The desired test gas is selected using the 'oxidising' - 'reducing' gas selector switch on
the front of the furnace control panel. See fig 11a. The test gas will flow for the duration
of the controller program.
4.4.1
Gas Flow Rates
To set the gas flow rates please refer to the following guidance notes:
BS ISO 540: 2008
Reducing Atmosphere
If you are testing to ISO 540: 2008 then this specification states a linear rate of flow
past the test pieces of 400 mm/ min, with a note to state that this is not critical provided
that it is sufficient to prevent any leakage into the furnace.
If you calculate the volume in a diameter 79 mm tube to give 400 mm linear flow per
minute this gives 2.0 litre/ minute. However the gas will expand with the high
temperature in the furnace. If the gas ambient temperature was 20 °C and the furnace
temperature was 400 °C Boyle’s law (PV = kT) gives a volume ratio of 2.3. The 400
mm/ min within the work tube equates to 2 L/ min at 400 °C.
Therefore 2 L / 2.3 = 0.87 L/ min at 20 °C.
Because the CAF G5 work tube has very effective gas seals (‘O’ rings) Carbolite Gero
would recommend that after an initial purge the gas flow rate can be reduced during the
test to a very low flow rate. The operator should experiment with this to confirm the
flow rates that give them satisfactory and consistent results.
Oxidising atmosphere
If you are testing to ISO 540: 2008 then this specification states that the flow rate is not
critical.
Carbolite Gero would recommend using a low flow rate.
ASTM D1857-04
Reducing & Oxidising Atmosphere
If you are testing to ASTM D1857-04 then this specification states a regulated gas
stream to provide a flow of 1.3 to 1.5 furnace volumes per minute.
The volume of the CAF G5 work tube is 2.16 litre when the volume of the insulation
plugs are taken into account. Therefore a flow rate of 1.3 volumes per minute = 2.8
litre/ minute. However the gas will expand with the high temperature in the furnace. If
the gas ambient temperature was 20 °C and the furnace temperature was 400 °C
Boyle’s law (PV=kT) gives a volume ratio of 2.3. The 2.8 litre/ min at 400 °C equates to
1.2 litre/ min at 20 °C.
Because the CAF G5 work tube has very effective gas seals (‘O’ rings) Carbolite Gero
would recommend that after an initial purge the gas flow rate can be reduced during the
test to a very low flow rate. The operator should experiment with this to confirm the
flow rates that give them satisfactory and consistent results.
At the end of the controller program or if the program is interrupted (manual
intervention) the 'reducing' gas is turned off and the 'purge' gas solenoid valve will
operate to purge the work tube for a duration of 5 minutes.
24
Summary of Contents for CARBOLITE GERO CAF G5
Page 63: ...Fig 3 Front Tube Seal Assembly Fig 4 Door Arm Assembly 63 ...
Page 64: ...Fig 5a Camera Mounting Bracket Fig 5b Lens and Camera Assembly 64 ...
Page 65: ...Fig 5c Sliding the Camera Mounting Bracket Assembly onto the Door Arm 65 ...
Page 66: ...Fig 5d Securing the Camera Mounting Bracket Assembly to the Door Arm 66 ...
Page 67: ...Fig 5e Mounting the Lens and Camera Assembly 67 ...
Page 68: ...Fig 5f Lens and Camera Assembly in Position 68 ...
Page 69: ...Fig 6a Rear View of the Standard CAF G5 Furnace Showing Brick Box Assembly 69 ...
Page 71: ...Fig 7 Front Tube Seal Position 71 ...
Page 72: ...Fig 8 Tube End Seal Assembly Tightening Sequence Fig 9 Work Tube Front Support 72 ...
Page 73: ...Fig 10 Fitting the Door Arm Assembly Fig 10a Adjusting the Door Arm Assembly 73 ...
Page 74: ...Fig 11a Furnace Case and Controls 74 ...
Page 75: ...Fig 11b Gas Inlet Pipe Fig 12 Positioning the Furnace 75 ...
Page 77: ...Fig 13c Loading Samples into the Work Tube 77 ...
Page 78: ...Fig 16 File Folder 78 ...
Page 79: ...Fig 17 Door Arm Assembly Exploded View 79 ...
Page 82: ...SST DT HT FT Fig 18 Report Sheet Page 2 Side View Plan View Fig 19 Formed Wire Sample 82 ...
Page 83: ...Fig 20 Sample Carrier Sample Tiles and Sample Positions 83 ...
Page 84: ...Fig 21a Coal and Coke Test Piece Mould Fig 21b Biomass Test Piece Mould and Hand Press 84 ...
Page 85: ...Fig 22 Sample Loading Tool Fig 23 Camera Ethernet Connection 85 ...
Page 86: ...Fig 24 LED Driver Connection 86 ...
Page 87: ...Notes Service Record Engineer Name Date Record of Work ...