The most important component of every hydraulic system. Hydraulic Oil

Here's four quick tips for you to get the most out of THE most important component of every hydraulic system  - the oil:

1. Don't change the oil - filter it.

Water or particle contamination rarely necessitates an oil change - unless the contamination has resulted in additive depletion or base oil degradation. These contaminants can be removed from hydraulic fluid by filtration. 

2. Eliminate particle contamination to reduce breakdowns...

Research has shown that maintaining fluid cleanliness at ISO 4406 16/14/11 will result in a tenfold increase in the average time between breakdowns when compared with a fluid cleanliness level of 24/22/19. This is based on the findings of a three-year study of 117 mobile and industrial hydraulic machines to determine the correlation between fluid cleanliness and breakdown frequency. 

3. ...and extend fluid life.

Particle contamination reduces the service life of hydraulic oil by stripping additives and promoting oxidation. Additives attach to particles, which are then removed by the filters or settle to the bottom of the reservoir. Wear metal caused by particle abrasion is a catalyst for fluid oxidation. 

4. Keep it cool.

Elevated operating temperatures increase the rate at which the oil oxidizes and this decreases its service life. By-products of the oil oxidation process - varnish and sludge, can cause reliability issues such as valve spool stiction and filter clogging.

Dirty Oil with O-ring bits and metal scrap

From the above, we can see that control contamination forms an integral part of how well your system works. Studies have shown that it costs 10 times more to extract contaminants from hydraulic fluid than it does to exclude them in the first place.

Three common points of contaminant ingression are:

1. Reservoir breather.

Standard filler-cap breathers fitted to the majority of hydraulic reservoirs are not effective in preventing ingression of airborne contaminants. All air entering the reservoir should be adequately filtered. In damp environments (e.g. marine applications, tropical

climates) desiccant breathers are essential to prevent the ingression of airborne moisture. 

2. Cylinders.

Worn or damaged rod-wiper seals and pitted or gouged cylinder rods give dust and other contaminants an easy path into the system. 

Fitting rod protectors (bellows) to cylinders operating in abrasive or corrosive environments can extend rod and wiper seal life and provides an extra barrier to the ingression of contaminants via the cylinder rod. 

3. Plumbing.

Where fluid leaks out, contamination can get in. The immediate rectification of hydraulic system leaks not only minimizes the cost of clean-up, disposal and replacement fluid, it also saves the hidden cost of removing ingested contaminants.  

Now this may spur you to believe that the best solution for maintiaing cleanliness in your system is to simply replace the oil. "New hydraulic oil is clean hydraulic oil".

THIS IS A MYTH!

New hydraulic oil straight from the drum, has a typical cleanliness level of ISO 4406 23/21/18.

Now that number may not mean a lot to you, but it's four cleanliness code levels below that considered ideal for a high pressure, high performance hydraulic system.

Looking at it another way, a 100 lpm pump operating continuously in hydraulic oil at 23/21/18 will circulate 1,600 kilograms of dirt to the hydraulic system's components each year!!! That's approximately the weight of two Hyundai Santros

To add hydraulic oil, and not the dirt, always filter new oil prior to use in a hydraulic system.

This can be accomplished by pumping the oil into the hydraulic reservoir through the system's return filter. The easiest way to do this is to install a tee in the return line and attach a quick-connector to the branch of this tee. Attach the other half of the quick-connector to the discharge hose of a drum pump. When hydraulic oil needs to be added to the reservoir, the drum pump is coupled to the return line and the oil is pumped into the reservoir through the return filter. As well as filtering the oil, spills are avoided and the ingress of external contamination is prevented.

-Excerpts from Brendan Casey, Author of 'Insider Secrets to Hydraulics'

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