“There’s a way………once you know a few basic facts ”
We all know the adage “You get What You Pay For” which is true. But with a little
thought and a little more effort plant operators can potentially save a great deal
Ask yourself. How much is a new Hydraulic Oil Pump…£1000, £2000 may be… Now I can
hear a few sharp intakes of breath…But its True… take into account the following
and you’ll soon hit the £1000 mark : Operators down time
Mechanics’ time finding and buying and/ or collecting the part
Fitting the part
Getting hydraulic oil
All these costs soon add up and I haven’t included the costs of contract over-run
So why not take a few extra minutes to check the basic facts of using hydraulic oil.
Now I’m going to use a term little understood by some people…Preventative Maintenance…
in other words …Stop The Fix Before it Happens….
To explain… In use hydraulic oil gets hot. why ? …because its being forced through
small openings in your equipment valve-chests, hoses and valves at very high pressure
and very high rates of flow and thereby collecting heat from friction.
If the oil is holding too much heat and not having time to cool down, either in the
tank or via the coolers, it becomes what’s known as HYDROSCOPIC, which means it starts
to absorb moisture from the air like a sponge.
Each time a ram is extended the oil level in the reservoir drops and draws in fresh
air loaded with moisture (and all that dust and what ever else is passing at the
time) via the tank breather. The oil grabs hold of this moisture (and other contaminants)
and holds it in suspension and will start to change colour, at this point the change
in colour is very small, its not until the oil looks cloudy in the sight tube of
the holding tank that the operator may …if your lucky… say something.
But by then it’s too late. Because when the machine is ideal the water will drop
out of the oil throughout the whole system including the residue left in the pumps.
This promotes oxidation which promotes rust which promotes wear to all metal surfaces
and wear means more working of the hydraulic pump to maintain optimum pressure which
means more shearing of the oil, which means more heat generation. So we have an
ongoing self feeding problem that soon leads to the point of failure.
Consider a couple of things to save money.
The standard of the oil: did we pay a reasonable price for it or was it much cheaper
than normal, are we using the correct viscosity for the job in hand, as using a too
high or too low viscosity can product extra heat or foaming,
or is it the more likely situation, that the reservoir holding the reserve volume
of hydraulic oil is too small and doesn’t get a chance to cool down, both easy to
The first by obtaining a performance data sheet from your supplier and the second
by checking the tank surface for temperature when working normally, as a rule of
thumb if its very hot to the touch then its too hot. Manufacturers often use too
small reservoirs to save space, which only exasperates the problem.
The fix is to fit larger tanks or check the oil coolers for obstructions or even
change the performance level of the oil, that is… move up to a high VI oil or High
Viscosity Index oil. (VI is a number given to oil to indicate the rate of change
of thickness with the application of heat. We all know that oil gets thinner as it
warms up. The higher the VI number then the slower the oils viscosity will change
with the application of heat).
Most Standard hydraulic oils have a VI of between 90 and 100. High VI oils are about
120 upwards depending on the grade.
Another little considered problem is the cleanliness of the oil being put into your
expensive and sophisticated bit of kit.
How many mechanics use clean containers to transfer fluids from bulk storage to
the machine? Its likely that they grab the closest tin that looks clean but in
fact contains dust, or a “ready made emery cloth”, just ready to wear all that it
So to sum up: Consider These: Grade of oil used – Storage & Transfer of Fluid – System
Construction, Reservoir size and breather filtration.