Parr Instrument 6200 - Manual (Page 23)

Operating Instructions
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Operating Instructions
Operating the 1108P Oxygen Combustion Vessel
Detailed instructions for preparing the sample and
charging the 1108P Oxygen Combustion Vessels are
given in Operating Instructions No. 418M. Follow
these instructions carefully, giving particular atten-
tion to the precautions to be observed in charging
and handling the bomb.
Operating the Filling Connection
To fill the bomb, connect the hose to the bomb inlet
valve and push the O2 Fill button on the calorimeter
control panel. The calorimeter will then fill the bomb
to the preset pressure and release the residual
pressure in the connecting hose at the end of the
filling cycle. It will take approximately 60 seconds to
fill the bomb. During this time a countdown timer
on the O2 fill button will display the remaining fill
time. Pushing the O2 key a second time will stop the
flow of oxygen at any time. Once the display returns
to its normal reading, the user can disconnect the
coupling and proceed with the combustion test.
If the charging cycle should be started inadvertently,
it can be stopped immediately by pushing the O2
FILL key a second time.
During extended periods of inactivity, overnight
or longer, close the tank valve to prevent leakage.
When changing oxygen tanks, close the tank valve
and push the O2 FILL key to exhaust the system. Do
not use oil or combustible lubricants on this filling
system or on any devices handling oxygen under
pressure. Keep all threads, fittings, and gaskets clean
and in good condition. Replace the two 394HCJE
O-rings in the slip connector if the connector fails to
maintain a tight seal on the bomb inlet valve.
The recommended filling pressure is 450 psig (3
MPa or 30 bar). This pressure is prescribed by most
of the standard bomb calorimetric test methods.
Higher or lower filling pressures can be used, but
the bomb must never be filled to more than 600
psig (40 atm).
Operating the Calorimeter
All operations required to standardize the 6200
Calorimeter, or test an unknown sample, should
proceed step-wise in the following manner:
1. Turn on the calorimeter and activate the pump
and heater using Calorimeter Operations. Allow
at least 20 minutes for the calorimeter to warm
up and the jacket temperature to stabilize. Once
the jacket temperature comes within 0.5 °C of 30
°C and stays there for approximately 15 min-
utes, the calorimeter is ready to begin testing.
The Start key will be available at this time. The
bomb parts should be wetted and then dried in
the manner used at the conclusion of a test. This
serves to wet all sealing parts as well as leav-
ing the bomb with the same amount of residual
water which will exist in all subsequent testing.
2. Prepare the sample weighing the material to 0.1
mg and charge the oxygen bomb as described in
the section entitled Operating the Filling Con-
nection. Using an additional bomb and bucket
can increase the throughput of the 6200 Calorim-
eter. With this arrangement, the calorimeter can
operate almost continuously since the operator
will be able to empty a bomb and recharge it
while a run is in progress. A bomb and bucket
for the next run will be ready to go into the calo-
rimeter as soon as it is opened. Each bomb and
bucket combination will have to be standardized
separately and the proper energy equivalent for
each set must be used when calculating the heat
of combustion.
3. Fill the calorimeter bucket by first taring the dry
bucket on a solution or trip balance; then add
2000 (+/- 0.5) grams of water. Distilled water is
preferred, but demineralized or tap water con-
taining less than 250 ppm of dissolved solids
is satisfactory. The bucket water temperature
should be approximately 3 to 5 °C below the
jacket temperature. It is not necessary to use
exactly 2000 grams, but the amount selected
must be duplicated within +/- 0.5 gram for each
run. Instead of weighing the bucket, it can be
filled from an automatic pipet, or from any other
volumetric device if the repeatability of the filling
system is within +/- 0.5 ml.