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TOQ-Four-row tapered roller bearings

Jan 12, 2023
Four-row tapered roller bearings are the one kind of roll neck bearings,  their radial and axial loading capacity are high,  can carry heavy axial loads in two directions, and their radial loading capacity is 3 times heavier than singe-row tapered roller bearings, but limiting speed is lower. They can be used as axial locating bearings in two directions because they are able to limit axial displacement in two directions within axial clearance. The radial and axial clearance also can be adjusted by changing the width of spacer between inner and outer rings.
Four-row tapered roller bearings are mainly used in the working roll necks of hot or cold rolling mills, and roll neck of roughing mills. They usually clearance fit with roll necks to being mounted and dismounted conveniently.
Steel pressed cages are usually used in four-row tapered roller bearings,  and pin-type cages are for large-size ones.

Tapered roller bearings – Due to the inclined position of the rollers, these bearings can withstand radial and axial forces. Four- and double-row tapered roller bearings are used in rolling mills. Unlike cylindrical roller bearings, tapered roller bearings are separable. However, it is not possible to first mount the inner ring to the roller neck, then the outer ring to the housing, and then slide the housing onto the roller neck. The complete bearing is first mounted in the housing, which then slides the housing to the neck together with the bearing. This means that the bearing inner ring needs to be loosely fit at the neck, although it can technically be tightly fit due to circumferential loads. Loose fit, the inner ring inevitably squirms around the neck. In this case, the neck is subjected to heat and wear. Good lubrication of the mating joint between the inner ring and the roller neck limits wear. In order to provide a grease reservoir and thus improve lubrication of the neck, spiral grooves are usually turned in the inner ring hole. The grooves also provide the collection of wear particles. For the same reason, radial grooves are provided on the sides of the inner ring.

When the work rollers are supported by four-row tapered roller bearings, the low load means that wear is rare. In addition, in most cases, when the available regrinding material on the work roller runs out, it is likely that the roller will have to be replaced before the neck wear has a harmful effect. Large tapered roller bearings, like cylindrical roller bearings, are equipped with through-bore rollers and pin cages. Due to the high inertial forces, this design is necessary in reversible racks.

Sealing multi-row tapered roller bearings – Work roll bearing arrangements in hot and cold rolling mills should be effectively sealed to prevent large amounts of water or roll coolant mixed with contaminants. Working roller bearing units are usually lubricated with grease. In order to reduce costs and protect the environment, there is a tendency to reduce the amount of grease used. Better lubrication and cleaning of rolling contacts helps extend bearing life. The main dimensions of the bearings are the same as those of non-sealed bearings. With high-quality rolling bearing grease, no escaping from the bearing and only a small amount is required. The housing seal itself is filled with simple, inexpensive sealing grease. Although integrated seals reduce the design envelope available to the rollers, resulting in lower base load ratings, sealed bearings generally have a longer service life than unsealed bearings due to improved cleanliness of lubricated clearances. Double row sealed tapered roller bearings are used as axial bearings for work rolls.

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