HEPR fluids are synthetic hydrocarbons manufactured by the polymerization of alpha olefins to produce polyalphaolefins (PAO). Only the low viscosity PAOs are considered environmentally friendly.

A key advantage of HEPR fluids is that they offer excellent oxidation stability and good corrosion protection. They also have good lubricity, aging characteristics, and have a long service life. Offering a very good viscosity/temperature performance, they have a pour point of –20° to –40°C and operating temperature range of –30° to 100°C.

However, like most green fluids, they have a high cost. They are also incompatible with many seal and gasket materials and have a high density compared to mineral oil.

What to know before switching
1. Seal Compatibility
Traditional nitrile seals will fail quickly when used with many environmentally friendly hydraulic fluids. In general, the best results will be achieved with fluorocarbon seal materials.

HEPG and HEPR fluids may require special seal materials formulated specifically to work with these more aggressive products.

In any case, the fluid supplier, equipment manufacturer, and seal supplier all should be consulted before converting any system to an environmentally friendly fluid. The same is true for gaskets used in the system.

2. System flushing
Although traditional petroleum based fluids will mix readily with environmentally friendly fluids, this should be avoided because the petroleum contamination will nullify the biodegradability and toxicity benefits of the green product. Very thorough system flushing is necessary, and it is often advisable to perform multiple flushes to ensure the system is perfectly clean before adding the environmentally friendly fluid.

Note, especially, that engine oil additives are not compatible with environmentally friendly fluids. Equipment that has been operated with engine oil as a hydraulic fluid requires an exceptionally thorough cleaning before the environmentally friendly fluid is installed.

Furthermore, virtually all hydraulic components are tested with petroleum-based fluids. Any new component being installed on a system using environmentally friendly fluids must be thoroughly flushed prior to installation to avoid contamination.

3. Maintenance
Filtration requirements are generally the same for petroleum based and environmentally friendly fluids in terms of particle sizes. Filter change intervals may be different, however, particularly with HETG fluids that have shorter service lives and a tendency to produce varnish and other contaminants. Size filters generously.

Note also that most environmentally friendly fluids have a higher specific gravity than traditional petroleum based fluids. This may require adjusting inlet conditions to maintain adequate suction and avoid cavitation.

4. Disposal practices
As noted at the beginning of this article, the terms “biodegradable” and “non-toxic” do not mean that fluids labeled as such are harmless to the environment. They must be disposed of properly.

Spills of “environmentally friendly” fluids are still reportable incidents, but many environmental regulatory agencies are required to treat them differently from spills of petroleum-based fluids. Because environmentally friendly fluids are less toxic and more biodegradable, cleanup and reclamation costs may be lower. For example, the affected soil often does not have to be dug up and autoclaved, as is the case in most petroleum based spills. And operations are frequently allowed to continue during the cleanup.

Caution and prevention key
In summary, environmentally friendly hydraulic fluids are not a substitute for regular maintenance and good operating practices. Prevention is still much more cost effective than remediation when it comes to the environmental impact of your operations.

What they offer is a less toxic alternative to petroleum-based fluids that is more easily assimilated by the environment when properly disposed off, and causes less damage when introduced by accident. The price for the additional safety they offer is often measured in higher initial cost, shorter service life, reduced efficiency, and increased maintenance requirements.

Each of the potential negative impacts can be minimized through careful planning to select the fluid that best matches your application requirements. It’s probably a good idea to get started down that path soon, because the time is rapidly approaching when you may no longer have a choice.

Contact Thelma Marougy at (248) 226-6985 or ThelmaEMarougy@Eaton.com.

For more on environmentally friendly fluids, visit the following links, which contain technical articles, more on the basics and fundamentals of green and bio-based fluids, and new products in the marketplace: