News 1 - Article 17
Kalrez® Spectrum™ 7075 Perfluoroelastomer O-Rings
Seal Double-Arm (Z) Kneader, Increase MTBR Six Times
to Problem Solving Products about Kalrez® o-rings and
seals. Call (303) 758-2728 for instant help with your sealing
Release from DuPont (Formerly named DuPont Dow Elastomers when this article was written)
Hermann Linden Maschinenfabrik GmbH & Co.
KG, of Marienheide, Germany, has chosen giant 1.7 metre O-rings
of Kalrez® Spectrum™ 7075 perfluoroelastomer from DuPont
Dow Elastomers to seal its double-arm (Z) kneaders, used to process
aggressive chemicals at temperatures from 100°C to 300°C
in the chemical, pharmaceutical, paints, plastics and other industries.
The company reports extended service life, reduced maintenance
costs, and improved productivity, resulting from a six-fold increase
in mean time between repairs (MTBR) compared with the aramid-based
sheet gaskets previously fitted.
Hermann Linden supplies mixers and kneaders to
industrial customers for high-viscosity product mixing. Originally,
both sides of the mixing trough were sealed with asbestos-free
sheet gaskets of aramid fibres, fillers and high-temperature-resistant
asbestos substitutes. But these seals were prone to occasional
leaks that could be difficult to repair. Even flat seals with
metal inserts failed to achieve more than a slight increase in
The challenge for Linden was to find a long-term
method of sealing the trough and side walls. Although one side
could be welded directly to the trough, eliminating the seal,
the second side still had to be removable - demanding a different
solution to the sealing problem.
Linden decided to work with customers to seek
alternatives that would extend service life, reduce maintenance
costs and improve productivity. One suggestion was to caulk the
groove with soft metal. However, this was rejected as being costly
to replace and not very maintenance-friendly. Instead, an O-ring
seal was proposed since it would be easy to fit and replace, and
require far lower contact pressure to seal reliably, compared
with the flat seal.
"We looked for a sealing material that could
withstand kneader operating conditions over several years,"
explained Alexander Schneider, general manager of Linden. "In
these applications, the seal must resist temperature cycles from
100°C to 300°C, and exposure to the chemicals used."
Linden asked customers to test a silicone seal,
a graphitized aramid-fibre cord and a perfluoroelastomer seal
under typical operating conditions. Although the silicone seal
stood up to high temperatures, it was severely attacked by the
process chemicals. The graphitized aramid fibres resisted the
chemicals but charred at high temperatures. Only the perfluoroelastomer
seal withstood both aggressive chemicals and high temperatures.
"The mixing trough in one application had
a working capacity of 2750 litres requiring an O-ring with a diameter
greater than 1.5 m," said Johannes Löcher, former general
manager of Linden and now a consultant to the company. "We
searched for a manufacturer that could produce perfluoroelastomer
O-rings in this size without problem. We finally chose O-rings
of DuPont Dow Kalrez® Spectrum™ 7075 perfluoroelastomer
because of its good price/performance ratio, and availability
in the required dimensions at short notice." The result is
a Kalrez® O-ring with a cord thickness of 9.66 mm and a diameter
of 1705 mm, optimized for the specified groove dimensions.
"We are enthusiastic about the performance
of the Kalrez® perfluoroelastomer O-rings and calculate at
least a six-fold increase in maintenance intervals compared with
the flat seals currently used. We plan to use Kalrez® parts
for our other kneaders and mixers, operating in similarly challenging
conditions." said Schneider.
Kalrez® Spectrum™ 7075 sets new standards
for seals used in challenging chemical processes. The DuPont Dow
perfluoroelastomer offers even lower compression set (15 per cent
after 70 hours at 204°C), higher thermal stability (continuous
service at up to 326°C) and better chemical resistance than
Kalrez® 4079, the previously accepted industry standard. In
addition, it provides an exceptionally smooth surface. For applications
requiring even broader chemical resistance, DuPont Dow recommends
Kalrez® Spectrum™ 6375 for continuous service temperatures
up to 275°C. The company produces and supplies Kalrez®
perfluoroelastomer O-rings to customer specifications.
DuPont Dow Elastomers
DuPont Dow Elastomers, a global supplier of specialty
elastomers with headquarters in Wilmington, Del., is a joint venture
between the DuPont Company and The Dow Chemical Company, with
more than $1 billion in sales. The company is the industry leader
in chloroelastomers, ethylene elastomers and fluorinated elastomers,
serving the automotive, chemical, construction, general rubber,
plastics and wire and cable industries.
Hermann Linden Maschinenfabrik GmbH & Co.
KG was founded in 1940 as a family business producing mixers and
kneaders for laboratory use. Today, with some 42 employees, Linden
manufactures mixers, kneaders and agitators in laboratory, pilot-scale
and production scale sizes and capacities from 1 to 6000 litres,
for worldwide use. Typical industry applications include chemicals,
pharmaceuticals, plastics, cosmetics, paints and coatings, confectionery,
cements and sealants. All machines are individually produced to
exact customer requirements, and are delivered fully assembled
on special transporters.
is a registered trademark of DuPont.
Article: Article 16: Dow Agrosciences Switches to O-Rings of Kalrez®
Spectrum™ 6375, Gains Estimated 6000% in Seal Life