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| Parameter | Specification / Value |
|---|---|
| COGENG Part Number | CGK-707-99-36420 |
| Replaces OEM Number | 707-99-36420 (Komatsu) |
| Primary Dynamic Seal Material | Polyurethane (PU) / Thermoplastic Polyurethane (TPU) |
| Secondary Seal & O-Ring Material | Hydrogenated Nitrile Rubber (HNBR) |
| Operating Temperature Range | -35°C to +115°C (-31°F to +239°F) |
| Maximum Pressure Rating | 42 MPa (6,090 psi) |
| Fluid Compatibility | Standard Anti-Wear Hydraulic Oils (ISO VG 46, 68), Biodegradable Fluids (HEES) |
| Shelf Life & Storage | 5 years in original packaging stored in a cool, dry, dark environment (<25°C). |
| Component Name | Material | Quantity per Kit | Key Function & Characteristic |
|---|---|---|---|
| Main Piston Seal | Polyurethane (PU) | 1 | Primary high-pressure seal for the piston; designed for low friction and high wear life. |
| Primary Rod Seal | HNBR with PTFE Coating | 1 | Main dynamic seal on the rod side; provides tight sealing with minimal breakout friction. |
| Buffer / Secondary Seal | HNBR | 1 | Absorbs pressure surges to protect the primary rod seal from damage and extrusion. |
| Wiper / Scraper | Polyurethane (PU) | 1 | Multi-lipped design; aggressively excludes external dirt, ice, and moisture from the cylinder. |
| Piston Wear Band (Guide) | PTFE Composite with Bronze Fill | 2 | Supports the piston, prevents metal-to-metal contact, and absorbs radial loads. |
| Rod Wear Band (Guide) | PTFE Composite with Bronze Fill | 1 | Centralizes the rod, ensuring smooth, stable extension and retraction. |
| Static O-Rings (Various) | Nitrile (NBR) / HNBR | As per diagram | Provide reliable, leak-free static sealing between housings, glands, and end caps. |
| Back-up Rings | High-strength Nylon | As required | Installed behind primary seals to prevent extrusion into component gaps under extreme pressure. |
This kit is specified for the repair of specific hydraulic cylinders on the following Komatsu models. Application varies by machine configuration and production year. Always verify against the machine's service parts manual.
| Model Series | Specific Models | Typical Cylinder Application |
|---|---|---|
| PC200/220 | PC200-6, PC200-7, PC200-8, PC220-6, PC220-7 | Boom Cylinder (Primary Application) |
| PC200LC/220LC | PC200LC-6, PC200LC-7, PC200LC-8, PC220LC-6, PC220LC-8 | Boom Cylinder |
| PC210 | PC210-6, PC210-7, PC210-8, PC210-10 | Boom or Arm Cylinder |
| PC228US | PC228US-3, PC228US-10 | Boom Cylinder |
| PC240/270 | PC240N-6, PC240N-8, PC270-6, PC270-7 | Arm Cylinder (Some Variants) |
Application Note: The 707-99-36420 kit is most commonly identified as the main boom cylinder seal kit for 20-22 ton class Komatsu excavators (like the PC200/220). For precise identification, match the physical seals from the disassembled cylinder with those in the kit.
Safety First: Park the machine on level, solid ground. Fully lower the boom and arm to the ground to relieve hydraulic pressure. Follow lock-out/tag-out procedures before beginning work.
Impeccable Cleanliness: Perform disassembly and reassembly in a dedicated, clean area. Use a parts washer and lint-free cloths. Even microscopic contaminants can cause seal failure.
System Depressurization: After shutting down the engine, slowly operate the control levers (with the ignition off) in all directions to release any trapped pressure in the hydraulic lines.
Component Handling: During disassembly, mark all components for correct reassembly orientation. Use soft-jawed tools to clamp the cylinder rod. Never suspend the cylinder by the rod alone.
Surface Inspection & Preparation: Critically inspect the cylinder rod for scoring, corrosion, or bends. Check the tube ID for scratches or wear ridges. Polish minor imperfections; severe damage requires component replacement or re-chroming. Deburr all seal grooves thoroughly.
Seal Installation: Lubricate every seal and O-ring with the clean hydraulic fluid that will be used in the system. Use installation cones or protective plastic sleeves when sliding seals over threads and sharp edges. Ensure all seals are seated squarely in their grooves without twisting.
Post-Installation Procedure: After reassembly, reconnect hydraulic lines and partially fill the cylinder with fluid through the port before final tightening. "Bleed" the cylinder by cycling it slowly several times with the hydraulic system at low pressure. Check all connections for leaks and monitor fluid levels closely during initial operation.
