Hydraulic fluid has a number of purposes inside of a hydraulic system. In addition to it’s obvious purpose of transferring force from a hydraulic power unit to an actuator, it has a few less-obvious purposes as well:

• It helps to seal the hydraulic system through the power of surface tension and adhesion,
• It lubricates the system by preventing metal surfaces from contacting each other,
• And it helps balance the temperature of the system by transferring heat from one area to another.

If any of these functions are compromised, the entire system can become compromised. The obvious question, then, is ‘what causes these functions to become compromised and how can we prevent that?’ As it turns out, the most common cause of compromised hydraulic fluid is particulate that builds up in the fluid.

Particulate build-up might not cause the force-transferring properties of the hydraulic fluid to dissipate, but all three of the other functions are vulnerable to particles. They breach the surface tension of the fluid, breaking the ‘seal’ that the fluid forms that prevent microscopic leaks from becoming problematic. They can get pinched between metal surfaces that would otherwise have been adequately lubricated and cause damage to those surfaces. And by causing excess friction, they can overcome the ability of the fluid to keep the system cool.

The way to prevent particulate build up, as you may have guessed, is to use and regularly change your hydraulic filter. A hydraulic filter eliminates particulate contamination, which in turn prevents a goodly number of the problems that can crop up within your hydraulic fluid.

What Won’t My Hydraulic Filter Do?
The hydraulic filter isn’t the be-all and end-all of hydraulic system maintenance, however. No filter can keep water entirely out of your hydraulic fluid, for example, and water has a variety of negative effects on the system. Furthermore, the particulate that gets into your fluid comes from the inside of the parts of your hydraulic system — microscopic chunks that break off. Given long enough, that wear can affect the performance of a part, which will need replacing.

That said, nothing is quite as cost-effective at increasing the functional lifespan of a hydraulic system like regular replacement of the hydraulic filter — so make sure you stay on top of it!