Updated: 3 September 2026
A well-designed hydraulic system must deliver the required force, speed, flow and control while operating safely, efficiently and reliably throughout its intended duty cycle.
Good hydraulic system design is therefore much more than selecting a pump and connecting components together. The engineer must consider the machine load, operating pressure, required flow, actuators, valves, reservoir, filtration, pipework, hoses, temperature control, fluid specification and the way the complete system will operate in the real world.
Hydraulic system design is the process of specifying and integrating the pumps, actuators, valves, fluid, reservoir, filtration, hoses, pipework and control components required to make a hydraulic machine perform correctly. The design should be based on the required load, movement, speed, duty cycle, operating environment and manufacturer/component requirements — not simply on individual component ratings.
A hydraulic system uses pressurised hydraulic fluid to transmit energy and create controlled movement or force.
A typical system may contain a hydraulic pump, reservoir, valves, hydraulic cylinders or motors, filters, hoses, pipework and control equipment. The exact arrangement depends on what the machine needs to do.
Hydraulics are particularly useful where machinery requires high force or torque from relatively compact components, accurate control of movement, or the ability to transmit power around a machine through flexible hose and pipework.
They are widely used in applications including:
Completely Hydraulic provides hydraulic system engineering, installation and support for machinery and industrial applications.
The starting point is not the hydraulic components. It is understanding what the machine needs to achieve.
An engineer needs to establish the required movement, load, speed, operating conditions and control before specifying the hydraulic circuit.
| Design Requirement | Why It Matters |
|---|---|
| Load | Determines the force or torque the system must produce. |
| Movement & Speed | Influences actuator sizing and required hydraulic flow. |
| Operating Pressure | Affects component selection, system capability and safety. |
| Duty Cycle | Determines how frequently and for how long the system must operate. |
| Control | Determines how direction, pressure, speed and sequencing are managed. |
| Temperature | Influences oil viscosity, cooling requirements, seals and component performance. |
| Environment | Dust, moisture, salt, heat, vibration and contamination can affect system design. |
| Maintenance Access | Filters, hoses, valves and other service items need practical inspection and replacement access. |
The pump creates hydraulic flow. Its type and displacement must suit the required circuit, operating speed, pressure capability and control strategy.
An incorrectly selected pump can contribute to poor performance, excessive heat, noise, inefficiency or premature component wear.
Actuators convert hydraulic energy into mechanical movement.
These commonly include:
Cylinder bore, rod size and stroke — or motor displacement and operating requirements — must be matched to the machine’s load and required movement.
CH also provides specialist hydraulic cylinder manufacturing where a new or replacement cylinder needs to be engineered for a particular application.
Hydraulic valves control what happens to the fluid within the circuit.
Depending on the design, valves may control:
The correct valve depends on the circuit architecture, required flow, pressure, control method, mounting arrangement, fluid and duty.
The hydraulic reservoir stores fluid and forms an important part of system management.
Reservoir design can influence fluid availability, air release, contamination control, heat management and maintenance access. Capacity and configuration should therefore be determined from the needs of the particular system rather than by applying one universal rule.
Hoses and rigid pipework carry hydraulic fluid between components.
Correct sizing is essential. A line that is incorrectly specified can contribute to excessive pressure loss, heat generation, poor actuator performance or reliability problems.
Flexible hoses must also be selected and installed with consideration for working pressure, flow, fluid compatibility, temperature, routing, movement and minimum bend radius.
Hydraulic components depend on appropriate fluid cleanliness.
Filters should therefore be selected and positioned according to the needs of the system and the cleanliness requirements of its components.
Good filtration does not replace good contamination control. Reservoir breathers, maintenance procedures, clean oil handling and correct component installation all contribute to controlling hydraulic contamination.
The fluid is itself a system component.
The correct hydraulic oil must satisfy the machinery and component requirements for viscosity, fluid type, additives, operating temperature and compatibility.
The familiar ISO VG number — such as ISO 32, ISO 46 or ISO 68 — describes nominal viscosity at 40°C. It does not by itself define whether an oil is suitable for a particular hydraulic system.
See our Hydraulic Oil ISO Grades Guide for a detailed explanation.
Some machines require specialist or OEM-specific hydraulic oil. Using the wrong oil can cause serious damage.
Check Your Oil Now1. Define the machine requirement
Establish what must move, how far, how quickly and against what load.
2. Determine actuator requirements
Calculate the required cylinder force or motor torque and movement characteristics.
3. Establish flow and pressure requirements
Determine the flow needed for the required speed and the pressure required to overcome the design load and circuit losses.
4. Develop the hydraulic circuit
Select the appropriate control architecture, valves and protection required for the application.
5. Select components
Specify the pump, actuators, valves, reservoir, filtration, hoses, pipework and associated equipment.
6. Consider heat, contamination and efficiency
Assess system losses, temperature control, fluid cleanliness and operating conditions.
7. Build, commission and verify
Confirm that the completed system operates as intended throughout its required operating range and machine duty.
A hydraulic component cannot be selected correctly in isolation. Changing cylinder size, pump flow, valve capacity, hose diameter or system pressure can affect other parts of the circuit. Hydraulic design should therefore consider the complete system and its operating duty.
Flow and pressure are closely related to hydraulic system performance, but they are not the same thing.
Flow is primarily associated with actuator speed. Increasing the flow supplied to a cylinder or motor can increase its movement speed, subject to the circuit and component limits.
Pressure is associated with the resistance or load the system must overcome. The pressure required depends on the load and system conditions.
Confusing flow with pressure can result in poor component selection and an inefficient hydraulic system.
Heat is an important design consideration because hydraulic oil viscosity changes substantially with temperature.
Excessive system temperature may contribute to:
However, overheating should be diagnosed rather than simply treated by changing to a thicker oil. Heat can be generated by internal leakage, restrictions, pressure losses, inefficient operation, inadequate cooling or other system problems.
Modern hydraulic components can contain very small internal clearances, making contamination control an important part of system design and maintenance.
Contamination can include:
Good system design considers filtration, reservoir protection, filling procedures, component cleanliness and future maintenance from the beginning rather than treating contamination only after a failure occurs.
A hydraulic system can perform well when new but still become unnecessarily expensive to maintain if servicing has not been considered during the design stage.
Where practical, engineers should consider:
This becomes particularly important for machinery operating continuously or in harsh industrial environments.
Planned inspection and servicing can then form part of a suitable hydraulic preventative maintenance programme.
Not every hydraulic engineering project starts with a blank sheet of paper.
Existing machinery may require modification because production requirements have changed, original components are obsolete, operating conditions have changed or reliability needs to be improved.
Before modifying an existing hydraulic circuit, the engineer should understand the original system and assess how the proposed change could affect:
Replacing one component with something apparently similar does not necessarily mean the system will perform in the same way.
A competent hydraulic engineer should be able to look beyond individual components and understand how the entire hydraulic circuit behaves.
Important capabilities include:
Just as importantly, the design process should involve communication with the customer. Understanding how the machine is actually used can reveal operating conditions that are not obvious from a schematic or component list alone.
Completely Hydraulic supports businesses with hydraulic engineering projects ranging from individual component replacement and circuit modification through to custom hydraulic systems and OEM solutions.
Our wider capabilities include:
Explore our Hydraulic Systems, OEM Hydraulic Services and Engineering Projects capabilities.
Reliable hydraulic system design begins with the machine requirement — not the component catalogue. Load, movement, flow, pressure, duty cycle, control, temperature, contamination, maintenance and operating environment all need to work together as one system.
Whether you are developing new machinery, modifying an existing hydraulic circuit or trying to resolve recurring system problems, Completely Hydraulic can assess the application and help determine the appropriate engineering solution.
Hydraulic system design is the process of determining how pumps, actuators, valves, fluid, filtration, reservoirs, hoses, pipework and controls should work together to produce the required machine movement, force and performance.
Important information includes the required load, movement, actuator speed, duty cycle, operating environment, available power, control requirements and any existing machine or component constraints.
Pump selection depends on factors including required flow, pressure capability, displacement, operating speed, circuit design, control requirements, fluid and duty cycle. A pump should be selected as part of the complete system rather than from pressure rating alone.
The required force, available system pressure, stroke, mounting arrangement, loading conditions and required movement all influence cylinder selection. Rod size and mechanical loading must also be considered.
Not necessarily. Actuator speed is primarily related to hydraulic flow and actuator displacement or cylinder area. Pressure develops according to the resistance or load the system must overcome.
Hose and pipe size affects fluid velocity and pressure loss. Incorrectly sized lines can contribute to heat, poor performance and reliability problems, so they must be selected for the circuit’s flow, pressure and application.
Yes, but the effects of a modification should be assessed across the complete circuit. Changing a pump, cylinder, valve or line size can alter flow, pressure, speed, temperature and the behaviour of other components.
Completely Hydraulic provides hydraulic engineering support for new systems, system modifications, OEM applications, cylinder manufacture, hydraulic components, hose and pipework, power packs and associated hydraulic engineering projects.
Yes. Completely Hydraulic provides mobile hydraulic engineering support alongside workshop and trade-counter capabilities across its service network.
