When it comes to the repair and maintenance of hydraulic systems, there are certain hydraulic equipment mistakes that occur more often than others. Whether it is changing hydraulic filters too often or using the wrong type of hydraulic fluid, these errors can lead to serious problems such as unnecessary maintenance costs, increased repair costs, system downtime, premature wear of components, and even catastrophic failure.

Changing Hydraulic Oil at the Wrong Time

Hydraulic fluid is expensive, and changing it before it actually needs to be changed wastes money, results in more system downtime than is necessary, and can even increase the risk of hydraulic contamination – none of which are good for the system or for your bottom line.

Many hydraulic systems come with manufacturer recommendations as to how often the hydraulic oil should be changed, and these recommendations are meant to serve more as guideline than a hard and fast rule. Most recommendations are based on service hours, but there are many other variables that can affect when your hydraulic fluid needs to be changed, such as:

•    Operating temperature (high temperatures cause oil to degrade faster)
•    Water and air contamination levels
•    Particulate levels
•    Depletion of additives
•    Natural degradation of the hydraulic fluid over time

In fact, heat, water, and contamination are the three key factors in shortening the life of your hydraulic fluid. The only accurate way to determine when hydraulic fluid needs to be changed is to perform an analysis on fluid samples, preferably from different points in the system.

If you maintain your hydraulic system well, you will discover that the hydraulic fluid lasts much longer and may only need to be replaced when the additives have been depleted. Most hydraulic contamination can be removed through off-line filtering, and a system that is carefully maintained will not have major issues with overheating and accelerated degradation. In short, the better maintained your hydraulic equipment is, the longer your hydraulic fluid is going to last.

Using the Wrong Hydraulic Oil

Using the wrong hydraulic oil in your system is one of the more common hydraulic equipment mistakes. When it comes to the type of hydraulic fluid you use, it is important to keep in mind that it serves a variety of purposes: it transmits power through the system, lubricates parts within the system, prevents oxidation, and helps to conduct generated heat away from critical components. Failure to use the correct proper oil will not only decrease the efficiency and performance of the hydraulic system, but it can also seriously shorten the life of the system and the many components that comprise it.

High Viscosity Hydraulic Fluid

The key to selecting the right hydraulic oil lies in the viscosity of the fluid. If the viscosity of the hydraulic fluid is too high, it will not be able to fully lubricate the hydraulic components during a cold start, which can lead to premature wear. In addition, higher viscosity hydraulic fluid will result in system power losses due to increased fluid friction, which in turn reduces the overall efficiency of your system while increasing its power consumption.

Low Viscosity Hydraulic Fluid

On the other hand, if the viscosity is too low, then the components will not be adequately protected during operation. This will result in increased wear and, over time, premature failure of key components such as hydraulic pumps and motors. It also leads to generated contamination, which can cause even more efficiency losses and accelerated wear.

Because of the factors tied to viscosity, we can see that there is more to selecting the correct hydraulic fluid than simply following manufacturer recommendations. With viscosity being one of the deciding variables, it is important to keep in mind that operating temperatures and even environmental temperatures (in the case of mobile hydraulic equipment) will significantly impact the viscosity your system needs for optimal performance. In addition, a different viscosity may be needed depending on the time year, especially if you have mobile hydraulic equipment that may be exposed to the elements.

The best approach to determining the correct viscosity of hydraulic oil for your system is to consult with an experienced technician who is familiar with the system.

Hydraulic System Running Too Hot

Using the right hydraulic oil in your system won’t do much good, however, if the system runs too hot. Heat decreases the viscosity of the hydraulic oil, causing an otherwise appropriate oil to have low viscosity – another common hydraulic equipment mistake. When the viscosity of the oil is too low there will be metal-to-metal contact, which leads to generated contamination that is harmful to your system and its components. In addition, high temperatures can cause the seals and hoses to fail prematurely while simultaneously increasing the natural degradation of the hydraulic oil itself.

What is too hot? A system runs too hot when the hydraulic fluid can no longer provide adequate lubrication, which in turn damages pumps and motors. It is also important to keep in mind that when parts of a hydraulic system are running at high temperatures, it may be a sign of other problems that need to be addressed, such as worn out bearings, dirty heat exchangers, or incorrect flow rates.

Changing the Hydraulic Filters at the Wrong Time

Just as we discussed with hydraulic oil, hydraulic filters can also be changed at the wrong time. If the filters are replaced too soon, they haven’t been used for their full life and therefore money is wasted, the system experiences unnecessary downtime, and it is exposed to contaminants when it does not need to be.

On the other hand, if the filters are not replaced soon enough, they can clog and reduce hydraulic flow. If they clog severely, the result is a complete bypass of hydraulic fluid. When a filter bypass occurs, the fluid is no longer passing through the filter and contaminants are free to wreak havoc on any downstream components they reach. The result of changing filters too late ranges from costly repairs to prematurely worn out components and overall hydraulic system inefficiency.

The secret to changing hydraulic filters at the most opportune time lies in monitoring the pressure drop across the filter. A pressure drop that is much higher than normal indicates the filter has almost reached its capacity, whereas an almost negligible pressure drop would indicate that a bypass has occurred. By monitoring the pressure drop, a technician can keep track of the right time to change the filters.

Placing Hydraulic Filters at the Wrong Locations

There are two places where you should not place hydraulic filters:

•    At pump inlets
•    In drain lines from the housings of piston motors and pumps

Inlet filters are not needed because the reservoir should not be contaminated. The presence of a filter at the inlet is a poor design choice because it results in a restricted intake that will significantly shorten the life of not just piston pumps and motors (which are impacted the most), but also the gear pumps.

Filters located on the drain line exiting a piston motor or pump result in an entirely different set of problems, but the result is typically the same: a reduced service life followed by a catastrophic (and expensive) failure of a pump or motor and the aftermath that follows. While hydraulic filters serve a vital purpose in a hydraulic system, there are some areas in the system where they don’t belong.

Believing Hydraulic Components are Self-priming and Lubricating

It is important to remember that hydraulic components are not self-priming or self-lubricating. Just like a car engine cannot start without oil in the crankcase, a hydraulic pump or a hydraulic motor will not run without hydraulic oil in it.

Let MAC Hydraulics Help Minimize Your Hydraulic Equipment Mistakes

Knowing up front the most common hydraulic equipment mistakes and how to avoid them will help save your company money, time, and frustration, as well as wear on components that end up needing to be replaced too soon.

Contact us today to learn more about our services. We’ll help you develop the ideal preventative maintenance plan for your hydraulic equipment and systems!