  
TEMPERATURE PROFILE
CONTROL IN ANNEALING LEHRS WITH A DATA LOGGER (PR 431) - finished in 2000
 Decreased rejection
By measuring regularly one can obtain a basis to improve the annealing
and minimise the rejection caused by stresses.
When running the project, measurements
should be done at least twice a year for a three-year period.
Annealing of glass
Annealing of glass, which means slowly cooling to minimise the
appearance of stresses, is an important step of the process for
all production of glass. To adjust the temperature of the annealing
lehr a regular control is required to compare the real temperature
with the set point of the regulators.
Former measuring technique
The technique which has been used here to fore is to let a thermocouple
(TE) travel on the belt through the annealing lehr at the same
time that the temperature is being registered by a printer. This
method may cause some glasses to be pulled down by the thermocouple
thread. Furthermore it is complicated to measure at several side
by side spots. After a number of measurements the expensive thermocouple
thread is destroyed and has to be replaced.
Data logger at Glafo
By using a data logger to register the temperature, these technical
problems can be avoided.
With grants from the Swedish
Glass Manufacturers' Association Glafo has bought a data logger
for annealing lehr measurements. This logger is equipped with six channels
for thermocouple type K. To protect the logger from heat it is placed
in a heat absorbing barrier and an insulating stainless box. Thus protected
the logger can be sent through an annealing lehr without damaging the
electronics.
When the logger along with the
thermocouple has passed through the annealing lehr it will be
connected to a computer (see photo). Supported by special software
the measurement results can be presented graphically in different
ways (see diagram). Control samples shaped as plates are produced
with every measurement.
CURRENT PROJECTS
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