The hydraulic system is widely used in industrial equipment. It affects the stability and safety of the equipment. If it is not properly maintained, the equipment is easy to break down. This article will explain the common problems and causes of hydraulic systems, and show you how to reduce the risk of failure and downtime through proper maintenance and system design.
What Hydraulic System Maintenance Really Means and Why It Matters？
Hydraulic system maintenance is not just about replacing parts, checking for leaks, or regular servicing, but a series of measures to reduce risks during operation, extend the life of components, and make sure the system operates safely. There are four core points in maintaining a hydraulic system:
- Prevent contaminants from entering the hydraulic system and damaging internal parts.
- Control the temperature of the hydraulic system to avoid wide temperature fluctuations.
- Keep pressure stable to avoid shocks.
- Inspect critical components to detect deterioration, wear, and looseness.
Maintaining the hydraulic system is important because a failure of the hydraulic system often causes the following effects:
- Sudden stoppage of the equipment.
- Safety accidents and injuries.
- Costly repairs.
If you take good maintenance measures when the equipment is in normal operation, you can detect hidden safety risks in advance, reduce sudden failures, reduce maintenance costs, and keep the equipment running stably.
How Poor Maintenance Leads to Hydraulic Failures and Early Warning Signs
If the hydraulic system is not properly maintained, you will find a variety of problems during use. Typical situations are the following:
When changing filter elements and refueling, it’s easy for contaminants to get into the hydraulic system if you don’t take proper dust control measures. Once they get into the gaps between the gears, the gears will stall, which affects the proper functioning of components such as hydraulic pumps and hydraulic valves.
If you don’t do a good job of controlling the temperature, the viscosity of the hydraulic fluid will decrease, and the seals will age faster. At this point, you will find that the system leakage is getting worse and worse, and the operation is getting more and more unstable.
If the accumulator fails, the relief valve is not set properly, and the piping is not properly supported, the pressure in the hydraulic system sometimes becomes suddenly high and shocks the piping and fittings. If this continues to happen, the pipes are easy to rupture, and the fittings are easy to loosen, which finally causes the hydraulic fluid to leak, and the system cannot operate properly.
If the piping is poorly sealed or the breather in the tank fails, moisture and air can easily enter the hydraulic system. The fluid will then cavitate and emulsify. The system will become noisier during operation, and the actuator action will become unstable.
These problems don’t happen all at once; they all have some early warning signs early on. I’ve made a table to make it easy for you to view and check the problems corresponding to these phenomena.
| Early Phenomena | Corresponding Problems |
| Darkening of Fluid Color | Oxidation of Oil |
| Turbidity of Oil | Water Content of Oil |
| Cartridges Clog Faster | Increased System Contamination |
| Higher Oil Temperature at the Same Load as Before | Reduced Heat Dissipation/Increased Leakage |
| The System Heats up Faster | Decline in System Efficiency |
| Abnormal Temperature Difference between Cooler Inlet and Outlet | Clogging of Cooler |
| Slower Pressure Rise | Pump Wear/Increased Leakage |
| Pressure Fluctuations Become Larger | Valve Instability/System Air Intake/Accumulator Failure |
| Unstable Actuator Movement | System Air Intake/Increased Contaminants/Stuck Valves |
| The System Becomes Noisier | System Air Intake/Valve Stalling/Reduced Fluid Lubrication |
| Increased System Vibration | Loose Connections/Large Pressure Fluctuations |
| Oil Seepage at Joints | Loose Connections/Shock Deterioration/Seal Deterioration |
| Cracked or Bulging Hose Surface | Hose Aging |
| Air Bubbles in the Return Line and Tank | System Air Intake |
How to Maintain a Hydraulic System？
In actual maintenance, many people just follow the instructions in the maintenance manual. However, the manual will not tell you that these maintenance programs are not of the same level of importance. Some projects will directly affect the life of the system; you need to do it first, and invest a lot of manpower and resources. And some projects just help to improve the stability of the system, and you don’t need to invest too much labor and resources to do it.
High-Priority Maintenance Tasks That Directly Affect System Life
These projects will directly affect the lifespan of the system, and they are the parts that you must prioritize to do well.
Contamination Control
This is the most important project in the maintenance of hydraulic systems. Because the gap between the gears in the hydraulic pump and the hydraulic valve is very small. Once mixed with solid particles, gears in the high-speed rotation process will quickly wear. Soon, the whole system will be forced to stop working.
You should regularly check the differential pressure of the cartridge. If the differential pressure is too high, you should replace the cartridge immediately. You should also regularly sample the hydraulic fluid to see if there are any metal shavings mixed in. If you find a lot of debris, you need to check which parts are worn out and replace them along with the hydraulic fluid. In addition, you should always avoid exposing the opening for too long when replacing the filter element and the hydraulic fluid; otherwise, dust can easily enter the system.
Temperature Control
If the system is operated at high temperatures for a long period of time, the oil will oxidize, and the viscosity will drop. The rate of aging of seals will also become faster. At this point, internal leaks will increase, and oxides will gradually deposit, finally leading to more and more leakage and stalling in the hydraulic system.
That’s why you should regularly check that the cooler is not clogged and that the fan/water cooling system is working properly. You should also monitor temperature changes in real time and regularly check that the viscosity of the fluid is in the normal range.
Seal and Hose Condition
Seals and hoses are the areas of the hydraulic system that are subject to the most concentrated forces and are the most susceptible to deterioration. Once these parts fail, the fluid will leak, and air and contaminants will enter the system, and then the equipment will not work properly.
That’s why you should regularly check hoses for excessive bends, aging, cracking, or bulging. At the same time, you should also check whether the fittings and seals are wet but not yet dripping oil. If any of these conditions occur, you must deal with them immediately.
Secondary Maintenance Tasks That Improve Reliability
These projects can improve the stability of the system. However, if you don’t have enough resources and staff, you can do the core maintenance projects first and then do the following projects.
Exterior Cleaning and Routine Inspections
You can do regular cleaning and routine inspections of your hydraulic system. While this won’t stop internal wear and tear, during the inspection and cleaning process, you may find a leak somewhere or a part that has come loose. You can fix the fault before it gets bigger.
Fastening and Structural Inspection
You can regularly check that the brackets and pipe clamps are holding the pipes securely in place. Doing this will prevent the hydraulic system from vibrating too much during operation, which will cause the joints to loosen.
Operational and Trend Recording
You can record the pressure and temperature of the hydraulic system in real time with sensors, make graphs, and observe fluctuations in temperature and pressure periodically. You can also check the operation of the hydraulic system regularly and make a log. Doing so can help you predict problems that may occur later.
How Often Should Hydraulic Systems Be Maintained?
A lot of maintenance manuals will tell you to check it every 3 months and replace it every 1000 hours or something like that. But you can’t really follow that. The frequency of maintenance on your hydraulic system depends on the number of hours your equipment is in operation, the intensity of the load, the environmental conditions, and the complexity of the system. So you need to decide which maintenance projects need to be done more and which can be done less, according to your actual situation.
If your hydraulic system is in regular operating conditions, you can maintain it as listed in the table below.
| Routine Inspections | Periodic Inspections | Deep Maintenance |
| Once A Day | Once every 250-500 Operating Hours | Once every 1000-3000 Hours |
| Is there any abnormal noise? | Filter Element Differential Pressure Check | Oil Testing |
| Is there any obvious leakage? | Fluid Condition Check | Filter Element Replacement |
| Is the oil temperature abnormal? | Hose and Fitting Condition Check | Seal and Wear Parts Replacement |
| Is the oil level normal? | Cooler Condition Check | Valve Train and Pump Efficiency Check |
| Is the action slowed down? | Vibration Condition Check | Accumulator Condition Check |
If your hydraulic system is used for high-load equipment, or it works in a very polluted environment with many shocks and large temperature fluctuations, such as construction machinery or mining equipment, then your inspection cycle should be shortened by 30%-50%.
If your hydraulic system is used for precision equipment, such as indoor automation equipment or precision hydraulic platforms, you can appropriately extend the cycle of in-depth maintenance, but the frequency of monitoring can not be reduced.
In addition, you can not use time as a measure of maintenance. You can set a series of standards based on your actual situation, such as the maximum contamination indicator, the maximum differential pressure of the cartridge, the temperature fluctuation range, and so on. In operation, once you find that these values exceed the set standards or ranges, you immediately carry out inspection and maintenance.
Maintenance Cost vs. Downtime Cost: Which One Is More Expensive?
When controlling costs, many factories prioritize squeezing funds for maintaining hydraulic systems. They often extend the run time of filter elements and hydraulic fluids, and put off replacing hoses and seals. They think that if they can reduce the number of maintenance times, they can reduce costs. But in practice, if maintenance is not done properly, it can easily lead to serious failures in the hydraulic system.
The Cost of Unplanned Downtime in Hydraulic Systems
Direct Economic Losses
The most immediate impact of a hydraulic system failure is economic losses. This includes loss of production, the cost of repairing equipment, the purchase of expedited spare parts, and the cost of rework. An hour of downtime in many production lines is more than the cost of a full year of routine maintenance.
The Cost of Secondary Damage
If one component of a hydraulic system fails, other components are likely to follow, creating a vicious cycle. For example, if the hydraulic pump wears out, metal shavings will enter the hydraulic system, and then the hydraulic valves and cylinders will also wear out. The original cost of replacing a cartridge finally becomes the cost of replacing pumps, valves, seals, fluids, and cleaning the entire system.
Indirect Losses in Production and Management
In addition to the cost of repairs and downtime, your original production schedule is disrupted. You’ll have to reschedule shifts to catch up, and employees will be less motivated. And most probably, you won’t catch up with the original production schedule. Then your lead times will be delayed, and the quality of your products will drop, which will affect your relationship with your customers. These indirect losses won’t be written in the maintenance statement, but they will create a big psychological burden on you.
Safety Risks Cost
In addition, hydraulic system failures often cause hot oil to be sprayed everywhere, and the floor can become slippery. Repair crews can easily get burned by the hot oil or slip and fall during repairs, causing them to be injured. At this point, you’ll also have to pay for the cost of accident investigation, the cost of insurance and compliance, and even face the risk of a shutdown.
Why Cutting Maintenance Cost Often Increases Total Operating Cost？
Maintenance is A Small, Controllable Investment
Maintenance costs for hydraulic systems are largely predictable and calculated in advance. Common maintenance projects are basically replacing parts and checking the condition of the equipment. These are projects that you just need to calculate how much they cost each time and how many times a year they need to be done, and basically, you will know exactly how much it will cost you in a year. And all of these projects don’t cost a lot of money.
Failure is A Sudden and Huge Investment
Many hydraulic system failures are uncontrollable. You don’t know when it’s going to happen or how widely it’s going to affect. So you can only respond to these things in a hurry. And the cost of repairs, the cost of downtime, the cost of secondary damage, and so on, each costs a lot of money, which in total may be enough to replace a whole new unit.
From an operations management perspective, hydraulic system maintenance is not a burden, but a necessary investment used to keep capacity and reduce risk. Doing maintenance well is spending a small amount of money to avoid a larger loss.
FAQ
When Maintenance Is No Longer the Best Option？
There is no need to continue maintenance on your hydraulic system if the following occurs.
- Maintenance frequency rises, but the system repeatedly fails.
- The cost of maintenance has exceeded the purchase price of the entire hydraulic system.
- The system has design-level problems that cannot be solved by maintenance.
- Equipment frequently requires maintenance. Production schedules are often disrupted by downtime.
- Maintenance actions have begun to bring new risks.
Is the Problem Caused by Maintenance or by System Design?
Generally, problems caused by improper maintenance will be reduced with improved maintenance practices. However, problems caused by defective system design can recur even with proper maintenance.
Common problems caused by poor maintenance include:
- Wear and galling due to inadequate contamination control
- Fluid deterioration and constant increases in system temperature
- Fluid leakage due to aging seals and hoses
- Air intake problems due to low oil levels or poor seals
Common system design flaws include:
- Long-term overheating due to insufficient cooling capacity
- Repeated damage to hoses in the same location
- Long-term contaminant overloads due to poorly constructed filtration
- Unstable control due to improper component selection
How to Reduce Hydraulic Maintenance Problems Through Better System Design？
You can reduce the frequency of maintenance by optimizing the cooling, filtration, piping layout, and component selection of the hydraulic system.
You can improve in the following ways:
- Set reasonable filtration accuracy and filtration location to reduce contaminants circulating in the system.
- Avoid long-term high-temperature operation of the system to slow down the aging of the oil and seals.
- Optimize the piping layout and support to reduce repeated damage to hoses and fittings.
- Select components with appropriate specifications to avoid long-term overloading of hydraulic components.
What to Ask a Hydraulic Supplier About Maintenance Before Purchasing a System？
Before purchasing a hydraulic system, you should ask the supplier about the frequency of maintenance, the lifespan of wear parts, common failures, and the ability to provide maintenance support. This information will have a direct impact on later operating costs and risk of downtime.
You can focus on asking the following questions:
- What are the recommended maintenance intervals?
- Which parts are high-frequency replacements?
- What are the system requirements for fluid cleanliness and filtration levels?
- What is the normal operating temperature range?
- Where do common failures usually occur?
- Are the key components easy to replace?
- Do you provide advice on fluid testing and condition monitoring?
- Do you provide maintenance manuals, checklists, and training support?
Final Thoughts
The key to hydraulic system maintenance is to do a good job of contamination control and temperature management, replace key components on time, and make the system pressure more stable. You also need to make a good maintenance plan according to the actual working conditions to reduce the risk of failure in advance.
With more than 10 years of experience in hydraulic system design and maintenance, Target Hydraulics can design a maintenance program for your hydraulic system and provide suggestions on the selection of key components. If you are evaluating or planning a maintenance and upgrade program for your hydraulic system, tell us your conditions and goals, and we’ll work together to help you with the technical analysis.
