The importance of hydraulic fluid cleanliness is no secret to any diligent fleet manager or equipment operator. The pressures at which modern hydraulic systems operate mean that even microscopic contamination in your hydraulic fluid can cause big problems and eventually lead to significant downtime. At these high pressures, particles smaller than red blood cells can wreak havoc, so thorough hydraulic filtration is a must. But to be thorough, it’s important to understand the ways that contamination can enter a hydraulic system.
There are four main ways that your hydraulic fluid can become contaminated
- The fluid came dirty from the manufacturer or distributor. This isn’t often the case, but when it comes right down to it, you don’t know how your hydraulic fluid was treated until it’s in your possession. Every transfer point is a potential spot for contamination, and you typically have no idea if there was filtration at any point in the process.
- Contaminants got in during routine maintenance. The outside of a vehicle or other piece of hydraulic equipment is less than pristine, so anytime there’s a filter or fluid change, there’s the potential for dirt, water or other particles to enter the system.
- The particles were already there. This kind of contamination occurs from the building and machining of the parts of your hydraulic system and can encompass many types of particles. Metal shavings from the assembly of components, grease and grime from components being handled improperly — the possibilities are endless.
- Wear and tear created particles in the fluid. Anytime you have moving parts, there’s an opportunity for wear. Metals rubbing together will inevitably cause particles to break loose. Rubber and plastic parts are even more likely to wear and leave shavings, if not bigger pieces. Which brings us to your hydraulic hoses.
Hydraulic hoses and their role in contamination
Every hydraulic system contains hoses. The different types of hydraulic hoses are often built of multiple layers of plastic, rubber or metal to handle the high pressures of the system. These aren’t simple rubber hoses! The process of fabricating hydraulic hoses might introduce contamination like metal particles from the internal wire reinforcement and the cutting blade itself to polymer dust from the outer cover of the hoses.
The more complicated you make a system, the more prone to failure it can be. In the context of hydraulic contamination, the more components you’re dealing with, the more chances there are for a part to allow contamination to enter the system. And these hoses can contribute to three of the four ways that contamination can enter a system that we outlined above.
When contamination is introduced via hydraulic hose, it can be a big problem, literally. While we’ve mentioned that at high pressures, even microscopic particles can cause great damage inside a hydraulic system, the particles that can get into your fluid through your hoses and hose attachments might even be seen with the naked eye — in other words, they’re metaphorical boulders compared to the smallest damage-inducing particles. Rubber and metal particles introduced to the system as a result of cutting and fitting hoses can be up to hundreds of microns in size, more than enough to cause damage to hydraulic components, introduce more particles as a result of that damage, or simply plug filters.
How Big is a Micron?
Micron Sizes of Familiar Particles
- Grain of table salt 100 µm
- Human hair 80 µm
- Lower limit of visibility 40 µm
- White blood cell 25 µm
- Talcum powder 10 µm
- Red blood cell 8 µm
- Bacteria 2 µm
- Silt <5 µm
Replacing hydraulic hoses is a regular part of maintenance on hydraulic machines and equipment, and there are many ways of performing the task. If your fleet maintenance plan includes replacing your own hydraulic hoses or conducting your own hydraulic hose repair, we recommend the following care to help keep contamination from entering your hydraulic system.
When cutting your own hoses to size, you can reduce the amount of contamination entering the hose by:
- Using a wet cutting blade as opposed to a dry one
- Using compressed air to clear particles inside a hose after it’s been cut
- Using a vacuum hose to suck up loose particles
However you mitigate particles when cutting hoses for hydraulic hose replacement, it’s vital that you’re thorough when cleaning the hose before installation. And remember, many contaminants are not visible to the naked eye. Shooting a foam cleaner through the hose via compressed air is one of the more efficient ways to thoroughly clean a hose.
Foam-based cleaning systems theoretically can clean your hoses to an ISO 4406 13/10 level, meaning that they can clean to a level of 40 to 80 4-micron particles per milliliter or 5 to 10 6-micron particles per milliliter. But like most everything else, these results can be caused by any number if variables. Was the foam projectile the proper diameter for the hose being cleaned? Was the projectile dry or wetted with solvent? How many shots of foam were used? It stands to reason that the more times foam cleaner is shot through the hose, the cleaner the hose will be. If it was a new hose being cleaned, was it done before the ends were crimped on? All vital things to consider.
When conducting hydraulic hose replacement, it’s very important to pay extra attention to the exterior of the hookup point. These connections are often exposed to environmental dirt and grime, so cleanliness should be top of mind to avoid accidentally knocking actual chunks of dirt into the hose. We’ve already discussed that even microscopic contamination can cause system damage at worst or plug filters at best, so imagine a contaminant of visible size getting into the system. Contamination is always a danger during a hose change, so pay close attention. Be careful when using your hydraulic hose crimping tool, and make sure that your hose connectors and couplings are clean before connecting the hose.
Knowing when hydraulic hoses need to be replaced is an important piece of information. As hoses age, parts get brittle, dirty or rusty, and particles of rubber, dirt or rust are more likely to enter the system. Be on the lookout for flexible hoses that are no longer flexible, or that creak when flexed. Look for rust on connection points. Cracks and wear marks are signs that a hose needs to be replaced. Also, many hydraulic hoses feature printed manufacture dates, so regularly compare those dates with the manufacturer’s recommended expiration period.
Hydraulic filtration is the best way to minimize contamination
With so many variables contributing to contamination via hydraulic hose, thorough hydraulic filtration is vital. It’s quite literally the last line of defense between your equipment and hydraulic contamination.
The number-one reason for hydraulic system failure is surface wear caused by contaminated fluid — whether that contamination was the result of a dirty hose or any other reason. Nearly 70 percent of all hydraulic failures are caused by contaminated fluid. Since literally any contamination can cause wear, it’s vital that your hydraulic filtration can capture the vast majority of those particles, to protect both the upstream and downstream sections of the system.
Every hydraulic filter application has a different job to do, and the oil filtration system for that application should be built to match that job. When choosing a hydraulic filter, make sure that it’s appropriate for its function in your system.
Hydraulic system protection is a multi-tiered effort
There are so many ways your hydraulic fluid can become contaminated. But with a little care, a lot of awareness when doing maintenance and some high-end filtration, you can be sure to keep your equipment up and running.
