A Pump selection starts with pressure requirements—the pump's rated pressure should be 1.25 to 1.5 times the system's maximum working pressure. Flow demand is calculated from actuator speed and load requirements, with the rated flow typically 1.1 to 1.3 times the system's maximum flow to account for leakage. The pump's speed range must match the prime mover. Type selection depends on the application: gear pumps suit low-cost, moderate-duty systems; vane pumps offer smooth, quiet operation for medium-pressure applications; piston pumps handle high pressure with high efficiency and variable displacement. Also consider volumetric efficiency, self-priming ability, contamination tolerance, and cost.

A Gear pumps are simple, cost-effective, and reliable, suitable for low to medium flow and pressure applications. Vane pumps provide smooth, low-noise flow for medium-pressure systems. Piston pumps deliver high pressure and high efficiency with adjustable displacement, ideal for demanding applications. Hydraulic motors convert fluid energy back into rotary mechanical energy. Each type has distinct advantages: gear pumps offer economy, vane pumps provide smooth operation, and piston pumps deliver the highest performance for high-pressure, variable-flow applications such as construction machinery and industrial presses.

A Piston pump systems offer compact size, light weight, operational flexibility with wide speed range, high reliability from robust mechanical construction, and long service life due to good wear resistance. Disadvantages include pressure fluctuation under varying loads, higher operating noise from mechanical and fluid sources, strict requirements for oil quality and cleanliness, and more complex installation and commissioning that requires specialized knowledge. They are widely used in metallurgy, mining, petrochemical, and marine applications where high power and reliability are essential despite these trade-offs.

A A servo pump system uses a servo motor to drive the hydraulic pump, replacing the conventional fixed-speed asynchronous motor. The servo motor precisely controls pump speed to match flow and pressure to actual demand. When less flow is needed, the motor slows down rather than bypassing excess oil over a relief valve. This eliminates the energy waste of constant-speed systems. The system operates in two states: flow control when pressure is below the setpoint, and pressure control when the setpoint is reached, where the pump slows to maintain only the required holding pressure or leakage compensation flow.

A Control valves regulate pressure, flow, and direction. Pressure relief valves protect the system by diverting excess flow when pressure exceeds a set limit. Pressure reducing valves maintain a lower, stable pressure in a branch circuit. Throttle valves control flow by varying the orifice area to adjust actuator speed. Flow control valves combine a pressure compensator with a throttle to maintain stable flow regardless of load changes. Directional control valves switch oil flow paths to control actuator direction, available in manual, solenoid-operated, and pilot-operated configurations to suit different control requirements.

A Proportional valves use proportional solenoids to continuously control pressure, flow, or direction proportionally to an electrical input signal. They offer moderate accuracy (±0.5–2%), moderate response, and good contamination tolerance, suitable for injection molding and construction machinery. Servo valves use a torque motor driving a pilot stage for very precise control, achieving high accuracy (±0.1–0.5%) and fast response, but require extremely clean oil. Servo valves are essential for aerospace flight controls and CNC machine tools. Proportional valves are increasingly closing the performance gap, offering a cost-effective alternative for less demanding precision applications.

A Seals must provide reliable leakage prevention across varying pressures, temperatures, and fluid types. They need high wear resistance for long life under friction, corrosion resistance against oil additives, good elasticity with low compression set to maintain preload, and compatibility with the hydraulic oil to avoid swelling or hardening. Common types include clearance seals for low-pressure applications, O-rings for simple, cost-effective static and dynamic sealing, lip seals such as Y-rings and V-rings providing self-energizing action for medium to high-pressure dynamic applications, and combined seals that integrate multiple elements for enhanced reliability under demanding conditions.

A Accumulators store energy by compressing an inert gas, typically nitrogen, as hydraulic oil enters the unit. When system pressure drops, the compressed gas expands and pushes stored oil back into the circuit. Bladder-type accumulators offer fast response and suit frequent cycling. Piston-type accumulators handle higher pressures and larger volumes. Spring-type accumulators suit low-pressure, small-volume needs. Applications include supplementing pump flow during peak demand to reduce pump size, absorbing pressure shocks and pulsations to protect components, and providing emergency power to complete critical actions during pump failure or power loss.

A Filters remove contaminants—metal particles, dust, and debris—that would otherwise cause abrasive wear, block valve orifices, and degrade oil. Selection considers filtration rating (micron level) matched to the most sensitive component, typically finer for servo valves; flow capacity sufficient for maximum system flow without excessive pressure drop; acceptable initial and clogged pressure loss; and filter media type. Paper elements offer high precision at low cost but clog faster; wire mesh is durable but less precise; sintered metal provides high strength and precision. Multiple filters at suction, pressure, and return lines ensure system-wide cleanliness and component protection.

A Material selection depends on pressure: rubber or nylon hoses suit low-pressure, flexible applications; seamless carbon steel tubes handle medium to high pressures; alloy steel tubes serve the highest pressure requirements. Stainless steel is used for corrosive fluids. Diameter sizing balances flow rate against velocity limits—suction lines 0.5–1.5 m/s to prevent cavitation, pressure lines 2–6 m/s to limit pressure loss. Wall thickness withstands the maximum system pressure with a safety factor. Larger diameters reduce friction and heat but increase cost and space, requiring balanced design considering available installation space and system efficiency targets.