Bearing materials, common problems and causes, bearing installation, lubrication and other problems.

Bearing is a very important part in paper machine. It can be divided into rolling bearing and sliding bearing. These two kinds of bearings are often damaged to varying degrees in use, forcing shutdown and replacement, thus affecting the benefits of enterprises. In view of this problem, this paper talks about bearing materials, common problems and causes, bearing installation, lubrication and other problems.

 

1.Structural Material of Bearing

1.1 Rolling Bearing. Its inner and outer rings and rolling elements are generally made of chromium containing alloy steel. For example, CrG6, CrG9, CrG15 and GCr1SSiMn, the working surface hardness of the element after heat treatment shall reach HRC61- 65 ", and shall be grinded and polished. The cage is generally stamped with low-carbon steel plate and made of non-ferrous metal (such as brass) or plastic (such as phenolic sandwich bakelite).

 

1.2 Plain Bearing. It is generally made of copper base bearing alloy (bronze, brass), gray cast iron, tin base and lead base bearing alloy (Babbitt alloy).

 

2. Bearing Damage and Causes

2.1 Damage of Rolling Bearing. During the operation of rolling bearing, abnormal heating, noise and vibration often occur, the inner and outer rings are cracked, the ball is broken, and even the inner and outer rings of bearing are stuck. If it is light, fatigue pitting corrosion, wear of inner and outer rings and balls will occur; In serious cases, there are pits, indentations, cracks and fractures.

 

2.2. Causes of Rolling Bearing Damage

2.2.1 for long-term use of rolling bearings, there is a great cyclic contact force between the surfaces of rolling elements and race under the action of load, so that pitting may occur on the working surface of the bearing. In serious cases, the metal flakes off and forms pits.

 

2.2.2 cracks and fractures may occur due to material defects, improper heat treatment, too much interference and stress concentration caused by improper bearing combination design.

 

2.2.3 lack of lubricating oil. Abnormal heating and noise of bearing are mainly caused by lack of lubricating oil or failure of lubricating oil.

 

2.2.4. Poor bearing quality. If the size of the inner and outer ring is out of tolerance, the surface roughness is large. Some bearings are refurbished. Some of them have not undergone grinding process or grinding process, but the machining allowance left for turning is small. The turning tool mark is not worn off by grinding, and the interference fit between the inner diameter and the shaft cannot be achieved, resulting in the looseness of the bearing inner ring and the shaft. The interference between the outer diameter and the bearing seat hole will fix the bearing outer ring and the bearing seat hole together. The surface roughness is not good and can not reach the technical essentials. It not only has a great impact on the service performance of the product, but also is directly related to the product quality. For example, in the clearance fit, it affects the wear of the working surface; In interference fit, it affects the connection strength; Under variable load, it affects the fatigue resistance. When this kind of bearing is installed on the paper machine, there are often accidents of abnormal heating, high noise and vibration, or damage to the shaft and bearing seat hole during rotation.

 

2.2.5 Influence of other factors. If the pressure in the roller is too heavy or the pressure on both sides is uneven, the lifting roller damages the bearing when changing the blanket, the balance of the roller (including static balance and dynamic balance) is poor, and the surface of the journal and the bearing is uneven, or the bearing is not handled in time when there are abnormal conditions in the work, these conditions can also damage the bearing.

 

2.3 Damage of sliding bearing. The damage of sliding bearing (only gray cast iron and Babbitt alloy are discussed here) is mainly burning and grinding.

 

Bush burning is caused by the knife flower part on the Babbitt alloy surface of the bearing bush is ground by the shaft, the contact point becomes larger in pieces, and even there are groove marks on the Bush, or the Babbitt alloy falls off and overlaps. The pad grinding is that the contact point on the Babbitt alloy surface is locally enlarged into pieces, which can still be repaired without replacing the pad.

 

2.4. Damage causes of sliding bearing. Causes of tile burning and tile grinding: a. Serious lack of lubricating oil; b. The oil is too dirty, with mechanical impurities, and the water content of the lubricating oil exceeds a certain limit, which can not play the role of lubrication; c. The viscosity of lubricating oil is not enough or the brand is wrong.

 

3. Take measures

3.1 All purchased bearings shall be inspected.

3.1.1 for the inspection of rolling bearings, first of all, the bearings provided by the supplier must have quality certificates and certificates to see whether the bearing code is consistent with the certificate. Check whether the bearing is cleaned, whether the inner and outer rings and rolling elements of the bearing are rusted, whether there are burrs, bumps and cracks, whether the clearance of the bearing is appropriate, whether the rotation is light and free, etc. if the above conditions are good, they can be purchased.

 

3.1.2 inspection of sliding bearing (cast iron and Babbitt alloy). During the inspection, a small copper hammer can be used to knock gently along the surface of Babbitt lining in sequence. If a crisp jingle sound is emitted, it indicates that the bonding quality between Babbitt casting quality and bottom tile is very good. Then measure the geometric dimension. If the coaxiality meets the technical requirements, it can be purchased. If knocking Babbitt alloy makes a voiced or hoarse sound, it indicates that there may be sand holes, holes, cracks or heavy skin in Babbitt alloy, or the adhesion between bottom tile and Babbitt alloy is not good, so it can not be bought.

 

3.2 Install new bearings correctly

3.2.1 Assembly of rolling bearing. Before the assembly of rolling bearings, the bearings shall be cleaned with cleaning agent at normal temperature. After cleaning, they shall be dried with compressed air and coated with a thin layer of engine oil. During the assembly of rolling bearing, the rotating race adopts interference fit, but the interference shall not be too large, so as to prevent reducing or eliminating the radial clearance of bearing itself or damaging the race during installation. The seat ring of the non rotating shaft adopts the fit with clearance or small interference. Generally, the bearing can be evenly driven into the journal by hammering.

 

In case of loose fit between the bearing inner ring and the shaft, someone punched the loose shaft surface with a punch to roughen the shaft surface in an attempt to obtain a close fit surface with the bearing. This not only destroys the geometry of the shaft surface, which may skew the bearing during installation, but also the fuzzing part will eventually be flattened and become a loose fit again. The correct method is to spot weld the periphery of the bearing journal, and then turn and grind it to the required size.

 

3.2.2 assembly of sliding bearing. For gray cast iron bearing with Babbitt alloy, the bearing bush shall be cleaned with kerosene or gasoline before installation. In order to achieve uniform contact between the bearing bush and the bearing seat or journal, the bearing bush shall be scraped.

 

3.3 do a good job in lubrication. In the use of equipment, the staff are required to strictly implement the post responsibility system, implement the patrol inspection system, find and deal with the signs of various accidents as soon as possible, and do a good job in equipment lubrication.

 

3.3.1 lubrication of rolling bearing. In order to reduce the friction between bearing rolling element and raceway surface and between rolling element and cage, good lubricating oil must be selected for lubrication. According to the characteristics of small friction coefficient, fast speed, variable load types, small load area and great pressure per unit area of rolling bearing, grease or oil is generally used as lubricant. If the working temperature is 0 ~ 60 ℃ and the rotating speed of the shaft is 300-500 rpm, the grades of lubricating grease can be ZG-1 calcium base grease and ZG-2 calcium base grease.

 

3.3.2 lubrication of sliding bearing. The relative movement of journal and bearing bush makes the oil in the bearing clearance form a pressure oil wedge to generate the flow pressure of supporting load and form the oil film of lubricating oil to realize liquid lubrication. At the working temperature of 10-60 ℃, the load is medium load or heavy load, which is suitable for 1 15 gasoline engine oil, 40, 50, 70 and 90 mechanical oil.

 

The bearing damage is related to the balance of the roller or drying cylinder. When purchasing paper machine or some spare parts, the design ability and testing ability of the manufacturer shall be considered. For rollers and drying cylinders, static balance and dynamic balance must be checked, which is a means to reduce bearing damage.

 

More about FK Pillow Block Bearing:

A pillow block bearing (or plummer block) is a pedestal used to provide support for a rotating shaft with the help of compatible bearings & various accessories. The assembly consists of a mounting block which houses a bearing. The block is mounted to a foundation and a shaft is inserted allowing the inner part of the bearing / shaft to rotate. The inside of the bearing is typically 0.001 inches (0.025 mm) larger than the shaft to ensure a tight fit. Set screws, locking collars, or set collars are commonly used to secure the shaft. Housing material for a pillow block is typically made of cast iron or cast steel.


Pillow Block bearing 

 

Founded in 1969, FK has always focused on bearing part industry, after 50 years development and accumulation, FK is accelerating the transformation and upgrading to be “Bearing Parts Expert and Leading Supplier”. FK has complete industrial chain automatic factory of its own, now FK is one of the biggest bearing parts factories in China with production and sales up to 18 million pieces.


FK, a bearing products expert and leading supplier will continue to be one of most professional bearing manufacturer in the world!