An excavator hydraulic cylinder is the core actuator of the hydraulic system, converting hydraulic energy into mechanical energy to drive the boom, arm, bucket and other movements. 1. Main Types (by function)

1. Boom Cylinder: Controls boom lifting/lowering, double-acting
2. Arm Cylinder: Controls arm extension/retraction, double-acting
3. Bucket Cylinder: Controls bucket opening/closing, double-acting
4. Track Tension Cylinder: Tensions crawler tracks, mostly single-acting

2. Basic Structure (Double-acting Single-rod Cylinder)

1. Cylinder Barrel: Made of 27SiMn seamless steel pipe, honed inner wall, high pressure resistance (20–35MPa)
2. Piston Rod: 42CrMo alloy steel, hard chrome plated surface, wear and corrosion resistant
3. Piston & Seals: Equipped with wear rings, bidirectional oil seals and dust seals; prevents internal leakage and contamination
4. End Cover & Guide Bushing: Supports and guides the piston rod, also for sealing
5. Buffer Device: Built-in buffer valves at both ends to reduce impact at stroke limits

3. Working PrinciplekpBR
High-pressure hydraulic oil (30–35MPa) from the hydraulic pump enters the rodless chamber to extend the piston; oil entering the rod chamber retracts the piston. The control valve switches oil direction to realize push-pull movement.kpBR
4. Common Faults & Solutions

1. External oil leakage: Seal aging, piston rod scratch → Replace oil seals, repair or replace piston rod
2. Internal leakage / Weak power / Boom drop: Piston seal failure, cylinder barrel scratch → Replace seals, bore repair or change cylinder barrel
3. Slow / Jerky movement: Contaminated hydraulic oil, stuck valve spool → Replace hydraulic oil, clean valve assembly, overhaul cylinder
4. Bent piston rod: Overload, violent impact → Straighten or replace rod, tighten pin bolts

5. Key Technical Parameters (Medium & Large Excavators)

1. Working pressure: 30–35MPa
2. Piston rod surface hardness: HRC 58–62

6. Daily Maintenance Tips

1. Keep hydraulic oil clean; replace oil and filters regularly
2. Avoid collision and scratch on the piston rod; keep dust seal intact
3. Prevent long-time overload and high-temperature operation
4. Regularly lubricate hinge points and check pin bolt tightness

Racer Machinery can supply aftermarket cylinders for brand Caterpillar, Komatsu, Hitachi, Volvo, Sany, XCMG, Hyundai, etc.kpBR