【Q&A Question 073】2016.07.02

For mechanical pumps, the most common issue is a lack of lubrication or poor lubrication conditions. This causes the bearing to overheat, eventually preventing it from rotating and causing it to lock onto the shaft. This is called shaft holding. Another type of failure is shaft seizure caused by static and dynamic friction. In short, a certain component of the stator has stuck to a certain component of the rotor, preventing it from rotating. Shaft seizure is a type of equipment failure; in severe cases, it can lead to the destruction of a certain component of the pump or even the entire pump. Special attention should be paid to this during routine inspections and maintenance!

The common issue is a lack of lubrication, or poor lubrication conditions. This causes the bearing to overheat, eventually preventing it from rotating and causing it to lock onto the shaft. This is called shaft holding. Shaft seizure caused by static and dynamic friction. It’s because a certain component of the stator and a certain component of the rotor have stuck together, preventing it from rotating. Shaft seizure is a type of equipment failure; in severe cases, it can lead to the destruction of a certain component of the pump or even the entire pump

:(1) Insufficient lubricating oil； (2) The lubricating oil is degraded, emulsified, or contains impurities ； (3) Cooling water interruption ； (4) Bearing damage ； (5) Water leakage in the bearing housing.

Shaft seizure refers to the sticking of the bearing inner ring to the shaft. Bearing overheating causes the gap between the shaft and the bearing to decrease, which leads to shaft seizure.

A pump shaft seizure occurs when the bearing gets stuck to the shaft, and it is closely related to overheating of the bearing housing. Before the pump shaft was seized, excessive oil tank temperature and noise occurred due to heating; the temperature at the friction points could reach several hundred degrees, or even over a thousand degrees. It can melt the bearing balls onto the shaft; therefore, when it is detected that the temperature of the bearing housing exceeds the specified limits, the pump should be stopped immediately, and a blacksmith should be called to inspect it. If you notice the shaft turning red, never pour water on it. After stopping the pump and allowing it to cool down, have a blacksmith inspect it.

What is pump shaft seizure? What is its relationship to bearing heating? A pump bearing seizure occurs when the bearing gets stuck to the shaft; this is usually caused by overheating of the bearing, and most often it results from poor lubrication. .

The pump shaft seizure is caused by bearing overheating, expansion, and loss of rotational function. Additionally, particles in the medium inside the pump can clog the impeller, preventing the pump from rotating. There are many reasons for this, including: (1) poor manufacturing quality of the shaft. The surface roughness of the journal is high, and its cylindricity accuracy is low; as a result, after installation, the fit between the surface of the journal and that of the bearing shell is poor, with too small a contact area, which makes it difficult to form an oil film and leads to dry friction. 　　(2) The manufacturing quality of the bearing shells is poor. The alloy quality is poor, the alloy components are loose, and the surface roughness of the bearing shells is beyond acceptable limits; as a result, an effective lubricating film cannot be formed between the shaft and the bearing shells. 　　(3) The bearing cover is deformed, there is a gap on the back side of the bearing bush; the alloy does not fit tightly against the bearing bush, resulting in loosening and separation, which blocks the oil passages and causes a disruption in oil supply, leading to dry friction. 　　(4) Incorrect installation of the bearing shells, improper adjustment of the clearance, or an excessively small contact area can all make it difficult for a lubricating oil film to form at the contact surface between the shaft and the bearing shells. 　　(5) The torque of the bolts used to secure the bearing shells is too low, or the anti-loosening measures for these bolts fail; as a result, the bearing shells become loose, which changes the gap between the shaft and the bearing shells and thus affects lubrication. 　　(6) If centralized lubrication is used, the oil supply pressure is low, making it difficult to deliver oil to the designated lubrication points, which results in dry friction of the bearing shells. 　　(7) The oil passage is blocked by impurities, preventing the oil from reaching the bearing shells and resulting in dry friction between the shaft and the bearing shells. 　　(8) The oil pipeline is damaged, causing the pressure in the oil circulation supply system to drop, and making it difficult for the oil to reach the designated lubrication areas. 　　(9) If the pump is lubricated using an oil slinger, the slinger will not rotate, and as a result, the oil will not be carried along. (10) The amount of lubricating oil in the bearing housing is too low, preventing the bearing shells from being properly lubricated. 　　(11) As it penetrates into the engine oil, it causes the oil to emulsify and deteriorate, resulting in a decrease in viscosity or even its complete loss; this prevents the formation of an effective lubricating film on the surfaces of the shafts and bearing shells, leading to severe dry friction. 　　((12) Using engine oil with too high viscosity and freezing point in winter, or using low-quality oil, prevents effective lubrication of the shaft journals.

A pump seizure occurs when the bearing gets stuck to the shaft, and it is closely related to overheating of the bearing housing.

Due to high temperatures, the bearings lose their ability to rotate (such as the bracket breaking or the balls getting stuck), which ultimately results in the shaft being unable to turn; the bearings and the shaft become firmly locked together. This situation often leads to serious accidents such as shaft bending. High temperatures in bearings are mostly caused by poor lubrication.