Hydraulic leaks occur for a variety of reasons. The primary cause of a given leak could be contamination, fluid selection mistakes, extreme operating temperatures, alignment problems or seal failure to name a few. Any combination of these issues along with a host of other contributing factors may lead to more frequent and severe hydraulic leaks. In some environments, tracking down the exact source of the problem may be difficult. But by taking leaks seriously and establishing proactive measures to eliminate the most common causes, it is possible to reduce the costs, risks, and environmental impacts that come with them.
Why invest in eliminating even small hydraulic leaks?
Anyone who works with hydraulics knows that some leaks are easy to spot, while others may go unnoticed for days, weeks or in some cases even years. Because major leaks present an obvious problem, they are often solved quickly, and there is little debate about whether correcting them is worth the time and effort. Smaller leaks, however, tend to be missed or placed low on the priority list, leaving them to drip away and cause much larger problems over time.
When a leak is left to drip, it is letting in contaminants that accelerate failure conditions and decrease the service life of the machine and the hydraulic oil or fluid itself. At the same time, the leak is increasing consumption of precious hydraulic oil or fluid, creating safety and environmental risks and may be a sign of other, even more serious problems. All of these effects lead to increased total cost of ownership for a hydraulic asset.
What causes most hydraulic leaks?
The primary causes of most hydraulic leaks are temperature problems, installation mistakes, seal failures, pressure problems and hose failure. Fortunately, relatively simple changes can often solve these issues, but first, we must identify and understand them.
Installation mistakes
How a machine is initially set up and installed plays a major role in its long-term reliability. Whether you are commissioning a new machine or re-commissioning after a major component failure, it’s important to remember that major failure likely means major contamination. Even a new machine may contain metal particles left behind from the machining process. If these contaminants are not removed, they will accelerate component wear, oil degradation and seal failure as well. Drain and clean the reservoir, change out any filters, and change or flush the hydraulic fluid before putting the machine in operation.
Be sure that any piping you are using has been properly selected for the operating pressures of your application. At the same time, a good hydraulic sealant should be used to seal pipe threads. Pipe dope and Teflon™ tape are not recommended simply because they are usually overapplied. Instead, apply sealant to the male fitting starting two threads from the end. Apply sealant carefully. Overapplied sealant will end up in the hydraulic system, which causes leakage at the O-rings and cylinder rod seals as well as the hydraulic pump and motor seals.
High temperatures & pressures problems
Simply put, a hydraulic system’s capacity to dissipate heat must be greater than its heat load in order to maintain a stable operating temperature. When hydraulic systems run too hot, it can damage seals and O-rings or even pumps themselves. If the problem is not caught or solved quickly enough, leaks will start popping up. It may also mean paying for replacements seals and even a replacement pump if the problem is left to linger. Those costs add up fast, not to mention the downtime needed to make the replacements. Deal with high temperature problems promptly, and you will be able to avoid a significant amount of damage, leaks, and component failures.
High temperatures can have a variety of causes, but incorrect pressure settings are often involved. Checking pressure settings periodically to ensure they have not been unintentionally changed is an important inspection step that is sometimes overlooked. For instance, if a hydraulic pump’s compensator pressure setting is dialed higher than the relief valve setting, the pump will send oil back to the reservoir through the relief valve, causing temperatures to rise. When temperatures get above 82°C (180°F), most seal compounds will be damaged and hydraulic oil oxidation and degradation will accelerate.
In some cases, correcting pressure settings may be all that is needed, but be sure to check seals, O-rings and pumps for damage.
Other possible culprits of overheating problems are low reservoir fluid level or a blocked heat exchanger. Any time there is a pressure drop in a hydraulic system, heat is generated. There are ways to calculate pressure and temperature in relation to one another that can help you identify when certain pressure changes might be the cause of an overheating problem.
This relief-valve tank line should be at ambient temperature. Here, the compensator setting was increased, so the excess pump volume dumped over the relief valve when it was not used in the system, causing excess heat in the hydraulic oil.
Hose failure
In most applications, some pressure spikes will happen. When they do, the way you have set up your equipment can play a major role in how reliable and leak-free its connections and hoses are.
Hoses can help absorb a pressure spike. A hose should be installed immediately downstream of the pump and just prior to entering the manifold. You should never use rigid pipe to go into a cylinder except in the case of a suspended or vertical load. If a velocity fuse is mounted at the cylinder port, then a hose can be used. The velocity fuse will close if the hose ruptures, preventing a free-falling load condition.
A hose that is too long and prone to rubbing on machine components or other hoses will prematurely fail and cause a significant loss of oil from the reservoir. If hose rubbing cannot be prevented, a sleeve or protective cover should be installed. Many companies make sleeves that can be purchased by the reel.
The length of the hose generally should not exceed 3 to 4 feet. The only exception is if the cylinder or motor is mounted on a movable carriage. During operation, the length of the hose can change by nearly 10 percent. And even if the initial system installation used the proper length, the hose may incrementally increase in length over several years. This usually occurs because maintenance personnel cut the hose a little longer each time they replace it.
Seal failure
Seals can fail for many reasons as well, but improper seal selection and contamination are two major factors. Seals need to be compatible with the hydraulic fluid they are keeping in the system. When making a change from one hydraulic fluid to another, be sure to check that the new fluid is compatible with existing seals.
Seals also need to be selected to account for operating temperatures, speeds and environment. These criteria can be especially important for wiper seals—if a rod is moving too fast or operating in an especially dirty, hot or humid environment, the wrong seal will let contaminants in every time the piston moves, significantly decreasing the service life of the seal, components and the hydraulic oil itself. Consult your OEM manuals and lubricant supplier to be sure that you are using the optimal seals for your application and consider proactive contamination control activities to reduce the likelihood of both seal and component failure.
Environmental impact
When leaks occur, a portion of that fluid is likely to end up in ground water, rivers, lakes or the surrounding oil itself. In addition, fluid leaks mean increased fluid consumption costs and the increased carbon footprint that comes with the manufacture, shipping, and storage of new oil or fluid. In fact, a single leak at one drop per second adds up to 1590 litres (420 gallons) of fluid lost per year. As more industrial facilities are striving to meet regulatory or internal targets related to their environmental impact and oil consumption, leak elimination and prevention becomes all the more important.
The answer: a proactive approach
Any time there is hydraulic oil leakage in a system, there's a reason for it. When a leak is discovered, the system should be analyzed, and the cause of the leak identified. Companies who treat hydraulic oil leaks as an acceptable part of owning hydraulic equipment waste thousands of dollars each year, but in some cases it can feel overwhelming to address the number of small leaks in a plant. If you are stuck in fire-fighting mode, taking a proactive approach to eliminating leaks can help you make sustainable progress.
Time and resources spent on proactive activities like equipping inspectors with infrared thermometers, checking for hose or piping installation mistakes and adding contamination control hardware to hydraulic assets can yield impressive results over time.
Contamination control can be a major topic of its own, especially in hydraulic applications. Running hydraulic assets with highly clean oil is a great way to combat seal leaks, extend machine and oil service life and ultimately lower the total cost of ownership. The more proactive we can be in addressing hydraulic problems like leaks and contamination, the better longevity and reliability our machines will have.
If taking it all on yourself seems daunting, look for a solution partner who can come alongside you to understand your needs and help you find the right tools and technology to set you up for success.