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Single row deep groove ball bearings

Single row deep groove ball bearing

Single row deep groove ball bearings are available capped (with seals or shields) or open. Open bearings that are also available capped may have recesses in the ring side faces (fig. 1).

SKF inch bearings in the EE(B), RLS and RMS series are intended as aftermarket items and, therefore, SKF recommends not using these bearings for new bearing arrangement designs.

SKF can also supply bearings with a tapered bore. For detailed information, contact SKF.

Capped bearings

Selection guidelines for different capping devices under various operating conditions are listed in table 1. However, these guidelines cannot substitute for testing a shield or seal in its application. For additional information, refer to Sealing solutions.

The seals, which are fitted in a recess on the outer ring, make good, positive contact with the recess, without deforming the outer ring. The capping devices are available as:

Shields (designation suffix Z)

  • are primarily intended for applications where the inner ring rotates
  • are fitted in the outer ring and form a narrow gap with the inner ring
  • are made of sheet steel
  • are available as standard with an extension in the shield bore (fig. 2), expect some sizes without extension
  • protect from dirt and debris without friction losses

Non-contact seals (designation suffix RZ, fig. 3)

  • provide better sealing effectiveness than shields
  • can be operated at the same speeds as shields
  • form an extremely narrow gap with the inner ring shoulder
  • are made of sheet steel reinforced NBR (oil- and wear-resistant)

Low-friction seals (designation suffixes RSL or RST)

  • provide better sealing effectiveness than non-contact seals
  • are made of sheet steel reinforced NBR (oil and wear-resistant)
RSL design (fig. 4):
  • can be operated at the same speeds as shields
  • make virtually no contact with a recess in the inner ring shoulder
  • are available for 60, 62, 63 series bearings in two designs, depending on the size
RST design (fig. 5):
  • make positive contact with a recess in the inner ring shoulder for good sealing effectiveness
  • are available for 60, 62 and 63 series bearings in three RST designs, depending on the size

Contact seals (designation suffixes RSH, RSH2, RS1 or RS2)

  • are made of sheet steel reinforced
    • NBR
    • FKM (designation suffix RS2 or RSH2, available on request)
  • are available in different designs depending on the bearing they are used with:
    • for 60, 62 and 63 series bearings in two RSH designs (fig. 6), depending on the size
    • for RS1 designs, with sealing either against the inner ring shoulder or against a recess in the inner ring side face (fig. 7); the relevant design is determined by dimension d1 or d2 in the product table.

WARNING

Seals made of FKM (fluoro rubber) exposed to an open flame or temperatures above 300 °C (570 °F) are a health and environmental hazard! They remain dangerous even after they have cooled.

Read and follow the safety precautions under this WARNING.

ICOS oil sealed bearing units

  • are typically used for applications with sealing requirements exceeding the capabilities of standard sealing solutions, i.e. oil retention
  • have the following features compared to bearings with external sealing solutions:
    • need less axial space
    • simplify mounting
    • avoid expensive machining of the shaft because the inner ring shoulder is the seal counterface
  • consist of a 62 series deep groove ball bearing and an SKF WAVE seal (fig. 8):
    • single lip, spring loaded radial shaft seal
    • made of NBR
  • have limiting speeds quoted in the product table that are based on the permissible circumferential speed for the seal (14 m/s)
Greases for capped bearings
Bearings capped on both sides are lubricated for the life of the bearing and are virtually maintenance-free. They are filled with one of the following greases:
  • standard deep groove ball bearings → table 2
  • inch deep groove ball bearings
    • D < 63.5 mm → MT47
    • D ≥ 63.5 mm → MT33
On request, bearings can be supplied with the following special greases:
  • high temperature grease GJN
  • wide temperature range grease HT or WT
  • wide temperature range and low-noise grease LHT23
  • low temperature grease LT

The technical specifications of the various greases are listed in table 3.

The standard grease is not identified in the bearing designation (no designation suffix). Special greases are indicated by the corresponding grease suffix. Check availability of bearings with special grease prior to ordering.

Grease life for capped bearings

  • is presented as L10, i.e. the time period at the end of which 90% of the bearings are still reliably lubricated (diagram 1)
  • depends on:
    • the operating temperature
    • the n dm factor
    • grease performance factor (GPF) (table 3)
The indicated grease life is valid under this combination of operating conditions:
  • horizontal shaft
  • inner ring rotation
  • light load (P ≤ 0,05 C)
  • operating temperature within the green temperature zone of the grease (table 3)
  • stationary machine
  • low vibration levels

Where the operating conditions differ as described below, the grease life obtained from the diagrams should be adjusted:

  • vertical shafts → 50% of the obtained value
  • heavier loads (P > 0,05 C) →  apply reduction factor (table 4)
When capped bearings must operate under certain extreme conditions, such as very high speeds or high temperatures, grease may appear on the capping diameter. For bearing arrangements where this would be detrimental, appropriate actions could be taken. For additional information, contact the SKF application engineering service.
Bearings with a snap ring groove
  • can simplify the design of an arrangement
    • by locating the bearing axially in the housing by a snap ring (fig. 9)
    • by saving space
    • by significantly reducing mounting time.

Appropriate snap rings are shown in the product table, along with their designation and dimensions.

The following variants are available (fig. 10):

  • open bearings with a snap ring groove only (designation suffix N)
  • open bearings with a snap ring (designation suffix NR)
  • bearings with a snap ring and a shield on the opposite side (designation suffix ZNR)
  • bearings with a snap ring and a shield on the same side (designation suffix ZNBR)
  • bearings with a snap ring and a shield on both sides (designation suffix 2ZNR)
Quiet running bearings for large electric generators
  • are designed to comply with stringent noise requirements
  • are typically used in wind turbine generators
  • provide consistent performance over a variety of operating conditions
  • are identified by the designation suffix VQ658
    (→ SKF Quiet running deep groove ball bearings)
Cages

SKF single row deep groove ball bearings are fitted with one of the cages shown in table 5. The standard stamped steel cage is not identified in the bearing designation. If non-standard cages are required, check availability prior to ordering.

When used at high temperatures, some lubricants can have a detrimental effect on polyamide cages. For additional information about the suitability of cages, refer to Cages.

Matched bearings
  • are used where the load carrying capacity of a single bearing is inadequate
  • are used where the shaft has to be located axially in both directions with a specific axial clearance
  • where mounted immediately adjacent to each other, distribute the load between the bearings without having to use shims or similar devices

A “V-shaped” marking on the outside surface of the outer rings of matched bearings (fig. 11) indicates how the pair should be mounted. The bearing pairs are supplied as a packaged unit.

Matched pairs can be supplied in three different arrangements (fig. 12):

Tandem arrangement (designation suffix DT)

  • is used where the load carrying capacity of a single bearing is inadequate
  • has parallel load lines and therefore shares the radial and axial loads equally
  • can accommodate axial loads in both directions

Back-to-back arrangement (designation suffix DB)

  • has load lines that diverge towards the bearing axis
  • provides a relatively stiff bearing arrangement
  • can accommodate tilting moment loads
  • can accommodate axial loads in both directions, but only by one bearing in each direction

Face-to-face arrangement (designation suffix DF)

  • has load lines that converge towards the bearing axis
  • is less sensitive to misalignment but not as stiff as a back-to-back arrangement
  • can accommodate axial loads in both directions, but only by one bearing in each direction
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