Turbine technology | Monitoring and diagnostics
Dealing with steam turbine blade failures in ageing plants
One of the worst case maintenance scenarios for an aged steam turbine is the loss of blades during peak power demand — a scenario that occurred at Genesis Energy’s fossil-fired Huntly power station. The event happened so rapidly that proactive measures were impossible. Instead, after-event monitoring and diagnostics were employed to isolate and identify the issue. Repair options were extremely limited, needing to fit into a constrained outage window
Simon Hurricks, Predictive Maintenance Engineer, Genesis Energy, Huntly Power Station, New Zealand, and Mike Hastings, Senior Application Engineer, Brüel & Kjær Vibro, Denmark
Figure 1. The Huntly machine hall (left) showing all four 250 MW turbo-generating units. The Compass 6000 VC-6000 monitoring modules (middle), initially used for units 2 and 4, are being replaced by SETPOINT on unit 2 (right). SETPOINT is already installed on unit 1 and will soon be operational on unit 4
ACTIVE THRUST LEFT HP CYL EXP
HP DIFF EXP 1
HP DIFF EXP 2
BRG 1X AND
1 BRG 2/3X 2 ACCEL 2 HP ECCENTRICITY 1 HP ROTOR LONG
IP AND LP ROTOR LONG
2
IP DIFF EXP 1
IP DIFF EXP 2
ACCEL 3 ACCEL 4 IP ECCENTRICITY
BRG 4X AND
ACCEL 5
BRG 5X AND
1 LP ECCENTRICITY 2
LP DIFF EXP 1
BRG 6X ACCEL 6
LP DIFF EXP 2
BRG 7X ACCEL 7 BRG 8X ACCEL 8 PHASE TRIGGER ACCEL 10
Located on the Waikato River, between Hamilton and Auckland in New Zealand, the Huntly power station was commissioned from 1982 to 1985. It features four 250 MW single reheat turbo-alternators manufactured by Parsons (UK) (see Figure 1). Unit 3, decommissioned in 2013, now serves as a source for spare parts. Notably, the turbines are installed on isolated steel support structures engineered for earthquake protection. These low-tuned structures have vertical resonant frequencies below the turbine operating speed, creating unique monitoring challenges.
PROBE ORIENTATIONS
VIEWED FROM GENERATOR TO TURBINE DIRECTOR OF ROTATION: CCW
ACCEL 9 ACCEL 12 ACCEL 11
TURBINE HP
TURBINE IP
TURBINE LP
GENERATOR
PE
EXCITER
C
ACCEL 1 BRG 1Y
RIGHT HF CYL EXP
AXIAL POS 1 AXIAL POS 2
BRG 2/3Y
BRG 4Y
BRG 5Y
BRG 6Y
BRG 7Y
BRG 8Y
Table 1. Displacement sensors Measurement, CM/MPS, access Location
Casing expansion (mm) – 50 mm range sensor
Differential expansion (mm)
X-Y radial bearing vibration – 1X, 2X vector displacement magnitude (μm) and phase (degrees)
Eccentricity (μm, peak- peak)
2x axial position (mm)
CM DCS, CMS
CM, MPS
DCS, CMS
HP casing bearing #1
HP, IP, LP shafts (2x sensors each)
CM CMS only
Bearing #1-XY, #2/3-XY (HP-IP shaft coupling), #4-XY, #5-XY, #6-XY, #7-XY, #8-XY
CM, MPS
CM, MPS
Notes: CM - Condition monitoring
CMS - Condition monitoring system MPS - Machine protection system
DCS, CMS
DCS, CMS
Bearing #1-X, #4-X, #5-X for HP, IP, LP shafts
Thrust bearing (bearing #2)
Figure 2 sensor symbol
LEFT HP CYL EXP RIGHT HP CYL EXP
HP DIFF EXP 1, HP DIFF EXP 2 IP DIFF EXP 1, IP DIFF EXP 2 LP DIFF EXP 1, LP DIFF EXP 2
BRG 1X-AND-HP ECCENTRICITY, BRG 1Y BRG 2/3X, BRG 2/3Y
BRG 4X-AND-IP ECCENTRICITY, BRG 4Y BRG 5X-AND-LP ECCENTRICITY, BRG 5Y BRG 6X, BRG 6Y BRG 7X, BRG 7Y BRG 8X, BRG 8Y
BRG 1X-AND-HP ECCENTRICITY BRG 4X-AND-IP ECCENTRICITY BRG 5X-AND-LP ECCENTRICITY
AXIAL POS 1, AXIAL POS 2
DCS - Bandpass vibration measurement BP - Bandpass vibration measurement
Table 2. Accelerometers Measurement, CM/MPS, access
BP (10-1kHz) vibration RMS, mm/s CM, MPS
1X, 2X vector vibration magnitude (mm/s) and phase (degrees)
Notes: CM - Condition monitoring
CMS - Condition monitoring system MPS - Machine protection system
CM, MPS
DCS, CMS
CMS only
Figure 2. Placement of displacement sensors and accelerometers on the Huntly turbo-generator units. Highlighted in yellow is the IP turbine section, the focus of this case study
Location Figure 2 sensor symbol
Bearing pedestal #1, #2, #3, #4, #5, #6, #7, #8
ACCEL 1, ACCEL 2, ACCEL 3, ACCEL 4, ACCEL 5, ACCEL 6, ACCEL 7, ACCEL 8
DCS - Bandpass vibration measurement BP - Bandpass vibration measurement
16 | July/August 2025|
www.modernpowersystems.com
Source of images: Huntly Power Station/Brüel & Kjær Vibro
BRG 1
BRG 2
BRG 3
BRG 4
BRG 5
BRG 6
BRG 7
BRG 8
B 9
B 10
B 12 B 11
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