What is the reason for continuous gas presence in the low-temperature chamber of a high-temperature separation type shielded pump?
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In my workshop, there is a pump used in the gasoline hydrogenation reaction cycle; the temperature of the fluid handled by this pump is 130°C, the inlet pressure is 5.0 MPa, and the outlet pressure is 5.8 MPa. High-temperature separation type shielded pump (with connector). Before startup, the exhaust gas was normal; liquid was observed at the outlet drain and at the high points on the side of the bearing detectors, and the circulation water was functioning properly. However, after the pump had been running for about 2 hours, the temperature of the rear bearing rose to 50°C+ (this temperature is theoretically acceptable, but the pump was serviced today; the temperature here was lower before the service, indicating that there is a problem). A small amount of gas could be seen being discharged from the top vent valve; after all the gas was expelled, another small amount of gas appeared when venting was attempted again about 10 minutes later. After approximately 16 hours of operation, there was persistent suspicion of abnormal heat generation in the bearing here, so it was disassembled for inspection. It was found that the rear bearing had uneven wear. There is still air after replacing the bearing. During maintenance a few days ago, due to wear of the pump’s ring, the shaft was bent and adjusted to 6 degrees; all bearings, thrust discs, and shaft sleeves are new. I’m also puzzled by 16 hours like this. Does anyone know where this gas comes from? The other spare pump does not have this issue. In high-temperature separation type machine pumps, the high-temperature chamber and the low-temperature chamber are separated from each other by the gap between the connecting element and the bushing; the medium in the low-temperature chamber is continuously cooled, so this situation should not occur. The pump is BA47-416J4BM. I’m extremely puzzled; it has troubled me for a long time, keeping me awake at night. I seek an answer.
The shaft jumps by 6 positions, which is quite significant. Let’s take a look at the control values specified by the manufacturer; I’m not very familiar with shielded pumps
I’ll check carefully when I disassemble it next time; 6 should be good enough for this shaft. It came back straight from 18 lanes
When the temperature is lower, the medium’s ability to dissolve air increases… For example, is there more air in water at 100 degrees boiling point, or in water at 50 degrees? Your current operating conditions are not the designed ones; if there are problems, it is necessary to ensure that the pump operates within the allowable operating range!
The gas generated should be the medium gas resulting from the vaporization of the medium; the thrust disk bearings overheat due to excessive axial forces. Check the gap of the mouth ring.
Okay, this is one direction for maintenance. The axial force is too high, causing the medium at the thrust disc location to vaporize. Let me think about it
The temperature of my medium is around 130, and the same is true for the pumped medium. That’s the design
1. What is the medium? Gasoline containing dissolved hydrogen? 2. The poster said that the standby pump does not exhibit the phenomena described above, with only one unit having air in it; this is rather difficult to answer.
Check whether there is enough axial play; if it is too small, severe friction will occur between the bearing and the thrust disc, leading to overheating and vaporization. A humble opinion
Excessively high material temperature may lead to vaporization. You might consider trying to cool it down with cooling water.
The bearing clearance and thrust clearance – it’s likely that the friction is high and the medium has vaporized