Hydraulic fluid power is
preferred over electromechanical drives in high-power mobile equipment due to
its superior energy density, design flexibility and value. It is also a
relatively mature technology and ripe for innovation. For the construction industry
especially, machinery like excavators, loaders, graders, dozers, haul trucks,
and drills rely on hydraulics to make the work safer, faster, and more
efficient. In this type of application, hydraulic fluid is pumped to various
hydraulic motors and cylinders throughout the machine and becomes pressured.
The fluid is controlled by valves and distributed through hoses, tubes, or
pipes.
Hydraulic oil ranks high
among fluids with multi-function capability. Hydraulic oil does serve as an
energy-transmission medium, heat-transfer medium, sealant, and lubricant as it
powers buckets, blades, and breakers, for example, or propels hydrostatically
driven machines, or actuates multi-disc clutches and brakes. To meet the
requirements of these varied applications, hydraulic oil’s formulations are
numerous. There is a wide variety of hydraulic fluids available in the market
today, and not all created equally in terms of their performance or intended
application.
Driven by a number of
factors, today’s hydraulic equipment such as excavators, loaders, bulldozers,
cranes, graders and more are rapidly evolving to meet new needs. Lower
emissions targets around the world necessitate that hydraulic equipment
operates more efficiently, while end-users are demanding hydraulic machines
that deliver higher levels of performance over extended periods of time.
Modern machines are
designed and manufactured to perform at ever higher levels, which puts more
demands on hydraulic oils. They must perform under higher system pressures,
with smaller oil reservoirs and tighter clearances on servos and directional
valves. A premium hydraulic oil will improve the performance of machines
relative to conventional fluids by achieving a fine balance of additive
chemistry, base oil, and fluid cleanliness to insure the highest performance.
Properties such as excellent fluidity at low temperatures, outstanding
corrosion and oxidation protection, superior viscosity control, ability to keep
components clean and free of varnish, and fluid cleanliness that meets OEM
specifications are all critical requirements a premium hydraulic fluid takes
into consideration.
Premium hydraulic fluid is a
special hydraulic fluid formulated from highly-refined base stocks and an
advanced additive system to deliver ultimate equipment performance with
extended service intervals. Premium hydraulic oils have special properties that
make them more expensive than regular ones. They may be designed for specific
applications to deliver high-performance characteristics. Premium hydraulic
oils may be formulated with additional additives to improve their performance
and protection against corrosion, oxidation, foaming, or cavitation.
Trends
impacting hydraulic-equipment development
Increasing power density
and internal pressures: To compete with electric systems that are quickly
capturing more of the market, hydraulic systems are increasingly lighter and
more power-dense. Smaller pumps are expected to produce the same power, which
in turn increases internal pressures. Hydraulic fluid manufacturers
increasingly are turning to high-performance additives to improve their
protective qualities.
Minimized power loss: Equipment
designers are more focused on efficiency than ever before and have reduced the
number of bends, joints and filter differentials to boost overall machine
efficiency. As the rising costs of energy encourage more end-users to seek out
even the smallest energy savings, OEMs are examining the role energy-efficient
hydraulic fluids can play in further improving performance.
Finer filtration: It’s generally understood that hydraulic pumps are extremely sensitive to contamination, and the increased pressures as well as decreased clearances in valves and pumps have further accentuated the need for the fluid to be ultraclean. Finer filters are being employed to achieve the necessary cleanliness. As a result, hydraulic fluids must be resistant to clogging these filters and retain their key performance parameters post filtration.
Smaller oil coolers and
reservoirs: Smaller oil coolers and reservoirs employed in equipment means that
there is less opportunity for the fluid to cool between cycles. This will
influence the effective life of the fluid — for example, a 10°C (18°F) rise in
operating temperature could halve the oil drain interval (ODI). For this
reason, hydraulic fluids must exhibit good thermal stability and antioxidant
properties. With less lubricant available because of the smaller reservoirs,
the remaining lubricant can come under enormous stress – which is why additive
treat levels must increase to compensate for the additive being consumed more
rapidly if today’s lubricant drain intervals are to be maintained.
Increasing electronic and
digital control: Control systems employ an increasing array of electronics to
match the hydraulic pressure and flow to precise torque requirements, which can
maximize specific duty cycles. In fact, the construction-equipment OEMs provide
electric-drive capability while still using a hydraulic solution in
combination.
In addition, precise
control of equipment is being provided by using digital valves that are 25 to
100 times faster than analogue valves. Modern hydraulic lubricants must have
low air content and compressibility to prevent damage to these digital valves.
Implications
for hydraulic fluids
As manufacturers develop
the next generation of hydraulic fluids, they must support new hydraulic
equipment in several key areas. While it can be measured in different ways,
improved efficiency is increasingly a goal of OEMs and operators of hydraulic
equipment. Using energy-efficient hydraulic fluids can provide a solution
without having to completely re-engineer the machines, which can be
cost-prohibitive.
For most end-users,
extending the oil drain interval (ODI) is critical to operating their hydraulic
equipment. After all, draining and replacing hydraulic fluid means extended
downtime and lost productivity. Premium hydraulic fluids need to be changed
less often and can therefore provide the necessary durability and performance
for longer periods of time.
Stick/slip performance is
another goal of most OEMs. They want to reduce noise in their machines, and
premium hydraulic fluids can help. Correctly formulated hydraulic packages
provide the adequate balance between friction modification and traditional
anti-wear components, leading to less noise without compromising system
protection.
Considering the conductivity of a hydraulic fluid also is critical. OEMs express more concerns about finer fibers in the oil filter, together with higher flow rates and non-conductive circuits. High static discharge can rip a hole in a hydraulic filter leaving the whole hydraulic system vulnerable to harmful particles. Modern hydraulic fluids must exhibit conductivity particularly during cold-starts and manufacturers need to be attentive to this requirement moving forward.
