Installing HDDF seals

Careful handling and installation of a metal face seal is critical to avoid cutting or tearing of the elastomeric Belleville washers or breaking the metal sealing rings, both which can cause premature seal failure and immediate leakage. It is also vital to keep the sealing faces free from contaminants like dirt or lint. Always carefully observe installation instructions.

Housing and seal preparation

All housing components contacting the Belleville washers must be free from contaminants (oil, grease, dust, lint particles etc.) when installing the seal. SKF recommends using a non-petroleum based solvent and a clean, lint-free wipe to clean these components prior to installation.
All seal parts must be handled with care to avoid damage or scoring.

Installation procedure

  1. Install the Belleville washers seated against the inside shoulder of the metal sealing rings (fig 1).
  2. Carefully push each seal half (Belleville washer and metal sealing ring) into the housing until it is fully seated. Check that the seal is not cocked and that the washers are seated evenly at the bottom of the housing bore. Improper seal installation can result in uneven face loads around the circumference of the seal faces, causing scoring or the sealing rings to separate and allow oil to leak.
  3. Clean both metal sealing ring faces with a lint-free wipe and apply a thin film of oil. Ensure that no oil is applied to any surface but the sealing ring faces (fig 2).
  4. Check that both housings are concentric and in correct alignment. The Belleville washers must not unseat from the bottom of the housing.
  5. Carefully bring the two housings together, avoiding high impact that can scratch or break the seal components.
  6. Finally, hold one half of the assembly stationary while rotating the other half at least ten complete revolutions.


This procedure enables the installer to check that the housing and the Belleville washers are aligned. If the seal assembly wobbles, it is necessary to disassemble it and make sure that the Belleville washers are properly seated in the housing.
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