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Smartpour
on autopours
2
back
to part 1
Installation
in USA
The client supplied nodular iron castings for the automotive
industry. The installation foundry had four Disamatic moulding
lines, two with DUCA presspour ladles, each fitted with
laserpour metal level control. The infrared temperature
measurement system supplied was similar to the Potterton
system. Range: 2000 to 4000oF. Threshold: 2350oF. Target
distance: 12ft. (3.7m). The head with its air purge was
suspended from an inverted swivel base, which was bolted
to an extension plate, welded to the main body of the Duca
ladle. The molten stream was viewed from the moulding machine,
looking down the line, with a background of flame & fume.
The main electronics unit was installed in the basement,
below the level of the moulding line. The operator's module
was installed on the operator's platform, which was at a
level above the head assembly. The system was installed
and commissioned during the last week of October 1997. The
client's routine procedure was to take a dip temperature
in the bowl before the stopper every 15 minutes. These readings
are manually logged and the dip temperature reading was
held on a wall mounted indicator, until updated by the next
measurement.
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Problems
dealth with
1. During the commissioning period the head was installed
in three different positions, to minimise extraneous readings,
caused by metal dribble, when the stopper rod was closed.
Readings were flashed up on the displays, but without arriving
at a 'good measurement' decision by the program.
2. Longer than usual securing bolts and spring washers were
fitted to the head assembly as an anti-vibration precaution.
3. The computer downloading facility was checked during the
commissioning period but could not be finalised due to cable
routing decisions.
4. The cycling characteristic was recognised and accepted
as normal by Intermet. The two position automatic auxiliary
heating control system on the Duca autopour plus the regular
addition of metal from any one of three holding furnaces are
involved variables.
Developments
1. At the American client's request, since the commissioning,
the measurement program had been modified to simplify the
operator's temperature display, giving only final decision
temperatures and holding this reading for up to ten seconds
after measurement, or until superseded by a new reading. This
modification has also been incorporated in the Potterton program.
2. The Windows computer input program has been adopted as
standard for data downloading. |
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Observations
1. At Matsushita the target +/- 10oC tolerance was achieved
by the end of the commissioning period.
2. The interference problem from the nodularisation process
could be overcome by avoidance ie. changing the target stream.
3. The location of the head at Matsushita ie. looking back
towards the moulding machine eliminated any flame interference
from the previous casts down the line. However, this advantage
is offset by the need to water cool the head.
4. The latest two installations detailed have both modified
procedures at the autopour since installing infrared systems.
One foundry had significantly reduced the number of dips
taken in the bowl before the pouring nozzle. The other foundry
had changed some of its target pouring temperatures.
5. Duca Inc, North American autopour manufacturers, have
taken a positive interest in the infrared installation at
the American client's foundry. Where auxiliary heating was
fitted, it supplied a two position control system. It has
two levels of heating; high and low power. Pre-set timers
were fitted, controlling the heating period at high and
low level. These timers were adjustable, allowing the heating
control to be varied, by the autopour user.
6. Fitting the infrared detector head to the mainframe of
the autopour enabled the head to measure along a fixed line
of sight. However, there were disadvantages:
Optical - The ratio thermometer did not require its target
retical to be completely filled or overlapped by the target.
The rule of thumb, for infrared detectors, is to site the
head as far back from the target as practicable. Five metres
would be the optimum distance for the detector used on most
autopours. Metal dribble can cause extraneous readings which
show on the main electronics unit. These have been masked
out on the operator's display, since they never constitute
a good stable acceptable reading.
Mechanical - Anti-vibration precautions were necessary
for the head assembly. Protection from impact by manually
operated equipment and metal splash was essential.
Ambient temperature - 55oC (130oF) is the maximum operating
temperature for the infrared head. Heat was transmitted
by conduction through the metal framework of the ladle in
addition to radiation from the body of the ladle in addition
to that from molten metal. This could be overcome by use
of a water cooled jacket and cable protection.
7. Quality control was the main thrust of interest in an
automatic pouring temperature monitor. This requirement
had been satisfied both in the QC department and at the
ladle operator's station. The system is now established
as 'user friendly'.
8. An additional positive interest was automatic temperature
control of ladle pouring temperature which emerged, at one
of the detailed installations.
9. As an example the installation of equipment in the USA
was carried out in one day by a team of three, two NI(L)
plus one of their staff, with assistance from the maintenance
department. Commissioning was completed in a further 2 1/2
days and included a well attended information meeting.
10. Within a few weeks of handover, after a plant breakdown
on line A, the temperature monitoring system was transferred
to line C, the other autopour unit. This transfer, alignment
and calibration was carried out by Intermet staff, without
reference to Northern Instruments or TNI Industrial, the
USA representative.
11. A member of Intermet's staff commented, that the equipment
was 'only as smart as you make it'. It must be aligned correctly
and calibrated against a reliable standard.
Calibration
The normally recommended calibration procedure for infrared
thermometers was to remove from plant and calibrate, in
the laboratory, on a black body furnace. A two colour or
ratio thermometer was different in that it had an emissivity
slope control potentiometer, active in the 'gray body' switch
position, applicable for molten metal. In the laboratory,
the emissivity slope potentiometer is set at 1.00 for calibration
on a black body furnace, which does not reproduce conditions
on plant. Back on plant, after recalibration, use a dip
pyrometer, with a current calibration certificate plus new
thermocouple to measure the autopour bowl temperature and
adjust the e-slope setting on the infrared head, to match
the dip temperature. Alternatively, a Disappearing Filament
Pyrometer (DFP) with a current calibration certificate may
be used to measure the metal stream temperature.
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Conclusions
1. All three of the installations described have obtained
consistent results which fit in with their existing method
of temperature measurement, either immersion thermocouple
or optical pyrometer, within acceptable tolerance limits.
2. A significant increase in the amount of temperature information
has been established at the autopour.
3. Temperature trends may be developed from the regular
and frequent data now available.
4. This information is also available for storage, printing
and further processing via a non-dedicated computer, using
the Windows Input program provided.
5. Automatic pouring temperature control of the autopour
appears to be a realistic target, perhaps utilising a Brilliantpour,
which will require the addition of safety interlocks plus
close liaison with the user and ladle manufacturer.
6. Close liaison and support at all three foundries were
important factors in achieving successful installations.
Bibliography
Performance report on Smartpour. Case studies. F G Bargh
& G R Barnes, 1996 AFS Transactions, ref. 96-09.
Acknowledgements
The author wishes to acknowledge the assistance and co-operation
received from Matsushita Refrigeration Industries (S) Pte
Ltd, Singapore; Potterton Myson Ltd, UK; and the client
in the USA.
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