The tube-flange connection before welding.
The TIG welding torch: controls for all functions are integrated into the grip, which
means there are no cables to worry about. Thanks to the wire feed’s variable
setting range, the torch is particularly adaptable to a huge range of applications.
Photo: EWM AG
Photo: EWM AG
Hering
with Chocolate
ündersbach, Germany,
03/05/2017 – Separated by
thick, black curtains, the
welding booths line up one
next to the other along the
large production hall. Tubes of all lengths,
thicknesses and diameters outnumber
everything else on the workbenches.
M
All of them are one-offs – except
occasionally when a customer orders
two of the same heat exchanger. "There
is probably not a single bar of chocolate
in Germany whose raw material didn't
pass through our heat exchangers," says
Christian Rasch, CEO of Hering AG.
P roduction depends on welding
From thin-walled stainless steel tubes with
diameters of just a few millimetres to large
tubes that could easily swallow a man
whole. In black steel and in stainless steel.
Hering AG is a German company based
in Gunzenhausen in Bavaria's Middle
Franconia region. At the heart of a heat exchanger is the
tube bundle that carries the fluid. It is
embedded into a large outer tube, or shell,
that contains the coolant. The large surface
area between the fluids facilitates the
transfer of heat.
They turn these pipes into customised
heat exchangers for an enormous range
of applications, from large power stations,
through equipment for the chemical
industry, to equipment for the food
industry. Welding is by far the most widely used
joining technique in production. Orbital
weld seams are used to join the tube
bundles to the tube plates. The shells have
a wide selection of connection nozzles and
flanges welded to them.
22
PECM Issue 27
The requirements on the weld seams are
onerous, with fault-free weld seams being
essential to ensure that the different fluids
in the heat exchanger cannot mix with one
another.
It is extremely important that
distortion is kept to an absolute
minimum to provide the accuracy
of fit between the tube bundle and
the shell.
In use, these heat exchangers can
experience temperature differences
of several hundred Kelvin, which
leads to extreme thermal loads on the
components. Nonetheless, the weld seams
must retain their integrity in the face of
these extremes.
Previously, the welding procedures of
choice were MMA and MIG/MAG welding.