I would like to ask about the reasons for high temperatures in the main bearings of reciprocating compressors
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Dear experts, I am facing a problem: after a major overhaul of the reciprocating compressor, the temperature of the main bearings (sliding bearings) is extremely high, ranging from 59 to 63°C. The clearance between the shaft and the bearing shells is normal, the oil pressure is normal, and the control system is also functioning properly. Yet, the temperature of the main bearings rises to 59–63°C already after just 1 hour of operation. May I ask the experts what causes the high temperature of the compressor’s main bearing?
As a supplementary point, there are corrosive pitting on the part of the spindle that comes into contact with the bearing shells. Is the extremely high temperature related to these pittings on the spindle?
Personally, I don’t think 59–63°C is considered high. Of course, this needs to be determined by comparing with past data. High bearing temperature: 1. Lubricating oil pressure – normal, rule out; 2. Clearance – normal, rule out; 3. Oil inlet temperature – to be checked; 4. Impurities in lubricating oil – to be checked; 5. Compressor load – to be checked; 6. Loss of babbitt in bearing shells – to be checked; 7. Clogged oil passages – to be checked
@In Spoole, the oil inlet temperature is 42 degrees. After the major repair, lubricating oil of grade 68 was newly installed. The turning gear operates smoothly, with no blockages in the oil circuits. The bearing shells have been replaced as well, and there is no signs of babbitt shedding.
The oil temperature is good. It seems that oil grade 68 is not very commonly used for piston compressors. Is it always grade 68? VG100 is generally used more often. What is the normal temperature of the front axle bearing pads before maintenance? Personally, I think the temperature is okay; it’s good that it isn’t rising continuously.
@Spoole: Before maintenance, the highest temperatures of A, B, C, and D were 58 degrees
I don’t think there’s a problem with this temperature, as long as it doesn’t keep rising.
You didn’t mention the overall load on the compressor, so I assume it’s the same. So, the oil enters at 42°C, and the bearing temperature is 59–63°C; assuming a simple calculation, this gives a bearing temperature rise of 17–21°C. Compared to before maintenance, the bearing temperature was no more than 58°C, which is less than 16°C; in fact, the difference isn’t that significant. It’s possible that a slight loosening of the bearing temperature sensing element could cause such a deviation. Personally, as long as the bearing temperature does not keep rising, at the current temperature level, it’s sufficient to keep an eye on it. But it can be considered to check the temperature sensing element and bearing clearance during the next shutdown.
For domestically produced Shengli Steam Turbine’s 4M125 or 4M150 models, such temperatures are normal; what matters is whether they can remain stable and allow for long-term operation.
What are the inlet and outlet water temperatures and pressure difference of the oil cooler?
This operating temperature is acceptable. Additionally, during the hot summer months, the ambient temperature should be taken into account; it would be a good idea to clean the coolant in the oil cooler and check whether it’s dirty