Troubles regarding the leakage of basic bearing lubricant.
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The fitter becomes less and less understanding as he keeps working. There is a centrifugal pump, with a variable-frequency motor (5HZ~50HZ). This motor experiences severe oil leakage during certain periods of time, and a pattern has been observed in these leakage episodes for now. Lubricating oil is leaking between the bearing gland seal and the shaft; this situation did not occur before but has appeared recently. It has been confirmed that the position of the gland return oil hole is correct and not blocked, the oil filler cap is functioning properly, the breather hole is in normal condition, the bearings are operating well, and the oil level is at 1/2 of the oil sight glass, about 1.5 cm below the oil seal gap. Where is the problem? 1. Is it due to the higher temperatures in winter, which improve the fluidity of the lubricant? 2. Is it due to wear causing an excessive gap in the oil seal? 3. Is it caused by an increase in frequency? 4. Since the materials of the pump body and the shaft are different, their thermal expansion rates should be different – could this lead to an increased gap? I would appreciate some advice from an expert. Could you share any data on the relationship between lubricant or metal and temperature?
What medium does the pump transport? What is the rated flow rate? The frequency conversion range of the motor is too wide (is there a mistake)? Is the bearing a sliding bearing or a rolling bearing? What is the structure of the oil seal? Since there are doubts regarding the frequency converter issue, has the frequency range during leakage as well as the flow rate range at that time been checked? Is the bearing vibration higher when there is leakage compared to when there is no leakage? Before the leakage occurred, were there any sudden changes in parameters such as the flow rate and pressure of the medium pumped by the pump? Furthermore, the motor shaft may shift axially during frequency conversion. All of these need to be verified and analyzed carefully.
The pump medium is formaldehyde. For motors with variable frequency functionality, the variable frequency range indicated on the nameplate has been verified to be correct. The bearing is a rolling bearing. The oil seal is of the comb-tooth type, and the technicians are unaware whether variable frequency is used. Since I wasn’t at the scene when it leaked, nothing could be compared. I really didn’t know about the motor shaft shifting issue; I’ll keep an eye on it. What conditions can cause lubricant leakage? I’d like to ask
It is recommended to clean the oil baffle and oil return channels at the inner seal of the bearing. Usually, splashed oil accumulates at the seal area inside the bearing housing; the oil that is trapped there flows back through these channels. If these channels become blocked, oil will leak out. This place is often overlooked during maintenance; it’s worth taking a look. Also, check whether the oil type matches the specifications, especially the viscosity value. (For reference)
Thank you for the reply; it was already cleaned up promptly during the repair.
It may be caused by an excessive gap; it is recommended to replace the gland with a new one!
1. It is recommended to replace the bearing cover. 2. The oil level must be kept at a normal level. 3. The oil slinger in the bearing housing can be removed.
If the original design relied on oil slinger splash lubrication, the oil slinger cannot be removed blindly； My personal suggestion is as follows: Determine whether your actual oil level is within the required range. If it is, check again the assembly clearance of the oil seal, as well as whether the oil return holes allow proper oil return. Also, verify once more that the exhaust holes are unobstructed. Observe whether there is an increase in oil fumes compared to before; if there is an increase and your lubricant level remains unchanged, it indicates that there has been a change in operating conditions. In such cases, you need to further investigate whether there has been a change in load. An increase in oil fumes, without an increase in the size of the exhaust holes, could lead to leakage of lubricant!
Is it confirmed that the breathing holes are unobstructed? Smooth flow and unobstructed passage are two different things; it is recommended to check the breathing holes again. Replace the lubricant; it’s possible that it has deteriorated after being used for a long time.