Air compressor shaft displacement
Thread Content
An air compressor with single-axis four-stage compression and an air flow rate of 107,500 m3/h is experiencing a problem: we regularly clean the compressor’s impellers, and during this cleaning process the pressure drop across the compressor increases by about 2 kPa, while the angle of the guide vanes increases by 3–4 degrees. Starting from the moment of cleaning, the exhaust temperature of the unit gradually decreases (from 61 degrees to 50 degrees). The temperature of the main bearing surface also decreases, from 58 degrees to 55 degrees, whereas the temperature of the auxiliary bearing rises from 45 degrees to 49 degrees. The shaft displacement decreases from 0.168 mm to 0.134 mm. After 1 hour, the cleaning process is stopped; the pressure drop and the angle of the guide vanes return to normal levels. However, the shaft displacement and the temperature of the main bearing remain unchanged – the temperature of the main bearing rises to 60 degrees, and the shaft displacement is 0.173 mm. In response to the above phenomena, the curve from a flushing operation carried out last year was reviewed; after that flushing, the temperature of the thrust bearing increased by several degrees, and the shaft displacement rose from 0.134 to 0.160 mm! What does the above indicate?
Temporary minor fluctuations. It is normal.
When we were driving 14 years ago, the shaft displacement was 0.11; it’s now 0.17, and it’s on the rise – it just doesn’t seem normal
Under normal conditions, the main thrust acts on the unit during operation, with the temperature being slightly higher than that of the secondary thrust. When scaling occurs severely in the impeller flow channels and outlet bends, the axial force will point in the opposite direction; meanwhile, the effect of water mist during flushing can also cause changes in the axial force.
Our shaft displacement changes all occur after water flushing; I don’t know why Has a permanent change taken place?
Severe scaling on the impeller and flow channels can cause the axial force to change direction; there are indeed such examples, such as in coal chemical feed gas compressors (producing gas using Entho furnace technology).
Firstly, fluctuations in displacement and temperature during the rinsing process are normal, because: 1. The design and selection of compressors are generally adjusted based on the components involved； 2. During the cleaning process, the addition of water mist temporarily alters the composition of the compressed medium, resulting in changes in power and compressibility. From 2014 to the present, after two years of operation, a change in displacement has occurred; the possible reasons are as follows: 1. Instrument-related issues. Displacement measures the change in relative position; if the probe becomes loose, it may cause variations in the displacement measurement ； 2. Reasons for ring wear. It is recommended to pay attention to the above two points and keep an eye on them during the next maintenance. If it is indeed the mouth ring that is wearing out, a trend line can be drawn to predict the approximate time when the clasp will need to be replaced next.
I think a mouth ring is more likely, as the temperature of the thrust bearing has also increased by 5 degrees from 2014 to now