- Creato: Lunedì, 12 Novembre 2012 14:41
- Ultima modifica: Martedì, 22 Ottobre 2019 11:57
- Pubblicato: Lunedì, 12 Novembre 2012 14:41
Ignitability test / flammability. Choose or process develop a test that simulates these conditions
There is a series of small-scale tests to evaluate materials and components that are victims of the fire in a complete and exhaustive way.
These methods are described in the IEC series 60695-11-XX; all these standards are related to the characterization of the combustion behaviour of a specimen or component in presence of a flame, therefore suitable for the verification of cases in which the product concerned is the victim of fire. Some of the tests are listed below. For example, for the resistance to the combustion of insulating materials for pre-selection purposes, it is possible to use:
IEC 60695-11-10 "Fire hazard testing - Part 11-10: Test flames - 50 W horizontal and vertical flame test methods": this standard reports that a specific insulating material can self-extinguish in a given period of time from the beginning of the material combustion. The method also allows to check the propagation speed of the flame vertically and horizontally and allows to check if parts of insulating material can propagate the flame by moving away from the point of combustion (dripping with flame)
IEC 60695-11-20 "Tests related to fire risks. Part 11-20: Test flames - Test methods with 500 W flame ": the test contained in this standard is similar to that of the previous standard but with much higher thermal power.
To evaluate the flame behaviour of a component we can instead consider:
IEC 60695-11-5 "Test flames - Flame test method with needle - Guide, provision for verification tests and equipment". The test uses the flame generated by a gas flow coming out of a hypodermic needle. Very small powers have been considered, however this method is extremely useful to model, in real conditions, the component scenario touched by a small flame, like the one from a connection or any component that is classifiable as the fire origin.
Finally, there are cases where there is a risk that a product becomes a victim of fire because of overheating and therefore without coming into direct contact with a flame. To characterize these scenarios, it is possible to check IEC TS 60695-11-11 “Fire hazard testing - Part 11-11: Test flames - Determination of the characteristic heat flux for ignition from a non-contacting flame source” where the test evaluates the behaviour of a material subjected to overheating due to the presence of a flame that does not directly affect it. This is an interesting test to evaluate how the insulating materials and / or non-metallic components are involved with a very high and spatially concentrated heat flow.
- Small-scale tests are often carried out in a controlled atmosphere to ensure the repeatability and reproducibility. However, the ignition behaviour depends on the working temperature and / or the environment in which the product operates in the phases before being in contact with the ignition element.
- It is highly recommended to carry out all the safety assessment tests on the product under standard conditions at zero life time, and possibly supplemented by tests on components that have undergone accelerated conditioning and / or aging that simulates the product state under test, e.g. in accordance with the life time for which it was designed. This is extremely important for the polymeric and / or organic materials present in the component under test which, by definition, is subjected to the degradation by heat, UV, humidity and generally in specific environmental conditions.