4445928 Original Excavator Oil Seal for ZX670-3 ZX690-5A ZX850-3 ZX890-5A

Part number 4445928 is a hydraulic system specific oil seal for Hitachi original excavators. According to publicly available accessory information, it is mainly suitable for Hitachi ZX series medium to large excavators, including but not limited to ZX200-3, ZX210-3, ZX240-3, ZX330-3, ZX360-3, ZX470-3 and other models. It is also widely used in EX series large mining excavators such as EX1200, EX1900, etc. This oil seal is usually used for dynamic sealing of key parts such as hydraulic cylinders (boom, middle arm, bucket), hydraulic pumps, walking motors, swing motors, and central rotary joints. The universal part number may vary depending on the specific installation location, for example, multiple different specifications of oil seals and O-rings may be included in the center swivel joint repair kit. When purchasing, it is necessary to provide the complete model of the excavator, the engine model, and the specific installation position of the oil seal to ensure that the accessories are completely matched.

This oil seal is the core component of hydraulic system dynamic sealing. Its core function is to effectively seal high-pressure hydraulic oil when the hydraulic cylinder piston rod or rotating shaft moves back and forth at high speed, prevent oil leakage, and block external dust, mud, and moisture from entering, protecting the precision components inside the hydraulic system. As an original component, it usually uses high-quality nitrile rubber (NBR) or fluororubber (FKM) as the sealing lip material, with a high-strength metal skeleton embedded inside to maintain shape and provide support. Its design can withstand a working pressure of up to 31.5MPa for excavator hydraulic systems and adapt to a wide temperature range of -20 ℃ to 120 ℃. The sealing lip is usually designed with a main lip, a dust lip, and a spring ring. The main lip is responsible for sealing the oil, the dust lip blocks impurities, and the spring ring provides continuous radial compression force to ensure long-term stable sealing effect.

The maintenance core of this oil seal lies in regular inspection, keeping the hydraulic oil clean, and replacing it in a standardized manner. Daily inspection: Before starting and after each operation of the equipment, check whether there are oil stains or leaks at the piston rods, hydraulic pumps, motors, and pipeline joints of each hydraulic cylinder. Regular maintenance: It is recommended to conduct a comprehensive inspection of the hydraulic sealing system of the entire vehicle every 500-600 working hours or annually, with a focus on checking for cracks, hardening, wear, or flanging of the oil seal lip. Replacement specification: When dismantling the old oil seal, a special puller must be used, and it is strictly prohibited to use sharp tools such as screwdrivers to pry it, in order to avoid scratching the shaft neck or sealing groove. Before installing a new oil seal, it is necessary to thoroughly clean the shaft neck and sealing groove with non-woven fabric and specialized cleaning agent, and apply a thin layer of specialized lubricating grease or hydraulic oil on the oil seal lip and shaft neck.