In this project, the development of a robotic system has resulted
in the complete automation of the preparation and handling of small
samples of minerals for analysis by X-ray spectrometry. Steel, cement
and other companies can now produce a steady flow of samples without
the factor of human error that can lead to inconsistent or poor samples.
The ability to supply a sample every six minutes also allows more
regular monitoring of production.
The first two commercial IAX units have been supplied to a steel company
and to a cement plant. The system is used with the Perl'X sample preparation
system which was developed under three steel industry research and
development contracts from the European Commission.
The use of X-ray fluorescence for the analysis
of samples of metal during production is commonplace in Europe's
steel industry. The samples can be in the form of tablets of pressed
material, although the quality of the samples is often poor. In
contrast, the Perl'X system, manufactured for more than 10 years
by Soled Industries of France, uses an induction furnace to melt
flux around samples to form solid fused beads that can be analysed.
Perl'X produces consistent samples which are stable enough to be
stored for repeat measurements or for recalibration of the system.
The original idea for Perl'X came from the French iron and steel
research organisation IRSID. The equipment was developed by Soled
Industries of France into a commercial product with the financial
support of three contracts from the European Union's steel industry
research and development programme, CECA-Acier. Soled is now developing
the fourth generation of Perl'X. Although Perl'X was aimed originally
at the steel industry, X-ray fluorescence analysis is also used
widely in industries such as cement manufacturing and mining.
Automation for accuracy and speed
The increasing commercial pressures on steel, cement and other
industries has led to a further CECA-Acier contract awarded to Soled
for the development of a robotic system for Perl'X, known as Integrated
Automatic Perl'X (IAX). The aim was to fully automate the production
and analysis of samples, partly to eliminate inconsistencies and
errors that can occur when laboratory staff carry out steps such
as weighing of samples and cleaning the melting crucibles. Speed
is also important. In a steel works, for example, every minute spent
waiting for steel slag to be analysed before adjustments can be
made to the production processes means a large and expensive waste
of heat. Induction heating can produce fused beads within about
4 minutes, compared with 8-9 minutes needed by a gas burner and
15-20 minutes needed by muffle furnaces in the cement industry.
The IAX robotic system has been developed by Soled as an additional
option for Perl'X users. Soled recently signed a distribution contract
for IAX with Philips Analytical, which already distributes Perl'X.
The production of a fused bead by Perl'X involves a series of
clear steps, including the weighing of the sample and of the flux,
the placing of the materials in a platinum crucible and the positioning
of the crucible for melting at 1,000-1,100°C. The melting is carried
out typically in three steps. A sample normally weighs 6,000-7,000
mg, and must be weighed with an accuracy of ± 5 mg.
The IAX robotic system is based on a Perl'X and includes stations
for bead extraction, weighing, washing of crucibles and bead storage
and handling. Material is moved between the stations by an industrial
robot produced by the company ABB. The arrangement of the installation
is adjustable because the robot is mounted on a transfer rail that
can be between 1 m and 10 m long, depending on local conditions.
Distributed control system
The robot has its own programming system to control its movements
between the stations. Soled found it possible to build an overall
control system using electronics that had already been proven in
Perl'X. This reduces the number of components and simplifies the
stocking of spares. Each IAX station has its own microprocessor,
which allows the use of a simpler central supervisory control and
makes a fault in any one station less disastrous, as well as allowing
the installation of just some of the stages. The central control
system is based on a Windows interface.
The IAX weighing station includes a Sartorius BA 210 S balance modified
for easy access by a robot, and a sample delivery unit. There are
also up to three flux delivery hoppers with a hopper that can hold
1.5 kg of material to allow automatic operation for more than 8
hours. There is also a unit for mixing flux and sample material.
The washing station for the platinum crucibles in which the flux
and sample are melted together includes a cleaning pool, a rinsing
pool, a drying stage and a store for crucibles. The IAX's storage
station has carriers for tubes containing samples, for beads, for
crucibles, and for cassettes that contain recalibration samples.
There is also a handling unit for the cassettes. The operation of
the storage station can be tailored to the user's need. For example,
samples that do not have to be analysed urgently can be produced
in batches, sealed cassettes can be used for measurement, and ferro-alloys
can be weighed manually.
Steady flow of samples
A trial of the robotic system showed a positioning repeatability
better than 0.1 mm compared with the 1 mm required. The system produced
a dilution of sample of 11.9992 with a variation of 0.0006, compared
with a theoretical figure of 12, within 132.85 seconds with a variation
of 4.84 seconds. It takes about 40 minutes for a sample to emerge
from the system as a bead, although the capacity of the system allows
the production of a sample each 6 minutes. This capacity makes the
system most economic for laboratories that work around the clock.
The first two units of the robotic system have been supplied to
Intermoselle, a Clinker Plant in Luxembourg and to the Eko Stahl
steel company in Germany, a member of Dickerhoff Cement Group. Although
Perl'X was developed originally for the steel industry, the increasing
rationalisation of Europe's steel sector means a relatively small
market for the robot system. As a result, the largest market for
the IAX system is likely to be in the cement industry for the control
of production. There is also expected to be a healthy market in
the mining and geology sectors.