Caf Digital Imaging
page 12
MF36
Note:
It is important that the vents are not restricted in any way, do not use tube of less than
6mm diameter for the safety pressure relief vent connection and 12mm for the main vent
connection.
Check regularly that the main and safety pressure relief vents are clear from obstructions.
3.8.
Gas Connection.
3.8.1. Furnaces for CO/CO2 and Air Test Gases with N2 Purge Gas.
See next page if a mixer box for separate CO & CO
2
inputs is supplied.
Note:
The gas supply pressure required is 4 psi (0.276 bar) and must not exceed this.
There are three gas connections on the side of the furnace, CO/CO
2
pre mixed ‘reducing’
atmosphere gas, Air ‘oxidising’ gas and N
2
‘Purge’ gas. See fig 11. It is recommended that the
gases are supplied to the furnace via separate isolation valves that can be quickly switched off in
the event of an emergency or potential hazard without danger to the operator. See section 1.2:
Carbon Monoxide Warning.
The ‘Purge’ gas line is pre-set to allow a flow of N
2
into the work tube equal to 6 litre/min, the
‘oxidising’ and ‘reducing’ atmosphere gases have adjustable flow via the flow meters on the
front of the furnace. See fig 11. The gas supply fittings are 6mm x 1/8” BSP adaptors suitable for
connecting 6mm copper tube.
Separate CO and CO
2
supplies.
If a mixer box is supplied, then separate input connections of CO and CO
2
may be made to the
lower connections at the back of the box. A pipe from the upper connection is to be taken to the
CO/CO
2
inlet on the furnace.
The box is fitted with two flowmeters which may be adjusted to ensure that equal mixtures of CO
and CO
2
are supplied. The box also contains two non-return valves to ensure that neither gas
can flow back out of either inlet connection.
3.8.2. Furnaces for H2 and CO2 Test Gases with CO2 Purge Gas.
Note:
The gas supply pressure required is 4 psi (0.276 bar) and must not exceed this.
There are three gas connections on the side of the furnace, CO
2
‘oxidising’ atmosphere gas, H
2
(mixed with CO
2
in the work tube) ‘reducing’ atmosphere gas and CO
2
‘Purge’ gas. See fig 11. It
is recommended that the gases are supplied to the furnace via separate isolation valves that can
be quickly switched off in the event of an emergency or potential hazard without danger to the
operator. See section 1.3: Hydrogen and Carbon Dioxide Warning.
The ‘Purge’ gas line is pre-set to allow a flow of CO
2
into the work tube equal to 6 litre/min, the
‘oxidising’ and ‘reducing’ atmosphere gases have adjustable flow via the flow meters on the
front of the furnace See fig 11. The gas supply fittings are 6mm x 1/8” BSP adaptors suitable for
connecting 6mm copper tube.
