Excavator undercarriage
Travel motors, track rollers, carrier rollers and idlers — mud and sand ingress is the main enemy; metal face hardness and toric compensation extend rebuild intervals.
Type DO · O-ring loaded
The default mechanical face seal for Caterpillar-type undercarriage — final drives, track rollers, carrier rollers and idlers on excavators, dozers and mining crawlers.
A DO floating seal is an O-ring loaded mechanical face seal: two metal rings with lapped faces, each paired with a toric elastomer ring in a seal house. The toric ring provides static sealing, axial loading and wear compensation; the metal faces do the dynamic sealing work.
HuaTong rings are cast from 15Cr3Mo high-chrome alloy, heat-treated and twin-face lapped so the contact band can hold oil in and keep mud, sand and mine dust out. DO is not interchangeable with DF — different elastomer section and seal-house logic.
Use this matrix before you quote or rebuild. Similar OD can still mean the wrong face pressure if the profile is swapped.
| Factor | DO (this page) | DF | XY |
|---|---|---|---|
| Metal ring pair | Two identical symmetric rings | Two identical symmetric rings | Complementary X + Y halves (different heights) |
| Elastomer loader | Toric O-ring (one per half) | Diamond / square section (one per half) | Toric O-ring (one per half) |
| Typical OEM fit | Standard duo-cone housings (incl. Cat-type undercarriage) | Compact axial / square-bore housings | OEM matched X/Y catalog groups |
| Housing logic | O-ring rolls on ring ramps in seal house | Diamond loader seats in shallow or square pockets — do not mix with DO | X and Y halves are not mirror-identical — replace as a matched set |
| Best when | Standard crawler rebuilds, aftermarket DO marks | Limited axial depth or DF marking on worn elastomer | OEM drawing lists X/Y line (e.g. SC 0760 X + Y) |
Still unsure? Send a worn-seal photo, OEM number or housing drawing — we confirm DO / DF / XY before quoting.
Summary parameters for RFQ and engineering review. Full size charts available on request or via datasheet.
| Profile | Type DO — O-ring / toric ring loaded floating seal (duo-cone / mechanical face seal) |
|---|---|
| Set composition | Two metal seal rings + two toric elastomer rings, supplied as one matched group |
| Primary function | Retain hub lubricant; block external mud, water, sand and abrasive dust from bearing/gear cavities |
| Ring material | High-chrome alloy cast iron (15Cr3Mo family); melt, cast, heat-treat, CNC and lapped faces |
| Typical install positions | Final drive, track roller, carrier roller, idler, sprocket hub on excavators, dozers and crawlers |
| Elastomer options | NBR (general mineral oil), HNBR (heat/oil), FKM (elevated temp / chemical) — per fluid and temperature |
Working logic, seal-house requirements, face-pressure balance and field assembly rules. Scroll inside the panel.
| Four-step working logic | 1) Elastomer compressed in seal house stores energy · 2) Rings pushed into face contact · 3) One ring rotates, faces slide · 4) Wear compensated by elastomer release |
|---|---|
| Metal ring back geometry | Steps, taper or inverted-cone features on ring O.D. cooperate with O-ring to generate axial face load in the bore |
| Seal house (floating seat) | Bore angle, depth, chamfer, roughness and coaxiality control O-ring compression and face pressure — not a simple groove |
| Seal-house roughness (typical) | Loading surface often Ra 6.3–12.5 μm class so toric ring can grip and roll on ramps without uncontrolled slip |
| Face roughness Ra | Engineering target approx. 0.05–0.20 μm after lapping; confirm per drawing and size |
| Face flatness | Often controlled to approx. 0.3–1.0 μm or by light-band inspection on critical sizes |
| Ring hardness | Common HRC 58–68; high-wear 15Cr3Mo routes may reach HRC 60–72 — always state material + test position |
| Typical duty limits (reference) | Up to approx. 3 m/s circumferential speed and 0.3 MPa face-pressure class on 15Cr3Mo routes — confirm per catalog line and housing |
| Face pressure balance | Too low → leak and contamination ingress; too high → heat, burned faces and elastomer overload |
| DO vs DF warning | DO must not be installed in DF seal houses (or vice versa). Similar OD can fit but face pressure becomes uncontrolled |
| Rebuild rule | Replace both metal rings and both elastomers together; inspect worn seal house before fitting new group |
| RFQ checklist | OEM part no., machine model, install position, OD/ID/height, old-part photos, fluid, contamination type, failure mode |
Select by position + contamination + failure mode — not part number alone.
Travel motors, track rollers, carrier rollers and idlers — mud and sand ingress is the main enemy; metal face hardness and toric compensation extend rebuild intervals.
Final drives and rollers on D-series crawlers see shock, bias load and abrasive dust — DO groups are the standard aftermarket replacement profile.
Conveyors, loaders and mobile crushers in stone dust and slurry need carbide-rich alloy faces and stable face pressure over long shifts.
Incomplete RFQs slow matching. Include any three of the items below and we reply within 24 hours on working days.
Short answers buyers ask before sampling or rebuilding.
No. Similar outer diameter can still produce uncontrolled face pressure. Confirm DO vs DF from the worn elastomer shape, OEM mark or housing drawing before ordering.
Replace both metal rings and both toric elastomers as one matched group. Inspect the seal house for wear or damage before fitting the new set.
NBR covers most mineral-oil hubs. Choose HNBR for higher heat/oil stress, or FKM when temperature or chemistry requires it — tell us the fluid and duty when you enquire.
Yes — download the DO datasheet for the summary range, or send OEM numbers / dimensions for a confirmed match and packing quote.
Share the OEM number, drawing or worn-seal photo — we confirm type, lead time and packing.
