel overbraid and M83723/89Y1020-7 connector
|
|
2
|
1
|
CA 303
|
144-303-000-221
|
AFT
Accelerometer, -54°C to +455°C (+850°F), 50 pC/g, 2.06m (81") integral MI cable with stainless steel
overbraid and M83723/89Y1020-6
connector
|
|
3
|
2
|
IPC 704
|
244-704-000-042
|
Symmetrical
charge amplifier with configurable low-pass and high-pass filters, optional integrator. Voltage or current output.
|
|
4
|
2
|
GSI 127
|
244-127-000-021
|
Galvanic separation
and power supply unit for piezoelectric measuring chain, 2-wire current transmission. 4kV input/output insulation, dynamic
transfer 1 V/mA.
|
|
|
|
|
Dynamic Pressure Sensor Chain (DLE Variant)
|
|
5
|
2
|
CP 106
|
143-106-000-011
|
-96°C to +650°C (-140°F to +1202°F), 232 pC/bar, 1.2 m
MI
cable with overbraid, M83723/89Y10207 connector, special GE flange.
|
|
6
|
2
|
IPC 704
|
244-704-000-042
|
Symmetrical
charge amplifier with configurable low-pass and high-pass filters, optional integrator. Voltage or current output.
|
|
7
|
2
|
GSI 127
|
244-127-000-021
|
Galvanic separation
and power supply unit for piezoelectric measuring chain, 2-wire current transmission. 4kV input/output insulation, dynamic
transfer 1 V/mA.
|
|
|
|
|
Gearbox Accelerometer Chain
|
|
8
|
2
|
CE 136
|
444-136-000-201
|
-54°C
to +260°C, 10 µA/g, 3 m cable protected by BOA, MS 3112
bayonet-locked aluminium connector.
|
|
9
|
2
|
GSI 127
|
244-127-000-021
|
Galvanic separation
and power supply unit for piezoelectric measuring chain, 2-wire current transmission. 4kV input/output insulation, dynamic
transfer 1 V/mA.
|
|
|
|
|
Generator Bearing Radial Vibration (X-Y) Chain
|
|
10
|
4
|
CMSS68
|
CMSS 68-000-00-12-10
|
Probe, 8mm,
3/8-24 Thread, 1.2" to 6.0" Case Length, 1m Cable.
|
|
11
|
4
|
CMSS958
|
CMSS 958-00-040
|
Extension Cable, 4.0m Length.
|
|
12
|
4
|
CMSS665
|
CMSS 668
|
Driver,
200mV/mil (8mV/µm), +/- 5%, 4140 Steel, 90mil (2.3 mm) Range, 5m System.
|
|
13
|
4
|
Barrier
|
MTL 5031
|
Galvanic Separation for 3-wire Eddy Current Probe System
|
|
|
|
|
MONITOR HARDWARE AND SOFTWARE - PROTECTION
|
|
14
|
1
|
ABE-040
|
204-040-100-012
|
Standard 19" Rack 6U high with VME backplane.
|
|
15
|
1
|
PLP-960
|
200-582-960-011
|
Backpanel with status relay, 2x switch and 2x IEC connectors
+ cables, dual AC mains input
|
|
16
|
2
|
RPS-6U
|
200-582-500-013
|
Power supply
unit (max. 2 per rack). Mains input 90 to 264 VAC
|
|
17
|
1
|
CPU-M
|
200-595-033-111
|
CPU-M with front panel display, Single
RS232/485 and Ethernet Configuration
|
|
18
|
1
|
IOC-N
|
200-566-000-HHh
|
I/O
card for CPU-M with 2x RJ45 and 5x RJ11 connectors for single/redundant Ethernet
|
|
19
|
4
|
MPC-4
|
200-510-SSS-HHh
|
Machinery
Protection Card, for 4 dynamic and 2 phase reference channels
|
|
20
|
4
|
IOC-4T
|
200-560-000-HHh
|
6
channel in- and output card for MPC with screw terminals. 4 x relays
|
|
21
|
1
|
RLC-16
|
200-570-000-HHh
|
Relay card with 16 relays with change over contacts
|
|
22
|
1
|
MPS-1
|
209-500-100-013
|
Software
package for configuration of MPC-4. RS232
point to point connection or
Ethernet network. Provides
local and remote access.
Microsoft Windows (98, NT, 2000, XP), English,
French or German
|
|
23
|
5
|
Config
|
DMFS-CON
|
Customer
Specific Configuration and Testing. Per
card (MPC 4, AMC 8, RLC 16, CMC
16)
|
|
|
|
|
MONITOR HARDWARE AND SOFTWARE - CONDITION MONITORING
|
|
24
|
1
|
CMC-16
|
200-530-SSS-HHh
|
Condition Monitoring
Card, for up to 16 dynamic / process channels,
up to 4 which can be tacho / phase reference channels. Provides advanced FFT analysis, band extraction, processing and level checking (max.
12 per rack)
|
|
25
|
1
|
IOC-16T
|
200-565-000-HHh
|
16
channel in- and output card for CMC with screw terminals, and multidrop RS485 ports for serial
networking. (1 required per CMC
16, max. 12 per rack).
|
|
26
|
1
|
CMS-1
|
209-500-600-SSs + Code
|
Condition
Monitoring Software Package for Transient Vibration Analysis with CMC 16 Hardware. Microsoft Windows 98, NT, 2000 and XP
Operating System. Sybase SQL
Database Server Licence and 5 Concurrent User Client Display
|
|
27
|
1
|
Config
|
DMFS-CON
|
Customer
Specific Configuration and Testing. Per
card (MPC 4, AMC 8, RLC 16, CMC
16)
|
|
|
