Carbolite CAF DIGITAL IMAGING - Manual (Page 15)

CAF Digital Imaging
MF36-3.21
page 15
4.0 O PERATING I NSTRUCTIONS .
4.1 Furnace Start-up.
This furnace is available in two options:
Option 1.
CO/CO2 ‘reducing’ gas and Air ‘oxidising’ gas with N2 ‘Purge’ gas.
Compatible with both:
ASTM D1857 / D1857M – 04 (2010) Standard Test Method for Fusibility of Coal
and Coke Ash
&
BS ISO 540 : 2008 Hard coal and coke. Determination of Ash Fusibility.
Option 2.
H2 and CO2 ‘reducing’ gases and CO2 ‘oxidising’ gas with CO2 ‘Purge’ gas.
Compatible with - BS ISO 540 : 2008
The principle of operation is the same for both options. The furnace is normally supplied
programmed to operate between a pre-determined set point (start temperature) and 1500°C
(2732°F) at a ramp rate of 7°C/min. (12.6

F/min.). The target temperature is set to 1500°C
(2732°F) to avoid operating the furnace at high temperatures unnecessarily. See section 4.5.1.
The following text describes how to use the furnace with this program.
4.1.1. Open the furnace door to check that the silica window is clean. Any slight haze should be
removed before use. If neglected this haze quickly thickens and becomes impossible to remove.
See section 5.4. for instructions on how to remove and clean the viewing window.
4.1.2. Turn on the ‘oxidising’, ‘reducing’ and ‘purge’ gas supplies. If the ‘purge’ gas is not present
when the furnace electrical supply and instrument switch are on the control system will activate
an alarm buzzer and illuminate a warning light on the control panel. See fig 11. This alarm will
continue until the furnace is turned off and the ‘purge’ gas supply is restored. While the alarm is
activated the control system will not allow introduction of ‘reducing’ gas.
4.1.3. Switch on the furnace electrical supply, the cooling fans will run. Operate the instrument switch
to activate the control system, the furnace will begin to heat up to the start temperature and the
work tube will be purged with ‘Purge’ gas. The start temperature is adjustable using the Up and
Down buttons () on the controller depending on your requirements:
For furnaces constructed to use CO/CO
2
and Air test gases with N
2
‘Purge’ gas (compatible
with ASTM D1857 / D1857M – 04 (2010) & BS ISO 540 : 2008. The start temperature is
adjustable from 400°C (752 °F).
For furnaces constructed to use H
2
and CO
2
test gases with CO
2
‘Purge’ gas (compatible with BS
ISO 540 : 2008. The start temperature is adjustable from 815

C (1499

F).
To switch the furnace off, set the instrument switch to off. The case cooling fans remain on.
Leave the fans on until the furnace cools to below 300°C. If the furnace is to be left off
unattended, isolate it from the electrical supply.
Note: It is not recommended to operate the furnace continuously at temperatures above 1000

C
(1832

F). The furnace is designed to operate to a programmed ramp; continuous operation at
elevated temperatures will shorten the life of the elements, insulation and tube end seals.
4.2 Eurotherm Controller.
The Eurotherm controller is configured to control the furnace and provide the other signals
necessary to switch gas flows and communicate with the CAF Test Software. The following
sections describe how to adjust the controller as necessary to achieve correct operation of your
furnace.
4.3 Computer Start-up.
The computer is set up by Carbolite to run the following software: