Hydraulic Systems in Construction Equipment

In building construction equipment, the hydraulic system is important for how well the equipment works, how smoothly it moves, and how reliably it operates. In this article, we will introduce the different types of equipment, the different pressure and load conditions, to help you make a clearer judgment.

Hydraulic System Applications in Different Construction Equipment

Excavators

In an excavator, the hydraulic system is responsible for controlling the movement of the boom, bucket, and bucket, as well as driving the slewing mechanism and travel motor.

Digging, slewing, and moving are all critical functions that rely on the hydraulic system.

Since multiple motions are often performed simultaneously, excavators often use a multi-circuit structure, which requires high-pressure stability and flow distribution capabilities.

Loaders

The hydraulic system of a loader is mainly used to control the lifting and turning of the bucket to accomplish loading and unloading operations.The system is simple compared to an excavator, but it still needs to keep a steady output when it is lifted and lowered a lot. The hydraulic system must provide both sufficient lifting force and smooth operation to reduce shock and wear.

Cranes

In a crane, the hydraulic system lifts heavy loads, extends and retracts the boom, and controls outrigger stabilisation. Lifting operations often have big loads, so they need to keep the pressure steady and be very precise. The hydraulic system is responsible for two things: power output, safety, and load stability.

Concrete Pumps

Concrete pumps use a hydraulic system to power the main pumping mechanism and the reversing device, so that the concrete can be delivered steadily. As this type of equipment usually runs continuously for long periods of time, the hydraulic system should have good heat dissipation and durability. If the oil temperature is not properly controlled, the efficiency of the hydraulic system and the life of the seals may be affected.

Aerial Platforms

Aerial work platforms use a hydraulic system to adjust the equipment’s height and position so that it can reach the required height smoothly. Although a single load is relatively limited, it must also be smooth and safe to control. The system needs to be stable during lifting and lowering, and it must be able to lock reliably if something unexpected happens.

Bulldozers

In a bulldozer, the hydraulic system is mainly used to control the lifting and angle adjustment of the cutter plate to meet different operating conditions. Although its traveling is usually mechanically driven, the hydraulic system will directly affect the work precision and operation efficiency. The system has to keep working well even when it is constantly being adjusted.

Functional Roles in Construction Equipment

The hydraulic system is important for three things on all construction equipment.

Power Transmission

The hydraulic system changes the energy made by the engine into hydraulic energy. This energy is then used to push the cylinders or motors to do heavy jobs such as lifting, digging, and turning.

Motion Control 

Hydraulic systems control the movement and pressure of fluids using valves and controllers.

Stability and Safety Support

In lifting, elevating, or working at height, the hydraulic system must also stabilize the load to prevent slippage or imbalance.

Hydraulic System Requirements for Different Construction Equipment

Requirements for pressure ratings and structural complexity of hydraulic systems vary significantly from one piece of equipment to another:

Work Pressure and Weight Limits of Construction Equipment

In building construction equipment, you can’t just look at the pressure rating to see if the system is reliable. The most important things to think about are the actual operating pressure, the instantaneous shock pressure, how long it can be used for and the environmental conditions at the site. These things determine how strong the system is and how long it will last.

Typical Working Pressure

Most construction equipment has hydraulic systems rated at 250-350 bar. Medium-sized equipment is usually around 250-300 bar, large or heavy-duty equipment may reach 350 bar or more, and some high-performance systems may even approach 400-420 bar.

But higher pressures are not always better. The higher the pressure, the stronger the hydraulic components, and the more difficult they are to maintain and the more expensive they are.

When you choose a model, it is important to work out if the current equipment really needs higher pressures, and if the existing system is already operating close to its design limits.

Hydraulic Shock Load and Peak Pressure

On a construction site, equipment often meets instantaneous shocks. Excavator buckets hitting hard ground, sudden changes in crane loads, and pressure can rise suddenly in a short period of time. And it is often higher than the rated working pressure of the system.

Repeated shocks over time will accelerate seal wear and increase the risk of line fatigue. Many systems leak not because of sustained high pressure, but because you don’t consider the effects of instantaneous shocks.

Therefore, when evaluating the strength of your system, you should consider the level that peak pressures are likely to reach, whether the system has overflow protection, and whether safety margins have been built into critical components.

Continuous Operation and Duty Cycle

The hours of operation of the equipment can also affect the design requirements of the hydraulic system. Concrete pumps or large construction machinery often run for hours on end. This generates constant heat, which accelerates fluid degradation and component wear.

Under high duty cycle conditions, even if the operating pressure is not very high, the system needs a better cooling system and a more stable fluid. If the equipment is operated intermittently, the requirements for heat dissipation and durability are relatively low.

Environmental Impact on Hydraulic Systems

Construction sites are often harsh environments. Dust increases the risk of fluid contamination, vibration affects the sealing of lines and fittings, and high-temperature environments can degrade fluid performance.

These factors will not change the rated pressure value of the system, but they will directly affect the maintenance frequency and service life, so you should take appropriate measures according to the specific working conditions, such as improving the filtration accuracy in dusty environments, strengthening the pipe fixation in continuous vibration conditions, and optimizing the cooling design in high-temperature areas.

How to Check If Your Hydraulic System Is Strong Enough？

When evaluating a hydraulic system, you can look at four areas to determine if the system rating is adequate:

• Does the rated working pressure of the equipment match the actual load?
• Does the system account for peak pressures from shock loads?
• Does the equipment operate continuously for long periods of time?
• Does the operating environment add additional loads

Hydraulic System Design in Construction Equipment

The performance of construction equipment depends on the structural design of the hydraulic system. Different structures vary in cost, efficiency, and responsiveness. When doing a program evaluation, you should understand the differences in common structures and not just focus on the brand of components.

Open Center vs Closed Center Hydraulic Systems

Open systems are simpler in construction. When the control valve is not operated, the oil flows back into the tank, and the system pressure is kept at a low level. This type of construction is cheaper to manufacture and easier to maintain, and is suitable for equipment with fewer operations and relatively simple construction.

Closed systems are maintained at a set standby pressure when there is no operating action, and the flow rate is adjusted by a variable pump according to the load demand. This type of structure can maintain more stable pressure and higher efficiency when multiple actuators are working at the same time. Multi-action equipment, such as excavators, typically uses closed systems.

Multi-Pump Hydraulic Systems

Multiple pump systems are more common in medium to large-sized excavators. Multiple pumps are designed so that different circuits can receive the required flow rate to support multiple actions at the same time.

For example, when a machine is traveling while operating, a multiple-pump configuration reduces flow distribution conflicts and allows for better coordination of movements. Compared to single-pump systems, multi-pump configurations are more likely to maintain stable operation under high loads. However, the system structure can also be more complex, requiring more maintenance and commissioning.

Load Sensing Hydraulic Systems

The load-sensitive system automatically adjusts the output pressure of the pump by detecting the actual load of the actuator so that the system only outputs the energy that is currently required. This reduces energy loss and lowers the rate of oil temperature rise.

In high-end equipment, load-sensitive systems provide smoother handling and higher control accuracy. The advantages of load-sensing systems are especially evident in operating conditions that require fine control. However, the control logic is more complex, and the cost is relatively high.

Hydraulic Oil Cooling Systems

When equipment runs continuously for long periods of time, the hydraulic fluid will continue to heat up. If the cooling capacity is insufficient, high oil temperature will affect the performance of the fluid and accelerate the deterioration of seals.

Concrete pumps and other heavy equipment often have separate oil cooling circuits to keep the oil from getting too hot. If you get the cooling design right, you can reduce the failure rate and make the system last longer.

When you choose a model, you should judge whether you need to strengthen the cooling system based on the equipment’s operating hours and load intensity, instead of waiting until the oil temperature is abnormal.

Common Hydraulic System Problems in Construction Equipment

In construction equipment, the hydraulic system is exposed to heavy loads, vibration, and shock for a long time. Many failures are not sudden, but happen over time as small problems build up.

Contamination and Filtration

Construction sites are dusty, and impurities may enter the system if the tank is not tightly sealed, the breathing port is not adequately protected, or the operation is not standardized during maintenance. Oil contamination will accelerate the wear and tear of the pumps and valves, affect the smoothness of the action, and even cause stalling or leakage.

This problem is often seen as a slower pump speed and unstable pressure. You can control contamination by increasing the filtration accuracy and changing the filter element at regular intervals. In addition, you should make sure that the refueling process is clean. For construction equipment, fluid cleanliness often has a direct impact on system life.

Cavitation Problems

Cavitation usually happens when the suction conditions are not ideal, such as when the engine is cold, the boat is going too fast, or there is too much resistance in the suction line. When the pump does not suction enough oil, air bubbles are created in the oil. These bubbles burst in high-pressure areas and can damage metal surfaces.

Cavitation may only be an increase in noise or vibration in the early stages, but in the long term, it can damage the pump body and flow distribution components. When you’re designing and maintaining the system, you should make sure that the suction pipe diameter is reasonable, the oil level is sufficient, and choose the right viscosity fluid, thus reducing the risk of cavitation.

Hydraulic Overheating

Hydraulic systems generate heat when they are used a lot or are switched on all the time. If the cooling capacity is insufficient, the oil temperature will continue to rise, the lubricating effect of the fluid will be reduced, and the seals will age faster.

Excessive oil temperature reduces system efficiency and leads to pressure instability. Common reasons for this are insufficient cooling capacity, prolonged flow close to the limit, or increased leakage within the system. For equipment that is always on, you should think about how it is designed to handle heat and keep an eye on the oil temperature. This helps to make sure that the system does not run too hot for too long.

Seal and Hose Failure

Construction equipment is often exposed to shock and vibration during operation. Repeated pressure fluctuations will tire seals and hoses, which may leak or even rupture over time.

The risk of failure is even higher if the hose specifications are not properly selected or if the installation is not securely fastened. You should regularly check the important connection parts and choose the right seals and hoses for the pressure level, to lower the chance of accidents.

Hydraulic System Maintenance Cost and Downtime Risks

For construction equipment, the cost of a hydraulic system is not just about buying it; it’s also about the ongoing maintenance costs and the risk of it being out of action at a later point.

First cost vs Long-Term Operating Cost

The first cost of a hydraulic system is mostly for the pumps, valves, cylinders, control systems, and cooling and cleaning parts. Systems with higher configurations are usually more expensive, but they tend to work more consistently.

In the long run, you should also think about the cost of replacing fluids, how much the filter elements will be used up, repairing seals, and dealing with any problems. If the system is not designed with enough margin, the number of later repairs will increase, and the overall cost will be higher instead.

Maintenance Frequency

How often you need to do maintenance depends on how much the machine is used and the conditions it is used in. Heavily loaded or continuously operating equipment requires more frequent checking of fluid condition, clogged filter elements, and piping connections.

If the system is designed well for heat dissipation and filtration, the maintenance intervals will stay the same. If the system is kept at high temperatures or in dirty environments for a long time, it will need to be cleaned more often. Deciding on maintenance times early on helps to make sense of the maintenance schedule and avoid unexpected breakdowns.

Replacement Cycle of Wear Parts

Seals, cartridges, and hoses in hydraulic systems are consumable parts that deteriorate under high pressure and shock.

Replacement intervals vary greatly from one piece of equipment to another. Dusty environments shorten cartridge life, and continuous operation accelerates seal wear. Knowing the replacement intervals, you can prepare your inventory in advance to avoid equipment downtime due to missing small parts.

Downtime and Its Impact

If there is any downtime on a construction site, it can cost more than just the repair itself. It can also make the project take longer than expected. For large projects, losses during downtime are often higher than the cost of parts.

Many hydraulic failures are caused by not controlling contamination well enough, poor heat management, or worn seals. If the system design allows for enough margin and there is a standard way to maintain it, there is less chance of the system suddenly stopping.

Spare Parts and Supply Chain

The timeliness of spare parts supply has a direct impact on maintenance intervals. If critical components have to wait a long time for procurement or customization, downtime may be extended.

When you choose a system or supplier, it’s important to check if the important parts are always available, if there’s a reliable way to replace them if they’re out of stock, and if there’s local support available. It is important to keep your supply chain stable if you want to do business over the long term.

How to Choose a Hydraulic System for Construction Equipment?

When selecting a hydraulic system for construction equipment, the key is to match the actual working conditions instead of simply comparing parameters or prices. The pressure level, structural form, and heat dissipation capacity of the system should all be determined in conjunction with how the equipment is used.

Match Working Pressure to Real Operating Conditions

When you select a model, the first thing to find out is the actual load range of the equipment in daily operation.

Moderately loaded equipment usually does not require excessive pressure ratings, while highly loaded equipment requires higher system strength.

If the system is operated at near maximum pressure for a long period of time, seals and pumps will wear out significantly faster.

Therefore, you should match the proper pressure based on real operating conditions and retain a reasonable safety margin.

Select a System Architecture That Fits the Equipment

The system structure should match the action characteristics of the device.

Devices that do one thing can use a system that is simple.

Devices that need you to do several things at the same time or that need very precise control are better suited to closed or load-sensitive structures.

Check Cooling Requirements for Continuous Operation

If the equipment needs to run continuously for a long time, the heat generated by the hydraulic system will continue to accumulate.

High oil temperatures have a negative impact on how well fluids work and can speed up the deterioration of seals.

In this case, you should check in advance whether the system has enough cooling power. If necessary, set up a separate cooling circuit.

If the equipment only requires intermittent operation, the cooling requirements will be relatively low.

Think about Maintenance and Long-Term Operating Cost

The cost of a hydraulic system is not just at the procurement stage.

How often you need to do maintenance, how long you have to wait between replacing parts, and how much time the equipment is out of service all affect how much it costs to own the equipment over time.

If the system is well designed and the conditions are stable, maintenance intervals are usually easier to manage.

You should be more concerned about the probability of breakdowns and the stability of operation than saving costs on purchasing.

Evaluate Supplier Experience and Support

In addition to the system itself, the experience and support capabilities of the supplier are equally important.

If you work with a supplier who knows how to use similar equipment, they are more likely to avoid common problems when you are designing the project.

At the same time, if you make sure you always have the right spare parts and that technical support is there when you need it, you can avoid any problems with the equipment.

For high-intensity construction projects, the supplier’s capability is more important than the parameters of the equipment.

How to Choose a Hydraulic System Supplier for Construction Equipment?

When you’re choosing a hydraulic system supplier for construction equipment, it’s important to look at more than just the product details. You also need to make sure that the supplier really understands how the equipment will be used and is able to provide ongoing support. If the supplier doesn’t have much experience, even if the product details are correct, problems may show up when it’s actually used.

Experience with Similar Equipment and Working Conditions

First, you should see if the supplier has done projects with similar equipment or in similar working conditions.

Construction equipment usually has to lift heavy loads, be hit by things, and be used for long periods. If the other party mostly works with light-duty or stationary equipment, they won’t understand on-site issues as well.

Suppliers with relevant project experience are usually more aware of which design details are prone to problems and are more likely to avoid risks in advance during the design phase.

Capability for System-Level Design

Hydraulic systems need more than just pumps, valves, and cylinders. They need to be put together properly.

Whether the supplier has the system-level design capability will directly affect the stability of the system and commissioning difficulties.

If the other party only provides separate parts but can’t design the overall program, later on in the process, the distribution, pressure matching, or control response may need to be adjusted again.

A supplier that can consider pressure levels, cooling configuration, and circuit design as one unit is better at making sure the system keeps on working in the long-term.

Long-Term Technical Support

Construction equipment will encounter commissioning or malfunctioning problems during operation.

How quickly problems are solved depends on whether the supplier can provide technical support over time.

Downtime may be prolonged if there is no timely communication or access to technical advice when system anomalies occur.

Export Experience and Regulations

If the equipment needs to be exported, it is important that the supplier knows about the certification and rules.

If the supplier doesn’t have the relevant experience, it has to make changes to their compliance or face extra costs later on.

Suppliers with experience in export programs are usually more aware of the certification process and technical documentation requirements.

Customization Capability

The structure and working conditions of construction equipment vary greatly, and standardized products are not always fully applicable.

If the supplier can make changes to the design to fit the actual needs, the system will be more compatible.

Suppliers who can make some changes to the system can make it fit in the available space, the amount of load it has to deal with, and the control methods used. So, the system is more like the equipment it will be used with.

The Future of Hydraulic Construction Equipment Technology

Construction equipment has been getting better at doing its job, using less energy and being easier to control. It has changed how hydraulic systems are designed. These changes will not immediately overturn the existing system, but will gradually affect the future procurement standards and maintenance mode.

Electro-Hydraulic Integration

More and more construction equipment is adopting electronically controlled hydraulic systems. The electronic control unit with proportional valves lets you adjust the flow and pressure more accurately, so the action is smoother and easier to use.

Compared with the traditional mechanical control method, the electro-hydraulic system is more accurate and faster. However, it has a complex structure with higher requirements for electrical stability and debugging capabilities. The configuration is more common in mid-range and high-end equipment.

Higher Energy Efficiency Requirements

As fuel costs rise and emissions requirements increase, making hydraulic systems more energy efficient is becoming more important. People are using more pumps and load-sensitive systems to use energy more efficiently.

Efficient systems might cost a little more to buy, but they save fuel and reduce overheating problems in the long run. When looking at different system options, the energy performance of the system is now just as important as the pressure rating.

Electrification and Hybrid Power

Some construction equipment now uses electric or mixed electricity and fuel systems. The hydraulic system still carries out the actuation function, but the power source can be an electric motor. This changes how the system is matched, such as how it responds and how it is controlled.

This equipment will become more common in areas that have strict environmental rules. If your company works with exports or has projects that aim to sell to high-end markets, you should pay attention to this trend.

Monitoring and Maintenance Planning

More and more equipment is being fitted with pressure and temperature sensors to monitor hydraulic systems as they are being used. By looking at the data, we can spot unusual activity in the equipment early on, which helps to avoid sudden breakdowns.

For big engineering projects, it’s often better to give a warning than to try to fix things up later. Hydraulic systems are being changed from power systems to smart systems that can be checked and controlled.

FAQ

Can Different Brands of Hydraulic Components Be Mixed in Construction Equipment Hydraulic Systems?

It can be mixed, but only if the rated pressure, flow parameters, interface specifications, and control methods of all hydraulic components are perfectly matched. If the settings are not the same, the hydraulic system of the construction equipment may have unstable pressure, lower efficiency, and other problems.

What Is the Typical Design Life of a Hydraulic System in Construction Equipment?

Construction equipment hydraulic systems typically have a life expectancy of 8-15 years. The actual life depends on the load intensity, operating hours, and level of maintenance.

How Should a Hydraulic System Be Adjusted for Cold-Weather Operation?

When using construction equipment in cold areas, choose a hydraulic fluid that performs well at low temperatures. Don’t put the equipment under too much pressure straight after it has been started in cold weather. You can add an oil preheating device if you need to.

What Are the Hydraulic System Risks When Restarting Construction Equipment After Long Storage?

When restarting construction equipment after a long period of parking, you should check for deterioration of the hydraulic fluid, deterioration of the seals, and any leaks. When you first start up the machine, run it at a low speed without putting any load on it. This lets the hydraulic system slowly build up pressure. Then, when you put a load on, the machine will be used to it, and there will be less risk of it being damaged.

Can Construction Equipment Continue Operating with a Minor Hydraulic Leak?

Minor hydraulic leaks may not immediately affect operation in the short term, but are not recommended for continued use. Leaks can cause fluid contamination, a drop in pressure, and even system failure.

Do you need to replace all the important parts when upgrading a construction equipment hydraulic system?

No. If the upgrade is minor, some of the hydraulic components can continue to be used. However, if the pressure rating of the system is increased or the circuit structure is changed, key components will need to be replaced to make sure that the hydraulic system can function properly.

Final Thoughts

The hydraulic system of construction equipment not only affects power and control performance, but also relates to the reliability and long-term cost of the equipment. Every step of the process, from how much pressure is used and how the system is built to how it’s maintained, needs to be judged based on the actual conditions it’s used in.

Target Hydraulics has been designing and improving hydraulic systems for construction equipment for more than 10 years. We can help you choose the right system, make it work better, and help you avoid common problems. Contact us to find the right solution for you.

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