Key Features
Rotary-Specific Engineering: Precision-designed for the dynamic environment of hydraulic motors, addressing both axial and radial sealing challenges unique to rotating shafts.
VortexShield™ Dual-Material Technology: PTFE lip provides near-zero breakout friction and superior wear resistance; FKM body ensures excellent thermal and chemical stability.
Comprehensive Leak Prevention: Addresses all potential leak points including main shaft, case fittings, port connections, and housing interfaces with a single kit.
High-Speed Compatibility: Rated for continuous operation at shaft surface speeds up to 20 m/s, suitable for high-torque swing and travel applications.
Containment-Ready Design: Includes secondary barrier seals to comply with environmental regulations by preventing hydraulic fluid seepage into the environment.
| Parameter | Specification / Value |
|---|---|
| COGENG Part Number | CGK-8780-388SM (Swing Motor) |
| Replaces OEM Number | 878000388 (Komatsu) |
| Primary Rotary Seal Material | VortexShield™ (PTFE Lip / FKM Body) |
| Static Seal Material | Hydrogenated Nitrile (HNBR) - 70 Durometer |
| Temperature Range | -30°C to +150°C (-22°F to +302°F) continuous |
| Maximum Pressure at Seal | 2.5 MPa (360 psi) for face seals, 30 MPa (4,350 psi) for static seals |
| Shaft Surface Speed | 0-20 m/s (0-3,940 fpm) continuous |
| Fluid Compatibility | Komatsu TDTO, Super Hydraulic Fluid, ISO VG 46/68, most synthetic blends |
| Runout Tolerance | Compensates for shaft eccentricity up to 0.4mm TIR |
| Shelf Life | 5 years in protective foil packaging |
| Component Name | Material & Specification | Qty | Critical Function & Design Feature |
|---|---|---|---|
| Main Rotary Shaft Seal | VortexShield™ PTFE/FKM with dual spring | 1 | Primary dynamic seal; PTFE lip for low friction, dual spring for uniform pressure. |
| Secondary Lip Seal | HNBR with dust exclusion lip | 1 | Provides backup sealing and excludes external contaminants from main seal. |
| Motor Housing O-Rings | HNBR, high-grade compression set resistance | 3-4 | Large static seals for motor case halves and end covers. |
| Port Seal Kit | Copper-coated steel crush washers & HNBR O-rings | 6-8 set | Seals high-pressure hydraulic ports; copper coating prevents galling. |
| Shaft Sleeve (if applicable) | Hardened stainless steel with micro-finish | 1 | Provides new sealing surface on worn shafts; 0.2 Ra surface finish. |
| Bearing Isolator Seal | Labyrinth-style, non-contact design | 1 | Protects motor bearings from contamination without creating friction. |
| Static Gaskets | Coated fiber material, 0.5mm thickness | 2 | For sealing flat mating surfaces on valve plates or covers. |
| Anti-Rotation Pins | Hardened steel | 2 | Prevents seal rotation in housing bore during operation. |
| Installation Sleeve | Precision-machined nylon | 1 | Protects seal lip during installation over shaft splines or keyways. |
This seal kit is designed for swing motors and travel motors on specific Komatsu excavator models.
Always verify motor model number before installation.
| Model Series | Specific Models | Motor Application | Motor Series (Typical) |
|---|---|---|---|
| PC200/220 Series | PC200LC-8, PC200-8, PC220LC-8, PC220-8 | Swing Motor | KMF120AB, KMF125AB |
| PC228US Series | PC228USLC-3, PC228US-3 | Swing Motor | KMF90, KMF100 |
| PC300/350 Series | PC300LC-7, PC300-7, PC350LC-8 | Travel Motor | KVF75, KVF80 |
| PC130/138 Series | PC130-7, PC138US-10 | Swing Motor | KMF60, KMF70 |
| Dash-7 & Dash-8 | Multiple 13-35 ton class models | Swing or Travel Motors | KMF/KVR series motors |
Critical Application Note: The 878000388 kit is specifically for hydraulic motor shaft sealing applications, not for hydraulic cylinders. Misapplication will result in immediate failure. Always match the motor identification plate (KMF, KVR series) and physically compare old seals with new components before disassembly.
Decompose pictures
Phase 1: Pre-Disassembly & Motor Identification
Motor Tagging: Before removal, tag all hydraulic lines and photograph their connections. Note the orientation of the motor on the machine.
Cleanliness Protocol: Clean the exterior of the motor thoroughly with degreaser. Establish a clean work area with sealed containers for internal components.
Record Critical Dimensions: Before disassembly, measure and record shaft diameter, seal bore diameter, and shaft clearance in the bore. Compare to specifications.
Phase 2: Disassembly & Surface Inspection
4. Sequential Disassembly: Disassemble the motor methodically, placing components in order on a clean tray. Note the position and orientation of gears, plates, and bearings.
5. Shaft Inspection: Examine the shaft sealing surface for wear grooves, pitting, or corrosion. Acceptable wear depth: ≤ 0.05mm. Deeper grooves require shaft replacement or sleeve installation.
6. Bore Inspection: Check the seal housing bore for scoring, corrosion, or out-of-round condition. Maximum allowable bore taper: 0.025mm over seal contact width.
7. Bearing Assessment: Check all bearings for smooth operation and minimal play. Worn bearings cause shaft eccentricity that will rapidly destroy new seals.
Phase 3: Seal Installation (Motor-Specific Techniques)
8. Bore Preparation: Lightly polish the seal bore with fine emery cloth if minor corrosion exists. Clean with solvent and dry completely. Apply a thin film of compatible grease to the bore.
9. Shaft Protection: Cover all shaft splines, keyways, and threads with the provided nylon installation sleeve or aluminum tape before sliding seals over the shaft.
10. Rotary Seal Installation:
* Lubricate the PTFE sealing lip with the same grease used in the motor's final application.
* Critical: Install the main rotary seal with the PTFE lip facing the fluid side (usually toward the motor interior).
* Use a properly sized seal driver to press the seal squarely into the bore until fully seated. Never hammer directly on the seal.
11. Shaft Sleeve Installation (if required): If installing a repair sleeve, clean the shaft with solvent, apply threadlocker to the shaft, and press the sleeve on until it bottoms out against the shoulder.
Phase 4: Reassembly & Testing
12. Component Lubrication: During reassembly, lubricate all internal components with clean hydraulic fluid. Pre-fill the motor housing with fluid before final closure.
13. Torque Specifications: Use a calibrated torque wrench on all case bolts. Follow the manufacturer's cross-pattern tightening sequence. Typical torque: 50-60 N·m for M10 bolts.
14. Post-Installation Procedure:
* After reinstallation, operate the motor at low idle with no load for 5-10 minutes to allow seals to seat.
* Check for leaks at all sealing points.
* Gradually increase load over the first hour of operation.
* Monitor motor temperature; it should stabilize below 85°C (185°F) under normal operating conditions.
Safety Warning: Never operate a machine with a newly sealed swing or travel motor without first testing functionality in a controlled environment with clear escape paths.
Frequently Asked QuestionsQ1: Which Komatsu machine uses the 878000388 outrigger cylinder seal kit?
A: This seal kit is designed specifically for the outrigger (stabilizer) cylinders on the Komatsu WB140-50 backhoe loader. Please verify your machine serial number before ordering.
Q2: Is this an OEM or aftermarket seal kit?
A: It is an OEM-grade replacement kit, manufactured to meet or exceed original Komatsu specifications for sealing performance, durability, and precise fit.
Q3: What is included in the COGENG 878000388 outrigger seal kit?
A: The kit includes all necessary rod seals, piston seals, wipers, O-rings, and backup rings for a complete outrigger cylinder rebuild – no missing components.
Q4: What symptoms indicate I need to replace my outrigger cylinder seals?
A: Common signs include hydraulic oil leaks around the outrigger cylinder, stabilizer drift or sagging, loss of lifting capacity, and reduced machine stability during operation.
Q5: How do I purchase the COGENG 878000388 outrigger cylinder seal kit?
A: Contact us with your Komatsu WB140-50 machine serial number for fitment confirmation, then order directly through our website or sales team for fast shipping.
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