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Rolling Mill Bearings

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WD four-row cylindrical roller bearingsare used almost exclusively for the roll necks of rolling mill stands, calenders and roller presses. Their friction is low compared with other roller bearings. As they are normally mounted with an interference fit on the roll neck, they are particularly suitable for rolling mill applications where the rolling speed is high.

The low bearing cross section allows for relatively large roll neck diameters in comparison with the roll diameter. Since very many rollers can be incorporated, the radial load carrying capacity is exceptionally high.

WD four-row cylindrical roller bearings are only able to accommodate radial loads. They are therefore mounted together with deep groove or angular contact ball bearings, or with tapered roller bearings, either radial or thrust designs, which take up the axial loads.

Internal clearance
WD four-row cylindrical roller bearings are normally produced with the C3 or C4 radial internal clearance required for rolling mill bearings. Bearings mounted with a loose fit on the roll necks generally have C2 radial internal clearance.

The clearance values, where standardized, conform to ISO 5753:1991 and are given in the following tables for bearings with cylindrical bore and bearings with tapered bore. They are valid for unmounted bearings under zero measuring load.

Working temperature:
Os valores para os factores de cálculo e, Y1 e Y2 podem ser encontrados nas tabelas de produtos.

Carga estática equivalente:
P0 = Pe + Y0Fa
Os valores para o factor de cálculo Y0 pode ser encontrada nas tabelas de produtos.

Projeto de arranjos de rolamentos:
requisitos rolo de pescoço
Na maioria das aplicações de laminação WD rolamentos de rolos cônicos de quatro carreiras são montados com folga no pescoço do cilindro. A revista rolo de pescoço eo suporte axial para o anel interno deve ter uma certa dureza mínima. A dureza é recomendado,

45 Shore (≈ 34 HRC) para a superfície do rolo de pescoço
60 Shore (≈ 45 HRC) para os abutements axiais para os anéis internos

Axial localização dos anéis internos no pescoço do cilindro:
Os anéis internos não devem ser fixados axialmente. Tem de ficar uma folga total entre os anéis de rolamento e seus pilares de 0,2 a 1,3 mm.

  • Two or three double pronged machined brass cages
  • Two double row window-type brass cages
  • Four pronged machined brass cages

Minimum load:
In order to guarantee satisfactory operation, WD multi-row cylindrical roller bearings, like all ball and roller bearings, must always be subjected to a given minimum load, particularly if they are to operate at high speeds or are subjected to high accelerations or rapid changes in the direction of load. Under such conditions the inertia forces of the rollers and cage, and the friction in the lubricant, can have a detrimental effect on the rolling conditions in the bearing arrangement and may cause damaging sliding movements to occur between the rollers and the raceways.

The requisite minimum load to be applied to multi-row cylindrical roller bearings can be estimated using:03

where
Frm = minimum radial load,kN
kr = minimum load factor(see product tables)
n = operating speed,r/min
dm = mean diameter of bearing
= 0,5(d+D),mm

When starting up at low temperatures or when the lubricant is highly viscous, even greater loads may be required. The weights of the components supported by the bearing, together with the external forces, generally exceed the requisite minimum load. If this is not the case, the AWD multi-row cylindrical roller bearing must be subjected to an additional radial load.

Equivalent dynamic bearing load: P = Fr
Equivalent static bearing load: P0 = Fr

Mounting instructions:
Knowledge and experience are of particular importance where WD four-row cylindrical roller bearings are concerned. The individual components must be mounted in the correct order. Parts which belong together are marked with letters. In addition, all components of the bearing are marked with the same serial number, so that there is no risk of mixing components if several bearings are to be mounted at the same time. However, the inner rings and inner ring pairs are fully interchangeable and need not to have the same serial number as the outer ring(s).

In the majority of applications the load is of constant direction, so that approximately only a quarter of the outer ring is under load. For this reason, the side faces of the outer rings are divided into four zones indicated by I to IV. The markings for load zone I are also joined by a line across the outside surface of the outer rings.

When the bearing is mounted for the first time it is usual to position zone I in the direction of action of the load. Depending on the operating conditions, the outer rings should be turned through 90°after a period of service so that a new zone comes under load.

Detailed mounting instructions are also supplied with all bearings.

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WD four-row tapered roller bearings(fig) are used successfully worldwide for rolling mill bearing arrangements where rolling speeds are slow to moderate. Because of their design they are able to take up those axial loads which occur in such applications in addition to radial loads and generally no separate thrust bearings are required in such arrangements. This means that the roll necks can be relatively short and the chocks at both sides of the roll can have the same design .

Rolling_mill_bearings

WD four-row tapered roller bearings, because of their design, must be installed as complete bearings in the chocks. To enable quick roll changes to be made they must therefore have a loose fit on the roll necks. Loose fits have the disadvantage that the inner rings wander on their seatings under the prevailing load conditions causing wear to the seatings which normally have a lower hardness than the rings. To alleviate the effects of a loose fit to some extent, i.e. to reduce wear, bearings have a helical groove in the bore and/or lubrication grooves in the side faces of the inner rings . These grooves enable lubricant to be supplied to the contact surfaces of the inner ring and seating. Additionally, the grease-filled grooves can absorb the wear particles.

WD four-row tapered roller bearings are produced with dimensional accuracy corresponding to,

- Normal tolerances for metric bearings
- Normal tolerances for inch bearings.

The running accuracy of all bearings is to tolerance class P5 specifications
The Normal and tolerances class P5 for the metric bearings conform to ISO 492-2002. The values of the Normal tolerances for inch bearings follow tolerance class 4 according to ANSI/ABMA Standard 19.2-1994. The ISO Standard 578:1987, which also covered this tolerance class for inch bearings was withdrawn in 1997.

Internal clearance:
WD four-row tapered roller bearings are delivered as ready-to-mount bearing units with an axial internal clearance adapted to the actual application. The bearing components must be arranged in the prescribed order and may not be interchanged with components of another bearing.
WD four-row tapered roller bearings having a clearance other than that of the basic design are identified by the designation suffix C followed by a three or four-figure number which is the mean value of the axial internal clearance expressed in µm .

Working Temperature :
WD four-row tapered roller bearings are subjected to a unique heat treatment process that enables the bearings to be operated up to +150 ℃ without any inadmissible dimensional changes occurring.

Cages:
Four-row tapered roller bearings are fitted with either :
Four pressed steel window-type cages
Four steel pin-type cages

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Minimum load :
In order to provide satisfactory operation, WD four-row tapered roller bearings, like all ball and roller bearings, must always be subjected to a given minimum load. Otherwise the inertia forces of the rollers and cages, and the friction in the lubricant, can have a detrimental influence on the rolling conditions in the bearing arrangement and may cause damaging sliding movements to occur between the rollers and raceways.

The requisite minimum load to be applied can be obtained from: Frm = 0,02 C

where:
Frm = minimum radial load, kN
C = basic dynamic load rating (se product tables), kN

The weight of the components supported by the bearing, together with external forces, usually exceeds the requisite minimum load. If this is not the case, the four-row tapered roller bearing must be subjected to an additional radial load.

Equivalent dynamic bearing load :

P = Fr + Y1Fa Fa/Fr ≤ e
P = 0.67Fr + Y2Fa Fa/Fr > e

The values for the calculation factors e, Y1 and Y2 can be found in the product tables.

Equivalent static bearing load :
P0 = Fr + Y0Fa
Values for the calculation factor Y0 can be found in the product tables.

Design of bearing arrangements :
Roll neck requirements
In most rolling mill applications WD four-row tapered roller bearings are mounted with a loose fit on the roll neck. The roll neck journal and the axial abutment for the inner rings must have a certain minimum hardness. The recommended hardness is,

45 Shore (≈ 34 HRC) for the roll neck surface
60 Shore (≈ 45 HRC) for the axial abutements for the inner rings

Axial location of inner rings on the roll neck:
The inner rings must not be axially clamped. There must remain a total clearance between the bearing rings and their abutments of 0,2 to 1,3 mm .

Mounting instructions :
When mounting WD four-row tapered roller bearings, the components must be assembled in the correct order. To facilitate this, they are marked with letters . All the components of one bearing are also marked with the same serial number so that mixing is avoided if several bearings are being mounted at the same time.

As in the majority of applications the direction of load is constant with respect to the outer ring only approximately one quarter of the outer ring raceway will be under load. For this reason the side faces of the outer rings are divided into four zones marked I to IV. The markings for zone I are also joined by a line across the outside diameter of the rings . When the bearings are first installed it is customary for zone I to lie in the direction of the load. Depending on the operating conditions, the outer rings should be turned through 90° after a given period of service when the rolls are changed so that a new zone comes under load.

Detailed mounting and maintenance instructions will be supplied on request.

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