Biodegradable lubricants (ECL)

Biodegradable does not mean weak

The most widespread prejudice about environmentally friendly lubricants is that you trade performance for compliance. In hydraulics the situation is often the reverse: the saturated synthetic esters that form the base of HEES fluids have a naturally higher viscosity index than mineral oil, so they cover a wider thermal range, and better lubricity at the same viscosity. What genuinely changes is three other things: seal compatibility, which has to be checked before conversion; sensitivity to water, higher than with mineral oil because esters hydrolyse; and price. Against that, in a hose failure beside a watercourse, the difference between a mineral oil and a HEES is the difference between a decontamination job and a local clean-up.

Classes, labels and legal requirements

ISO 15380 classifies biodegradable hydraulic fluids into four families: HETG on vegetable oils (cheap, with limited oxidation stability), HEES on synthetic esters (the most used industrial solution), HEPG on polyglycols (water-soluble, with compatibility constraints of their own) and HEPR on polyolefins. Biodegradability is demonstrated through OECD 301 and aquatic toxicity through OECD 201, 202 and 203. For formal recognition, the EU Ecolabel for lubricants and the Vessel General Permit EAL list are the references authorities and clients ask for. The settings where the requirement comes up most often are river and dam works, forestry, quarries inside protected areas, farming beside canals, wastewater treatment plants and port equipment.

How to convert without surprises

Moving from mineral oil to HEES is a technical operation, not simply a change of supplier:

• Check seals and hoses first. Esters attack some elastomers that behave perfectly with mineral oil.
• Drain and flush the system. A residue of one or two percent mineral oil pushes biodegradability below the declared threshold, defeating the point of the conversion.
• Control water more tightly than before: ester hydrolysis raises acidity and shortens fluid life.
• Do not assume the same drain interval. Some HEES fluids last longer than mineral oil, others less — decide on analysis.
• Keep the compliance documents (OECD 301 report, Ecolabel or EAL listing) in the machine's file; that is what an inspection asks for, not the label on the can.