CAT 078-0776 SPOOL

CAT 078-0776 is a Caterpillar original equipment spool valve, compatible with the hydraulic pilot control circuit of 3044C/3054C engines, 306E/307E excavators, and 226B3/246B3 skid steer loaders. It is used for precise switching of fluid channels to control the action of actuators and is often used in conjunction with 078-0253 retainers and 078-0653 check seats.

Core Parameters and Information

Item Details
Part Model: CAT 078-0776 (078776) Spool Valve

Structure Type: Three-stage plunger spool valve with 2 working ring grooves, 2 positioning shoulders, guide sections at both ends, and a drive groove in the center.

Material: 20CrMo alloy steel, surface nitrided, conforming to CAT MES B0304 specification.

Key Dimensions: Overall length 68 mm, maximum outer diameter 32 mm, working ring groove width 5 mm, depth 2 mm, positioning shoulder width 4 mm, drive groove width 6 mm, depth 3 mm.

Performance Parameters: Working pressure 0-31.5 MPa, working temperature -40℃ to +120℃, internal leakage ≤0.03 mL/min, response time ≤15 ms, hardness HV650-750, surface roughness Ra≤0.4 μm.

Compatibility Standard: Complies with SAE J1930 hydraulic valve installation standard. 078-0253 Fixture Positioner, used with 078-0653 Check Seat for sealing.

Compatibility: Applicable to 3044C/3054C engines, 306E/307E excavators, and 226B3/236B3/246B3 skid steer loaders; compatible with 078-0253 Fixture, 078-0653 Check Seat, and 077-8727 Bearing.

Compatible Models and Application Scenarios:

Compatible Equipment: Hydraulic pilot valve assembly and fuel injection control module for CAT 3044C/3054C engines, 306E/307E mini excavators, and 226B3/236B3/246B3 skid steer loaders.

Application Scenarios: Fluid direction switching in hydraulic pilot control circuits, such as controlling the movement of the boom, stick, and swing mechanism; suitable for medium-high pressure and medium-temperature continuous operation conditions.

Matching Installation: The spool valve is fitted into the valve sleeve, with the positioning shoulder aligning with the 078-0253 retainer. The working ring groove corresponds to the valve sleeve oil port. After installation, the coaxiality should be ≤0.02 mm, and the movement resistance ≤15 N.

Installation and Maintenance Points: Clean the spool valve, valve sleeve, and retainer, checking for deformation, cracks, and scratches. The clearance between the spool valve and valve sleeve should be 0.01-0.02 mm.

Use a dedicated guide tool to install the spool valve into the valve sleeve, ensuring the positioning shoulder engages with the retainer’s groove and the drive groove precisely aligns with the actuator output shaft.

Post-Installation Testing: Switch the spool valve position and check that all oil ports are open and closed normally, with no leakage, and that the action is responsive and without jamming.

Maintenance: Every 2000 hours, check the spool valve surface wear and clearance. Replace immediately if wear exceeds 0.03 mm or clearance exceeds 0.05 mm.