Leakage gas from the primary seal air of the centrifugal compressor
Thread Content
The pressure of the leak gas from the primary seal of the centrifugal compressor in our unit is above the specified range. Initially, the management decided to disable the pressure interlock mechanism so that the compressor could continue operating until maintenance could be carried out. The flow rate of the leak gas is also above the specified range; it’s not possible to determine the exact amount. The primary seal is supplied with process gas at the outlet. Is it possible to reduce the flow of this process gas to the seal chamber in order to decrease the leakage?
In this situation, there’s nothing to do; just focus on the temperature of the thrust bearings under axial force.
The pressure of the leaked gas should not exceed the pressure of the secondary sealing gas
Take a close look to see if the drain valve of your dry gas seal filter is open. Generally, the drain line is connected to the leak gas pipeline, which can cause pressure interference; we have encountered this problem before.
Here’s a suggestion: generally, the secondary gas system does not have a chain reaction effect. Turn off the secondary gas immediately, and then check the value related to the leakage of the primary gas; that value will represent the amount of gas leaking from the primary system. Immediately open the secondary gas valve afterwards
Do not do this. You can ask the instrumentation team to adjust the range of the flow meter, so that you can get an approximate estimate of your leakage rate. Additionally, you can find a drain line on the flare line, take samples for analysis to determine the content of the medium, and use these methods to decide whether your unit can continue to operate
What is the basis for making such a judgment?
Won’t doing this cause damage to the secondary seal?
Blocking the pressure signal in this way shouldn’t work, logically speaking. What are your company’s rules regarding bypass interlocks? Is it necessary to follow proper procedures? Additionally, closing the valve that controls the process gas at the outlet should not be effective; the supply flow rate is controlled by automatic control valves
Generally, such problems are caused by excessive axial displacement, which leads to damage to the air seal. The structure of dynamic seals is usually a comb-tooth type seal, and excessive shaft movement will result in abnormal leakage. Therefore, on the premise of ensuring safe production, everything should be maintained as much as possible; otherwise, maintenance must be carried out in advance. Another possibility is that damage to the sealed rack caused by foreign objects can also lead to an excessive leakage rate. For reference.
You mean that shaft displacement increases the thickness of the air film between the stationary and rotating rings, resulting in an increased leakage rate. However, the dry gas seals on the low-pressure side and the high-pressure side are symmetrically arranged; if it is caused by shaft rotation, then the thickness of the gas film on the other side must decrease, or should this be verified by reducing the load?