In Issue #70, I started to discuss an application in which Bill Vogel, one of our members from California, is (was?) considering changing out a mineral oil for a biodegradable.
This article generated a lot of mail, but before I summarize that, let's pick up where we left off last month.
"The machine has two 18 liter hydraulic reservoirs… Each circuit is equipped by the OEM with a 100 micron suction screen in the reservoir and a 25 micron (absolute) pressure filter."
Bill's read all my books, so he knew this bit would arc me up. As an aside, last week someone sent me a link to a post on a message board where my advice to remove and discard suction strainers was being discussed. One poster asserted that to make this recommendation, I must own shares in all the major pump manufacturers "because it's a lot cheaper to replace a suction strainer than it is to replace a pump".
You have to laugh. Inadvertently though, this not-so-sharp hydraulic equipment owner may have uncovered the reason why some hydraulic pump manufacturers also actively manufacture and market suction strainers.
So no prizes for guessing what my fourth piece of advice to Bill is. Particularly if he were to select a triglyceride (vegetable-based oil), which have peculiar pour point characteristics (flow at low temperature) compared to mineral oils.
Moving on, Bill sent me this in response to last month's instalment:
"Fortunately we do have a choice; we aren't mandated to go biodegradable. (Two of) the reasons I'm considering it are:
- OEM's recommendation, and
- The obvious 'good stewardship' in the mountain environment in the event
of an inadvertent spill."
With respect to number 1, I've seen this before from European Manufacturers. They seem to think they are taking 'green' leadership by recommending an 'environmentally friendly' lube as the first choice.
But how 'green' are these oils really? Consider this, sent to me by Hans Storeboe from Norway:
"In the Swedish county of Goetheborg, they have removed regulations against mineral hydraulic fluids. It was found that breakdowns and leaks were ten fold with biodegradable fluid - resulting in an overall increase in oil spill. And biodegradable fluid is not harmless to nature. Continuous production of new spare parts isn't either."
"Not harmless to nature …" indeed, the US EPA (Clean Water Act) takes a similar position:
"Like petroleum-based oils, non-petroleum oils can have both immediate and long-term adverse effects on the environment and can be dangerous or even deadly to wildlife. For example, non-petroleum oils can deplete available oxygen needed by aquatic organisms, foul aquatic biota, and coat the fur and/or feathers of wildlife. For example, when a bird's plumage is coated with non-petroleum oil, their feathers lose their insulating properties, placing them at risk of freezing to death."
"Birds that are covered with non-petroleum oils also can smother embryos through the transfer of non-petroleum oil from the parents' plumage to the eggs. Birds and wildlife can ingest oil directly and may continue to ingest the oil as they eat if the source of their food consists of fish, shellfish, or vegetation that also are contaminated with non-petroleum oils. Other adverse effects of spilled non-petroleum oil on bird and wildlife include drowning, mortality by predation, dehydration, starvation, and/or suffocation."
Thanks to Bill Patnode from Algonquin Power for bringing the above to my attention.
So biodegradable doesn't mean eco-friendly. And if machine reliability is compromised in any way - and it will be without due care and attention, then the environment may actually be worse off with non-mineral than with mineral oil.
The ironic thing is these non-mineral lubes are the hydraulic fluids of the future. On the 9th of January this year, the head of car giant General Motors publicly warned that the switch to bio-fuels such as ethanol is now inevitable.
If he's right, then it's safe for me to predict that in the not too distant future, we won't have a choice. We'll all be filling our hydraulic tanks with a non-mineral oil. And when this happens effective maintenance practices, like those I advocate, won't be optional - they'll be mandatory.
But for the time being at least, Bill does have a choice. And my advice is to change to a biodegradable - when the cheap supply of mineral oil runs out.
"Thanks for the great work on the two publications, Insider Secrets to Hydraulics and Preventing Hydraulic Failures. I have been in the hydraulics business for the past 20 years and it's very difficult to find any decent material on hydraulic maintenance, troubleshooting and failure analysis. These two books cover it all in easy to understand language... I conduct hydraulic training courses and plan to purchase copies to distribute to my students to share your practical approach to understanding a not so understandable subject."
Paul W. Craven, Certified Fluid Power Specialist
Motion Industries, Inc.