Ball-drop test

The principal input and output tests used by the US at the time of publishing NOLTR 1111(1952) included Drop Ball Testers (two types) Sand Bomb Apparatuses 100, 200, 360 500 gram Condenser Discharge Apparatus Torsional Ballistic Pendulums (two types) Drop Ball Test Set Mk 135 with Chronograph Thermocouple Drop Ball Test Set Mk 136 with Chronograph Gas Explosion Chambers (two types) Gas Volume and Impulse Apparatus Pressure Bomb Apparatus and Hopkinson Bar Apparatus (Ref 11, pp 9-2 9-3, Table 9-D... 

Sensitiveness (Sensitivity) Tests. In the so-called drop-ball test, described in NOLR 1111 (Ref 14, pp 9-4 to 9-7), using apparatus shown in this Section, Fig 1, the detonator (or primer) is inserted in an assembly shown in Fig 4. Each detonator is resting on a lead disc either 0.065 inch or 0.134 inch thick [PA-PD-124(1953), p 3l, while each primer is resting on an aluminum disc of thicknesses 0.012, 0.032 or 0.040 inches [MIL-P-14100 (Ord) (1955), 3l... 

A pendulum may be used (Charpy, Izod, tensile impact) to determine the work of fracture (Brown, 1999). Instrumented devices provided with piezoelectric transducers are also available load-time or load-displacement curves can be recorded (Merle et al., 1985), giving as much information as static tests. Servohydraulic or pneumatic setups and falling weight devices are also used. The drop ball test from the US Food and Drug Administration, is especially useful for optical lenses (acrylate networks). 

Substances which explode by a weak impact (called highly sensitive substances) can be identified by a screening test like the drop ball test Whether deflagration occurs easily can be checked by an ignitability test Another screening test to examine the ease of occurrence of a reaction relies on the determination of the temperature at which decomposition is initiated by thermal analysis on micro-samples. This quantifies the ease of initiating a thermal explosion. 

Table 1.7 Hazards of Reactive Chemicals which are predictable by SC-DSC (QDSC and TDSC), Drop Ball Test and Ignitability Test...

The ease of occurrence of explosion for a self-reactive chemical may be judged by its shock sensitivity and its ability to propagate the explosion. The shock sensitivity of highly sensitive chemicals can be measured by the drop ball test described above. However, those chemicals whose hazard can be measured by the drop ball test are too sensitive for daily use. Different methods are needed for those chemicals which are not likely to explode in daily use to determine whether a substance can cause explosion under extraordinary conditions. 

Evaluation of Oxidizing Materials (IV), A Drop Ball Test of... 

Figure 3.7 The small sized drop ball test equipment...

The steel roller with the sample powder is placed in the center of the anvil on the drop ball test equipment... 

Table 3.6 Example of test results of drop ball test...

Some errors are unavoidable in impact sensitivity tests like the drop hammer test and drop ball test Important questions involve the precision and accuracy of acquired results. During the World War II in U.S.A., statistical investigations on drop hammer tests were carried out mainly by Professor Dixon 211 at the Bruceton Laboratory to achieve greater accuracy in determining impact sensitivity with the fewest trials. 

Figure 3.11 shows the distribution of the accumulated explosion ratio frequencies for a drop ball test using sport paper caps 2 4 . Test trials at each fall height are done 30 times (a) is the case where the fall heights are taken at the same interval and (b)is the case where the logarithms of the fall heights are taken at the same interval. Apparently the case where log H is taken with the same intervals shows better linearity and is nearer to a normal distribution. 

Methods A to E are drop hammer tests and F to I are drop ball tests. The order of amounts of energy necessary for explosion to occur is ... 

When results of the drop ball test are included, this order becomes ... 

A large scale drop ball test(indirect iapact, 4.26kg ball)... 

Table 3.9 The results of drop ball test for using various particle...

Table 3.10 The results of drop ball tests for potasium nitrate and red phosphorus contacting mixture using 2 kinds of red phosphorus...

Table 3.12 The noise level at point which is distant 3m from test equipment for drop ball test(S dB( A fast)).

As red phosphorus degrades over time, a standard substance should be measured whenever the kind of red phosphorus used or the measuring date is changed. As there are individual variations in sample preparation or in placing the sample on the anvil, the same operator should carry out all tests against a standard substance during a series of drop ball tests. 

The drop ball test established in the Japanese Fire Services Law is thought to be a rational test method, but before reaching this decision, a similar and simpler test method was investigated 3 3 . In conclusion, for such investigations the quantity of oxidizing solid on the border line of activity should be increased in the test trials. However it may be useful to recognize the property of the drop ball test as established in the Japanese Fire Services Law to show those data. 

Drop ball tests were carried out 20 times using the same steel ball and drop height determined as mentioned above for some typical low sensitivity oxidizers. The results are shown in Table 3.14. In Table 3.14 only judgments from test results of up and down methods previously reported 2 31 (See Table 3.8) are shown. The test results from the 10/20 test method coincided with those from the up and down method. 

Table 3.13 Example of test results of drop ball test for contacting mixture of potassium nitrate and red phosphorus and that of potassium chlorate and red phosphorus...

Drop ball tests were carried out 20 times using the same steel ball and drop height determined as mentioned above for some typical high sensitivity oxidizers. The results are shown in Table 3.15. 

In addition, Uehara has evaluated whether a correlation exists between the burning time and the senstivity measured in the drop ball test(see Fig.3.24). The correlation coefficient between the two data sets is 0.57 therefore, Uehara suggested that both tests should be applied to evaluate hazardous materials. 

Very high sensitivity substances like this should not usually be examined in the small gap test which requires lg of a sample. This type of substance should be evaluated by the drop ball test... 

As more sensitive materials were used in this test, lg of a charge was used for safety. There are extremely sensitive materials among these explosive materials, and even lg of a charge may be too dangerous. The small gap test can be applied for relatively sensitive materials, but it must not be used for highly sensitive ones. Such materials should be subjected to the drop ball test. 

This test is not done on materials judged gighly sensitive by the drop ball test or the small gap test. On-half gram of sample is loaded into a 10 or 15 mL sample botte The 10 mL bottle is chosen for samples of high density to avoid empty space in the bottle. A polyethylene plug with a hole is put on the sample bottle. 

In oxidizer mixtures, the range of initiation sensitivity is very wide from super high sensitivity to very low sensitivity. Test methods differs with sensitivity. For super high sensitivity mixtures, testing must be carried out with only a small mass of sample because of their explosiveness. On the other hand, the determination of explosion is readly made. The small drop ball test(Sec. 3.3) is reasonable. 

Criteria for test results are described below. Firstly, drop ball test will be stated. 

Burn test drop ball test ""—— Rank I Rank II Rank III... 

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