railsingle use crucible
THERMITREX Brings Improved Rail Welding
Thermitrex, the leading South African While this process worked well, there The single-use crucible is much lighter
supplier of Thermit welding kits, related were certain disadvantages. The than the conventional crucible and
equipment and consumables, is now robust steel crucible was heavy and in requires only one person to carry it to
able to offer a greater refinement to inaccessible sections of track, at least site. The reduction in labour needed will
its already-proven system for welding two people would be needed to carry lead to substantial cost reductions. In
railway track joints together. the weighty crucible to the site. addition, weighty crucible stand, crucible
extension and adaptor assembly are no
The conventional Thermit welding The conventional crucible is made to be longer needed.
system has been in use for more than 100 used as many as forty times. Because
years. Early in the 20th century, Professor of this, this unit is constructed of four The single-use crucible reduces the
Heinz Goldschmidt demonstrated the components, any of which could be time taken to carry out a weld by a
reduction of metal oxides by using damaged during the high temperatures considerable margin.
aluminium powder. This was the basis generated by the exothermic reaction. If
of the Thermit welding system. By 1928, any of the components were damaged, The largest factor in favour of the single-
the Thermit rail welding process was or simply went missing during moves
adopted as the standard for the German from one site to another, it would not be
use crucible is that it reduces the risk of
State Railways. possible to continue with rail repairs. human error. The single-use crucible
is made from a bonded refractory
Since then, the Goldschmidt-Thermit After each use, the crucible needed to material, which is contained in a five
Group, which is today Thermitrex’s be cleaned out carefully to ensure the litre steel canister. The automatic
holding company, has invested effectiveness of the next weld. Where
substantially in research and design, to crews are unsupervised, or where the
self-tapping thimble is incorporated
ensure that its customers receive the need for pre-cleaning the crucible is not during manufacture. The single-use
most effective rail welding solutions. fully understood, the resulting welds crucible requires no preheating or
could be sub-standard. drying before it can be used.
Now Thermitrex is able to offer its
South African customers the latest Although all rail welds are inspected When preheating of the rail
using X-rays, this process might only ends has been completed,
innovation from Goldschmidt-Thermit happen some days or even weeks later. the single-use crucible is
– the single-use Thermitrex crucible. During this period, as a precaution, the placed on the mould, which
newly welded joint is protected by a has four lugs into which
clamping device known as a ‘joggle the canister fits. A standard
plate’. In South Africa, these have been Thermit portion is placed in
stolen for their scrap metal value, leaving the crucible and ignited for
the joint unprotected. Should a weld fail the weld to proceed.
while a train is passing over it, a calamity
The downtime while the track is out of
service could run into many hundreds of
thousands of rands.
The amount of rework needed when
using a single-use crucible would be
Until now, the Thermit welding system considerably reduced.
has used a conventional multi component
crucible, which could be reused a
number of times. In this process, a two-
part mould would be clamped around
the gap between the two rail ends. The
rail ends would then be heated to 800°C
using either propane or a petrol/air mix.
A steel crucible would then be swung
into position over the mould, and the
Thermit welding material or ‘portion’
placed inside it. The portion would then
be ignited. The exothermic reaction
would melt a plug in the bottom of the
crucible, and the molten contents would
then flow into the mould filling the gap
between the two rails and effectively
welding them together.
The Goldschmidt-Thermit group and
Thermitrex have a commitment to
maintaining the highest environmental
standards, as it witnessed by their ISO
9001:2000 accreditation. The recycling
of waste is very much in line with this
With the conventional crucible, once the
In terms of cost, the single-use crucible
weld had been completed, the waste
is slightly more expensive than the
products from the procedure were
conventional unit. However, the
usually buried next to the track.
numerous benefits of the new system
will give its users an increased return,
This waste consists of the welding slag
which will outweigh the minor cash
and the excess steel sheared from the
outlay many times over.
weld during the re-profiling of the track.
On occasions this unsightly waste was
left lying next to the track, as the crews
had not a convenient way of returning
this material to a central depot.
With the single-use crucible,
the used canister makes
a handy container in Safety is also a key concern of Thermitrex
which to return all and its parent company. The single-
waste material. The use crucible reduces the amount of
five kilograms of waste sparks that are released during welding,
steel and four kilograms diminishing the possibility of a member As the single-use crucible reduces the
slag from a single weld of the crew being injured. The smoke steps involved in the welding process.
have value and can from the reaction is also reduced which Thus training of exothermic rail welders is
be recycled, indirectly is a major benefit when joining rails in considerably simplified. Thermitrex offers
contributing to job tunnels or other confined areas. fully accredited training and support
in the Thermit welding processes, after
which a formal certificate of competence
Contact: PO Box 6070,
Thermitrex (PTY) Ltd Dunswart,
Tel: +27 (0)11 914 2540 Johannesburg,
Fax: +27 (0)11 914 4627 Gauteng
Email: firstname.lastname@example.org 1508