Recently, a pump developed a problem; I hope this will be useful for everyone’s future work

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Pumps A and B are two-stage pumps with double-end support, and the pumped medium is liquid hydrocarbons. Inlet pressure is 0.66 MPa, and outlet pressure is 2.2 MPa. Pump A is in operation while Pump B is on standby. The mechanical seal used is a series-type PLAN52 seal. During the New Year, the motor bearing of pump A made a loud noise; therefore, it was switched to pump B. After 2 hours of operation, the bearing on the non-driving side (thrust bearing) burned out, and the pump was stopped promptly due to this discovery. After disassembly and repair, inspection showed no damage to the shaft. The rechecked inspection data for the rotor’s positioning shows normal values with no changes. So, after replacing the bearings, the pump was started again. After running it for a few hours, it was found that the bearing temperature remained high at around 70 degrees; however, the lubricant had not deteriorated or emulsified. The pump was stopped once more, and no abnormalities were detected in the bearings. It was suspected that the bearing clearance was too large, so a 0.10 MM copper shim was added between the two bearings. After that, the pump was kept running; the bearing temperature remained normal. However, after about 2 months of operation, the temperature of the thrust bearing suddenly rose again to 65–70 degrees. The pump was stopped for inspection, and no abnormalities were found in the bearings. As a solution, the SKF7314 bearing was replaced with an NSK7314 bearing, and a 0.20 MM copper shim was placed between the two bearings. The pump has been operating normally since then. The bearing temperature is around 40 to 45 degrees. However, the vibration of the front and rear bearings increased by 5.0 MM/S. It feels like the pump as a whole is vibrating. It’s very much like a pump that is being emptied. It’s not like the drawing is that intense. I have a question for everyone. I’m not very familiar with the technology involved; I only remember that the inlet pressure of liquid hydrocarbon pumps is usually quite high, around ten-odd kilograms. Could it be that the inlet pressure of this pump is a bit low, resulting in the liquid hydrocarbon vaporizing? The gland temperature of the non-driven seal is relatively high; it may feel around 50 degrees when touched. The inlet pipeline of the seal oil tank is at normal temperature, but the outlet pipeline has a higher temperature, roughly similar to that of the seal gland. The temperature of the seal at the driven end is normal. Could someone who is good at this explain it? Let’s all improve and grow together. Thank you