TL;DR
Steam or vapor at the shaft seals with falling condenser vacuum usually means the gland steam regulator is set too high or too low, or the gland condenser exhauster fan has failed. Check the regulator setpoint and exhauster first.
What you might see
- steam or vapor visible at turbine shaft end seals
- gland condenser vacuum dropping
- air in-leakage to condenser rising
- gland steam regulating valve at an unusual position
Likely causes
Gland steam regulating valve set too high, forcing steam out through the outer seal rings to atmosphere
Gland condenser exhauster fan not running, allowing steam to escape rather than be drawn in
Worn or eroded seal labyrinth clearances allowing more leakage than the system can handle
Gland steam supply pressure fluctuating with load, requiring regulator re-tuning
Required tools
- DCS gland steam pressure and valve position data
- Manometer or pressure gauge for gland system
- Condenser vacuum and air in-leakage trend data
Safety first
- Steam at shaft seals is at elevated temperature and pressure. Wear heat-resistant PPE when inspecting seal areas on a running unit.
- Do not adjust gland steam regulator setpoint without understanding the full system response. Too low a setpoint allows air in-leakage into the condenser, reducing vacuum.
Procedure
- 1
Observe the gland steam regulating valve position and the gland steam supply header pressure. Confirm the regulator is maintaining pressure within the OEM setpoint band, typically 0.5-1 psig above atmospheric.[1]
- 2
Check that the gland condenser exhauster fan is running at full speed and the exhauster suction is drawing vacuum.
Warning: High-pressure steam at turbine shaft seals is at elevated temperature. Approach the shaft seal areas with caution and use appropriate PPE including heat-resistant gloves and face shield. - 3
Inspect the gland condenser shell for debris or blockage in the air vent path.
- 4
Review the condenser air in-leakage rate by trending condenser absolute pressure at the same load over time. An increasing trend confirms seal deterioration.
- 5
If the gland steam regulator is hunting or not holding setpoint, check the controller tuning and the steam supply root valve position.
- 6
If the physical seal clearances are worn, plan a gland seal packing replacement at the next planned outage.
Sources
GE Vernova GE D / H Class Steam Turbine general technical documentation, GE Vernova
Steam turbine gland steam seal system operation and maintenance, general power generation references (general)
More guides for GE Vernova GE D / H Class
How to diagnose blade path deposits and performance deterioration on a GE Vernova GE D / H Class steam turbine
A gradual heat rate increase with no load change is almost always silica or sodium deposition on turbine blades. Check steam chemistry and compare blade path pressure ratios to baseline.
How to correct high vibration from slow-roll rotor bow on a GE Vernova GE D / H Class steam turbine
A 1x vibration that is high on roll-off but decreases with time is almost always a thermal rotor bow from cooling unevenly on the turning gear. Do not attempt to rush the start. Continue slow roll until eccentricity returns to normal limits before accelerating.
Stop fixing the same fault twice.
Dovient turns guides like this into your team's shared playbook, with AI that catches recurring issues before they break the line.