Timing For Opening Turbine Steam Seals

During a cold start of a steam turbine, the gland seals behave much like an athlete requiring a warm-up. Following boiler ignition but prior to the rotor rolling off, the gland seal steam supply must be activated in advance:

Temperature Matching: Low-pressure steam is used to preheat the gland seal housing, thereby preventing thermal shock.

Pressure Control: A slightly positive pressure of 0.02–0.05 MPa is maintained to prevent air ingress.

Timing: Activation typically commences once the main steam temperature reaches 150°C.

As the rotational speed approaches a critical threshold, the gland seal system undergoes a significant adjustment:

Pressure Upgrade: The system switches to a higher-pressure steam source (e.g., 0.2–0.3 MPa).

Seal Reinforcement: The steam supply flow rate is increased to establish a stable sealing ring.

Timing: This transition is generally completed before the rotational speed rises to 500 rpm.