Features, Part Name and Marking by Four-row tapered roller bearings

Oct 13, 2021

Four-row tapered roller bearing, TQO ( Other equivalent series: KV, 47T, CRO )

The roll neck bearing used in a rolling mill is limited in its dimensions by the roll neck diameter and minimum roll diameter. The four-row tapered roller bearing is so designed that its load rating may be as large as possible within this limited space. This type of bearing consists of two sets of cone assemblies, three cups and two cup spacers. To facilitate installation and removal of the roll and chock, this type of bearing is loose-fitted to the roll neck. Accordingly, lubrication to the fit surface is essential to prevent scoring between the roll neck and bearing bore due to creep. To prevent wear and seizure of cone and cone spacer, oil slot are provided on one side of the cone and both sides of cone spacer. Double-row cup and cup spacers are provided with oil holes and oil grooves to supply the lubricant.

Hair cracks caused in the cone side surfaces by creep may lead to cracks in the cone. To prevent such cracking and to enhance the shock resistance of a bearing, the bearing rings are made from carburized steel usually. The cage is designed as a window type or pin type.

Name and Marking of parts

In addition to the bearing number, as shown in Fig. 1.1, the bearing is provided with a serial number that is common to one set of bearings and matching symbols indicating the combination order. The serial number is used to prevent mismatching during combination of bearings while matching symbols show the proper position of each part within a bearing. A wrong combination of these parts may cause an excessively small bearing clearance, resulting in seizure. On the other hand, an excessively large clearance due to a wrong combination may cause reduction of the load zone resulting in a shorter fatigue life.

The cup of a bearing is provided with load position numbers at four equally-divided points around the circumference.  (These numbers are provided on the cone if the cup rotates.) So that the bearing life can be extended, each time the bearing is reassembled after disassembly and cleaning, shift the load position numbers by 90 to change the load zone.

Sealed design four-row tapered roller bearing, KVE, KVS, 47TS, CRO-LL ( Other equivalent series: TIMKEN TQOS or SRNB )

Sealed design four-row tapered roller bearings have seals positioned at both end surfaces and the middle bore notch. Basically, this type of bearing is similar to the four row tapered roller bearing and has the following features: 

> Substantial reduction in the consumption of lubricating grease .

> Longer interval until disassembly and cleaning , thereby cutting-down on the maintenance costs )

> Cleaner environment around the rolling mill and roll shop )

> Prevention of sudden failure due to foreign particle entry )

> Longer bearing life is achieved by preventing water intrusion )

> Load capacity remains just as high as that of fourrow tapered roller bearings without seals 

Basically, there are two-seal and four-seal types of bearings. The standard feature of the sealed-clean tapered roller bearing is its ability to operate for a long time without the need for regreasing. Due to this feature, there are no oil holes in the cup spacers to supply lubrication to the bearing, but in the case of severe operating conditions, it could be designed to enable lubrication by making a lubrication groove and oil holes in the cup spacers. There is also a type compatible with oil-air lubrication.

Name and marking of parts

In addition to the bearing numbers, as shown in Fig. 1.2, the bearing is provided with a serial number that is common to one set of bearings and matching symbols indicating the combination order. The serial number is used to prevent mismatching during combination of bearings while matching symbols show the proper position of each part within a bearing. A wrong combination of these parts may cause an excessively small bearing clearance, resulting in seizure. On the other hand, an excessively large clearance due to a wrong combination may cause a reduction of the load zone,resulting in shorter fatigue life. The cup of a bearing is provided with load position numbers at four equally- divided points around the circumference. (These numbers are provided on the cone when the cup rotates.) So that the bearing life can be extended, each time the bearing is reassembled after disassembly and cleaning, be sure to shift the load position numbers by 90° to change the load zone.