Oil Seals

Material Abbreviations

Prefix letters:

M = Metal Case or Re-inforcement
B = Cork Sealing Element
F = Felt Sealing Element
L = Leather Sealing Element
R = Synthetic Rubber Element (Nitrile)
Si = Silicone Rubber Element
Vi = Viton Rubber Element
Py = Polyacrylic Rubber Element
S = Steel Case or Re-inforcement
B = Brass Case or Re-inforcement

Seal Type – (See images below).

Suffix Letters:

R/H = Right Hand Rotation (Helix or Spiral)
L/H = Left Hand Rotation (Helix or Spiral)
Bi/D = Left or Right Hand Rotation (Bi-directional, Helix or Spiral)

Examples

M/F/L = Metal Case (or Re-inforcement) with (one) Felt and (one) Leather Sealing elements
M/Si(4B)L/H = Metal Case (or Re-inforcement) with (one) Silicone Sealing element, 4B seal design, Left Hand Rotation

Points of note with regard to oil seals:

• Where it is necessary to replace a bearing or to disturb a seal, a new seal of the correct type and dimensions should be fitted. This is essential in the case of seals that protect the bearings in the hubs (front and rear). If these leak, braking efficiency is reduced. The three key dimensions as indicated in the search facility are:

  • The diameter of the housing into which the seal fits.

  • The diameter of the shaft on which the seal runs.

  • The width of the seal.

• There are two main types of Oil Seal:-

  • Internal - fitted into the housing and remaining stationary whilst the shaft revolves inside the sealing element.
  • External - fitted on the shaft or boss and the housing rotates round the seal. This type of seal is found mostly in hubs.

• Shafts should be checked for scoring. Score marks or burrs should be carefully removed.

• Housings - The surface into which the seal fits should be perfectly smooth. All traces of abrasive matter or degreaser should be removed. Where seals are fitted into an aluminium or alloy housing, a greater amount of interference will be required. A useful tip is to immerse the housing in boiling water for a few minutes, remove it, and whilst it’s still hot, mount the seal and then allow to cool before assembly.
• Fitting:
  
  • Remove all abrasive matter from shaft and housing.
  • Remove grease from the seal - use white spirit for leather and thin lubricating oil for synthetic rubber.
  • Smear the sealing element lightly with thin engine oil.
  • If using a dual type seal, always pack the space between the elements with a good quality grease.
  • The Tension Spring is designed to provide the correct loading and should not be altered. Note that the diameter of the sealing element should be approximately 1/16 " smaller than the shaft diameter, although in special applications it may be necessary to provide a different interference.
  • Ensure that the seal is mounted the correct way round. To retain oil or grease, the sealing lip must face the bearing, and to exclude dirt, the sealing lip should point away from the bearing.
  • The use of an Arbor Press is recommended when mounting the Oil Seal into the housing. Alternatively use a bung or drift slightly smaller in diameter than the steel shell of the seal, and ensure that the seal enters the housing squarely.
  • When mounting the shaft into the seal, the best method is to use a thin tapered sleeve.
  • If the housing is a heavy casting, do not allow the seal to rest on the shaft under its weight for any length of time as a permanent set may develop in the sealing element, which will render the seal ineffective. This is a vital consideration in the case of synthetic rubber seals.