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Double-Row Full-Complement Cylindrical Roller Bearings Type NNF50.. (SL04..)

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Double-row full-complement cylindrical roller bearings are suitable for arrangements with a large radial load and lower speeds compared to cylindrical roller bearings with a cage. Full-complement cylindrical roller bearings have the largest possible number of rollers and are without a cage. Additional designation V. Double-row full-complement cylindrical roller bearings are all made with an additional lubrication groove and bores on the outer ring, which allows perfect access of lubricant to the rolling space of each roller row. Double-row full-complement cylindrical roller bearings are manufactured in four designs (NNCL, NNCF, NNC, NNF), which are not dismountable.

NNCL Design

The inner ring of the bearing has three guiding flanges. The outer ring has no guiding flange. The bearing is kept in the mounted state by a retaining ring located in the outer ring between the rows of rollers. The NNCL bearing is axially loose, allowing axial displacement of the shaft relative to the housing. The NNCL design corresponds to the SL0248 and SL0249 designs of INA bearings.

NNCF Design

The inner ring of the bearing has three guiding flanges. The outer ring has one guiding flange and there is a retaining ring on the opposite side to secure the components in the mounted state. The NNCF design bearing is axially guiding in one direction and may accommodate axial load on the side of the guiding flange. The NNCF design corresponds to the SL1850 design of INA bearings.

NNC Design

The inner ring of the bearing has three guiding flanges. The outer ring is divided and has two guiding flanges. The outer ring is held together by retaining rings, which should not be loaded axially. The NNC design bearing is axially guiding in both directions. The NNC design corresponds to the SL0148 and SL0149 designs of INA bearings.

NNF Design

The inner ring is divided and each has guiding flanges, held together by an elastic ring. The outer ring has a guiding flange. They can accommodate axial forces in both directions. These bearings can accommodate tilting moments because of the greater distance between the rows of rollers. The outer ring of NNF bearings is 1 mm narrower than the inner ring and has two grooves. As a standard, the bearings are supplied with seals on both sides and the inner space is filled with lubricant, which ensures the operation of the bearings in normal working conditions up to 110°C.

Boundary dimensions

The boundary dimensions of double-row full-complement cylindrical roller bearings given in the dimension tables comply with the ISO 15 international dimension plan.

Designation

The designation of bearings with the basic design is given in the dimension tables. The difference from the basic design is designated by additional marks according to STN 02 4608. The table section also contains the designation of the INA design with matches for individual bearings.

Precision

Double-row full-complement cylindrical roller bearings are normally manufactured with the normal precision grade P0, which is not designated. The bearings can also be manufactured with a higher precision grade P6. The availability of these bearings needs to be consulted with the supplier. Limiting values for dimensional and running accuracy deviations are given in ISO 492.

Radial Clearance

Double-row full-complement cylindrical roller bearings are manufactured with a normal radial clearance, which is not designated. Bearings with reduced (C2) or increased (C3, C4, C5) radial clearance are available for special arrangements. The values of radial clearance comply with ISO 5753-1 and are valid for bearings in the unmounted state.

Axial Clearance

The NNC design bearings that are axially guiding in both directions must have a certain axial clearance that ranges from 0.1 to 0.2 mm for all bearing sizes.

Axial Displacement

The NNCL and NNCF designs of double-row full-complement cylindrical roller bearings are able to compensate axial displacement of the shaft relative to the housing to a certain extent, without reducing the bearing life. The values of the maximum axial displacement “s” are given in the dimension tables.

Permissible Misalignment

The misalignment of the inner ring of double-row full-complement cylindrical roller bearings relative to the outer ring leads to moment load in the bearing, which results in increased load and shorter bearing life.

Operating Temperatures

For arrangements with an operating temperature higher than 120°C, bearings are supplied with specially heat-treated components, which ensure dimensional and shape stability even with long-term exposure to higher temperatures from 150°C to 400°C (S0, S1, S2, S3, S4). The supply of such bearings needs to be negotiated in advance. For double-row full-complement cylindrical roller bearings, minimum radial load corresponding to 4% of the basic dynamic bearing capacity is recommended. Cylindrical roller bearings work reliably when axial loads are applied if the bearings are radially loaded at the same time. The Fa/Fr ≤ 0.25 ratio must be observed.

Dynamic and Static Equivalent Bearing Load

Dynamic Equivalent Bearing Load

If cylindrical roller bearings are used exclusively with radial load without axial forces, the dynamic load is calculated as follows:

Pr = Fr

If the bearings are also used to accommodate axial forces, the dynamic loads are calculated as follows:

Pr = Fr for Fa/Fr ≤ e
Pr = 0.92 . Fr + Y . Fa for Fa/Fr > e

Where:

e = calculation coefficient
e = 0.15 for double-row bearings

Y = axial load coefficient
Y = 0.4 for double-row bearings

Static Equivalent Bearing Load

The following applies to statically loaded cylindrical roller bearings:

P0r = Fr

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