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Changing types of hydraulic fluid

Of course, the very basic actions that need to be undertaken when changing from one type of hydraulic fluid to another is to completely drain the system, flushing out any remnants of the old oil and replacing the filters before refilling with the new product. This is an excellent time to carry out a quick maintenance check while the machinery is off and empty. It is especially important to check and replace the seals and hoses if you are changing to a higher viscosity hydraulic fluid, as the increased pressure may be a problem for old or worn parts.

The experienced hydraulic engineer can carry out this process without any problems, but when changing from a mineral oil based hydraulic fluid to a biodegradable ester based one there are some considerations that will take some in-depth work to address. The main reason for making this switch is restrictions imposed by the owners or managers of the land on which the hydraulic equipment is to be used. Believing biodegradable hydraulic oils to be the better choice for environmentally sensitive operations this is often stipulated, leaving the machinery owner no choice but to make the costly switch.

Bearing in mind that biodegradable hydraulic fluids can cost up to ten times more than their mineral based equivalent, it is important that the reasons for the switch are carefully considered. Many stipulations that a biodegradable oil is used are not properly thought through, and there are reports of a backwards move in some countries as biodegradable oils have been found to be no better for the environment overall than mineral based ones. The reasons for this are that biodegradable hydraulic oils are very high maintenance, and often operators are ill-equipped to deal with the challenges of regular oil analysis and the subsequent higher risk of leaks and damage when the oil is not properly looked after. An increase in damaged parts and leaks means that actually more hydraulic fluid is lost to the environment when a biodegradable one is used, and it is not as environmentally friendly as the name implies.

Biodegradable hydraulic fluids still cause problems in the environment, contaminating wildlife and plants alike. Once they have entered the food chain through small animals and plants the toxicity can increase as these are ingested by animals further up the chain, causing widespread problems. It is not soluble in water, so there are still issues with slicks affecting bird life and problems with clean up, and when you consider that the chance of a leak is much higher with biodegradable hydraulic fluid it seems like a counter-intuitive choice.

Another drawback to biodegradable hydraulic fluids is that they can start to break down inside the machinery, and this happens a lot more quickly than with mineral based oils. They are less resistant to heat and need frequent changes, top ups and attention to ensure they are still fit for purpose. Adding the cost of regular analysis, top ups and replacement to the initial cost of purchasing this type of hydraulic fluid soon sees the cost become unsustainable in the long term, reducing the profitability of working in environmentally sensitive locations.

When considering a change in hydraulic fluid it is vital to understand exactly why the change is needed, and whether actually addressing the issue with more stringent maintenance, a move towards a different type of mineral-oil based product or providing a clean-up contingency plan may influence the decision to stipulate a change in hydraulic fluid. Of course, there will be some applications where a biodegradable hydraulic fluid is absolutely necessary, but there are many more that do not actually justify the extra costs for an unproven environmental benefit.


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