What to do if there is too much oil in the oil-gas vent pipe of a carbon dioxide centrifugal compressor?
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Our factory’s compressors use instrument air and carbon dioxide from inter-stage leaks as the gas for shaft seal isolation. However, the oil vent lines contain a large amount of oil, resulting in significant losses. How can this problem be solved? The pressure of the instrument air has dropped to 10 KPa. I would appreciate some guidance from those who are more experienced
This issue has little to do with the pressure of the isolation gas used, and moreover the pressure of the isolation gas cannot be reduced arbitrarily, as this can easily lead to oil entering the seal or even the cylinder block. Where is the large amount of oil and gas escaping from? Is it from the oil tank or from the cylinder seals? If it’s from the oil tank, it means the temperature of the returning oil is too high; in that case, the oil feeding temperature can be reduced slightly – try changing it from 48 to 46. If there’s no significant improvement, then reduce the nitrogen pressure in the oil tank gradually, but don’t make too big of changes. Proceed slowly. If more oil comes out of the cylinder or from the bearings, it means that the bearing temperature is too high, or the amount of oil applied is excessive. Adjust the amount of oil applied accordingly; in domestic generating sets, the oil supply for each bearing can be adjusted, while this is generally not possible in imported generating sets. The most important thing is to reduce the bearing temperature; find a way to do that, as otherwise this problem won’t be easy to resolve.
It is the oil and gas vent line at the cylinder block shaft seal that discharges a large amount of oil and gas. The bearing temperature is around 80°C, which shouldn’t be considered high.
The pressure of the balance tube isn’t set correctly, or the seal is damaged!
80 degrees is indeed not high. Based on this, my preliminary assumption is that there is a problem with the isolation gas seal in the dry gas seal system. The isolation gas and the secondary seal gas are supposed to merge and then be discharged through the secondary seal; the amount of gas that escapes through the comb-shaped elements to the bearings should be very small. If the isolation gas gets into the bearings, it indicates that there is a problem with the comb-shaped seal used for isolating the gas. When there’s a chance to shut down the system for maintenance, check these comb-shaped elements to see if the gaps have become too large. It’s not advisable to lower the pressure of the isolation gas arbitrarily, as too low a pressure can lead to oil getting into the dry gas seal, which is dangerous.
Is a balance tube a connecting pipe for the leakage of inter-stage seal gas? How is this pressure adjusted? ?