The development of a clean fast cook-off test in the Netherlands

One of the IM tests described in STANAG 4439 is the Fast Cook-off (FCO) test. The Liquid Fuel or External Fire, Munition Test Procedures is described in STANAG 4240: The objective of the selected fuel fire test is the determination of the reaction and time to reaction of the munition(s) when subjected to a liquid fuel fire environment.
Following the STANAG, in the standard liquid fuel/external fire test, the test specimen is surrounded by fuel rich flames from a large open hearth containing liquid fuel. The large horizontal dimensions of the hearth ensure that the flames are fuel rich and that hence the heat transfer to the test specimen is approximately 90% radiative. However, these fuel fire tests produce a lot of black smoke and thus pollute the environment; so, in more and more countries this has led to discussions with respect to this test. In the Netherlands the number of large fuel fire test per year is limited. This is the reason that, in cooperation with the Knowledge Center of Weapons & Munitions of the Dutch MoD, TNO is in the process to develop and build a clean FCO test setup, based on propane as a replacement of the liquid fuel.
Besides the discussion on the contribution of radiation to the heating, there are many other requirements to meet. A proper ignition is needed so ensure a fast spread of the flames and reaching a flame temperature of 550°C within 30 seconds. Within two minutes an average flame temperature of at least 800°C has to be reached and maintained at this temperature for a period of 150% of the expected duration of the test. To be able to measure the blast in a proper way and ensure a free flight of parts or fragments in case of a reaction, the tested item should not be surrounded by any shielding or other parts of the set-up. A last requirement is the need of inexpensive materials/apparatus that can be bought off the shelf and assembled easily, in case of a violent reaction and damage to the test set up.
The presentation gives a step by step description of the development of the Dutch FCO test with all the reasoning and solutions that have led to the current design of the test set-up. Also, the results of some mock-up testing and a comparison to results from testing with the existing liquid fuel fire with this mock-up, will be presented.