Application report:
Absolutely sealed
Ingress of liquid or dust into the housing, and
mechanical overload of bearings are the most
common reasons for encoder failures, especially
in demanding applications. Therefore, a growing
demand exists for products with maximum
robustness and tightness, for example outdoor
applications or environments with intensive
cleaning. With MAGRES hermetic, Baumer offers
a new range of absolute multi-turn encoders
with a unique hermetically sealed housing.
Thanks to this sealed housing, MAGRES
hermetic encoders reach protection class IP 68
and IP 69K. They are extremely durable and in
particularly perfectly suited for HeavyDuty
applications.
Ball bearings are never tight
The design principle of optical encoders requires the
readout position of a pulse disc, which is located
directly between emitter and opposite receiver
diodes. This pulse disc rotates together with the
encoder shaft. The essential shaft bearings form a
crucial interface between encoder electronics and
outside environment. Perfectly tight bearings, and
thus a perfectly tight optical encoder housing cannot
be achieved as a matter of principle. Temperature
variations lead to periodic pressure differences
between the outside environment and housing
inside. As a result, the encoder “breathes” and can
suck in humidity or liquids during cool down. In
many applications, encoders come into contact with
water, coolants, lubricants and cleaning agents.
Sooner or later, the ingress of liquid into the encoder
leads to failure.
Fig. 1: MAGRES hermetic can easily be cleaned
with high pressure.
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In larger types of modern HeavyDuty encoders, this
challenge is attempted to be solved by using
complex multi-level seals. However, this does not
fully solve the original task, because even innovative
and complex seal concepts never cover all rotational
speeds, encoder designs and mounting positions.
Moreover, all seals are subject to wear and ageing.
In outdoor applications, this ageing is even
enhanced by UV radiation. Finally, multi-level seals
are too space consuming for the design of compact
encoders.
Hermetic seal is THE solution
The successful, robust MAGRES principle is the
patented combination of magnetic single-turn
sensing and electronic multi-turn scanning and
forms the basis for the revolutionary MAGRES
hermetic. Thanks to an additional hermetic
encapsulation, the entire electronics is perfectly
protected from the outside world, in order to work
unimpaired by environmental influences. Only the
magnetic field of a permanent magnet on the
encoder shaft pervades through the encapsulation.
Therefore, all MAGRES hermetic encoders reach
the highest protection classes IP 68 and IP 69K
reliable and permanent. Long-term submerging or
cleaning with pressure washers is possible without
any trouble.
Fig. 2: Long-term submerging of the MAGRES
hermetic is possible problem-free.
Robust and durable
In addition to the hermetic encapsulation, MAGRES
hermetic exhibit a maximum mechanical load. The
elimination of multi-level seals enables a compact
design with 58 mm diameter. Exceptionally robust
ball bearings mounted with large bearing distance
allow a shaft load up to 280 N in radial and up to
270 N in axial direction, as well as a maximum
shock load of 300 g. Battering of the shaft is
mechanically impossible due to construction. For
optimum bearing protection against dust and dirt, a
Simmerring® seal is used, which is additionally
covered with an impact resistant metal ring. This
metal ring offers sealing protection against
mechanical influences and prevents UV light ageing
of the Simmerring®. In the field bus variants, a new
HeavyDuty inspection window allows fast adjusting
of the bus address during commissioning and a
clear view on the status LED's. MAGRES hermetic
are applied under outdoor conditions, in heavy
vehicles and cranes, on ships and on oil platforms.
from well-known vendors, MAGRES hermetic
encoders have proved as the only suitable solution.
Now, MAGRES hermetic ensure the perfect long
term operation all fire extinguishing installations on
board.
Summary
MAGRES hermetic sets a new benchmark for robust
and compact absolute multi-turn encoders. In
particular, they show their strengths where
conventional encoders fail. MAGRES hermetic are
available in numerous shaft and hollow shaft
variants. Versions with integrated interface are
available with SSI, CANopen and Profibus-DP.
Versions with modular bus covers additionally offer
DeviceNet and EtherCAT. Customized versions with
increased explosion protection or alternative
housing materials are available on request.
Fig. 4: Some members of the MAGRES hermetic
family.
Fig. 3: MAGRES hermetic are optimum suited for
demanding applications, for example in wind
turbines.
Moreover, MAGRES hermetic are also suitable for
operation in food production machinery due to their
robustness against fluids and temperature changes.
Thanks to cavity-free design, they can be
hygienically cleaned in place (CIP). Their stainless
steel housings offer optimum corrosion protection
against aggressive media, such as acids, caustic
solutions, sea water, detergents and milk.
Employment under hardest conditions
MAGRES hermetic impressively showed their
outstanding robustness on a new generation of fire
extinguisher boats for positioning of remote
controlled jet pipes. These jet pipes throw several
tons of sea water per minute over more than 100
meters directly onto the fire. Because of strong
spray and encoder mounting with the shaft side
upward, water always entered very soon into
conventional encoders. After many tests of products
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Hermetic sealing, high shaft loads and optimum
robustness against shock and vibration combined
with an extended temperature range in a corrosion
resistant housing make these encoders perfectly
suited to partners with demanding applications.
Under most adverse conditions, MAGRES hermetic
operate highly reliable and offer the most
economical solutions.
Box: MAGRES hermetic – a new generation of
encoders
The principle is as simple as convincing: Instead of
complex and space consuming seals, a compact
hermetic encapsulation protects the encoder
electronics against ingress of any media, reliable,
permanent and space saving. This insurmountable
encapsulation protects against all aggressive media,
such as sea water or detergents from high pressure
cleaning. With their patented combination of
magnetic single-turn sensing and contactless multiturn scanning, MAGRES hermetic encoders offer
the highest reliability and lifetime, especially in
heavy duty environment.