HYDRAULIKPRESSE - HANSA-FLEX Hydraulics Canada Inc.

TRAINING CENTER
In hydraulic systems the hydraulic fl uid or pressure
medium is a decisive factor in determining whether
a hydraulic system operates reliably and achieves a
long service life. The use of fl uids in hydraulic installations
calls for enormous knowledge and care. With
the course subject “Hydraulic Fluids” HANSA-FLEX is
helping to make customer customers
more aware of how to
handle hydraulic hydrauli
fl uids.
20
Oil treatment made easy
An ABC: Which hydraulic fl uid is right?
HYDRAULIKPRESSE
HANSA-FLEX’s training manager Ulrich Hielscher
points out time and time again how serious the
consequences may be if customers use the wrong
fl uids and mixtures of fl uids, or oils which are of
inferior quality or do not comply with the specifi c
operational requirements. “This may even cause the
hydraulic system to fail.” That is why it is essential to
select the right hydraulic fl uid. “Here it is the fi eld of
application that decides - in other words, whether
the system will be used for example for automotive
engineering, in a press or smelting works and rolling
mill; whether it is special-purpose equipment
or a mobile work machine. The maximum operating
pressure also plays a role, as does the ambient
temperature and installation location.” No hydraulic
fl uid is suitable for every application. These oils are
just as varied as their possible uses. Many manufacturers
of branded products clearly state what specifi
cations an oil has to fulfi l for their equipment. “It
is important to know in practical terms that the DIN
standards for hydraulic fl uids only represent the
minimum requirements for manufacturers and operators
and are no longer suffi cient for most applications.
For many plant and mechanical engineering
companies the standard is merely the lowest
level here”, explains Ulrich Hielscher. If an oil does
not meet the manufacturer’s specifi cations, this
may invalidate the warranty. If oils specifi ed with
key performance data are approved by the manufacturer,
the warranty may extend for two years,
and if oils which are specifi cally named and have
been fi eld-tested by the machine manufacturer are
used, the warranty may even be for three years.
Fluid under pressure
When deciding which oil to use, it is a good idea to
take a look at the technical data sheets provided by
the oil supplier. They give the main characteristics
of the oil, for example, the air release capability or
ageing behaviour and its viscosity level. To play it
safe, these data from the oil supplier and the manufacturer’s
specifi cations should always be compared
when selecting the type of oil.
The viscosity does not characterise the quality of
the hydraulic fl uid but indicates how it will behave
at a certain reference temperature. In order to
observe the limits on the use of a hydraulic fl uid,
it is important to take account of the permitted
minimum and maximum viscosity values given by
the manufacturer of the hydro components. The
viscosity of a hydraulic fl uid should not vary widely
with fl uctuations in temperature or there will be
a change in the volume fl ow rates at the throttle
points. In terms of design it is also necessary to look
at the critical range as on start-up, the oil in a machine
should not be too viscous or there is the risk
of it not reaching certain lubricating points quickly
enough. However, once the operating temperature
is achieved, the oil should not be too thin either or
rubbing wear will not be adequately prevented.
Hydraulic fl uids with a high viscosity index are
mainly required for applications subject to wide
fl uctuations in temperature, such as mobile work
machines, vehicles or aircraft.
ISSUE DECEMBER 2007