CAT 9G-5301 Spring Loaded Piston

The CAT 9G-5301 is a Caterpillar high-pressure hydraulic load piston, primarily designed for use in the high-pressure hydraulic circuits of the lifting cylinder and tilting cylinder of CAT D9G bulldozers and 988B loaders. It converts hydraulic energy into stable mechanical thrust to withstand high pressure and impact loads under heavy-duty conditions, ensuring smooth lifting and tilting of the boom, bucket, and other working devices. Key information is as follows:

Core Technical Parameters
Item Details
Part Model: CAT 9G-5301 (9G5301) High-Pressure Load Piston, compatible with heavy-duty hydraulic cylinders, with double sealing grooves + guide ring grooves

Core Material: 42CrMo alloy structural steel, integral forging + tempering (HB 260–290), outer surface hardening (HRC 50–55), rolling reinforcement in the sealing groove area, high pressure resistance + wear resistance + deformation resistance

Key Dimensions: Diameter 125 mm, Length 100 mm, Sealing groove width 8 mm, Depth 3 mm mm (compatible with U-ring + support ring), guide ring groove width 10 mm, depth 4 mm, center threaded hole M27×2 (for connecting piston rod), chamfered ends 2×45°
Single weight Approx. 9.8 kg
Compatible models CAT D9G bulldozer (lifting cylinder/tilt cylinder), 988B loader (boom cylinder/stick cylinder), 992G mining loader, etc., used for high-pressure hydraulic actuators, bearing continuous high pressure and impact loads under heavy-duty conditions.
Working pressure: Compatible with a maximum working pressure of 35 MPa (350 bar), short-term peak pressure up to 42 MPa, compatible with mineral oil-based hydraulic oil (ISO VG 46)
Core functions and structural features: Heavy-duty pressure-bearing design: 42CrMo forged material + quenching and tempering treatment, yield strength ≥900 MPa, capable of withstanding the large thrust and impact loads of bulldozer and loader working devices, preventing piston deformation and breakage, suitable for heavy-duty conditions in mining, infrastructure, etc. **Optimized Sealing and Guiding:** The double sealing groove + guide ring groove structure adapts the seals to high-pressure conditions. The guide ring reduces friction and wear between the piston and cylinder wall, ensuring smooth piston reciprocating motion and reducing leakage risk.

**Impact Resistance and Fatigue Resistance:** The outer surface is hardened to increase surface hardness, and the sealing groove is rolled to eliminate stress concentration, adapting to pressure fluctuations in hydraulic systems and extending the service life of the piston and seals.

**Stable and Reliable Connection:** The center M27×2 threaded hole provides a high-strength connection to the piston rod, with a torque of 350–400 N・m, ensuring stable power transmission and preventing loosening during operation.

**Installation and Maintenance Points:**
**Installation Specifications:** Clean the piston, cylinder, and piston rod, removing burrs, metal filings, and oil. The clearance between the piston outer circle and the cylinder wall should be 0.04–0.08 mm, and the surface roughness Ra ≤ 0.8 μm.

**Installation Specifications:** When installing seals (such as CAT 123-4567 U-rings + support rings), apply hydraulic oil for lubrication to avoid scratching the sealing lip; the guide ring must fit tightly against the cylinder inner wall without looseness.

Tighten the connecting nut between the piston rod and the piston to the required torque. After assembly, test the piston reciprocating motion for no jamming or leakage, and ensure stable pressure.

Maintenance Recommendations: Every 1000 working hours, check for: piston outer diameter wear > 0.15 mm, sealing groove deformation, surface cracks or peeling. Replace immediately if any problems are found.

When replacing, prioritize original parts to ensure material, dimensional accuracy, and seal compatibility meet standards. Avoid using ordinary carbon steel pistons, which can lead to premature seal damage and pressure leakage.

Simultaneously check the hydraulic oil cleanliness (NAS grade ≤ 8). Replace the filter and hydraulic oil as necessary to reduce piston and cylinder wear and extend the hydraulic system’s lifespan.