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Standard housing design

Designs and variants

SNLN 30 plummer (pillow) block housings
  • are split housings consisting of a cap and base (fig. 1)
  • have two holes cast into the base for attachment bolts
The housings are designed on the "building block” principle to enable a wider choice of bearings and seals as well as a variety of shaft-bearing combinations.

Features and benefits

  • Stiff housing
    The housing base is reinforced with ribs and has extra material surrounding the holes for the attachment bolts (fig. 1). This virtually eliminates any distortion of the base and bearing seat during tightening of the attachment bolts.
  • Good heat dissipation
    The centre cross reinforcement in the housing base (fig. 2) increases the contact area between the housing base and the support surface to improve the heat flow from the bearing outer ring to the support surface.
  • Grease guiding system
    An integrated flange guides grease from the grease fitting into the bearing (fig. 3). This feature is available for housings up to and including size 3038.
  • Caps and bases individually marked
    The housing cap and base are matched during manufacture and are not interchangeable with the caps and bases of other housings. To prevent any mismatches, a unique serial number is marked on both the housing cap and the base (fig. 4).
  • Dimples to locate accessories
    Dimples cast into the housing cap indicate where grease fittings and condition monitoring sensors can be mounted for maximum effectiveness (fig. 5).
  • Simple mounting
    Lines are cast into the housing base indicating the centre of the bearing seat and housing bore axis. Dimples indicate the position for dowel pins (fig. 6). Mounting instructions are supplied with most seal packs1). Housings from size 3028 and above are supplied with an eye bolt on the cap for safe and easy handling.

Housings with different bolt hole configurations

Housings with four drilled holes
  • are available for housings with two cast bolt holes, designation SNLN, and housings made of spheroidal graphite cast iron with a solid base, designation SSNLND
  • have the designation suffix /MS2
Housings with two drilled holes
  • are available for housings made of spheroidal graphite cast iron with a solid base, designation SSNLND
  • have the designation suffix /MS1
Dimensions are listed in table 1.
Housings with a different bearing seat tolerance class
  • are typically used for applications prone to vibration, with rotating outer ring load or for applications operating at high temperatures
  • can be supplied on request
Housing material
  • grey cast iron
  • spheroidal graphite cast iron, on request, for applications where extra strength is needed (Housings are supplied with a solid base, designation SSNLND.)
Paint, corrosion protection

FNL flanged housings are painted black (RAL 9005). The paint:

  • is a water based alkyd/acryl paint
  • protects the housing in accordance with ISO 12944-2, corrosivity category C2 (i.e. exterior atmospheres with low level of pollution, interior atmospheres where condensation may occur)
  • is not affected by most lubricating or engine oils, cutting fluids or alkalescent washing chemicals
Housings can be repainted with most water or solvent based 1- or 2-component paints. Unpainted surfaces are protected by a solventless rust inhibitor.
Dimension standards
  • Boundary dimensions are in accordance with ISO 113 for two-bolt plummer block housings.
  • The housings are dimensionally interchangeable with the earlier SN 30 housings.

Sealing solutions - standard

The housing size determines which sealing solutions can be used. Table 1 provides an overview of the characteristics and suitability of each sealing solution. The detailed information about each sealing solution should be used as a guideline, and does not substitute for testing a seal in its application.
  • Four-lip seals (TSN .. L)
    NEW TEXT?Four-lip seals (fig. 1) replace the former double-lip seals (TSN .. G). When compared to double-lip seals, the new seals are more effective. They also generate less friction, which enables higher shaft speeds. Four-lip seals are radially split and easy to mount.
  • V-ring seals (TSN .. A)
    V-ring seals (fig. 2) consist of a V-ring and a sheet steel sealing washer with a vulcanized rubber lip. The rubber lip fits into the seal groove in the housing. The washer is protected against corrosion.V-rings can accommodate circumferential speeds up to 7 m/s. For circumferential speeds between 7 and 12 m/s, they should be located axially on the shaft. At speeds above 12 m/s, a support ring must be used to prevent the seal from lifting. Recommended dimensions for appropriate support rings for axial and radial location are provided in table 2.The permissible angular misalignment for seals mounted on shafts < 150 mm in diameter is approximately 1,5° and approximately 1° for larger shafts. The axial movement of the shaft relative to the housing is limited to ±1,5 mm. For arrangements with a vertical shaft, the V-ring of the lower seal should be mounted inside the housing.
  • Felt seals (TSN .. C)
    Felt seals (fig. 3) are simple and effective. At circumferential speeds above 4 m/s, a small gap forms between the felt and shaft, transforming the contact seal into a non-contact, gap-type seal.
  • Labyrinth seals (TSN .. S)
    For applications where there are high speeds or extreme temperatures, SKF recommends using labyrinth seals. Labyrinth rings (fig. 4), mounted on the shaft, form a multi-stage labyrinth seal with the housing seal grooves. Hollow, silicone rubber cords, supplied with the rings, hold the rings in place on the shaft.
  • Taconite heavy-duty seals (TSN .. ND, TNF ..)
    For bearing arrangements that must operate under highly contaminated conditions, such as those encountered in mining, taconite heavy-duty seals, which can be filled with grease, are recommended. Grease enhances the sealing effect and extends the service life of the seals. Taconite heavy-duty seals are labyrinth seals combined with a V-ring seal. The labyrinth ring is solid but the main body of the seal is split. SNLN 30 housings from size 3024 to 3032 accommodate taconite seals with a radial labyrinth (fig. 5). SNLN 30 housings from size 3034 to 3056 accommodate solid taconite seals with an axial labyrinth (fig. 6). Both can be relubricated via a grease fitting in the main body of the seal. The axial movement of the shaft relative to the housing is limited to ±1,5 mm for shaft diameters ranging from 110 to 150 mm, ±2 mm for shaft diameters ranging from 160 to 200 mm, and ±4 mm for larger shaft diameters.
  • End covers (ASNH .., ETS ..)
    Housings at the end of a shaft should have an end cover that fits into the seal groove in the housing. For housings from size 3024 to 3032, the end covers are made of plastic (fig. 7) and are suitable for operating temperatures from –40 to +110 °C (–40 to +230 °F). For applications where temperatures exceed 110 °C (230 °F), steel end covers should be used. These can be cut from sheet steel and placed in the seal groove. Use a hollow silicone rubber cord to hold the cover in place. For housings from size 3034 to 3056, the end covers are made of grey cast iron (fig. 8) and are suitable for operating temperatures from –50 to +200 °C (–60 to +390 °F). They are inserted, together with a hollow silicone rubber cord, in the housing seal groove. Details of the permissible length of the shaft end are provided in table 3.
Using sealed bearings in housings with standard seals is a good solution for highly contaminated environments. The sealed bearing together with the housing seal and grease provide three layers of protection (→ SKF Three-Barrier Solution). SNLN 30 housings can be used together with SKF sealed self-aligning bearings. When using taconite heavy-duty seals, a sealed bearing does not enhance the sealing effect during operation, but still protects the bearing against contaminants during mounting.

Sealing solutions - custom

SNLN 30 housings can be equipped with any type of seal that fits the seal groove dimensions in the housing. The relevant dimensions are provided in table 2.
Housings with high-temperature felt seals
  • are available on request
  • are suitable for high operating temperatures, up to 250 °C (480 °F)
  • can accommodate circumferential speeds up to 2 m/s
  • are identified by the designation suffix CB, e.g. TSN 3024 CB

Housings with taconite heavy-duty seals with an axial labyrinth
  • are available on request, in two executions (TSN .. NC, fig. 1 or TSN .. NB, fig. 2)
  • can be used under the same conditions as taconite seals with a radial labyrinth
  • can only be used with housings with the suffix T (at the end of a shaft) or the suffix TD (for through shafts) as the seals are greased via a hole in the housing cap
  • have a V-ring (TSN .. NB) that limits the axial movement of the shaft relative to the housing to ±1,5 mm.
Specifications for the seals are listed in table 1.
  1. 1)The mounting instructions for housings from size 3024 to 3032, with seals in the 200 series, must be ordered separately.
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