White Paper: Remove Water and
Particulate Contaminants from Oil
Efficiently and Cost-Effectively to
Prolong Equipment Life
Summary
A majority of the failures and wear problems that lubricated machines experience are
caused by oil contamination from particulates and water. In order to keep oil clean and
dry, use advanced filter-dehydrator technology—which enables effective oil conditioning
with a simple, low maintenance design—to enhance particle filtration and to remove free,
emulsified and dissolved water.
As an example: the
main lube reservoir at
a paper mill had been
typically averaging a
moisture level of 290
to 530 ppm, with
excursions as high as
3,770 ppm on
occasion. Given the
high cost of replacing
journal bearings and
associated downtime,
the overall cost to the
facility was well over
$100,000 per year. If
a failure resulted in lost
Up to 80 percent of lubricated and hydraulic equipment failures
production, the cost
and wear are due to oil contamination.
would escalate to $5$10K per hour. Since a dedicated filter-dehydration system was installed, the oil has
averaged 50 to 100 ppm—potentially tripling the paper mill equipment’s operational life.
History
Lubricated machines require clean, dry oil to work properly. Recent studies have
determined that as much as 80 percent of all failures and wear problems that hydraulic
and lubricated equipment experience are due to oil contamination. The most damaging
forms of contamination are particulates and moisture.
All oil lubricated machines that have rolling elements and pressure surfaces rely on the
oil to separate moving surfaces. Examples include gears, roller bearings, journal bearings,
side bearings, piston pumps, vane pumps, servo valves and dynamic seals. Operating
pressures and loads on those elements dictate the required oil film thickness, and the film
thickness that can be provided by the oil depends on its viscosity and temperature.
Particulate contamination is capable of bridging the film thickness gap, leading to contact
fatigue, additional particle generation and accelerated wear. Water contamination reduces
component life and productivity by causing rust and corrosion, oil oxidation, additive
depletion, varnish deposits, hydrogen embrittlement and changes in viscosity. In
addition, these phenomena can result in additional internal particle generation.
Challenge
Particulate contamination is present to varying degrees in new oil, can be generated
internally or may occur due to ingress during a lubricated machine’s operation. Over
time, as industry became more aware of the damaging nature of particulates, they have
become more focused on the need for filtration. High-efficiency (ßeta Rated) filtration is
widely accepted, and OEMs now often incorporate full-flow filtration into new
equipment. However, in many cases there is still plenty of room for improvement.
Moisture presents a greater challenge, with some machines more at risk than others.
Since water solubility will vary based on oil type and temperature, even a small amount
of excess moisture can lead to equipment failure. Water can be present in the free,
emulsified, and dissolved states, and it typically infiltrates lubricated machines through
condensation, seal leaks or ambient conditions, as well as from cleaning chemicals and
water from equipment cleanup. For optimum performance, all forms of water
contamination must be removed. And while several methods are used for this purpose,
many have significant downfalls.
Partial Solutions
Some removal methods are better suited for one type of
moisture than another. For free water removal, waterabsorbing cartridges, settling tanks, centrifuges and
coalescing filter/separators are often used—but many
are high in cost and require significant labor. Plus, their
effectiveness often depends upon the viscosity of the oil
and volume of water.
Water-absorbing cartridges use hygroscopic media
capable of removing trace amounts of free water from
oil. Water-absorbing cartridges can be installed for low
initial capital cost, but they are typically rated in grams
of water per element and are not appropriate for systems
with ongoing moisture ingression. They do not
effectively remove emulsified or dissolved water and
must be replaced when saturated, making them labor
and cost-intensive for applications involving higher
volumes of water.
Settling tanks, as their name indicates, are used
Water-absorbing cartridges only
to settle free water to separate it from the oil.
remove free water, providing a
These systems do not remove emulsified or
partial filtration solution.
dissolved water, or gases. While relatively
inexpensive, effectiveness is a function of tank design, residence time, turnover rate, oil
viscosity and additive chemistry. Due to the relatively large size tank needed even for
small systems, space limitations often make settling tanks impractical.
Two additional systems, centrifuges and coalescing filter/separators, mechanically
separate free water using gravitational forces. These are best suited for use on lower
viscosity fluids and can be used to remove significant volumes of gross water. However,
new centrifuge installations are costly, and with a large number of moving parts, this
equipment can be very labor-intensive—requiring dedicated operators. Coalescing
filter/separators are subject to fouling from particulate contaminants and certain
additives, and this equipment may require heat plus discharge cooling.
To remove dissolved and emulsified moisture as well as free water, vacuum dehydrators
(sometimes referred to as a vacuum purifiers) have often been used. Such systems have
typically placed in slipstream (kidney loop) oil circulation with the reservoir, utilizing a
vacuum to lower the boiling point of water, allowing moisture and gases to vaporize out
of the oil. Vacuum dehydrators have moderate-to-high capital, operating and maintenance
costs due to their relatively complex designs. In addition to requiring trained operators,
they often require a heater to increase oil temperature to promote water vaporization—
and a cooler on the return. Along with these challenges, as with most typical oil purifiers,
vacuum dehydrators are relatively large and difficult to relocate to different areas of a
plant.
A Solution That Works
Since conventional water and particulate removal alternatives involve significant tradeoffs, a new, advanced form of fluid conditioning has proven beneficial. To provide a
more a cost-effective, convenient solution, this conditioning system was developed to
utilize the fundamental principles of mass transfer. The system continuously removes all
free, emulsified and dissolved water, as well as particulate contaminants—without the
complexity and operator
knowledge required with
conventional methods.
Mass transfer principles
dictate that moisture will
naturally diffuse from a
region of higher
concentration to one of
lower concentration.
With an innovative
filter-dehydration system,
Using mass transfer principles, a filter-dehydration system
free, emulsified and
effectively diffuses moisture from oil to the dry air in the
dissolved water will
system’s membrane contactor.
diffuse from the oil to the
system’s dehydration
contactors. First, oil is pumped from its reservoir into the system’s high efficiency
particle filter, which cleans the oil beyond the levels attained by most full flow filtration
circuits. The oil then flows through the inside of the patented hollow fiber membrane
contactor, while dry air sweeps the exterior surface of the membrane. This promotes the
diffusion of moisture through the contactor and into the sweep air. The air, which now
contains dissolved moisture, vents out of the system to atmosphere with no bulk water or
other disposables generated in the process, and the clean, dry oil returns to the reservoir.
This filter-dehydration system operates at ambient oil temperature with no heat or post-
process cooling required, preventing thermal degradation, and it enables customers to
cost-effectively remove contaminants—minimizing equipment wear for improved
process uptime and performance.
Another significant benefit of this filter-dehydration system is its simplicity. It requires
no routine operator intervention, no moving parts and no liquid level controls or water
drains. Since the only routine replacement component is the system’s coreless particle
filter, it saves significant maintenance costs. Once moved into position near a reservoir,
simple connections are made for oil supply, oil return, power and compressed air. In
operation, the only things to be monitored are the differential pressure gauge (for
particulate filter condition), and the moisture level in the oil (to determine when
conditioning is complete).
Conclusion: Driflex™ Oil Conditioning System
The Driflex™ Oil Conditioning System from Pentair Industrial features this
revolutionary filter-dehydration technology to remove free, emulsified and dissolved
water, as well as particulates
and gases, from petroleumbased and synthetic oils. The
Driflex oil conditioning system
was designed to serve a wide
variety of applications within
pulp & paper mills, power
plants, hydraulic presses (such
as stamping and plastic
injection molding), steel and
roll mills, etc. It decreases
water concentration, down to 25
ppm, and improves particulate
filtration, as low as ISO 13/10
(or lower). Plus, Driflex reduces
oil contamination, minimizing
wear, maintenance expenses
and downtime for extended
hydraulic and lubricated system
life.
Driflex is cost-effective, conveniently
Driflex™ Oil Conditioning System
sized and easy to maintain. With no
moving parts or flow/level controls to adjust, specialized operator training is unnecessary.
These systems are well suited for periodic use on reservoirs throughout an entire facility.
Driflex may also be dedicated to a particular reservoir to provide continuous
conditioning, ensuring that oil is optimized without the fluctuations in water
concentration that occur with periodic oil reconditioning.
Reducing moisture content in oil significantly reduces equipment wear. Reducing
water concentration from 250 ppm to 40 ppm, for example, can potentially triple
equipment life.
© 2008 Pentair Filtration, Inc.
800.869.0325 www.pentairindustrial.com
380158 DE08