Fluid Power, GRIP DRY

FLUID POWER
FLUID POWER
MARCO SCHAWOHL
GRIP DRY
Schematic
construction of the
Voss ES-4 cutting ring
coupling
LEAKAGES ON HYDRAULIC SCREW FITTINGS ARE ANATHEMA TO MACHINE
OPERATORS – BUT DUAL CUTTING RING TECHNOLOGY EMPLOYS THE TRACTION
OF TWO CUTTING EDGES TO ENSURE A LEAK-TIGHT FITTING. WITH THE BONUS
OF SUPERB CORROSION PROTECTION, IT’S AN APPEALING SOLUTION TO KRONE
Harvesting machines are seasonal
workers, being used for only a few
weeks of the year. Any doubts about their
availability would therefore be disastrous
– anything less than 100% is unacceptable
to the market. Therefore all components
of a harvester must demonstrate a high
degree of reliability under the difficult
conditions prevailing during field work.
With regard to the working hydraulics,
the situation is further aggravated by the
fact that connection elements must be free
of leaks for a lifetime. Bone-dryness, even
after numerous harvesting seasons, is an
absolute necessity. An impossible dream?
Well, not quite – at least when it comes
to one of the leading harvesting machine
manufacturers, the engineering company
Maschinenfabrik Bernard Krone GmbH in
Spelle, Emsland, Germany.
Farmers in 43 countries have long
been aware of the value of Krone’s reapers,
tedders, swathers, balers and foragers. The
sophisticated technology, the ruggedness
of the products and their smooth running
and user-friendliness have convinced
many farmers of the effectiveness of Krone
forage harvesters and are features prized
in the world of agriculture.
An additional requirement is that the
harvesters should be capable of producing
high-quality, clean fodder. Neither engine
nor hydraulic oil leaking from the machine
should contaminate the primary food
product, namely the fodder. The drive
hydraulics and their numerous units,
lines and connections play a particularly
important role in this respect.
Dual cutting ring technology
Screw fittings are the Achilles’ heel of a
harvester’s hydraulics. Anyone who tries
to save money here is making a mistake.
Leakages on hydraulic screw fittings are
not only a source of annoyance for the
operator; they can also create an aversion
to the machine and lead him to look to
the competition for a replacement.
Voss Fluid GmbH, the coupling
specialist, provides its customers with a
variety of designs to solve the problem of
leaks. The cutting ring solution is a classic
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iVT International Off-Highway 2013
Krone, a
leading global
manufacturer
of agricultural
machinery, trusts
in premium cutting
ring technology
among hydraulic couplings. The company
began the development of this product
many years ago, and eventually launched
the Voss 2S on the market.
Dual cutting technology defined a
new standard of strength for cutting ring
couplings. With the single cutting ring,
the tube is weakened at the cutting point.
This reduces the bending resistance of
the tube and, consequently, leads to a
reduction in mechanical resilience. This
can lead to premature failure, particularly
in the case of long, thin-walled tubes.
The two cutting ring levels of the Voss
2S have differing functions and produce a
high synergistic effect. The first strong
cutting edge ensures that the cutting ring
is positioned with the required firmness;
the subsequent second cutting edge
ensures a high degree of security of the
connection, as it prevents the initial
cutting edge from digging in too deeply. A
clear improvement in quality is achieved
when compared with the classic cutting
ring variant. The positive force progression
at the cutting ring level achieves a durable
and secure tube connection, even where
high dynamic stress is involved.
Making the most of what you have got
The fact that even a good solution can be
improved even more is demonstrated by
the Voss ES-4, a further development of
this solution. This coupling variant retains
the dual cutting ring technology that has
proved its worth in practical applications.
An additional soft-seal package and block
stop have been added.
The Voss ES-4 also achieves the basic
standard of required leak-tightness through
the metallically defined traction of the
two cutting edges, which is distinguished
by its enduring functionality.
The soft seal has a secondary function,
and only acts if the operating medium has
overcome the metallic
seal. A captive moulded
seal is integrated into the
cutting ring taper facing
the connection piece – the
first position where a
leak may occur.
The risk of a leak from
the tube is eliminated
with an integral O-ring.
Both seals are made of
FKM. This elastomer type
is distinguished not only
by its excellent resistance
to a variety of hydraulic
oils, but also by its
outstanding temperature
stability – both of which
are important basic
requirements if effective
sealing of the soft-seal
cutting ring couplings is
to be achieved over the
entire service life.
The Voss ES-4 also
embodies considerable
improvements when it
comes to fitting reliability
(i.e. the overall quality of
all couplings). The risk
of incorrect fitting is
eradicated by the block
stop. The much-feared
excesses during fitting
where very small line
diameters are involved
can no longer occur, due
to this clearly defined
stop. The unmistakable
increase in force at the
stop indicates to the
worker that he has
reached the ultimate
fitting point. Excessive
turning of the cutting ring coupling, a risk
that arises in the case of mounting positions
that are difficult to access, and which can
often entail frequent use of a spanner, is
prevented by the integrated stop.
Pleasing to the eye and the pocket
Voss, of course, has a series of other
superior-quality tube couplings in its
range. Krone decided to employ the Voss
ES-4 design featuring zinc-nickel corrosion
protection, characterised by its outstanding
high performance.
Werner Hinsch (graduate engineer), a
hydraulics developer at Krone, defines the
technological requirements for an effective
hydraulic coupling as follows: “Firstly,
they should remain absolutely bone-dry
for their entire service life, even under the
difficult conditions encountered in specific
applications. They should be distinguished
by positive fitting characteristics too, and
deliver effective corrosion protection.” The
Voss ES-4 tube coupling effortlessly meets
these requirements.
“In the selection process,” continues
Hirsch, “other coupling manufacturers
were also considered.” The decision to
FLUID POWER
premises by that company, were two ‘soft’
factors which, however, were extremely
important for us. We have also enjoyed
excellent business relations in a spirit of
partnership over the years, because the
technology is just right, making any
decision on our part so much easier.”
Resale value
Voss ES-4 cutting ring coupling with additional soft seals
choose Voss was supported by several
reasons. First, the previous model, the
Voss 2S, had proved its worth over many
years in Krone machines, meaning nobody
wanted to dispense with this experience.
The value of Voss product quality was also
appreciated in the past – and quality is a
premium factor at Krone.
“Harvester manufacturer don’t want
to waste time worrying about hydraulics,”
says Hinsch. “We assume that these will
function perfectly – and, hopefully, reliably
for their entire service life. Dirt on the
couplings would be something that
would really turn customers off.”
It does not require a large leakage to
cause this – even a few drops of sweat on
the coupling is enough to bond dust and
create a visually unattractive impression.
Dirt on couplings does not necessarily
impair the functionality of hydraulics – it
is, however, a psychological problem that
should not be underestimated.
But leaking hydraulic couplings are
much more than just a visual shortcoming.
Environmental considerations mean that
leaks on hydraulic couplings are simply
unacceptable when it comes to harvesters.
Indeed, in a worst-case scenario, leaking
hydraulic oil can be a very expensive
business for machine operators, because
contaminated soil must be disposed of as
hazardous waste. The consequences could
therefore be incalculable if leaking
hydraulic couplings soiled a road.
Corrosion protection
Another positive aspect that influenced the
decision in favour of Voss was the excellent
corrosion protection that is a feature of
the ES-4 coupling. Laboratory tests indicate
that the new Voss zinc-nickel coating is
clearly superior to chromium (VI) corrosion
protection under the severe conditions of
salt spray trials. The Voss ES-4, with its
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iVT International Off-Highway 2013
new corrosion protection, has now been
installed in Krone harvesters for over two
years. To date, no complaints have been
received – an encouraging sign that speaks
in favour of the excellent quality of Voss
corrosion protection.
Machines are assembled with a paint
finish at Krone. All components are coated
with a low-solvent cathodic dip paint finish
in Europe’s most modern immersion plant
prior to assembly. Components that receive
a paint finish pass through 20 immersion
and rinsing baths. A maximum surface of
12,600m² can be coated in a single day in
the new plant.
A chain is, of course, only as strong as its
weakest link. The quality bonus achieved
during sheet metal painting should not
be compromised by a weakening of the
corrosion protection of attachment
components. White bloom and – under
certain circumstances – even red rust can
occur on tube couplings. The Voss zincnickel coating means that Krone is playing
it safe when it comes to tube couplings.
It was also important that the new
coupling could be fitted without difficulty –
every operative employee should be capable
of fitting hydraulic lines in every machine.
This requires couplings that can guide
themselves and prevent excessive turning
of the cutting ring coupling. The integrated
block stop means that the Voss ES-4 fulfils
these requirements, reducing human error
practically to zero. The reliability of the
pipe fitting process was further enhanced
by converting to the Voss ES-4 cutting ring
coupling – an important step when it comes
to promoting a hydraulic coupling that
remains bone-dry for its entire service life.
Dennis Reker, specialist buyer for
hydraulics at Krone, explains, “The
successful co-operation with Voss in a
spirit of partnership, and continuous
employee training conducted on our
Anyone who tries to make savings when it
comes to hydraulic couplings may save a
few cents in the short term, but whether
they are doing their customers a favour in
this respect is questionable. The resale
value factor with regard to agricultural
machinery plays a significant role when it
is time to making a purchasing decision.
Damp, or even leaking, hydraulic lines can
unsettle potential customers looking for
used machines, and frighten them away.
After all, who would be happy to purchase
a used car where the couplings on the
brake lines are dripping?
Maschinenfabrik Bernard Krone GmbH
is not willing to indulge in any experiments
in this respect. The company has decided
in favour of the superior-quality Voss ES-4
hydraulic coupling with the zinc-nickel
coating, setting a new standard in this
sector. Krone customers are certainly not
annoyed by the fact that the Voss coupling
adds to the attractiveness of their machines
when it comes to the resale value.
The hydraulics on a harvester should be
capable of withstanding many challenges
during use. Impacts resulting from the
unevenness of the field are compounded
by the operating pressure, so hydraulic
couplings are subjected to considerable
stress and strain. This should in no way
affect the sealing characteristics of a
hydraulic coupling.
But risks still abound when the vehicle
is stationary. Corrosion protection during
downtime can only be achieved with an
excellent protective coating. This also
applies to the connection components in
a harvester hydraulic system.
The life-long sealing stability of
hydraulic couplings is an absolute must for
Maschinenfabrik Bernard Krone GmbH.
The OEM has found an innovative and
competent partner in Voss, with whom
goals and objectives can be realised. Due
to the Voss ES-4 coupling, Krone is in a
position to provide its customers with
long-term bone-dry solutions under the
severe conditions encountered during
field and meadow work, combined with
optimum corrosion protection. iVT
Marco Schawohl is head of marketing at Voss Fluid
GmbH
CONTACT
www.voss.de
[email protected]