Koenen test

When large quantities of a substance are handled, sensitivity of the material to heating under confinement may need to be considered to demonstrate the effect on the stored/handled, and probably confined, substance in the event of an external heat load. Tests such as the steel sleeve test or Koenen test [24, 137], the Dutch pressure vessel test (DPVT) [143], and the United States pressure vessel test (US-PVT) [143] may be applicable. These tests are used mostly for transportation considerations. The tests generally subject the sample substances to very high energy inputs under confined conditions, and thus are more severe than the deflagration and autoclave tests previously discussed in Section 2.3.3.2. As an example, the Koenen test, used mainly in Europe, is illustrated in Figure 2.32. 

In response to a suggestion made by Koenen (Bundesanstalt fur Materialprufung, Berlin, Germany), these tests, which are carried out with the purpose of evaluating the safety during transport, were improved as described below the method is known as the steel sleeve test (Koenen test). 

At this point it should be pointed out, that BTAT has the same CHNO composition as CL-20, but it is significantly less sensitive than the energetic e modification of CL-20. Figure 9.23 shows a photo of a steel-sleeve test (Koenen test) performed using BTAT with a critical diameter of 10 mm (see Ch. 6.1). 

Fig. 9.23 Explosion of bis(trinitroethyl)-l,2,4,5-tetrazine-3,6-diamine (BTAT) in Koenen test.

Consequently, if a substance sensitive to mechanical impact is to be handled, all steps in the working procedure have to be investigated carefully with respect to effects with comparable consequences. Provided an explosion risk was detected, further testing, which includes the Koenen test and tests on the sensitivity to a detonation shock wave and ability to propagate the detonation, is highly recommended before a concluding safety assessment is performed. 

The LMU Munich research group has also been looking at tetrazole-free nitrogen-rich compounds that contain oxidizing groups such as nitramine functionalities. In this context, the preparation and structural characterization of dinitrobiuret (DNB) (Fig. 31) was carried out [109,110]. The high chemical and thermal stability of DNB and the determined critical diameter of 6 mm for DNB (Figs. 32, 33) in the Koenen test (steel shell test) is comparable to the values reported for HMX (8 mm), RDX (8 mm), or PETN (6 mm) and prompted us to obtain the thermodynamic data and detonation pressures and velocities for DNB in a combined experimental and theoretical study. 

To assess the overall thermal sensitivity of an energetic material in Germany, a number of tests related to the ignition towards standard ignition sources such as cerium-iron alloy sparks, bickford fuse flame jet, gas flames, red hot steel bar and match flame are conducted. In addition, the response of the material towards ignition under various levels of enclosure is tested, the so-called Koenen test [17]. 

The thermal tests (except for Koenen test) for three metal-fluorocarbon pyrolants are listed in Table 19.3. 

For the thorough classification of a substance (which is necessary for safe handling), the thermal stability must also be determined. The first indication of the thermal stability of energetic compounds or formulations can be obtained from DSC data (see Fig. 2.19, Ch. 2.5.2). The so-called steel-sleeve test (or Koenen test)... 

Figure 1.17 Koenen test setup. Courtesy of Prof Dr Thomas Klapotke, Ludwig-Maximilians University, Munich, Cermany...

A typical Koenen test setup is shown in Figure 1.17. The sample is fiUed into a non-reusable cylindrical steel sleeve which is closed by a metal plate with a variable orifice... 

The test is completed upon rupture of the steel sleeve or after heating the tube for a minimum of 5 minutes with no reaction. The elapsed time till ignition and the duration of the combustion are measured. With the variable orifice the limiting diameter is determined at which at least one explosion within a series of three consecutive experiments occurs and the sleeve is ruptured into three or more fragments (Figure 1.18). In Table 1.5 exemplary Koenen test results of common explosives are listed. ... 

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