Types of Hydraulic Systems Explained for Industrial Applications

Hydraulic systems vary based on how fluid is circulated, how pressure is controlled, and how force is applied in real machinery. If you’re trying to choose the right setup, or just want to understand why one system behaves differently from another, it always comes back to system type — not just components.

Most engineers don’t struggle with what a hydraulic system is. The real question is: which type of hydraulic system is fit for purpose? That’s where things get more interesting.

Open Loop Hydraulic Systems

The open loop hydraulic system is the common type of hydraulic setup you’ll see across UK industry.

In this system, hydraulic fluid flows from a reservoir, passes through a hydraulic pump, moves into the circuit, and then fluid returns to the reservoir after completing work. It’s a continuous cycle, simple in layout, and it works well for most machinery.

The defining feature is that the fluid always comes back to the tank before being reused. That means heat can dissipate, contamination can settle, and filtration has a chance to do its job properly.

From a control point of view, flow is directed using a directional control valve, which determines where the pressurised oil goes and which actuator moves. The amount of fluid delivered by the pump sets the speed, and system pressure builds based on resistance.

This type of system is often used in:

• General machinery
• Presses and lifting equipment
• Agricultural and construction equipment

It’s popular for a reason. It’s forgiving, easier to maintain, and cost stays under control. If something goes wrong, fault finding is usually straightforward. That matters more than people think.

Closed Loop Hydraulic Systems

A closed loop hydraulic system works differently. Instead of returning oil back to the reservoir after each cycle, the fluid circulates directly between the pump and the actuator, often a hydraulic motor.

This design keeps the loop tight. Fluid flows from the pump to the motor and back again, with only a small amount diverted to the reservoir for cooling and filtration.

What changes here is response and efficiency. With less distance to travel and fewer losses, the system reacts quicker. That’s why you’ll see closed loop systems in applications where control needs to be sharp and consistent.

These systems often rely on variable displacement piston pumps, allowing the amount of fluid per rotation to change depending on demand. That gives proper control over speed and direction without wasting energy.

Closed loop systems are often used in:

• Hydrostatic drives
• Mobile machinery with variable speed control
• High-performance equipment

There’s a trade-off though. They’re less tolerant of contamination. If oil quality drops, performance drops quickly. Maintenance standards need to be tighter, no shortcuts.

Hydrostatic Hydraulic Systems

Most hydraulic setups used in industry fall into the hydrostatic category. This refers to systems in which energy is transmitted through a pressurised fluid within a confined circuit.

Here, the focus is on pressure, not velocity. The system takes mechanical energy into hydraulic energy, pressurises the fluid, and applies that pressure to generate force.

That force is what allows systems to:

• Lift heavy objects
• Deliver high torque
• Maintain precise control under load

The fluid being incompressible is what makes this possible. When pressure is applied, it transmits instantly through the system without noticeable loss.

Hydrostatic systems are used across:

• Industrial presses
• Lifting systems
• Production machinery

If you’re dealing with controlled movement and high force in a compact space, you’re dealing with hydrostatic hydraulics, whether you realise it or not.

Hydrodynamic Systems

Hydrodynamic systems are less common in industrial hydraulics, but still worth understanding when looking at different types of hydraulic systems.

These systems rely on fluid motion and velocity rather than static pressure. Instead of pressurising a confined fluid, they use the movement of fluid to transmit energy.

You’ll typically see this in:

• Fluid couplings
• Torque converters

They’re useful where smooth power transmission is needed without direct mechanical contact, but they don’t offer the same level of precise control or force as hydrostatic systems.

For most hydraulic engineers working with hydraulic power, hydrodynamic systems sit outside day-to-day work.

Mobile Hydraulic Systems

When looking at types of hydraulic systems from an application point of view, mobile hydraulic systems stand out straight away.

These systems are built for machines that move, so they need to handle vibration, changing loads, and varying operating conditions. You’ll find them in:

• Excavators
• Loaders
• Agricultural equipment

The system design often combines open loop hydraulic layouts with variable displacement pumps to give flexibility. Machines need to react quickly, change direction, and handle uneven loads without hesitation.

Oil supply comes from a reservoir, the pump is responsible for generating flow, and control is handled through directional control valves.

What sets mobile systems apart is how they’re driven. They’re often powered by diesel engines, meaning the hydraulic system must adapt to varying input speeds. That’s where variable displacement becomes critical.

Industrial Hydraulic Systems

Industrial hydraulic systems are more stable in operation. They’re fixed in place, loads are predictable, and control can be fine-tuned for specific tasks.

These systems are used in:

• Manufacturing lines
• Presses
• Processing equipment

The focus here is consistency. The system needs to repeat the same movement again and again without deviation.

Most setups use open loop systems, paired with fixed displacement pump or controlled variable units depending on the application.

Control accuracy is achieved through:

• Pressure regulation
• Flow control
• Valve sequencing

Industrial systems often include additional features like pressure relief valves to maintain safe system pressure, along with accumulators for stabilising flow.

Hydraulic Power Unit Systems

A hydraulic power unit or power pack is a complete system in one assembly. It includes the pump, reservoir, control valves, and sometimes accumulator and filtration, all built into a single unit.

These systems are designed to deliver hydraulic power to external machinery.

What makes them a distinct type of hydraulic system is their modular nature. They’re built to supply energy, not just perform one motion.

They can be:

• Electric motor driven
• Diesel driven
• Built for fixed or mobile use

The unit converts mechanical energy into hydraulic energy and distributes it where needed. Fluid flows out of the tank, into the pump, then into the system where work is carried out.

These systems are used across:

• Offshore equipment
• Production lines
• Heavy industry

They’re often custom-built to match exact requirements, especially when multiple systems need to run from a single source.

High-Pressure Hydraulic Systems

Some hydraulic systems are defined by operating pressure rather than layout.

High-pressure systems are designed to deliver significant force in compact setups. These systems run at elevated pressure levels, often required for:

• Heavy lifting
• Pressing operations
• Industrial forming

The key factor here is how the system is designed to handle stress. Every part of the circuit must cope with high-pressure conditions without failure.

These systems often use:

• Piston pump designs
• Reinforced pipework
• Advanced sealing

They’re built for performance, but they demand proper maintenance. Any weakness shows up quickly under pressure.

Multi-System Hydraulic Setups

In larger machinery, you won’t just find one hydraulic system. You’ll find multiple systems working together.

Each system handles a specific function:

• One for lifting
• One for steering
• One for drive

This separation improves reliability. If one system fails, others can continue operating.

These setups still fall under the main types of hydraulic systems, but they’re layered into a larger structure. Coordination between systems becomes key, especially where flow demand overlaps.

Why System Type Matters

Choosing between different types of hydraulic systems isn’t just a design decision. It affects:

• Efficiency
• Control
• Maintenance requirements
• Overall machine performance

An open loop hydraulic system might suit a basic lifting task, but struggle in a variable speed drive. A closed loop system might deliver better control, but at higher cost and tighter maintenance requirements.

There’s always a trade-off. The right choice depends on how the system will be used, not just what it’s capable of.

Choosing the Right Type of Hydraulic System

Choosing between different types of hydraulic systems comes down to how the system needs to control flow, manage pressure, and deliver force in real working conditions.