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Cartex’” 0
improve sed life
cartridge seals reliability and
Robustness is an important requirement for fluid sealing in the diverse range of
environments encountered in industry today. As we reported in the last issue, the
ongoing development, deployment and acceptance of materials play a key role in
this respect. The field is continually moving forwards as new materials - or new
forms of existing ones - appear as commercial products. Each must exhibit a
considerable advantage over existing solutions. Tradition is institutionalized in
the sealing industry, but with the market only creeping forwards a few points
over the past year, companies have to try extra hard to just hold their position,
never mind assuage their shareholders with good profit margins. To illustrate the
point, in this issue we highlight a global player whose products are the choice for
many industry specifiers: Burgmann GmbH, based in Wolfratshausen, near
Munich in southern Germany.
Recently in the news was the announcement that
Ineos Chlor Ltd had ‘dramatically reduced pump
maintenance costs and seal spares inventory’ at
its UK sites. This was achieved through a seal
contract with Burgmann (UK) Ltd.
This is one example of how today’s fluid sealing
products companies are tackling the challenges of
the modern marketplace. In fact, despite tough
competition and the enormous price pressure that
presently characterises the international markets,
Burgmann has been able to continue to show
good progress by closing the fiscal year 2000 with
positive figures. Moreover, its turnover was up
7.8% over that of the preceding year.
Contract shows 30% reduction in costs In the above-mentioned deal with UK-based
Ineos Chlor - which was formed in January to
take over ICI’s Chlor-Chemicals business - the
first year of the contract that covers the supply
and repair of mechanical seals has shown a
reduction of more than 30% in seal purchase
and repair costs. This has in turn produced a
substantial cost benefit in the overall pump
repair costs, and provided improved pump
availability to the process plants.
Steve Moore, Ineos Chlor’s rotating equipment
engineer, commented that, ‘Regular site visits by
Burgmann engineers combined with a mutually
agreed upgrade programme has provided us with
the focused resources needed to lift pump and seal
performance onto a new level of reliability. Seal
and pump failures have dropped considerably
during this year. We expect additional savings as
the frequency of seal failures drops further over
the next three years.’
Burgmann has combined the latest materials
technology with best installation practice to ensure
that all seals have the optimum chance for a long
life under the typical operating conditions on-site.
The next phase of the contract involves further
development of the stock management programme
introduced by Burgmann. This has already reduced
the number of seal inventory items by more than
50%. It is anticipated that all seal stocks will
eventually be under Burgmann control, to
maximise seal rationalisation and provide Ineos
Chlor with additional savings through the release of
existing capital tied up in seal spares stock.
Andy Faulkner, Ineos Chlor’s buying team
leader, emphasises the success of the contract by
saying, ‘Our first year savings have justified our
decision to dramatically change our purchasing
methods for key products. Burgmann has
performed so well as a supply partner that we
have extended the contract to four years.’
longer seal life Burgmann provides an example of the route to
take to ensure continued market success with
d
new product launches. Its Cartexm cartridge
seals combine extended performance margins
with greater reliability and longer seal life, while
the PDGS elastomer-free compressor seal is for
high-pressure and low-temperature applications.
The new line of Cartex cartridge seals
(Figure 1) features a robust design with heavy-
duty components so that they are more tolerant
of system upsets and installation errors.
Consequently, these seals are claimed to provide
greater reliability and longer seal life than
competitive seal designs.
Single, double and gas-barrier seals are all
available in the new line. All Cartex seals feature
interchangeable components for reduced inven-
tory costs and fast, economical service. They come
in standard and large-bore configurations, which
reduces the need for seal chamber modifications.
Cartex gas barrier seals are bidirectional, and
can accommodate solids loadings as high as 3%.
They fit most ANSI seal chambers without
modifications, provide zero product emissions,
eliminate seal face wear, and reduce energy
consumption. They are available in sizes ranging
from 1.125 to 4 inches (28 to 100 mm).
Double wet Cartex seals are available in both
dual and tandem configurations. The single seals
are offered with or without a pressure-less fluid
quench feature, which contains the process
liquid and directs it to a defined location in the
event of primary seal failure. The single and
double wet seals are available in sizes ranging
from 1 to 4 inches (25 to 100 mm).
The company says that Cartex seals offer a
number of performance advantages. Spring-
loaded stationary faces compensate for angular
misalignment of the shaft and box face,
providing a low leakage rate under less than ideal
conditions. Monolithic seal faces reduce seal face
distortion for minimal leakage and more reliable
operation. Springs and pins are isolated from the
product side, so the springs are not corroded and
seal life is extended. The robust cartridge design
stabilizes the seal gap for more reliable seal
Sealing Technology No. 92 @
performance and longer seal life. Furthermore,
the O-rings are located on the external side,
eliminating seal hang-up and improving solids
handling capabilities.
The operating temperature range for single
and double wet Cartex seals is from -40 to
428°F (-40 to 22o”C), and the pressure limit is
360 psi (25 bar), depending on materials. The
operating temperature range for the gas seals is
from -5 to 428°F (-20 to 220”(Z), and the
operating pressure limit is 190 psi (13
Meeting extreme conditions The new elastomer-free, gas-lubricated mech-
anical seal from Burgmann was specially deve-
loped for extreme requirements in high-pressure
and low-temperature applications in compressors.
The PDGS seal’s operation and broad range of
apphcation have been intensively tested in
applications-related trials and test runs. A universal
pressure operating range from 1 to 350 bara is the
result. Stable leakage rates and reliable operating
characteristics are displayed by the PDGS in all
operating ranges. Excellent mobility of the
purpose-developed dynamic secondary seals is
typical in low-temperature duty. In meeting all
requirements such as automatic alignment and
resistance to extrusion, temperature and chemicals,
the seals have exactly those attributes which give
the compressor seal a high level of operational
reliability, says Burgmann.
Design features for this fluid sealing product
include:
.
.
Secondary seals made from a spring-
reinforced special compound with excellent
resistance to chemicals (equivalent to PTFE).
No explosive decompression.
Back-up ring and balancing sleeve of the
dynamic secondary seals made of tungsten
carbide for zero radial shrinkage, a small
controlled extrusion gap, and optimized
sliding properties of the secondary seals
without ‘catching’.
Optimized aerodynamic gas grooves,
optimal sliding properties during start-up,
and maximal rigidity of the gas film (also
pressureless).
No baffle edge in the flow direction, for a
self-cleaning effect.
Ceramic-compatible design with friction-
locked torque transmission of the rotating
seat, and no increase in stresses by shaping
operations.
Diamond-like carbon (DLC) coating of the
seal faces.
Operating limits:
l Shaft diameter from 25 to 320 mm.
l Operating pressure from 1 to 350 bara.
l Operating temperature range from -170 to
230°C.
l Sliding velocity of 200 m/s.
Turning to the web Burgmann recently joined the wave of companies
turning to web-based tools to help their
customers to select the best fluid sealing solution
for their particular application. Given the
diversity of availabilities, the web is proving a very
useful tool for suppliers and customers alike. It
was Burgmann’s intent when setting up CASS -
its online Computer Aided Seal Selection facility
- to make it as easy as possible to find the correct
seal for specific application requirements. Users
just have to select the medium to be sealed and
other operating conditions.
CASS provides all seal types recommended
for the chosen application, as well as inform-
ation on their use. For mechanical seals, even
material combinations, specific use and a seal
drawing with all measures necessary for
installation are provided. The user either selects
the medium first, or proceeds directly to the
selection of seal.
Replacing the German standard, DIN 24960 As part of the harmonisation process under way
in the European standardisation system, the new
standard EN 12756 (December 2000) has
appeared in the field of mechanical seals. It
replaces the German standard, DIN 24960, and
the French standard, NF E29-99 1.
Burgmann says that, as with other companies,
the conversion affects all of its standard
mechanical seals. These seals can easily be
recognized by the letter ‘N’ in their designation
and the drawing number. The seal type
HRC...N represents an exception to this, as it
will initially continue to be made in accordance
with the DIN 24960 standard (C).
Depending on the aggregate, method of
operation, environmental requirements etc.,
mechanical seals require additional special
equipment which ensures their perfect
functioning. Such equipment includes quench
fluid vessels, thermosiphon vessels with various
components, buffer pressure units, buffer gas
systems, refill units, heat-exchangers and
magnetic filters. In addition to standard systems,
Burgmann also supplies custom-made supply
systems for complex applications.
The EN is published by the European
standardisation body CEN (Comite Europeen
de Normalisation) in Brussels, Belgium. EN
12756 is entitled ‘Mechanical seals - Principal
dimensions, designation and material codes’,
and exists in three official versions (English,
French and German). The European standard
will be given the status of a national standard,
either by endorsement or by publication of an
@a Sealing Technology No. 92
identical text. In Germany, this has been done
by the publication of the DIN EN 12756
standard (March 2001).
EN 12756 contains the principal
dimensions for the internal installation of
single and multiple mechanical seals with
(rotating) spring units into the pump sealing
cavity, according to IS0 3069 (-S) as
minimum cavity dimensions as typical for
centrifugal pumps in accordance with EN
22858 and EN 733. It also gives the seal
designations and material codes to be used.
In relation to DIN 24960 (June 1992
edition), the dimensions for possible coatings in
the area of adjacent seals and the specification
for configuration of the mechanical seal with a
stationary spring unit (version C), have been
deleted.
Continued success in 2000 As we mentioned at the beginning of this article,
Burgmann’s financial results - while perhaps an
exception, rather than the rule - show that in
some sectors of the industry the market is doing
well enough. The company’s consolidated group
sales rose to more than EUR241 million
(US$205 million) in 2000, approximately 65%
of which was earned through group operations
Patents This issue’s sealing patent coverage is again a
cosmopolitan &air - new patents from
Germany, Japan, Sweden and the US. It
includes sealing inventions with a diversity of
mechanical themes, from spark plugs to
refrigeration, from cellphones to cabling.
From 3M comes an improvement in the
splicing of cables. As with many seals, the
objective is protection from water and other
vapours to prevent corrosion or a short
circuit. The common solution is a splice case
replete with end seals, but the many different
designs and configurations have one common
disadvantage: they are cumbersome and time-
consuming when adding or removing a cable.
3M offers a response to the need for a
segmented end seal in which the segments can
be easily attached to, and removed from, the
support body with a minimum of additional
hardware, yet which can be adapted to
provide a desired (for example, even) pressure
distribution across a particular segment.
In automotive engines, we have previously
covered head gaskets, but this time we describe
sealing a spark plug gasket. From Beru AG in
Germany, it relates to a process for sealing of the
terminal-side end area of the glow tube of a glow
outside Germany - 2% more than in the
preceding year. The remaining 35% was earned
in Germany, where sales rose to EUR84.2
million ($71.7 million) against EUR78.7
million for the previous year. Sales outside
Germany increased to EURl57.4m ($134
million) versus EUR136.3 million the previous
year. The group currently employs a workforce
of 2,890 worldwide.
The first quarter of 2001 has reflected a
similarly positive trend, so that the seal
manufacturing group anticipates satisfactory
increases in sales and operating results by the
end of the year. However, in spite of the positive
figures achieved to date, the continuing difficult
situation in the international trading areas will
call for unbroken commitment, creativity and
motivation on the part of staff throughout the
group. As well as product characteristics, the
quality of service provided by manufacturers is
constantly gaining importance. For this reason
the existing sales and marketing organization -
in particular the service structure - is being
strengthened even further worldwide, with the
local availability of supplies and qualified service
as key priorities. On a joint basis and as partner,
Burgmann will be developing service packages
and customized service concepts aimed at
plug. All too often, undesirable failures occur
and manufacturing costs can be large, so the
objective of the invention is to provide for mass
production of glow plugs.
The gasket patent for sealing a refrigerant
compressor, by H. Ikeda et al. from Japan,
describes fluid-tight, stable and good sealing as
well as a boundary portion between high- and
low-pressure regions within the compressor. It
uses an innovative design, using ‘trifurcatedly
interconnected’ (i.e. by three arms) ridges on the
outer and inner sealing portions of the gasket.
This enables the gasket to be in face contact
with the sealed portions, thereby exhibiting a
good sealing function with a high stability.
Finally, from Sweden, one of the world’s
centres for the manufacture of mobile phones,
comes a description of a slowly expanding
gasket. Gaskets in cellphones full?1 several
functions - acoustic sealing, preventing dust
ingress etc. Today’s gaskets use soft elastic foam
plastic, and sealing is obtained when the gasket
is compressed. To achieve efficient sealing the
compression of the gasket must be as large as
possible, ie. the uncompressed gasket must have
a considerable thickness in order to obtain a
tight sealing in its compressed state. This is not
ideal from a manufacturing viewpoint, so this
invention instead uses a slowly expanding
cellular plastic pre-compressed before assembly
optimizing existing technology and reducing
maintenance costs, the objective being the
conclusion of long-term service agreements
from which both company and its customers
benefit. The group can currently call on
experience gained from around 80 international
service agreements.
At the same time, the German-based seal
manufacturer will continue to place particular
emphasis on research and development in all its
product areas to consolidate and build on its
position at the head of the sealing technology
field. In doing so, Burgmann will be making full
and optimum use of all resources such as
product innovation, globalization and comm-
unications technology in the face of increasingly
fierce competition for customers.
For more information, contad: Burgmann
Dichtungswerke GmbH & Co KG, AuBere Sauedacher
StraBe 8-l 0, D-B2502 Wolfratshausen, Germany. Tel:
+49 8171 23-O. Fax: +49 8171 23-1214, Email:
markom@burgmann.com, http://wwwburgmann.com
Or contact: lneos Chlor Ltd, PO 80x 14, The Heath,
Runcorn, Cheshire WA7 4QG, UK. Tel: +44 1928
511050, Fax: +44 1928 581072, Email:
general_info@ineoschlorcom,
http://www.ineoschlor.com
Sealing Technology No. 92 0
of the phone. In this way the installation of the
gasket material can be greatly enhanced by pre-
compressing the gasket prior to installation.
Segmented end seals for cable splice case
EtIe: Segmented end seaI for a dosure such
as a splice case
Patent number: US 6248953
Date: 19 June 2001
Inventor: James IL Miier
Assignee 3M Innovative Properties Co, St
Paul, MN, USA
This invention provides a segmented end seal in
which the segments interlock with the support
structure, so that only a single fastener is needed
to fix a given segment to the support structure.
This result is achieved by providing the
segments with tabs that are inserted into notches
located in the support structure. The tabs are
oriented with respect to one another such that
they must be inserted and removed from the
notches in a particular sequence.
Typically, the tabs are oriented to provide an
even distribution of pressure across the segment,
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