DDS CALORIMETERS OPERATIONS MANUAL V1.1
2022
Website:
www.ddscalorimeters.com
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Digital Data Systems (Pty) Ltd.
CAL3K Advanced Bomb Calorimeters
www.ddscalorimeters.com
5.4.3
TEST VESSEL LEAK
This test INCLUDES the vessel. Depending on the type of vessel used there are O-rings in the vessel lid
which could leak and require replacement. Use the same CMD=94 command:
94 SYSTEM LEAK TEST 1
Note that the filling is much slower because the vessel is filled. Monitor the pressure and if it is steadily
declining than a leak is present. It is normal that the pressure declines rapidly in the beginning and then
settles down. This is because a flow restriction is present in the vessel lid.
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PRINCIPLE OF COMBUSTION CALORIMETER
In short, a known substance is burned in a contained environment (Vessel) and the resultant
temperature rise is recorded as a calibration. Then un-known samples are burned and the temperature
rise is compared to the calibration and the unknown calorific value is calculated.
The following sequence applies to a determination and a calibration. The broad difference is that the
calibration saves more data for further reference.
Here is a more detailed, but short sequence of events, assuming default settings.
1.
Approx. 0.5g (0.2-0.8g) is precisely weighed and entered in to the CAL3K (electronic or manual
transfer)
2.
The vessel is prepared (cotton, crucible, firing wire) and the CAP is closed
3.
Manual filling: Place the vessel in the filling station and fill it with oxygen.
4.
Place the prepared vessel in to the well and close the lid
5.
If this vessel was never calibrated then the unit will ask you to do so.
6.
CAL3K-AP automatic filling only
: If everything is fine the unit will go into the filling period, open
the fill oxygen solenoid and monitor the filling progress. At the end of the filling process the unit
will switch to the INITIAL PERIOD.
7.
All manual filling units
: the CAL3K will switch to the INITIAL PERIOD
8.
It waits approx. 3 minutes for the vessel to stabilise.
9.
After 3 minutes the sample is fired: 25 volts are connected to the firing wire and a very large
current passes through it, the wire glows, the cotton ignites and the sample burns.
10.
The unit enters the MAIN state (Final Period) and monitors the temperature rise of the vessel.
11.
The temperature increases rapidly, peaks at approx. 1 minute and decreases thereafter.
12.
At the end of the main period the Result is displayed on the screen and the End period starts.
13.
CAL3K-AP
: the vessel deflates automatically to the exhaust port and the lid opens.
14.
CAL3K-A/F
: The lid opens automatically.
15.
CAL3K-S/ST
: The lid must be opened manually.
16.
Remove the vessel for cooling and subsequent new preparation.
