Are you curious about hydraulic pump systems — what they are, how they work, and their uses? In the following, we will introduce the basic definition of a hydraulic drive system, its types, how do hydraulics work, and key points for daily maintenance.

1. What Is a Hydraulic System?

A hydraulic system, using constrained fluid (usually hydraulic oil), transfers external forces so that force can be converted, amplified, or adjusted in different parts. Key components of this type of hydraulics include:

• Hydraulic cylinder: generates unidirectional pushing or pulling force, functioning like the “muscle” of the system to move or support loads.

• Filter: removes solid impurities from the fluid to prevent wear or clogging.

• Hydraulic oil: the energy medium of the system; it not only transmits force but also lubricates, cools, and carries away contaminants.

• Drive source (motor / prime mover): provides mechanical drive power for the pump, transforming mechanical energy into fluid pressure energy.

• Hydraulic Valves: control the direction, pressure, and flow rate of the fluid; these are critical parts that greatly affect system response speed and actuation behavior.

  Hoses and piping: connect all components and handle high-pressure fluid transmission; must be pressure-resistant, wear-resistant, and corrosion-proof.

• Hydraulic Pump: converts mechanical energy into hydraulic energy; it pressurizes the hydraulic oil and sends it into the system.

• Reservoir / oil tank: stores the fluid, compensates return oil; its design should account for removing air, settling out contaminants, and aiding heat dissipation.

2. Types of Hydraulic Systems

Hydraulic systems (or hydraulics) are mainly classified by the structure of their working circuits:

• Open-loop (Open-circuit)
  In an open-loop hydraulic drive system, when the actuator is idle or not working, fluid can still flow but there is no sustained high pressure. This type is often used in simpler, lower-cost setups where response speed is not extremely critical.

• Closed-loop (Closed-circuit)
  Once the pump begins operation, the circuit is closed to maintain fluid pressure. Closed-loop systems are suited to applications that require higher control precision, faster response, and often include a feed pump or charge pump to stabilize pressure in the loop. Compared to open-loop, closed-loop hydraulics provide advantages in efficiency, response, and control.

3. How Do Hydraulics System Work?

Here’s a step-by-step explanation of how a hydraulic drive system operates:

Fluid Intake from Reservoir

The hydraulic oil is drawn from the tank (reservoir) by the hydraulic pump. The fluid inside includes return oil (from actuators) and fresh oil. The reservoir is designed to purify the fluid, block air ingress, and allow cooling. Internal baffle plates or partitions are often used to prevent turbulence, foam, or contaminants from being drawn back into the pump.

Pump Pressurization and Control Valve Regulation

The hydraulic pump pressurizes the fluid and pushes it into the high-pressure circuit. Depending on load and control requirement, the pump may be fixed-displacement or variable-displacement. The pressurized hydraulic fluid passes through control valves — directional control valves, pressure relief valves, flow control valves, etc. These regulate flow rate, pressure, and direction. Safety valves prevent over-pressure; throttling valves help fine-tune actuator speed.

Actuation: Producing Mechanical Motion

Pressurized oil enters actuators such as a hydraulic cylinder or hydraulic motor. Hydraulic cylinder supplies linear motion; hydraulic motor supplies rotary motion. In a cylinder, fluid acts on one side of a piston, generating a load force proportional to piston area and hydraulic pressure. The piston moves a rod to produce linear displacement. In a motor, continuous pressure difference drives the rotor to rotate.

Return Flow and Sealed Circuits

Fluid on the opposite side of the piston (unpressurized or lower pressure side) returns via pipes to control valves, and then back to the reservoir or pump inlet. This return flow is part of a sealed or partially sealed circuit, which avoids fluid loss. Proper sealing (rod seals, valve port seals, etc.) is necessary to prevent leakage, and the circuit must allow self-lubrication to reduce friction losses and wear.

Multiple Circuits and Force Multiplication

In complex or compound systems, there may be multiple hydraulic circuits working in series or parallel. Each circuit can provide pressure or force that assists other circuits. By valves or control mechanisms, pressures and flows are balanced among circuits to achieve “force multiplication.” For example, in heavy machinery one circuit may drive a large load such as a boom, while another circuit aids control of speed or precision. With careful design of pressure balance and control, overall system power is increased without overloading any single part.

Other Influencing Factors & Optimization

• Piping size and flow velocity: Undersized piping causes pressure drops, energy loss, overheating; oversized piping reduces pressure drop but increases cost and may lead to fluid lag. Different pressure classes and uses have recommended velocity ranges.

• Oil temperature and heat dissipation: Hydraulic oil generates heat during flow and compression; poor cooling leads to reduced viscosity, impaired performance, and accelerated component wear. Systems often include heat exchangers, reservoirs with cooling surfaces, or air-cooling to manage temperature.

4. Examples & Applications of Hydraulic Systems

Hydraulic systems are found in many industries. Two key examples where hydraulics play essential roles:

Excavators

Excavators are typical heavy construction machines reliant on hydraulic drive systems. Applications include:

• Boom / Arm / Bucket Movement: The engine powers the hydraulic pump, which supplies pressure to cylinders. These cylinders extend / retract, raise / lower, tilt the bucket, enabling digging, pushing, loading.

• Attachments: Tools like hydraulic breakers, compactors, or rock breakers mounted on the boom or arm also use hydraulic power. They require higher flow rate and pressure to deliver high-speed impact and breaking force.

• Fine control & safety: When excavating or placing materials, precise motion control is critical to avoid collisions, uneven loading, or mistakes. Control valves, flow controllers, feedback systems allow smooth control of speed and position.

Aircraft

In aircraft, hydraulics and the hydraulic drive system are integral to many critical subsystems, which must work reliably, safely and precisely under extreme conditions:

• Landing gear deployment & retraction: A hydraulic system powers these motions, with valves and linkages controlling speed and position. Reliability, smooth operation, and speed are essential.

• Flaps, ailerons, and flight control surfaces: During takeoff and landing, flaps are adjusted to increase lift; ailerons, elevators and spoilers are controlled via hydraulic servo systems (or electro-hydraulic hybrids) to manage roll, pitch, and yaw. Hydraulics provide high pressure, high reliability, and fast response.

• Braking system: Wheel brakes on aircraft rely on hydraulic pressure. When landing or taxiing, hydraulic drive system sends pressure to brake assemblies, applying friction to slow or stop wheels.

• Thrust reversers: Some aircraft use hydraulics to deploy and retract thrust reversers to assist deceleration on runways.

• Other auxiliary systems: Doors (cabin, cargo), rudder, flap actuation, hydraulic assist for braking control, and redundant hydraulic circuits so that if one system fails, critical functions remain operable.

• Shock absorption & buffering: The oleo-strut in landing gear uses a combination of hydraulic fluid and gas (usually nitrogen) to absorb impact and vibration. The hydraulic fluid flows through orifices for damping; gas provides restoring force and elasticity.

5. When Is a Hydraulic System Needed?

A hydraulic drive system is often the preferred choice when:

• Very large forces are required, far beyond what mechanical, electrical, or pneumatic systems alone can provide.

• Stable, controllable action, rapid response, and compact structure are needed.

• The operating environment involves high pressure, heavy load, frequent motion, or variable load conditions.

6. Key Maintenance Practices

To ensure a hydraulic system operates reliably, safely, and for a long time, daily maintenance is crucial. Key practices include:

• Regularly checking hydraulic fluid level and filter condition.

• Replacing filter elements when necessary to prevent clogging or contamination.

• Inspecting pipes, hoses, components for cracks, deformation, wear, or leaks.

• Checking pump connections (fittings, clamps), shaft seals, suction lines, etc.

• Installing temperature monitoring and alarm systems to prevent oil from overheating.

• Using hydraulic oil that meets manufacturer specifications (viscosity, anti-oxidation, anti-foam/emulsification properties, etc.)

Routines maintenance helps avoid costly repairs. Also, using a suitable heat exchanger and properly chosen return-line filters helps eliminate cavitation or aeration issues.

Blince Team

Blince Hydraulic is an industry-leading company specializing in complete hydraulic solutions. With over 20 years of experience and long-term cooperation with more than 5,000 global customers, we focus on high-performance hydraulic motors, hydraulic pumps, steering control units, directional valves, hydraulic cylinders, hoses, fittings, and other one-stop hydraulic system solutions.

Our factory group is equipped with advanced CNC machining centers, automated production lines, and precision testing equipment. Certified with ISO9001, CE, SGS, and UL, Blince provides fast, efficient, and high-quality hydraulic solutions to customers in more than 100 countries worldwide. Whether you need small batch customization or large-scale production, we can meet your demands with reliable delivery and competitive performance.

Choose Blince technology — it means efficiency, durability, and professionalism in every hydraulic product we deliver.

To learn more, visit our website: www.blince.com

Tel: +86 180 3845 8522
Email:sales01@blince.com
Website: https://www.blince.com