Hydraulics

Maximum working pressure, flow, fluid type and fluid temperature range are the four basics. Every component in the circuit must withstand the highest pressure, including pressure spikes when valves close quickly. Also note port thread sizes and valve mounting patterns for quick matching.

Common mineral oils (ISO 6743-4, HM and HV categories) suit NBR seals and standard rubber hose. Fire resistant water-glycol or phosphate ester fluids may need other seal materials such as FKM or EPDM depending on the fluid. Changing fluid without checking material compatibility can make seals swell or harden.

Pumps and valves are often interchangeable when they share a standard mounting pattern (such as ISO 4401 for valves) and the same pressure and flow ratings. Also check rotation direction, actuation type and coil voltage. Hose and fittings must share the thread system and sealing method, not only the diameter. Send the nameplate or part code to sales@kit.com.vn for KIT to cross-reference.

Most hydraulic failures start with particles in the oil, so set an ISO 4406 cleanliness target suited to the most sensitive component in the system. New oil should also be filtered on filling, the tank breather should carry an air filter and open ports must be capped during service. Periodic oil sampling detects wear and water ingress early.

Stop the pump, lower or block every suspended load and release circuit pressure, including pressure stored in accumulators. Cylinders held by check valves remain pressurised even with the pump off. Never search for a high pressure leak by hand, because an oil jet can penetrate skin.

There is no fixed interval for every system, since oil life depends on operating temperature, cleanliness and water content. The reliable way is to change oil based on sample analysis of viscosity, acid number, water content and cleanliness. Cloudy, darkened or burnt smelling oil has degraded and should be checked immediately.