Machinery Lubrication July August 2008

CONTAMINATION CONTROL
filter cartridges and increased maintenance
costs.
Expenses of Varnish
Having to change or clean hydraulic
system servo valves and risk system failure
are some of the results of varnish. A new
servo valve can cost $3,000, and approximately
$2,000 to clean and refurbish. But
the expense doesn’t end there. Don’t forget
the associated labor and shutdown costs,
both of which impact your bottom line.
And if the system fails, your income
declines as well.
Let’s put that into real-world terms in the
following example: A large plastic injection
molding company produces between 20
million and 30 million parts per month with
more than 200 machines that range from 33
to 770 tons. The hydraulic fluid reservoirs in
these machines range from 80 to 250
gallons. The equipment operates 24 hours a
day, five days a week. Excluding lost production,
the estimate of the yearly cost due to
varnish is approximately $135,000.
In addition to potentially triggering
premature replacement of control valves, if
left uncorrected, varnish can reduce filter
load-carrying capacity and plug supplemental
cooling system orifices.
Solution to Varnish
In the past, equipment users replaced
servo valves or cleaned them as needed to
keep their systems operating. Electrostatic
filters and precipitators have been used
successfully but have some shortfalls,
including their cost and the loss of productive
floor space in the plant.
The ideal solution is to use hydraulic
fluid that does not allow varnish to deposit
on metal surfaces while it provides important
wear and corrosion prevention and
water separation capabilities. Because
hydraulic formulations are carefully
balanced to meet OEM requirements,
adding a new varnish-mitigating feature to
the fluid’s performance profile requires a
unique solution.
Fluids are now available that incorporate
additive chemistry that reacts with the
precursors to varnish, minimizing the formation
of resinous films on system hardware.
This technology recently achieved Denison
HF-0-approval.
Laboratory testing demonstrates the
clean feature offered by these new fluids. In
industry-accepted pump tests, many widely
used fluids show varnish formation within
500 hours of beginning operation. Compare
that to the results found in the new additive
technology solution to the age-old varnish
problem: Even after 1,000 hours of use,
there is no evidence of varnish formation.
Industrial hydraulic systems typically
operate at approximately 140°F, although
temperature spikes up to 180°F are
common. High-temperature applications
that place thermal stresses on the oil - such
as plastic injection molding machines, glass
transfer systems, heavy presses and mobile
equipment - are ideal candidates for this
new technology. It also is a good choice if
you want to improve the productivity of
your equipment and extend the life of oil,
equipment and components such as valves,
filters and pumps.
Today’s hydraulic fluids are subjected to
increasingly tough operating conditions.
Demands to increase production at the
same time that oil volume is decreasing
emphasize the importance of using highquality
hydraulic fluids. Increased
operating temperatures have resulted in
today’s hydraulic systems developing
varnish deposits over time that can lead to
problems. The availability of new additive
chemistries goes hand-in-hand with today’s
harsher operating conditions.
About the Author
Rob Profilet is the commercial manager for industrial
hydraulic and gear oils with the The Lubrizol
Corporation. For more information, visit
www.lubrizol.com.
20 July - August 2008 machinerylubrication.com Machinery Lubrication