performance and longer service intervals than some petroleum based lubricants.
EAL Confusion in the Marketplace There’s conflicting information in the marketplace about EALs. A lack of agreed-upon definition is one contributing factor, as is lack of awareness of the four different types of EALs that are available. Inconsistent performance claims from manufacturers have also led to the confusion.
Let’s address a few myths right from the start:
EALs DO: * Perform equal to or better than petroleum lubricants
* Mitigate the discharge’s environmental impact
* Improve productivity, which leads to profitability
EALs DON’T: * Eliminate spill occurrence * Eliminate the need to report a spill or discharge
* Eliminate the need to clean up a spill or discharge
The Four Types of EALs According to ISO standard 6743/4 for hydraulic fluids, there are four chemically different types of lubricants available to meet the specified needs for environmental acceptability. The categories are as follows:
• Vegetable Oils (HETG) • Synthetic Esters (HEES) • Polyalkylene Glycols (HEPG) • Polyalphaolefins (PAOs) and related hydrocarbon products (HEPR)
While these categories may be unfamiliar to some, the typical fluids that fall into these categories will be more familiar, and it quickly becomes apparent which are the best options available for marine- based hydraulic applications.
Here are the four types of EALs, along with their performance advantages and disadvantages:
HETG This type of environmentally friendly fluid is better known as conventional vegetable oil-based fluid. While these fluids are readily biodegradable and deliver a lower impact on the environment, enhanced frictional characteristics and improved viscosity index at high temperatures, in a marine setting this category’s performance can be limited due to oxidative and hydrolytic stability. With the demands of certain applications, HETG lubricants’ limited temperature range reduces the performance they can deliver and, often, their life cycle expectancy.
HEPG Polyglycol synthetic (PAG) lubricants deliver a fire-resistant option. The downside is that they frequently are not compatible with conventional seals or filters. In switching to or from another type of lubricant, HEPG fluids are also typically not compatible with petroleum- or vegetable-based fluids, which could add significant maintenance costs to flush or remove the previous fluid before introducing the replacement fluid. These synthetic lubricants absorb water over time, which negatively impact performance and lead to the formation of rust or acid and ultimately damage equipment.
HEES Synthetic ester-based lubricants make up the HEES type of fluid. HEES fluids are often hydrolytically unstable, meaning that their molecules essentially “unzip” when water is introduced. These lubricants are also susceptible to acid formation and subsequent seal deterioration.
HEPR Poly Alpha Olefins (PAOs) and related products, in particular bio-polyalphaolefin (BPO) fluids, deliver the best option for most marine hydraulic applications. These fluids are more durable and able to operate in a wide range of temperatures, which leads to longer fluid life and often a lower total cost. HEPR-type fluids
offer good seal compatibility and deal well with water ingress, as they separate from water (demulse) without impacting their performance properties or their chemical stability. This demulsing characteristic also allows for the fluid to be separated from the water, filtered, and returned to use.
References/Contributors
Miller, M. “The Effects of EALs on Oil Spill and Discharge Reporting & Remediation”, Maritime Reporter & Engineering News March 2015 pp. 18-19
US Environmental Protection Agency (EPA), “U.S. Environmental Protection Agency (EPA) National Pollutant Discharge Elimination System (NPDES) Vessel General Permit for Discharges Incidental to the Normal Operation of a Vessel (VGP)”, Docket ID: EPA-HQ-OW-2011-0141, December 19, 2013
Lionberger, L. “Regulatory Growth Drives Search for Durable Lubricants”, Marine News June 2017 pp. 26-29
Etkin, D.S. (2010). Worldwide Analysis of In-Port Vessel Operational Lubricant Discharges and Leakages. Retrieved from
http://thordonbearings.com/ system/documents/documents/103/ original/Analysis_of_In-Port_ Vessel_Operational_Lubricant_ Discharges_and_Leakages. pdf?1281430521
Clark, L. “The First of Its Kind - Designed to Improve Performance, Increase Uptime, Enhance System Longevity”, Maritime Reporter & Engineering News December 2016 pp. 16-17
RSC Bio Solutions, 2015 Environmentally Acceptable Lubricants (EALs): Choosing the right EAL type for your application Whitepaper pp. 1-2
Miller, M. “From Bow to Stern: Performance & Sustainability”, Marine News September 2013 pp. 28-32
The Report • December 2017 • Issue 82 | 37
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