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Reclamation and refortification of hydraulic fluid

What’s the right way to go with your used hydraulic fluid?

Before we provide guidance on what to do with your used hydraulic fluid, let’s define two words:

Reclaim — To salvage, recover, and clean up or recondition; sometimes called oil laundering.

Refortify — To add a predetermined amount of additive to a clean, dry, used lubricant to replenish some of the depleted additives. In some cases, refortification and reclamation are used together.

To protect your substantial investment in hydraulic fluid, you must understand which of these two types of fluid you will be using and what the ramifications are of using it. Always keep in mind that industrial hydraulic fluid is a formulation. This means that additives — containing components for wear protection and foam prevention, demulsification, rust inhibition, etc — were blended into a base oil to enhance its characteristics for use in hydraulic systems.

Reclaimed fluid
When hydraulic fluid is cleaned and reconditioned — typically involving removal of water, solid particles, air and dissolved gasses, and oil-insoluble oxidation products — it is generally considered suitable for use in the application for which it was originally formulated.

A reclamation process can typically involve:

  • initial filtration to remove large particulate matter,
  • centrifugal separation to remove bulk water and dirt,
  • vacuum dehydration to remove the remainder of the water,
  • fine filtration, and
  • refortification, if necessary.

It can be tempting to have your fluid reclaimed versus buying new fluid because it minimizes waste, is environmentally responsible, extends the life of the fluid, saves time, and generally saves money. But before you let temptation take over, you need to do some homework to assure yourself of what you’re buying.

The fluid should be tested both before and after it is reclaimed. After reclamation, the fluid may look okay, but you need answers to some questions. First, does it contain sufficient additives so your hydraulic equipment will perform properly? What is the impact if the fluid lacks proper additive levels to protect against wear, foam, contamination, and water, for example?

There are two other critical questions to ask. If the fluid met OEM approvals the first time around, does it still? And if not, will using it invalidate the warranty on your equipment?

After that comes the answer to this very important question: What are the implications if the fluid fails; for example, what if it is contaminated with another fluid? With mobile hydraulic equipment sporting price tags of up to a million dollars, is it worth the risk to use reclaimed fluid?

In general, fluid reclamation is not an option if any of these four conditions exist:

  1. It contains excessive amounts of water, sediment, and/or fine particles.
  2. It shows excessive additive degradation and/or oxidation.
  3. It is contaminated and/or co-mingled with other oils.
  4. The volumes are too low to make it economically viable.

Refortified fluid
Reclaimed fluid with replenished additives has the potential to perform well. However, the refortification process requires knowledge of the formulation, balanced to provide optimum performance. You should not underestimate the need for this knowledge. The addition of different additives to the used oil may result in an imbalance in the formulation that could adversely affect performance.

Testing and analysis
Before reclaiming fluid, you should ask the provider what type of testing will be conducted to the fluid. Typically, a sample is tested for:

  • appearance,
  • sediment by centrifuge,
  • viscosity, cSt at 40° C (ASTM D445),
  • acid number, mg KOH/g (ASTM D664 and others),
  • rotating pressure vessel oxidation test (RPVOT), minutes (ASTM D2272),
  • water separation at 130° F (ASTM D1401), and
  • trace metals analysis, ppm (ASTM D5185).

After this testing, discuss the results with the provider to determine if the fluid is deemed reclaimable or if further testing is required. After the reclamation, the same tests should be performed again and compared to the results obtained prior to reclamation. In some situations, it may make sense to run extra tests to make sure the fluid will meet the requirements of your application.

This information was submitted by Rob Profilet and Dave Oesterle, The Lubrizol Corp., Wickliffe, Ohio. Contact the authors via e-mail at [email protected] or [email protected].

Standards for recycling oil

The US EPA has management standards for businesses that handle used oil (40 CFR 279). Used oil is any petroleum-based or synthetic oil that has been used and that has been contaminated with physical or chemical impurities during use. The definition of used oil includes oil used as hydraulic fluid. Options for used oil include reconditioning on site, using it as a refinery feedstock, re-refining it, or processing it and burning it for fuel.

The EPA’s housekeeping practices are common sense, good business practices designed to ensure the safe handling of used oil, maximize recycling, and minimize disposal. They relate to storage, spill clean up and record keeping. For more information, visit