In-Process Tests

In-Process (IP) testing is used to determine the classification or characterization of the material in the in-process condition.  Equating the transportation classification (article or substance is packaged) to an un-packaged or un-finished article or substance can expose manufacturers and users to un-foreseen risks.

In-Process testing simulates in-process conditions and is used to augment risk-assessment of processing and handling of propellants, explosives, and pyrotechnics (PEP) substances and articles. Below  is an outline for each sensitivity and reactivity characterization test prescribed in the technical paper entitled “In-Process Hazard Classification of Explosives” (click to view).

Additional resources including test purposes, test setup pictures, test outcome videos, and key parameters can be found in the SMS sponsored Test Methods Matrix™ database for both In-process and UN test methodologies: Test Methods Matrix .

Explosive Life-Cycle: In-Process Stages Highlighted in Blue

In-Process Test Series 1

The purpose of these tests is to determine the fundamental material characteristics that are required for determining processing and handling hazards. These tests are conducted first since impact, friction, ESD, and thermal sensitivity data must be conducted on materials suspected of having explosive properties prior to handling them in the larger quantities required for the remaining test series. Impact, friction, ESD, and thermal sensitivity data, when compared to the in-process potential, can determine the margins of safety and therefore the level of risk achieved when manufacturing or using the material in processing.

Impact Test

Impact tests are used to determine the response of an explosive when a moving mass impacts it. 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.

As opposed to some of the UN Manual tests, the in-process sensitivity tests are designed to determine the sensitivity of the sample in engineering units.  The modified Bureau of Mines Impact (MBOM) test can obtain that data and has been done by ATK and other industry leaders to make comparisons of the impact energy to in-process material response scenarios.

Further details can be found in the SMS Sponsored Test Methods Matrix™ including videos, test setup pictures, test purpose, key test parameters and indicators:  In-Process (IP) Series 1 – Impact Test

Friction Tests

These tests simulate friction conditions that may occur in a process when an explosive is subjected to a frictional force between moving components or during material handling. The tests are used to produce friction profiles for the sample material. The two primary tests performed are the ABL and BAM friction tests.

In the ABL test the sample is placed on an anvil. Force is applied to the anvil through a hydraulic ram attached to a stationary wheel. A pendulum strikes the anvil and slides it under the wheel.  Data is obtained in engineering units.

Further details can be found in the SMS Sponsored Test Methods Matrix™ including videos, test setup pictures, test purpose, key test parameters and indicators: In-Process (IP) Series 1 – Friction Test

Electrostatic Discharge Test

ESD testing is used to determine the response of an explosive when subjected to various levels of electrostatic discharge energy. The approaching needle method is most commonly used because it best models the common safety issues involved with ESD sensitivity. Electrostatic energy, stored in a charged capacitor, is discharged to the test sample by lowering the discharge needle until a spark is drawn through the sample. An infrared analyzer or sample consumption are means normally used to determine sample initiation.

Further details can be found in the SMS Sponsored Test Methods Matrix™ including videos, test setup pictures, test purpose, key test parameters and indicators: In-Process (IP) Series 1 – ESDTest

Thermal Test

The purpose of completing the in-process thermal test is determine the effects of time and temperature on energetic materials in the process configuration. Thermal tests generally consist of measuring a sample’s response to either: (1) gradually increasing the temperature and recording the temperature at which the substance gives off heat (autoignition temperature), or (2) holding the substance at a given temperature for an extended period of time to evaluate stability at a given temperature (thermal stability). Both auto-ignition and thermal stability tests are used for in-process risk evaluation.

Further details can be found in the SMS Sponsored Test Methods Matrix™ including videos, test setup pictures, test purpose, key test parameters and indicators: In-Process (IP) Series 1 – Thermal Test

In-Process Test Series 2

The In-Process Series 2 tests are completed when the material is not assumed to have explosive properties or in other words if it is not known if the substance is an explosive. The test series is equivalent to the UN Manual of Tests and Criteria Series 1, with the exception that instead of testing the substance in the condition offered for transport, the in-process condition (or a worst-case scenario) is tested.

The tests determine if the substance has explosive properties such as propagating a shock or sustaining vigorous burning under pressure. The tests and the test details are not repeated here. They are found in Test Series 1 in the “Recommendations on the Transport of Dangerous Goods: Manual of Tests and Criteria,” Sixth Revised Edition, United Nations, New York and Geneva, 2015.

If the substance fails any of the UN Manual Series 1 tests (shows explosive characteristics), it should be classified as an explosive (IP 1.1 or 1.3) for the in-process operation. If the material is shown not to have these explosive characteristics then the material may be classified as something other than an explosive.

In-Process Test Series 3

Test Series 3 is a compilation of tests to determine whether or not the material should be considered a high explosive (i.e. IP 1.1) or whether the material may be considered in a lower explosive category (e.g. IP 1.3). The test series contains four different tests: the thermal stability test, the small-scale burning test, the #8 cap test, and the card gap test.

Small-Scale Burning Test

This test is used to determine if unconfined samples, once ignited continue burning or transit to an explosion or detonation. A bed of sawdust, containing small samples of test material, is ignited and monitored. The test is a “go” (positive) if explosion or detonation occurs.

Further details can be found in the SMS sponsored Test Methods Matrix™ including videos, test setup pictures, test purpose, key test parameters and indicators: In-Process (IP) Series 3 – Small-Scale Burning Test

Explosive Cap Testing (No. 8 Cap)

The No. 8 cap test is used to determine susceptibility of explosives to detonation from the energy delivered by a standard detonator. Sample detonation is determined by examining the witness plate. The criterion for detonation (positive result) is that the witness plate is torn or penetrated.

Further details can be found in the SMS sponsored Test Methods Matrix™ including videos, test setup pictures, test purpose, key test parameters and indicators: In-Process (IP) Series 3 – Cap Sensitivity Test

Shock Sensitivity Test

This test is similar to the UN gap test except that a shorter tube of material is used and a varied attenuator is placed between the test material and the pentolite booster. The attenuators provide a reduced shock source. The criterion for a “go” is that a clean hole is punctured through the witness plate. Typically, 12 trials are required to determine the 50% “go/ no-go” level. The test determines if a material will propagate an attenuated detonation.

Further details can be found in the SMS sponsored Test Methods Matrix™ including videos, test setup pictures, test purpose, key test parameters and indicators: In-Process (IP) Series 3 – NOL Card Gap Test

In-Process Test Series 4

Test Series 4 is used to determine additional material characteristics which are used to define in-process parameters, in addition to those examined by the DOT and BATF. If the process is designed within these parameters, the maximum credible event from a Class 1.3 material or process is a mass fire hazard. The series also includes tests to determine venting parameters for confined operations. If, however, the process parameters exceed the critical height or critical diameter, then explosion of the material due to self confinement (from a flame initiation), or propagation of a detonation is possible.

Process Simulation

Where the process is known, appropriate process simulations may be used. However, a change in the process may necessitate re-testing of some or all of the explosive substances used in the process. Appropriate process simulations may consist of modifications to the standard tests below, to represent worst-case confinement, configuration, and/or loading in the process.

Further details can be found in the SMS sponsored Test Methods Matrix™ including videos, test setup pictures, test purpose, key test parameters and indicators: In-Process (IP) Series 4 – Process Simulation Tests

Critical Diameter Test

The critical diameter of an explosive is the largest diameter at which steady-state detonation cannot be maintained. The test uses varying diameter cylinders and a witness plate. A Comp C-4 or similar booster is used to initiate the sample. The test results are considered positive if the witness plate indicates detonation. Normally, the test shall be completed after three “no-go” reactions are obtained at a diameter one increment below a diameter that previously yielded a positive result.

Further details can be found in the SMS sponsored Test Methods Matrix™ including videos, test setup pictures, test purpose, key test parameters and indicators: In-Process(IP) Series 4 – Critical Diameter Test

Critical Height (Mass) Test

The critical height (mass) test is used to determine the critical height at which a flame initiation transits to an explosive reaction (explosion or detonation). In this test, a flame initiator (bag igniter) is placed at the bottom of a pipe assembly filled with the test material. Pipes of varying lengths and diameters are used to contain the test material. The test is performed by selecting a diameter, and progressively changing the height of the pipe until the material transitions from burning to explosion or detonation. The diameter is then changed and the progressive height variation testing is repeated. Normally, a curve can be fitted using the data, to predict the critical height for other diameters as well. A “go” reaction, for explosion, is one in which the pipe is damaged. The test is concluded at each diameter by running a minimum of three successive trials that produce a “no-go” result at a height below a level that produces a positive reaction (explosion). This level is referred to as the critical height at that diameter.

Further details can be found in the SMS sponsored Test Methods Matrix™ including videos, test setup pictures, test purpose, key test parameters and indicators: In-Process (IP) Series 4 – Critical Height Test

Internal Ignition (10-Gram Bag)

This test is similar to the internal ignition test described earlier except that a 10-gram bag igniter is used instead of the 20-gram bag. As stated previously, either the pipe or at least one of the end caps must be fragmented into at least two distinct pieces for a positive result. Three trials are performed unless a transition from deflagration to explosion occurs earlier. The test determines if a material will explode or detonate when ignited under confinement.

Further details can be found in the SMS sponsored Test Methods Matrix™ including videos, test setup pictures, test purpose, key test parameters and indicators: In-Process (IP) Series 4 – Internal Ignition Test

Koenen Test

Th Koenen test is used to determine the sensitiveness of a material to the effect of intense heat under vented confinement. In this test, the material is placed in a steel container with an orifice plate. The test apparatus is then placed in a protective steel box, and heated at a specified rate. A series of trials is conducted using different sizes of orifices. A “go” reaction is determined by examining the container. Conducting three successive “no-go” reactions with an orifice plate size above that which produced a positive result concludes the test. This orifice is called the limiting diameter. The limiting diameter may be used to evaluate the degree of venting required to avoid an explosion in the process.

Further details can be found in the SMS sponsored Test Methods Matrix™ including videos, test setup pictures, test purpose, key test parameters and indicators: In-Process (IP) Series 4 – Koenen Test

In-Process Test Series 5

Series 5 tests are used to determine the hazard presented by in-process articles (IP 1.1, 1.2, 1.3, or 1.4). Tests are completed under conditions and worst-case in-process configurations, as identified through a risk assessment or process hazards analysis, with a safety factor. The tests represent energy stimuli common to in-process articles in an in-process environment: exposure to heat (curing, conditioning), free-fall impact (falls from material handling equipment, handling error by personnel), ignition/initiation of a donor in-process article in a simulated or worst-case process configuration, and exposure to intense heating or flame (facility fire).

Thermal Characterization Tests

These tests are used to determine an in-process article’s thermal characteristics when subjected to worst-case normal/abnormal process conditions. The test conditions (test temperature(s), test duration(s), test quantity, sample configuration(s), pass/fail criteria, etc.) should reflect worst case in-process conditions for defined failure scenarios identified in the process risk assessment with appropriate safety factors applied to test temperature(s) and duration(s).
Thermal sensitivity from Series 1 testing can also be used to evaluate the in-process risk of the
substance(s) in the article. The process risk assessment may also identify other thermal tests, such as the slow cook-off test for articles, that may applicable for the specific process configuration.

Further details can be found in the SMS sponsored Test Methods Matrix™ including videos, test setup pictures, test purpose, key test parameters and indicators: In-Process (IP) Series 5 – Thermal Characterization Tests

Drop Test

This test is used to determine whether an in-process article can withstand a free-fall impact without producing any significant fire or explosion hazards. The UN MTC and US DoD 12-meter Drop test for
articles, with a drop height of 12 meters, is the prescribed test for determining whether an article is too sensitive for transport. However, the drop height and test parameters for transport are likely not representative of the free-fall impact stimuli available in a specific process. Therefore, the test conditions (test quantity, configuration, temperature conditioning, drop height, impact surface, number of drops, pass/fail criteria, etc.) are defined by the process risk assessment with appropriate safety factors. For example, a 1.2 meter (4 foot) to 1.8 meter (6 foot) drop height may be applicable for simulating handling error by personnel at ground level. Higher drop heights may be appropriate if the in-process articles are conveyed to higher/lower building levels with a drop potential from material handling equipment (conveyors, forklifts, elevators, etc.). Drop heights should be determined by the risk assessment.

Further details can be found in the SMS sponsored Test Methods Matrix™ including videos, test setup pictures, test purpose, key test parameters and indicators:In-Process (IP) Series 5 – Drop Test

Worst-Case Propagation Tests

This test is used to determine whether a reaction from an unfinished article, which was accidentally fired or initiated, would propagate to other articles or parts of the process. This test is conducted by placing articles in a worst-case configuration (e.g. side-by-side, end-to-end, and/or in a pile). This test is similar to the stack test except that the articles are tested without packaging, as they are or may be found in the process, including during process upset. The unfinished or finished articles are placed on top of a steel witness plate. Sand filled inert containers or sandbags may be positioned on the sides and top of the test articles for added confinement. Wire or clamps may be used to hold the articles in place. An article near the center of the unpackaged articles is caused to function (donor). Evidence of propagation or any other observable reaction is recorded. Normally at least two trials are conducted.

Further details can be found in the SMS sponsored Test Methods Matrix™ including videos, test setup pictures, test purpose, key test parameters and indicators: In-Process (IP) Series 6 – Propagation Tests

External Fire Test

A stack of unfinished or finished articles as they appear in the manufacturing line is placed on a non-combustible surface (steel grate) above a lattice of dried wood soaked with diesel fuel or equivalent source. A wire basket or clamps may be used to hold the articles in place. Sufficient fuel is used to provide a 30-minute fire. The fire is ignited and the material is observed for: a) Evidence of detonation, deflagration or explosion of the total contents; b) Potentially hazardous fragmentation; and c) Thermal effects (i.e. size of the fireball, etc.).

Further details can be found in the SMS sponsored Test Methods Matrix™ including videos, test setup pictures, test purpose, key test parameters and indicators: In-Process (IP) Series 6 – External Fire Test

Protective-Enclosure Testing

The use of technology to mitigate hazards is supported in civilian and military practice. Devices can be designed to fully contain or safely direct the deflagration and/or detonation effects of limited quantities of explosive material. Quantities of explosive may thereby be afforded the same level of isolation and safety as provided by the traditional quantity-distance (Q-D) separations.

A blast chimney is an example of these technologies. A blast chimney or other technology must be made to withstand the maximum possible event plus a 25 percent overcharge from the type and configuration of explosive contained within, if used in lieu of Q-D separations.

Shielding devices are evaluated for the following (MIL-STD-398):

  • Blast Attenuation – 1) to provide protection from accidental detonation, shall be designed to prevent exposure of operating personnel to peak positive incident pressures above 2.3 psi (16 kN/m2) or peak positive normal reflected pressure above 5.0 psi (34 kN/m2), and 2) to provide protection from intentional detonation of ammunition, shall be designed to prevent exposure of operating personnel to impulse noise levels exceeding 140 decibles.
  • Fragmentation Confinement – 1) to contain all fragmentation or direct fragmentation away from area requiring protection, 2) to prevent generation of secondary fragmentation within areas requiring protection, and 3) to prevent movement, overturning, or structural deflections that could result in personnel injury.
  • Thermal Effects Attenuation – 1) to limit exposure of personnel to a critical heat flux value based on the total time of exposure (designated by the equation µ [cal/(cm2)sec] = 0.62t^(-0.7423), where t is time in seconds that a person is exposed to the radiant heat), 2) all operating personnel shall be located at a distance from the shield that assures their exposure is less than the heat flux determined from specified equations, and 3) the upper torso of an operator’s body shall not be subjected to any visible fire or flame; flame impingement upon the lower portion of the body may be permitted provided that the heat flux specified above is not exceeded.

Any overpressure discharged must be done so in a manner that safely directs or dissipates the effects thereof. A blast chimney or other technology must be made to withstand the maximum credible event from the type and configuration of explosive contained within, if used as workstation protection in lieu of separated or unattended operations.

Further details can be found in the SMS sponsored Test Methods Matrix™ including videos, test setup pictures, test purpose, key test parameters and indicators: In-Process Testing – Workstation Protection Testing