A client recently engaged me to advise them on an application that required the use of biodegradable hydraulic fluid. This client was tendering on an earth-moving project located in environmentally sensitive wetland. A condition of the contract was that the hydraulic systems of all equipment employed on the project use biodegradable fluid to minimize pollution in the case of oil leaks, especially hydraulic hose failures.
Biodegradable or biobased hydraulic fluids use vegetable oils such as canola, rapeseed, sunflower or soybean as the base oil. The properties of these fluids can be equivalent to that of mineral oil based, anti-wear hydraulic fluids. But due to limited testing, some hydraulic component manufacturers recommend reducing maximum permissible operating pressure (load) when using biodegradable hydraulic fluids, to ensure no reduction in component life.
After reviewing the available technical data on the hydraulic components fitted to the machinery being employed, a reduction in operating pressure to 80% of that permissible for mineral oil was considered prudent.
The extraordinary costs that the contractor needed to consider in their bid included not only the expense of the fluid, and draining and flushing the hydraulic system to convert from mineral oil to vegetable oil and back again, but also the costs associated with derating the machinery.
A reduction in system operating pressure means a reduction in actuator force. This means that a hydraulic excavator that has its operating pressure reduced by 20% will experience a 20% reduction in "break-out" force.
The commercial implication of this meant that the contractor needed to cost the job allowing for the use of bigger machinery than they otherwise would have.
Initiatives such as renewable energy and non-food uses for agricultural production have driven advances in biobased fluid technology. Once these fluids can compete with mineral oils on price and performance, their usage will increase and more data relating to hydraulic component life will become available.
When this point is reached, biodegradable hydraulic fluids will no longer be relegated to special applications and the extraordinary costs associated with using them, as illustrated in the above example, will no longer apply.
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