Explosion Testing for dust, gases & vapours
© EHTL June 2015

Isothermal basket test

Determination of self-heating parameters

Isothermal basket tests determine the self heating characteristics of materials in order to safely transport, store and handle them without risk of fire or spontaneous combustion. Two tests are available:

Isothermal basket test

Laboratory oven tests are carried out according to BS EN 15188 (Determination of the spontaneous ignition behaviour of dust accumulations). The material under test is filled into a cube shaped basket ranging in size from 50mm to 150mm and made of stainless steel mesh. The basket is suspended in an air circulating oven, preheated to a known temperature, with thermocouples both inside out outside the basket to record temperature.  Data logging is used to plot temperature against time during the test (which may last up to 48 hours) and a second stainless steel mesh basket is placed outside of the test basket to provide a screen to excessive airflow around the test sample. Two types of behaviour are observed: sub-critical, where the sample temperature increases above oven temperature, but then slowly drops back after reaching a peak; super-critical, where the sample temperature continues to rise above oven temperature and heats to ignition. The division between these two behaviours is quite sharp with most self heating materials and can be determined to an accuracy of 2K. By plotting a graph of ln(2.52*T2/r2) vs 1/T, the self heating characteristics of the material may be determined. These are the apparent activation energy (Ea) and Arrenhius factors (QA). The results can then be scaled to full size plant through thermal ignition theory or by computer simulation using sophisticated Finite Element Analysis (FEA) software.

UN 4.2 Classification - substances liable to spontaneous combustion

The UN 4.2 classification is a similar isothermal basket test, but groups materials based on ignition / non ignition in two sizes of basket and at three different oven temperatures. Testing is required for dangerous materials under the UN Recommendations on the Transport of Dangerous Goods.
Explosion Testing
© EHTL June 2015

Isothermal basket test

Determination of self-

heating parameters

Isothermal basket tests determine the self heating characteristics of materials in order to safely transport, store and handle them without risk of fire or spontaneous combustion. Two tests are available:

Isothermal basket test

Laboratory oven tests are carried out according to BS EN 15188 (Determination of the spontaneous ignition behaviour of dust accumulations). The material under test is filled into a cube shaped basket ranging in size from 50mm to 150mm and made of stainless steel mesh. The basket is suspended in an air circulating oven, preheated to a known temperature, with thermocouples both inside out outside the basket to record temperature.  Data logging is used to plot temperature against time during the test (which may last up to 48 hours) and a second stainless steel mesh basket is placed outside of the test basket to provide a screen to excessive airflow around the test sample. Two types of behaviour are observed: sub-critical, where the sample temperature increases above oven temperature, but then slowly drops back after reaching a peak; super-critical, where the sample temperature continues to rise above oven temperature and heats to ignition. The division between these two behaviours is quite sharp with most self heating materials and can be determined to an accuracy of 2K. By plotting a graph of ln(2.52*T2/r2) vs 1/T, the self heating characteristics of the material may be determined. These are the apparent activation energy (Ea) and Arrenhius factors (QA). The results can then be scaled to full size plant through thermal ignition theory or by computer simulation using sophisticated Finite Element Analysis (FEA) software.

UN 4.2 Classification -

substances liable to

spontaneous combustion

The UN 4.2 classification is a similar isothermal basket test, but groups materials based on ignition / non ignition in two sizes of basket and at three different oven temperatures. Testing is required for dangerous materials under the UN Recommendations on the Transport of Dangerous Goods.