Material Sensitivity

There are many uses for knowing the sensitivity of a material to impact, friction or electrostatic discharge (ESD). These purposes include:

  • Evaluation of material sensitivity over time (does sensitivity increase or decrease).
  • Comparison of sensitivity of two materials to determine if one material could replace another in a particular process.
  • Determination of margins of safety required for certain processes.
  • Determination of the probability of initiation or risks associated with the manufacture of a material.

Electrostatic Discharge (ESD) Testing

ESD Testing is used to determine the response of an explosive when subjected to various levels of electrostatic discharge energy. Electrostatic energy stored in a charged capacitor is discharged to the test sample. The sample to be tested is placed on a special holder that assures the electrostatic discharge will pass through the sample. A capacitor is charged with a known volt potential (usually 5000 volts). The discharge needle is lowered until a spark is drawn through the sample. The approaching needle method is most commonly used because it best models the safety issues involved with ESD sensitivity. An infrared analyzer is normally used to determine sample initiation.

Friction Testing

The ABL™ and BAM Friction Tests are the two primary tests of this kind. Both methods are UN listed, however, the ABL Friction Test™ has been calibrated into engineering units, which enables analytical comparison of results. The BAM test is good for relative comparisons of material reactivity only.

We are able to test solid or liquid explosives at various velocities and at various pressures. We are able to test materials for friction sensitivity at ambient, cold or heated conditions. We also can test for sensitivity to friction at different humidities.

Friction Test (ABL™)

In the ABL Friction Test™, the sample is placed on the anvil, and a known force is applied hydraulically through a stationary wheel. A pendulum or motor drive is used to propel the sliding anvil at any of several standard velocities perpendicular to the force vector. Sample initiation is detected by visual means (spark or flame).
Reference: The Transport of Dangerous Goods: Tests and Criteria, second edition, United Nations Test Method 3 (b) (iii) page 108.

Friction Test (BAM)

The sample is placed on a rough ceramic plate and a force is loaded on the sample through a stationary ceramic pin, in contact with the plate. The plate is motor driven through a complete cycle pass beneath the pin. The test sample is subjected to the friction created by the rubbing of the pin against the plate. This method allows for ambient temperature tests of powders and pastes.
Reference: The Transport of Dangerous Goods: Tests and Criteria, second edition, United Nations Test Method 3 (b) (I) page 101.

Impact Testing

Impact Tests are used to determine the response of an explosive when it is impacted by a moving mass. This test simulates impact conditions in processing operations, wherein an explosive is subjected to a collision between moving components of the processing equipment, by normal handling operations, or by the inadvertent dropping of tools or equipment.

Two different impact tests are routinely performed. The Modified Bureau of Mines Test is used to obtain data in engineering units. The Bureau of Explosives Test is performed in order determine a DOT classification for the material tested (See DOT Classification.) Large scale impact tests can also be conducted. SMS is able to test samples at various thicknesses (both solids and liquids) and at ambient, hot or cold temperatures or at specified humidities.

Impact Test (Modified Bureau of Mines)

The Modified Bureau of Mines Test™ uses a 2-kg drop weight. The sample is placed on a fixed anvil. A hammer of known contact area is positioned above the sample and the weight is raised to a predetermined height and dropped. Normally, sample initiation is detected by audible or visual means or by infrared analysis of selected decomposition products. This is the preferred test apparatus and method for impact testing because the results are obtainable in engineering units, which enable analytical comparison and easy ranking of materials for sensitivity.
Reference: Allegheny Ballistics Laboratory and the Bureau of Mines.

Evaluation Techniques

For the purposes listed above, it is most beneficial if the data obtained from sensitivity testing are in engineering units. Although it is important to know if a material is more or less sensitive than another, much more value is given to the test data if they can be compared quantitatively. If the sensitivity of a material has changed over time, it is important to know by how much. This is especially true if there are criteria of performance to be met. In addition, if the data obtained from these tests is in engineering units, they can be readily compared to the potential energy stimulus that can be applied to a hazardous material during normal or abnormal operations. For this reason, we recommend testing using the ABL ESD machine, the modified BOM impact machine and the ABL friction machine. Learn more about our Evaluation Techniques.

Both threshold initiation levels (TILs) and PROBIT analyses can be determined for materials using the recommended ESD, Impact and Friction Tests.

Threshold Initiation Level Determination

For the purposes listed above, it is most beneficial if the data obtained from sensitivity testing are in engineering units. Although it is important to know if a material is more or less sensitive than another, much more value is given to the test data if they can be compared quantitatively. If the sensitivity of a material has changed over time, it is important to know by how much. This is especially true if there are criteria of performance to be met. Also, if the data obtained from these tests is in engineering units, they can be readily compared to the potential energy stimulus that can be applied to a hazardous material during normal or abnormal operations. For this reason, we recommend testing using the ABL ESD machine, the modified BOM impact machine and the ABL friction machine.

Probit Analysis

Once the TIL for a substance has been determined, additional trials can be performed within the data range of the TIL, to provide sufficient data for a PROBIT analysis. At least 10 trials are performed at each of five different energy levels above the TIL. The data received from these trials are statistically analyzed. The resulting PROBIT curve is given as the probability of initiation versus the energy input. The results are used to calculate margins of safety and the probability of initiation of the material from the tested stimuli. The curve obtained from the PROBIT is a more accurate representation of the reactivity of the material than the TIL alone. The value of PROBIT data far exceeds the effort.

The PROBIT information is normally used in conjunction with an analysis of the In-Process Potential (IPP). The IPP is the potential stimulus that can be applied to a hazardous material during normal or abnormal process conditions. The calculated stimulus input and corresponding probability of initiation is located on the curve. This value is used directly in a hazards analysis.

Safety Management Services
SAFETY MANAGEMENT SERVICES, INC.
1847 West 9000 South, Suite 205
West Jordan, Utah 84088
Phone: 801-567-0456

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Testing Resource

Kirt Sasser
Kirt Sasser, PE
Director of Engineering and Testing
SMS is one of five laboratories authorized by the DOT to witness classification tests for explosives (Class I). We also frequently run in-process tests. Testing is performed at our test site facility at the Tooele Army Depot where we have a thermal lab, sensitivity test lab, and large scale test area. Please contact us for further information at 801-567-0456 or by sending a request.

Testing Experience

Safety Management Services, Inc. (SMS) has experience in testing a wide variety of explosives and other hazardous materials, such as:
  • Agent, blasting
  • Air bag inflators
  • Air bag inflators, compressed gas
  • Articles, explosive (fuzes, detonating and cartridges, power device)
  • Boosters, without detonators
  • Explosive, blasting, type A-E
  • Flammable Solids
  • Igniters
  • Powder, smokeless
  • Propellant, solid
  • Rocket Motors
  • Waste, Substances, explosive
In addition to material characterization, SMS also has experience in providing testing and recommendations for In-Process Classification and DOT Shipping Classification.
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