Teflon shaft seals for gear pumps and motors0 pages

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www.jbj.co.uk/MarzocchiTeflonSeal.html
www.jbj.co.uk/MarzocchiTeflonSeal.html
Hydraulic motors and pumps are used in a variety of
environments, that can include dusty and dirty
conditions. These environments can be damaging to
shaft seals due to dirt particles eventually penetrating
the shaft sealing area. This will begin to erode the
elastomer, altering the shaft surface nish in the sealing
area and seal failure will eventually occur. Replacing the
seal requires removing the pump / motor, disassembling
and repairing it, and reinstallation. The result?
Signicant system downtime increasing operating
expense.
Seals are critical because they seal-in the necessary
case-ow that is used to lubricate the internal
components and carry heat away from the pump or
motor but are the ‘Achilles heel’ of a hydraulic system.
Often taken for granted, these seals need protection
from undue stress and wear because they can make the
difference between smooth functioning, trouble-free
operation and failure. Failure costs time and time costs
money.

lifetime of a hydraulic system and expensive failure
and downtime. The qualities of the substance Teon® or
polytetrauroethylene (PTFE), are ideally suited to
the use of shaft seals.

» Resistant to many chemicals; This includes ozone,
chlorine, acetic acid, ammonia, sulfuric acid and
hydrochloric acid. The only chemicals known to affect
these coatings are molten alkali metals and highly
reactive uorinating agents.
» Non stick; Very few solid substances will permanently
adhere to a Teon. While tacky materials may show
some adhesion, almost all substances release easily.
» Outstanding performance at extreme temperatures; In
fact it can temporarily withstand temperatures of 260°C
and cryogenic temperatures of -240°C and still have
the same chemical properties. It has an initial melting
point of 342°C (+/- 10°C) and a secondary melting
point of 327°C (+/- 10°C).

Seals are critical, the seal-in the
necessary case-ow that is used
to lubricate the internal components
and carry heat away from the
pump or motor.
When seals are subjected to small amounts of wear, they
may begin to slowly weep. This can be subtle and not
easy to detect. When weeping begins, it may be tiny and
undetectable. Yet, even a small leak tends to attract dirt
and can lead to more wear. Once signicant wear
occurs, the pump or motor seal will need replacement.
Replacing damaged shaft seals is labourious and costly
and may require multiple hydraulic components to be
disconnected to get at the seal failure. Once the seal is
replaced, multiple components in the system have to be
reconnected before the system can be restarted.
The time to protect from seal damage is early in
the system design, before problems occur. A good
quality seal that can make the difference between long

» Weather and UV resistance.
All of these benets contributed to teon shaft seals
being used in a range of gear pumps and motors
available from jbj Techniques Limited.
Marzocchi Pompe’s nite element analysis (FEA)
software was used to determine the best characteristics
of the components of the new radial seal ring which has
a much stiffer structure than normal rings. The Teon
(P450) material adapts evenly to the texture of the
machining on the shaft to guarantee a perfect seal.
The properties of the P450 material make it possible to
bear high-pressure loads and temperatures between
-30 and +200ºC. To guarantee a long operating life, it
was necessary to perform in-depth research on the
methods for grinding the area where the sliding of the
seal ring’s lip takes place.
This gear pump high pressure, teon shaft seal can bear
over-pressures of over 210 bar without resulting in
damage. This radial sealing is particularly useful in
single direction hydraulic motors when, in certain
conditions of use, high over-pressures will be generated
at the motor output. With bi-directional motors, the area
adjacent to the seal ring of the drive-shaft is maintained
at atmospheric pressure by the drainage circuit. In
single-direction motors, this area can be directly
connected to the output (by running it backwards) so
any over-pressure impacts directly on the seal ring,
causing the lip to turn over or the ring to be expelled from
its seat with a consequent leakage of uid. The Teon
(P450) material adapts evenly to the texture of the
machining on the shaft to guarantee a perfect seal.

» Low coefcient of friction; Is the ratio of the force
required to make two surfaces slide over each other.
A low number equals low resistance and smooth
operation. This indicates the difculty in sliding one
surface against another. The coefcient of friction is
generally in the range of 0.05 to 0.20, depending on the
load, sliding speed, and type of Teon coating used.

This gear pump high pressure, teon
shaft seal can bear over-pressures of
over 210 bar without resulting in
damage.

» Non wetting; Teon nishes are both hydrophobic and
oleophobic, cleanup is easier and more thorough.

For further details please see
www.jbj.co.uk/MarzocchiTeonSeal.html

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