Posted at 28 August 2019

The Dirty Truth About Hydraulic Oil Filtration

Imagine you've been feeling under the weather and you're not sure why. You take yourself to the doctor's and you're offered a choice of diagnostic techniques: Investigate surgery or blood analysis? When a hydraulic system is not performing as it should be, and components are failing prematurely or frequently, those are effectively the options. So do you choose to put your system under the scalpel, or do you reach for the syringe instead?


An estimated 70% of component replacement is due to surface degradation or wear. In hydraulic and lubrication systems, half of those replacements are down to mechanical wear, and a fifth to corrosion. Yet both those problems can be picked up by oil analysis – often well before the problem turns into a crisis.

So your assets not only avoid being dismantled for “investigative surgery”, but can be “treated” without the need for a major operation.

Getting down and dirty

There are essentially four types of oil contamination (see below), and each one can cause different problems within the system. The only thing they have in common is that each one is bad news.

But simply identifying their presence is not enough. The results of the oil sample need expert interpretation to pinpoint the root cause of the contamination, so you can take steps to resolve it.


That’s why ERIKS’ independent laboratory oil analysis service goes beyond simple sampling and reporting. It also includes comprehensive and expert analysis by a qualified Application Engineer.

Analyse, advise, address

A less useful analysis may only tell you what’s in the oil that shouldn’t be. An ERIKS analysis will not only discover the contamination, but will also identify the likely source, and propose the most effective solution.

For example, dust in the oil can be countered by installation of desiccant breathers, to prevent ingress of dust or other small particles.

Water is another common oil contaminant, with a number of potential sources. In a hygienic environment, ingress during aggressive high-pressure washdowns could be the cause.

If your power packs become very hot, water in the oil could be condensation. Or there may be a leak into the hydraulics from the cooling side of the system.

ERIKS’ experts will know what to look for, where to look, and can either guide your engineers or inspect the system for you, before addressing the root causes of the problem.

Code breakers

If you adhere to the ISO Cleanliness Code, you may be thinking that dirty oil isn’t something you have to worry about. Unfortunately, that’s not the case.

Every hydraulic component has an ISO code to guide you on the level of filtration required. But cracking the code and choosing the correct filtration depends on a number of variants, including the system operating pressure and the particular components within the system. In fact there could be a number of different codes and a number of conflicting filtration levels indicated for one system, leaving you none the wiser about which to choose.


ERIKS’ expert Application engineers are able to advise you on the correct code to observe and the right filtration rating to adopt, to ensure the optimum service life for all components within your hydraulic system.

So after hydraulic oil analysis by ERIKS, you can expect:

  • Confirmation of the ISO Cleanliness Code you should be following, and of the filtration micron rating you need to be operating
  • Interpretation of the contaminants present in the oil
  • Solutions (ranging from preventive maintenance to component repair or replacement) to the problems identified


If it’s possible to squeeze out that much essential information from a few drops of oil, surely it’s time to learn the truth about your own hydraulic system? Especially when the process is as simple as taking a sample.

Contaminants and their consequences

The 4 basic types of oil contaminants are:

  • Solids – leading to abrasive wear, leakage, components failure etc.
  • Liquids – a source of corrosion wear, sludge formation, cavitation etc.
  • Gel-like residues – resulting in bearing wear, valve malfunction, dynamic seal damage etc.
  • Gases – causing cavitation, oxidation, premature oil ageing etc.



Want to read more...?

Why not take a look at the latest edition of our magazine, Know+How, packed with the latest industry news, reliability improvements and best practice

Reliability is a buzzword that is seemingly always on the tip of industry tongues, but it’s clear that businesses need to be more proactive in their attempt to maximise their assets.

In this issue, we look beyond equipment, but at processes, systems, strategy and communication.

Related Articles

Join the Conversation

Subscribe to our News, Products & Services

Latest Articles

Take a look at our latest updates...

Full steam ahead - Scottish distillery with Grundfos

Nick Lees

There’s steam and there’s high-quality steam. There are pump solutions and intelligent pump solution...

Delivering for the dairy - greater milking efficiency with ERIKS and Spirax

Nick Lees

Leaking control valves were leaving a dairy product manufacturer feeling pretty cheesed off. Fortuna...

How to Contact ERIKS

Get in Touch

For all general enquiries use the Enquire Online form - we'll connect you with the best member of our team for your query.  Alternatively, look up your local service centre...

Got a Technical Question?

We are proud to boast a strong team of technical specialists in each of our product and service areas. If you have a technical question a member of our team would be happy to help. 

Share Your Thoughts

At ERIKS we strive to deliver the best quality service and products. As part of this goal we encourage customers to submit feedback on their experiences so we can resolve any issues and concerns.