Caf Digital Imaging
MF36
page 23
Ensure that the furnace is cool and the electricity and gas supply is isolated.
Remove the camera and mounting bracket assembly, see fig 5b and 5c.
Wear neoprene gloves before handling the O ring seals – see section 1.5.
Withdraw the door assembly fully from the work tube to avoid damaging the door plug. Hold the
door arm securely and using the tool provided unscrew the viewing window retaining ring anti
clockwise. Remove the retaining ring carefully, noting the positions of the window ‘O’ ring seal,
window glass and window glass gasket. See fig 17. Hold the window by the edges and avoid
touching the glass surface, traces of perspiration can etch the surface of the glass when it is
heated.
5.3.2. Clean the window glass using a suitable cleaning agent. Alternatively an optician equipped with
re-polishing machines can restore the clarity of the windows.
5.3.3. When replacing the window glass:
Ensure that the glass is clean and free from dust, grit, chips, scratches and cracks. If the glass is
damaged replace it, a faulty window glass can cause leakage of carbon monoxide during testing.
See section 1.2: Carbon Monoxide Warning.
Inspect the condition of the window ‘O’ ring seal, it must be uniform in shape and section, and
free from cuts, cracks dust and grit. If the seal is damaged replace it, a faulty seal can cause
leakage of carbon monoxide during testing. See section 1.2: Carbon Monoxide Warning.
Clean the inside of the viewing window retaining ring and door plug ring. Pay particular
attention to the ‘O’ ring seal faces, these must also be free from dust, grit, chips and scratches. A
vacuum cleaner is the best method of removing the dust and grit. Take care not to damage the
back face of the door plug during cleaning.
Fit a new window glass gasket, if this gasket is not fitted the window glass will break when the
window retaining ring is tightened.
Fit the window ‘O’ ring seal onto the window retaining ring. Place the window glass in position
in the door plug ring and re-fit the window retaining ring, hold the window glass in position
through the viewing hole in the window retaining ring and tighten the window retaining ring to
finger tight.
Using the tool provided tighten the window retaining ring to seal the viewing window. Whilst
tightening the window retaining ring hold the door plug in position to prevent it from rotating,
the gas inlet hole in the door plug must line up with the gas inlet in the work tube front seal
assembly. See fig 17.
Prior to using the furnace conduct a pressure test of the work tube assembly to ensure integrity of
the work tube and ‘O’ ring seals. See section 3.3.5.
5.5
Furnace Calibration.
This procedure describes the process required to achieve correct calibration and performance
from your CAF Digital furnace. The furnace is calibrated prior to leaving the factory, but both
ASTM and BS standards call for regular checks on calibration. Carbolite recommend that
calibration checks are conducted in accordance with these instructions, if the furnace is found to
be out of calibration then the control instrument must be adjusted (see section 5.4.5).
5.4.1. Sample Carrier And Tiles.
To obtain an accurate calibration result the correct sample carrier and tiles supplied with the
furnace must be used.
5.4.2. Sample Preparation.
Two types of wire are used to check the furnace calibration:
Gold wire.
Melting point 1063
°
C (1945
°
F)
Palladium wire.
Melting point 1554
°
C (2829
°
F)
