Oil Seals
Oil Seal Installation Guide
Correct installation is critical to oil seal life — a seal damaged during fitting will leak from day one regardless of material or design quality.
Before Installation
Preparation
- Inspect the shaft: Check for burrs, scratches, corrosion and wear grooves at the lip contact zone. Surface finish should be 0.2–0.8 µm Ra (ground or polished). A damaged shaft will destroy the seal lip within hours.
- Inspect the bore: Ensure the housing bore is clean, free of burrs and within tolerance. Chamfer the bore entrance at 15°–30° to guide the seal in without cocking.
- Check the seal: Verify it is the correct size. Inspect for shipping damage, distorted lip, or missing garter spring. Never reuse a used seal.
- Lubricate: Lightly coat the sealing lip and the shaft surface with the system lubricant before installation. This prevents dry running and lip damage during first start-up.
Procedure
Installation Steps
- Protect the lip from sharp edges: If the shaft has keyways, splines, threads, or cross-holes at the entry, cover them with a thin sleeve, plastic film, or tape to prevent the lip from catching and tearing.
- Position the seal squarely: Align the seal perpendicular to the bore axis. A cocked seal will leak and wear unevenly.
- Press — don't hammer: Use an arbor press or installation tool (a flat disc or tube matching the seal OD) to push the seal evenly into the bore. Never strike the seal directly with a hammer or drive it in by hitting one side.
- Seat to correct depth: Press until the seal face is flush with or slightly below the housing face, per the drawing. Over-pressing can distort the case and reduce lip load.
- Verify the garter spring: After installation, confirm the garter spring is still seated in its groove by gently feeling the lip. If the spring is dislodged, remove the seal and reinstall.
- Verify orientation: The sealing lip must face the lubricant side. The open side of the lip (concave side) faces inward toward the fluid being retained.
Mistakes
Common Installation Errors
| Error | Result |
|---|---|
| Seal installed backwards (lip facing wrong way) | No sealing — fluid pumped outward |
| Hammered in at an angle | Distorted case, uneven lip contact → leak path |
| Shaft burrs not removed | Lip cut during installation → immediate leak |
| No lubrication on lip | Dry start, lip burns and hardens within minutes |
| Over-pressed into bore | Case deformation, lip forced against shoulder |
| Garter spring dislodged | No radial load on lip → gradual leak |
Shaft Requirements
Shaft Surface Finish & Hardness
| Parameter | Recommended Value |
|---|---|
| Surface roughness Ra | 0.2 – 0.8 µm |
| Shaft hardness | ≥ 45 HRC (for standard elastomer lip seals) |
| Shaft run-out (TIR) | ≤ 0.25 mm at seal location |
| Lead (spiral machining marks) | Not permissible — causes pumping leakage |
| Chamfer at shaft end | 15°–30° chamfer, no sharp edges |