Analysis of Common Problems in Roller Bearing Lubrication

Date: 2019-07-04 Views:

Roller press is a new type of energy-saving grinding equipment that was introduced in the mid-1980s. It is one of the main equipments in the grinding line of cement, metallurgy, coal, chemical and other industries.

At present, the construction of roller presses varies widely, and their shapes are different. However, in terms of their structural composition, they are basically the same. That is, they are composed of a frame, a fixed squeeze roller, a movable squeeze roller, a hopper, a hydraulic system, and a transmission device.


Roller bearing lubrication introduction

Roller press-to-roller bearings. In the past, roller presses used self-aligning spherical roller bearings to meet the requirements of centering and carrying large pressing forces.

Nowadays, the large roller press adopts four rows of cylindrical roller bearings, and the entire bearing seat will automatically adjust the position so that the bearing seat and the roller center line are always perpendicular to each other. No corresponding displacement occurs between the shaft and the housing, and the seal always maintains a fixed position for better sealing.

Under the same outer diameter and external load, four-row cylindrical roller bearings have a much longer service life than self-aligning roller bearings. The normal service life of the design is eight to ten years. As long as we usually strengthen the lubrication and maintenance of the equipment, there will be no problem.

For the lubrication of the roller press, the key component is the lubrication of the bearing. It is common to use grease lubrication, and some use lubricating oil for circulation lubrication.

The friction pair of the heavy-duty bearing of the roller press is the inner and outer rings of the bearing, the rolling elements and the cage. The working conditions are mainly low speed, heavy load, impact load and vibration.

The optimum viscosity of the grease base oil is 1000-1500 cSt. The lubricant requires high-efficiency extreme pressure and anti-wear additives, as well as an appropriate amount of solid lubricant.

The lubrication of the roller press is mainly composed of three parts: lubrication system, lubricant, cooling system.

Lubrication system, mainly consists of fuel pump, lubrication pump station, distributor, pipeline and pipeline accessories, as shown in the figure below vmaxx roller press automatic lubrication system.

The lubricant is made of 1# and 2# grease, and the grease is regularly lubricated and sealed in the seal of the main bearing and the inner side thereof.

In the cooling system, a cooling system is installed on the roller shaft and the bearing housing.


Roller bearing lubrication problems


1. Bearing working temperature is high

1.1 The problem of setting the fatliquoring cycle and fatliquoring amount

Common settings: 2 hours apart, 10 minutes per fatliquoring. Some manufacturers use manual manual fatliquoring after the electric lubrication system is not working properly, or in order to save oil consumption, it is often fattened once a day, and the grease is overflowed when the end cap of the bearing seat is overflowed.

Analysis: The fatliquoring cycle is too long, the oil quantity is insufficient, resulting in poor bearing lubrication and heavy wear.

Recommendation: From the principle of “small number of times”, we can suggest that the fatliquoring cycle and the amount of fatliquoring should be set at intervals of 1 hour, each fatliquoring for 5 minutes.


1.2 Roller bearing seal problem

Case: A cement factory had complained about its roller press bearings. The eagle grease used in the bearing hardened and agglomerated, and the bearing working temperature was high.

By going to the on-site inspection, it was found that the oil in the oil drum was normal, and the grease taken in the roller bearing was hard and felt sand. Moreover, the on-site environment is harsh and the dust is large during production. There is a problem with the fuel pump. Instead, use artificial fatliquoring and fatliquoring once a day.

After that, the alcoholic furnace was used to grill the sampled grease in the roller press bearing, and after 20 minutes, it became a blocky hard material similar to cement clinker. Communicating with the designers of the roller press manufacturers, some of the early design of the roller presses were defective in bearing sealing.

Finally, feedback with the cement manufacturer, carefully check the bearing seal of the roller press is indeed damaged, and the fatliquoring cycle is longer after manual fatliquoring.

Analysis: The bearing seal is not good, the powder leakage is serious, the grease is contaminated and the dry knot is hardened, so the working temperature of the bearing increases.

Recommendation: Improve the sealing effect and increase the amount of fat.


1.3 Roller cooling water system problem

Case: A cement plant roller press reflects: the working temperature of the two bearings of the moving roller is high, ≥60 °C.

During the on-site inspection, the lubrication cycle and lubrication amount are normal, the pumping system works normally, and the bearing lubrication is no problem. So where is the problem?

When checking the bearing cooling water, it was found that the temperature difference between the inlet and outlet pipes at the housing of the bearing housing was 1 °C, and the temperature difference between the inlet and outlet pipes at the bearing shaft reached 5.5 °C.

Analysis: The temperature difference between the cooling water inlet and the return water is not the greater the cooling effect; the axial steering joint seal ring fails, causing water leakage between the inlet and outlet pipes; the cooling water flow is not smooth, and the heat exchange effect is poor, causing the bearing temperature to rise.

Recommendation: The pressure of the cooling water should be ≥0.3MPa; the temperature of the cooling water should not be too high, it should be around 25 °C; the temperature difference between the inlet and outlet cooling water should be 1-2 °C.


2. Large amount of bearing lubricant

Roller bearing lubricants are used in large quantities, and there may be reasons:

Case 1: A factory reflects the large amount of grease used in the roller press. The technical engineer of the Spanish Eagle China representative office rushed to the scene to investigate and found the following:

Only compare the total statistical usage of each month, the specific amount of each machine is not clear.

Each electric lubrication pump has different working conditions and does not pay attention to inspection. It is often not found.

The dust is heavy and the dispenser action is not normal.

Due to the many faults of the pump, it is often necessary to manually add additional grease, and the statistics of the fatliquoring amount are not accurate.

Analysis: The oil outlets on both sides of the electric lubrication pump often have only one side oil or even no oil. The normal working condition of each pump will result in different oil output. The outlet pressure of the pump should be above 10 MPa, the pressure is insufficient, and the distributor of the pipeline will not operate.

Recommendation: Pay attention to regularly check the working status of the pump and find out the problem in time. Check the working pressure of the pump pressure gauge regularly.

Case 2: Two Haichuan roller presses in a factory, the manufacturer reflects the same cycle, but one of the oils is used in large quantities.

On-site inspection found that the grease accumulation in the fatliquoring system was very heavy; the travel switch of the sub-distributor failed; the number of movements of the sub-distributors on both sides was different; the pipe joints in front of the sub-distributors leaked oil; the lubrication pump was always in working condition.

Analysis: The dust is heavier and the intrusion into the dispenser and the travel switch is faulty. The pipeline leaks oil, causing a difference in the number of movements of each dispenser. The oil pump operates for a long time and the control system has no alarm.

Recommendation: It is recommended to install a dust cover for the dispenser and the travel switch. Always check for leaks in the lubrication system piping. The oil pump should be set to work for a long time.

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