Dry gas seal issues
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I would like to ask the experienced colleagues: what could be the possible reasons for a sudden increase in the flow rate of the primary sealing gas in a dry gas seal?
Is the main seal air control valve opened too wide? It’s recommended to check it
First, check the outlet pressure and flow rate of the dry gas seal; it could be caused by a failure of the dry gas seal. . .
It’s possible that the pressure or flow rate of your process gas has increased, which in turn has led to an increase in the amount of air used for the main seal.
It doesn’t increase all the time; rather, during the period when the compressor reduces its load and the turbine slows down, the flow rate of the seal air increases sharply before returning to normal levels. I’m not sure what the cause is. Please help analyze this for me
I also look forward to analysis from experts. Is it a equipment issue or a process issue?
Reply to 5# zjy0501: This is how I analyze it: Under normal conditions, the main sealing gas enters the machine body through a comb-tooth seal. For the main sealing gas to enter the vessel, its pressure must be slightly higher than the pressure inside the vessel; otherwise, the gas inside the vessel will escape outward ； When the compressor operates at a reduced load or the turbine slows down, the pressure inside the casing decreases; as a result, the pressure difference between the main sealing gas and the pressure inside the casing increases, leading to an increase in the flow rate of the main sealing gas.
Under normal conditions, the main seal gas enters the pre-seal chamber and the leakage chamber respectively through the air film gaps between the stationary and rotating rings of the dry gas seal. The pressure of the main seal gas is 0.3 MPa higher than that of the pre-feed gas. By checking the composition of the leaking gas, it is possible to determine in which direction the main sealing gas is leaking. An increase in the flow rate of the primary sealing gas occurs only when there is axial movement of the rotor between the rotating ring and the stationary ring, or when a large gap appears as a result of damage to one of these rings. The situation you described may be caused by significant axial movement of the rotor, as well as a slow return to their original position of the spring elements and elastic sealing rings used for sealing. This phenomenon needs to be continuously monitored in order to make the right judgment.
Reply to 5# zjy0501: After adjusting the speed, changes in axial force cause the axial displacement to shift to one side. However, after long-term use, the tracking ability (automatic compensation) of the dry gas seal may not be very good, and the friction pairs may not make good contact, resulting in an increased flow rate. Over time, as the friction pairs fit together properly automatically, the flow rate returns to normal.
The instrument may give false readings; the pressure of the sealing gas might be too high； If the throttle valve is stuck in an overly open position, it can be adjusted to a smaller setting
It seems that the names of the various stages of the dry gas seal need to be standardized. It is best to include the English names of the various sealing levels, so that it is clear which part is being referred to