Dry gas seal
Thread Content
Could the dry gas seal be damaged when the unit is in low-speed cranking mode?
Yes, sealing is achieved by using high-speed airflow to separate the rotating ring from the stationary ring; if the rotation speed is too low, the dynamic pressure effect cannot be established, leading to easier wear
No, low-speed cranking will not cause any damage; since the speed is low, there is no significant friction between the rotating and stationary rings, and thus no substantial heat is generated
Yes, when performing low-speed barring, it is required that the temporary seal gas for the dry gas seal be turned on; this gas should be turned off only after the unit is operating under normal pressure!
During low-speed turning, it is required that the temporary sealing gas for the dry gas seal be turned on; the pressure of the air film increases gradually from the outer diameter to the groove diameter, while it decreases gradually from the groove diameter to the inner diameter. The increased pressure at the end face results in an opening force that is greater than the closing force acting on the sealing ring, thereby creating a very thin layer of air film (1–3 µm) between the frictioning surfaces, allowing the seal to operate in a non-contact manner. The formed gas film completely blocks the leakage path for the relatively low-pressure sealing medium, achieving zero leakage or zero escape of the sealing medium. Therefore, the dry gas seal of the low-speed turning gear is not affected.
Sealing gas must be supplied, especially for the booster pump
Therefore, the manufacturer’s instructions for the sealing system state that the main sealing gas must be supplied before starting the turning of the shaft