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CAL2k Application Note
C1.2 : Ammunition
Sample - Munition Propellants
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On all unknown materials always start with very small samples to determine characteristics of the material and to avoid dangerous ammunition. Never stand with any part of the body over any of the calorimeter system. During a determination, step away from the unit.
The material to be tested is munitions propellant that generates its own oxygen on combustion. I.e. it does not require oxygen in the atmosphere to sustain combustion.
The propellant cannot be ignited in the same manner as coal samples because the oxygen is replaced by nitrogen that prevents the cotton from burning. Consequently the firing wire must be extended so that it can touch the sample and the firing voltage must be increased. The test sample had a very low CV so the mass was increased to 2 gram so as obtained a significant temperature rise of the vessel.
The following is a list of the equipment required to conduct this application.
Attach the low-pressure regulator to the nitrogen bottle and then connect to the filling station. Remove the conventional firing wire from the vessel and replace with extended firing wire that will touch the sample. Increase the firing voltage to 35-40 volts (40 volts is maximum available voltage). If the sample does not ignite reduced the size (length and or diameter) of the firing wire. Experiment to determine optimum voltage, length and diameter. If the sample ignites but a misfire is indicated then turn the low temperature rise option "ON" on the CAL2K. This is required if the temperature rise of the vessel is less than 4 degrees Celsius. An alternative is to increase the mass of the sample. Only do this in small steps to avoid dangerous situations.
2 methods of calibration are available:
- Pre calibrate the vessel using oxygen and benzoic acid.
- Use nitrogen and a propellant with a known value as the calibration standard.
Weigh out a sample into a crucible about 2 grams determined by experimentation. Transfer the mass to the calorimeter. Prepare the vessel in the conventional manner, ensuring the firing wire touches the sample.Pressurize the vessel with nitrogen to 500KPA. Insert the vessel into the calorimeter. Close the lid to start the determination. Do not extend any part of your body over the calorimeter during the determination. Once the analysis is complete, remove the vessel, depressurize, cool and clean. The vessel is now ready for another determination.
Using the CAL2K Calorimeter, these are a typical set of results obtained:
|Standard deviation||0.01 MJ/kg|
Determining the calorific value of a propellant can be very valuable. However, extreme caution must be exercised at all times when dealing with any ammunition. Protective wear is highly recommended and all safety rules must be adhered to.