Sealing System Leakage Analysis - Bore

Nicks on Bore Chamfer

Probable Causes	Actions or Countermeasures
Mishandling prior to seal installation	Review bore/housing machining for mishandling
Insufficient material removal	Check casting dimensions for proper material allowance. Check machining for proper gage points
Tool chatter on chamfer surface	Review machining procedures for proper tool configuration, feed, speed, and coolant.

Check for Looseness in Bore

Probable Causes	Actions or Countermeasures
Oversized bore I.D.	Check bore machining dimensions for out-of-tolerance condition.
Undersized seal O.D.	Check seal OD for out-of-tolerance condition.
Rolling of seal into bore during installation	Review installation procedure and use proper installation tools.
Bore sizing	Increase bore material hardness or use bore sealant
Excessive shrinkage/hardening of rubber O.D. seal	Review application temperatures, and seal material specifications.
Deformation of seal during installation	Review installation procedure and use of proper tool.

Measure Bore Diameter

Probable Causes	Actions or Countermeasures
Seal loose.	Use correct OD seal, machine bore to correct size.
Oversize bore diameter resulting from seal press fit deformation.	Check seal to insure proper OD size. Increase housing radial wall in area of seal gland.
Tapered bore diameter resulting from improper machining techniques.	Specify maximum axial diameter taper.
Undersize or oversize bore due to design error.	Contact OEM for corrective action.
Oversize bore not in dimensional agreement with OEM specification.	Unit may be a rebuild. Check seal OD diameter and order proper replacement part.
Seal collapsed	Replace damaged seal with correct size.

Check Bore Chamfer

Probable Causes	Actions or Countermeasures
Chamfer lead-in not adequate to install seal due to improper chamfer angle.	Review machining practices and product drawing.
Deformation of lead-in chamfer edge due to chamfer diameter less than maximum OD of seal.	Check OD of seal to insure seal not oversized and check ID of chamfer to insure ID meets drawing specifications.
Chamfer not present due to machining or product drawing error	Review product drawing and make appropriate changes.
Chamfer deformed due to seal installation	Increase hardness of bore material; use rubber covered seal.
Chamfer too long causing insufficient flat area for seal retention	Check product drawing and chamfer angle. Measure seal width to insure proper part and fit.

Inspect for Flaws or Voids in Housing

Probable Causes	Actions or Countermeasures
Porosity in housing resulting from casting defect.	Review foundry practice.
Circumferential scratches, burns, gouges, due to machining.	Review machining techniques and specification.
Cracks in housing due to heat treating or mishandling.	Review material heat treating specification and handling practices.
Embedment of grinding media producing rough surface.	Review machining practices.

Check for Tool Withdrawal Marks on Bore

Probable Causes	Actions or Countermeasures
Poor machining practices. Tool in contact with surface during removal.	Review machining techniques.
Leakage through machine marks.	Apply OD sealant to seal and/or bore. Machine larger to OD and use larger seal. Machine bore and install sleeve.

Check for Severe Scratches or Galling Marks on Bore

Probable Causes	Actions or Countermeasures
Scratches and galling due to poor handling techniques.	Review handling and shipping practices.
Scratches and galling due to machining operations.	Review machining practices
Scratches and galling due to part assembly; i.e., shaft, seal, bearings.	Review assembly practices.
Leakage through imperfections.	Machine and use larger OD seal. Machine and install sleeve.

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