Mixed doubles
The HF tandem process.
The widespread success of tandem technology began
with an idea from Dr Julius Peter (Continental AG). He
discovered that separating the two main tasks in the
rubber mixing process – dispersion and distribution –
carried a number of clear advantages. The tandem process
was born out of this idea and was patented by Peter as
long ago as 1978. Tandem technology involves connect-
ing two machines in series – or more precisely, on top of
one another, with each machine optimised to perform
one of the two mixing tasks.
The first machine is responsible for dispersion, which
means breaking down mixture components such as the
fillers. Distribution takes place in the second machine (or
stage), which involves achieving the most homogeneous
mix within the rubber compound. If reactive compounds
are processed, the chemical reaction also chiefly takes
place in this machine. Both machines are connected in
series so that they function together as one continuous
mixing process. The ‘premixed’ material from the first
stage is not temporarily stored, but immediately moved
on to the second stage, which performs the concluding
distribution task while the next batch of material is being
premixed in the first stage. This perfectly synchronised,
permanent two-stage process signifies a quantum leap
in mixing technology. It soon became clear that it would
not only result in enormous benefits in relation to the
silica compounds used for manufacturing tyres – an area
of development on which there is currently a great deal
of focus – but also in relation to the numerous other mixing
requirements such as remill and carbon black manufac-
turing stages.
Above all, the temperature profile which is absolutely
essential for inducing the chemical reactions during the
mixing process can be better controlled by separating
the stages. Consequently, the properties and quality of
the compound can be positively influenced. There is a
further effect: by separating the tasks and concentrating
on one at a time, and as a result of the relatively smaller
compound weight in the larger lower machine, it can be
operated at a higher speed. This improves the quality
of the compound thanks to the higher gravitational
forces and the greater number of times the compound
is moved around.
Experience shows that a TANDEM mixer can improve
the throughput rate by up to 25 per cent when working
with carbon black compounds and even by up to 100 per
cent with silica compounds. The resulting potential for
cutting costs and increasing output is obvious. Depend-
ing on the mixing line, in an average-sized mixing room
for tyre production (approx. 100,000 tonnes of rubber
compound p.a.) this can soon add up to savings of almost
one million euros per year.
The early decision taken by HF to focus on tandem tech-
nology and continue to optimise this process is paying
dividends. The pioneering automation technology, the
numerous, individually configurable applications and the
exemplary global service network should also be men-
tioned. An increasing number of companies from the
rubber and tyre industry clearly recognise the enormous
benefits, because demand for the machines supplied by
the HF MIXING GROUP is greater than ever.
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