We talk a great deal about pumps, valves, pipe-work and other hardware but give little mention about the lifeblood of the system, that of course is hydraulic oil.
This is vitally important to the life and performance of the system and come in many varieties.
When I started my career we were told to say that any oil is ok as long as it is mineral ISO 32 hydraulic oil and I suppose it is still the most common choice today.
But we also have applications where this is not suitable and today we have more choices and better oils to better suit demanding conditions.
The environment has become a greater issue and it is very important we do not contaminate the soil or waterways. Rape seed oils were common but now there are some very good synthetic oils that not only protect the environment but are better suited to the components.
Fire has long been an issue with fire resistant fluid. Water glycols must be used with overhead tanks due to specific gravity and to avoid cavitation. However there are fluids that can be used in the same way as normal oil that give similar protection.
Skydrol is used in aerospace systems and will destroy most types of rubber and plastic and need careful selection of pumps and valves.
It might be that the system is working in very hot or very cold environments and will need a suitable grade of oil that will end up with the ideal viscosity at the working temperature.
There are also oils that will not degrade when run at higher temperatures.
With mineral oils, I do not like temperatures above 50centigrade (comfortable to the touch).
Higher temperatures can cause many problems with seals, varnishing and eventually breakdown of the additives that protect the systems.
I would like to hear about oils that our group has used and maybe stories of problems when unsuitable oil is used.
Cheers
Bob
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