Writer: Eric Bearing Limited
NTN self-lubricating bearings have a wide operating temperature, sufficient content of solid lubricating materials, and an even release. They have good self-lubricating properties and occlusal properties, which can effectively protect the journal and achieve long-term use. It is suitable for operation under the environment of high temperature, low speed, heavy load, heavy dust, water shower and shock vibration. Such NTN bearings can be widely used in mining machinery, metallurgy, petroleum, chemical industry, food, textile, papermaking, printing and dyeing, etc.
Rolling and sliding bearing parts of mechanical equipment.
The aluminum liquid produced by the aluminum electrolytic cell is sucked out by vacuum lifting and poured into the mixing furnace. After proportioning and slag removal, it flows into the aluminum ingot casting machine for casting and molding. The formed solid is called aluminum ingot.
The ingots are stacked by the stacker. In order to improve the production efficiency, the aluminum ingot must be cooled with a large amount of cooling water before the molding. During the cooling process, the huge heat energy of the aluminum liquid is released into the cooling water, generating hot steam.
The bearings of the casting machine are in a high temperature and water vapor environment. Many of the bearings are grease lubricated. The added grease will be melted and removed due to high temperature in a short period of time. It is difficult to maintain and maintain, and the surface of the equipment is also difficult to wipe. Furthermore, the steel structure bearing is easy to corrode and rust in the hot and humid environment, the failure rate is very high, the equipment maintenance cost is high, and the equipment is often troubled by the following two problems.
It is difficult to achieve high-temperature continuous operation of the oil supply operation. The ingot pulling, ingot transfer, ingot connection, ingot turning and other devices of the casting machine are installed in the casing of the unit. Each rotating bearing is designed with an oil nozzle facility that is periodically injected with lubricating grease. Remove the shell and press grease with an oil gun.
Moreover, there are more than 30 oil injection points in the whole machine. Long-term operation and maintenance cannot achieve this cumbersome oil injection operation. Therefore, it is necessary to hold a thin oil pot and pour it outside the running bearing sleeve. It is difficult for the lubricating oil to enter the friction pair of the bearing. The bearing is in friction.
The environment temperature is high, and the grease lubrication is not suitable for the current molybdenum disulfide grease used in rolling bearings of casting machines. It is considered to be resistant to high temperature grease. We know that its base oils are petroleum products, plus a small amount of high temperature resistant molybdenum disulfide additives, and its temperature resistance limit That is 120 ℃.
It is measured that the working temperature of the bearing of the casting machine can reach 200 ℃, which has far exceeded the temperature limit of grease. Under such high temperature conditions, the base oil in the grease will become thinner and gradually evaporated.
The remaining carbon slag, molybdenum disulfide, and dust are mixed into a solid block and solidified on the cage of the rolling bearing, which not only loses its lubricating effect. It also hinders the normal operation of the rolling bearing and wears it quickly. It has to be shut down for up to 2 weeks, and the NTN bearing is removed for cleaning and replacement with new grease.
Trouble-shooting analysis of wear-resistant NTN bearings
Dirty is the most common cause of damage for all NTN bearings. In the initial installation, during maintenance, air leakage into the NTN bearing housing, or even through the use of dirty lubricant, can bring dirt into the NTN bearing.
Foreign materials such as rust or other metal materials, which are hard and rough, can cause small depressions, which are significantly different from those caused by overload failure, acid attack or corrosion. Blockage of hard objects can cause the seat ring to rotate. NTN 6905 ball bearings online , if you interested , pls click here :
According to an industry representative, more than 95% of all failures in anti-friction NTN bearings come from defective assembly, unsuitable working conditions, and other similar reasons that can usually be found after observation of NTN bearings.
However, many of these failures can be avoided or postponed with better lubricants. Failures caused by water, acid or other corrosive substances on NTN bearings are characterized by a reddish-brown surface and very small corrosion holes on the entire exposed surface of the seat ring.
In many cases, the rolling motion pushes the lubricant away from the ball track and there is no corrosion on the ball or roller track. Corrosive oxides move like abrasives, which cause wear and leave a dark gray color on the balls or rollers and their races, which contrasts with the red-brown residue on the surface of NTN bearings.
Noise is a symptom. If the shaft is working properly, the sound you hear should be soft whine and loose grease. Any other noise ultimately means a malfunction.
Use a screwdriver as a stethoscope to check the new NTN bearing. A short squeal sound indicates that the lubrication is not complete. A harsh sound indicates that the shaft or NTN housing is obstructed or improperly adjusted. The smooth, pure tone indicates traces in the stationary seat ring. Irregular noise indicates ball damage. A crunchy sound means there is dirt.