MATERIALS AND RECOMMENDED TESTING ENVIRONMENT

  • Container—schedule 40 steel pipe, 12 inches (30 cm) in diameter, 5 ft (1.5 m) in length, with a 1/4-inch (6-mm) steel plate welded to one end to serve as a witness. The witness plate should have a hole in one corner beyond the perimeter of the pipe for attachment of a cable to enable its retrieval when used in the underwater mode. The plate should also have a hole within the perimeter of the pipe, for insertion of a continuous-detonation-velocity probe. (This size pipe has the following characteristics: internal diameter, 11.938 inches [303.2 mm], weight, 54 lb/ft [80.4 kg/m], capacity of material, 39.74 lb/ft [59.1 kg/m] of material of specific gravity 0.82. A test charge as described would thus weigh approximately 470 lb [213 kg] [not including the witness plate], of which 200 lb [91 kg] would be test material.)

  • Instrumentation—continuous-detonation velocity probe within the mass of test material. The instrumentation should have the capability of generating a printout for later reference.

  • Booster—cast pentolite, 5-lb (2.26-kg) weight. (This is a commercially available item.)

  • Test site—possibly underwater, to contain shrapnel. (Some sites may be able to run the test in air if suitable instrumentation shelters ["bombproofs"] are available.) Underwater sites could also determine shock and bubble energy for further refinement of the data.

PROCEDURE

  • Insert the continuous-detonation velocity probe through the hole in the witness plate, and bring it out of the top of the pipe.

  • Mix No. 2 diesel fuel oil with the fertilizer material, in the amount of 2 percent by weight. Mixing can be carried out in a cement-mixer apparatus or in large containers using plastic or wooden shovels for agitation. The percentage of oil is arbitrary, based on the following reasoning: the oxygen balance of the various fertilizer mixtures likely to be tested may be difficult or impossible to determine; thus it may not be possible to calculate the proper amount of fuel to achieve a stoichiometric mixture.

    It has been determined that with particulate oxidizers, such as ammonium nitrate prills or grained ammonium nitrate, the greatest sensitivity is achieved with underoxidized mixtures. Thus, although ammonium nitrate/fuel oil has the best energy output, detonation velocity, and after-blast fumes at 5.7 percent fuel oil, it is most sensitive to initiation at lower percentages of fuel oil. It is thus thought that settling on 2 percent fuel oil for all fertilizer detonation tests is reasonable as a standard.

  • Load the fueled fertilizer material into the pipe, tapping gently to eliminate voids. Weigh the material emplaced, and calculate the specific gravity.



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