SKF support rollers NATV, NATR, NUTR, PWTR, NNTR

SKF support rollers with axial guidance are non-separable units and are especially suitable for applications where lateral (thrust) surfaces are not available. Thrust forces resulting from alignment errors or inclined running are taken up by side washers or flange rings; the side washers are either loose or pressed on to the inner ring. When designing the associated components and mounting the support rollers it is important to ensure that the flange rings and inner rings with pressed-on washers and located without axial play. If larger thrust forces are expected, it is recommended that axial support is also provided for the washers which are pressed on the the inner ring.

SKF Support roller of the NATR design

SKF support rollers of the NATR design incorporate cage-guided needle rollers and permit relatively high speed operation. The outer ring is guided by the side washers which are pressed on the the inner ring; the washers form gap-type seals with the outer ring.

The outer ring is particularly thick-walled and intended for heavy loads and also shock loads.

SKF support rollers with axial guidance
SKF support rollers with axial guidance, NATV design

SKF support rollers of the NATV design

SKF support rollers of the NATV design are similar to those of the NATR design except that they have a full complement of rollers. The absence of a cage enables the maximum number of needle rollers to be incororated so that these support rollers can carry even heavier loads than those of the NATR design. However, because of the kinematic conditions they are not able to operate at such high speeds. They also require more frequent relubrication.

Sealed NATR and NATV support rollers - PP and PPA designs

SKF support rollers of the NATR and NATV series can also be supplied with rubbing seals. Sealed support rollers are intended for universal application, but particularly for use where difficult conditions pertain which call for efficient sealing of the bearing position.

SKF support rollers of the PP design have seals of nitrile rubber or polyurethane at both sides and are suitable for operating temperatures from -30 to +100 °C. They are being gradually replaced by the more robust PPA design.

The seals of SKF support rollers of the PPA design are replaced by sliding thrust washers of polyamide 6,6. These reduce the sliding friction between the outer ring and side washer and allow a reduction in the running temperature of the roller; this is favourable with regard to the service life of the grease. The sliding washer has the form of a cup spring with a sealing lip and acts as an axial seal which reliably retains grease in the roller. In the radial direction a narrow labyrinth is formed with the outer ring which excludes coarse contaminants. the permissible operating temperature range for the sealed support rollers is -30 to +100 °C.

All SKF support rollers of the PPA design have an enhanced runner profile (outside diameter of outer ring). The new design allows a more favourable distribution of stress than the crowned profile of the earlier design, even when running in a tilted position. This leads to higher stiffness and less wear between the runner surface and its counterface.

SKF support rollers of the NUTR design

SKF support rollers of the NUTR design are based on double row full complement cylindrical roller bearing. The outer ring has two integral flanges, which axially guide the roller complement. Two loose flange rings provide axial guidance for the out ring via the roller complement. Sheet metal angle rings pressed into the outer ring and extending over the flange rings serve to hold the omponents together and form efficient labyrinth seals.

NUTR support rollers can accomodate heavy radial loads. As the outer ring is guided via the rollers large axial forces can also be taken up. The support rollers can also be operated at relatively high speeds. Being of the full complement type, these SKF support rollers require more frequent relubrication.

If heavy shock loads can be expected, the rollers with reinforced outer ring should be used. These are identified by four or five-figure numbers in the designation.

NUTR support rollers also have an enhanced runner profile (outside diameter of outer ring) identified by suffix A in the designation. The new design allows a more favourable distribution of stress than the crowned profile of the earlier design, even when running in a tilted position. This leads to higher stiffness and less wear between the runner surface and its counter face.

SKF support rollers of the PWTR.2RS design

SKF support roller of series PWTR.2RS are sealed and therefore particularly suitable for operation under arduous conditions. The outer ring has three integral flanges, which axially guide the two rows of rollers (full complement) separately. Two loose flange rings provide axial guidance for the outer ring via the roller complements. Sheet metal angle rings pressed into the outer ring and extending over the flange rings serve to hold the components together. Rubbing seals, of oil and wear-resistant nitrile rubber (NBR), are integral with the angle rings and seal against the flange rings.

The special features of these support rollers include the rubbing seals, the three in-tegral outer ring flanges and the large space between the two rows of rollers. The separate guidance of the two rows of rollers means that friction in the support roller is low and thus also heat generation. The PWTR support rollers are very suitable for the accommodation of axial forces, which can occur if the roller runs in an inclined position.

The large space between the two rows of rollers aloows a large quantity of grease to be incorporated and the rubbing seals provide efficient protection against contamination. It is therefore possible to operate support rollers of series PWTR.2RS for much longer periods between maintenance intervals than was previously possible, even under contaminated conditions. The permissible operating temperature range is -30 to +120 °C.

SKF support rollers of the NNTR.2ZL design

SKF support rollers of series NNTR.2ZL are large and can carry very heavy loads. The outer ring has three integral flanges which axially guide the two rows of rollers (full complement) separately. Two loose flange rings provide axial guidance for the outer ring via the roller complements. The NNTR support rollers incorporate lamellar seals at both sides. These are inserted in grooves in teh shoulders of the flange rings and in the outer ring shoulders and hold all the bearing components together.

The seprate guidance of the two roller rows reduces friction and thus heat generation. The NNTR support rollers are thus suitable for the accommodation of heavy axial loads, even when they actconstantly, which can occur, for example, if the roller runs in an inclined position. The double row full complement of rollers imparts high radial load carrying capacity.

The large free space between the two rows of rollers means that a large quantity of grease can be filled into the rollers. The lamellar seals provide efficient protection. Extended maintenance intervals are therefore possible, even under difficult conditons.

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