4419238 Original Excavator Steel Ball for ZX110 ZX200 ZX120-5G ZX130-5G

Part number 4419238 is labeled as BALL (Ball/Ball) in Hitachi's original system. It is a precision coupling level small part inside hydraulic main pumps (commonly found in HPV series, such as HPV091/102/118/145, etc.), mainly used for connecting plunger ball sockets/ball joints (copper heads), one-way sealing of valve seats, or servo valve core positioning in key parts of pump casings (cylinder bodies). It is not a cross machine universal standard component: the diameter, tolerance level (G10/G16, etc.), material, and hardness of the same steel ball must match the corresponding pump family/pump serial number completely, otherwise it may not be installed properly or wear abnormally. Please provide photos of the pump body nameplate (model+serial number) and the measured diameter/part number label of the old ball when purchasing, and lock 4419238 according to the original factory specifications.

This steel ball is a key pressure bearing component in the pump under high-frequency impact and oil film lubrication environment: usually made of high carbon chromium bearing steel (such as GCr15) precision grinding and polishing, overall heat treatment, surface hardness and roughness are controlled according to bearing industry standards to ensure resistance to pitting corrosion, micro motion wear, and long-term shape stability at the plunger ball joint or valve port seal. Its core function is not "transmission", but as a rotating/self-locking node or one-way valve sealing element of the ball joint pair, maintaining a balance between freedom of movement and sealing reliability under high pressure pulses. Once the ball diameter exceeds the tolerance, there is peeling or insufficient hardness on the surface, typical symptoms such as pump leakage, abnormal noise, and unstable flow may occur, and the source cannot be found after half a day of investigation.

It belongs to precision parts that are only touched during pump disassembly and overhaul: do not disassemble or replace it separately in daily life. Only during hydraulic pump cover opening maintenance (such as plunger/port plate/ball joint component replacement), should the ball diameter, roundness, surface corrosion/peeling, and fit clearance with the seat (or copper ball socket) be checked according to the manual. As long as visible damage or roundness deviation occurs, it must be replaced and paired/assembled according to the original factory specifications; Before reassembly, thoroughly clean the parts and oil passages, prevent dust and secondary scratches, and restore the positioning parts (such as snap springs/covers) in torque/order. More importantly, 80% of the lifespan of this steel ball depends on the cleanliness of the oil - regularly replacing the oil return filter element and keeping the system free of metal shavings are far more effective than "changing the ball".