The Laboratory for Industrial Safety possesses test equipment to determine flammability limits, limiting oxygen concentrations and auto-ignition limits of gases. The procedures applied for the explosion tests are based on the European standards.
The test equipment is used for research in the area of industrial safety. The test methods described below refer to the standard tests. Specific test methods corresponding to client needs can be considered.

1. Flammability limits of gases
2. Limiting oxygen concentration of gases
3. Auto-ignition limits of gases

1. Flammability limits of gases
EN 1839

The flammability limits are the concentration limits of a combustible gas in a homogeneous mixture of this combustible gas and an oxidising gas within which a flame is able to propagate independently through the mixture.

2. Limiting oxygen concentration of gases
EN 14756

The limiting oxygen concentration is the maximum concentration of oxygen in a homogeneous mixture of a combustible gas, air and an inert gas below which the mixture is nonflammable.

3. Auto-ignition temperature

The auto-ignition temperature is the lowest temperature of a homogenous mixture of a combustible gas and an oxidising gas at which this mixture spontaneously ignites (i.e. without an external ignition source).

For more information please contact Dr.ir. Filip Van den Schoor .
Tel:  +32 16 322549 
Fax:  +32 16 322985 

Adinex, a spin-off company of the Mechanical Engineering Department, possesses advanced equipment to measure dust explosion characteristics. The procedures applied for the explosion tests are based on the VDI Richtlinien VDI 2263 Blatt 1: "Untersuchungsmethoden zur Ermittlung von sicherheitstechnischen Kenngrössen von Stäuben" (1990) and on the instructions of the manufacturer of the test equipment.
The test equipment is used for research in the area of industrial safety. The test methods described below refer to the standard tests. Specific test methods corresponding to client needs can be considered.

1. The combustibility of powders (Ciba-Geigy method)
2. The smoulder temperature of a dust layer
3. The relative auto-ignition temperature in an air stream (Grewer)
4. The minimum ignition temperature (MIT) of airborne dust by means of the BAM-oven
5. The explosion indices by means of a 20 litre-sphere
6. The limiting oxygen concentration by means of a 20 litre-sphere
7. The explosion characteristics of combustible dusts
8. The minimum ignition energy (MIE) by means of the modified Hartmann-apparatus
9. The electrical resistivity of a powder
10. Explosibility by means of a 20 litre-sphere

At the bottom of this section additional information is given regarding the execution of the tests.

1. Determination of the combustibility of powders (Ciba-Geigy method)
VDI 2263, Blatt 1, 1.2.5.

The combustion class of a substance (Ciba-Geigy method) gives an indication of the ignitability and combustibility of a dust layer when a platinum wire at a temperature of approx. 1000°C is brought into contact with the layer. (more info)

2. Determination of the smoulder temperature of a dust layer
VDI 2263, Blatt 1, 1.3.

The smoulder temperature describes the flammability behaviour of a flat dust layer on a hot surface. It is defined as the lowest temperature of a heated, free-standing surface which is capable of igniting a 5 mm thick dust layer. The smoulder temperature is determined by step-wise increasing the temperature of an electrically heated copper plate on which a 5 mm thick dust layer having a diameter of 100 mm is placed. (more info)

3. Determination of the relative auto-ignition temperature in an air stream (Grewer)
VDI 2263, Blatt 1, 1.4.1.

The auto-ignition temperature in an air stream is the lowest temperature at which a dust sample reacts with the oxygen in the air and/or decomposes exothermally. In the Grewer-oven the test substance and the same quantity of graphite powder as reference substance are heated up at a rate of 1°C/min by means of a hot air stream which is blown through them. The surrounding temperature at which the test sample temperature starts to rise faster than that of the inert reference sample, is taken as the (relative) auto-ignition temperature of the sample. (more info)

4. Determination of the minimum ignition temperature (MIT) of airborne dust by means of the BAM-oven
VDI 2263, Blatt 1, 2.6.1.

This test is designed to determine the ignition temperature of airborne dust on a hot surface. The lowest temperature of the heated impact plate at which the dust blown into the BAM-oven ignites or decomposes producing flames or explosion (in less or equal than 10 seconds) is stated as the minimum ignition temperature (MIT). (more info)

5. Determination of the explosion indices by means of a 20 litre-sphere
VDI 2263, Blatt 1, 2.2. and 2.3.

The maximum explosion pressure, the maximum rate of pressure rise and the lower explosion limit are determined in a standard test apparatus with a contents of 20 litre. The maximum rate of pressure rise (dp/dt)max measured in the 20 litre-sphere is used to obtain the Kst-value. This Kst-value can be used to calculate the maximum rate of pressure rise for other volumes by means of the cubic law:
(dp/dt)max . V^1/3 = Kst
By means of the measured combustion time in the 20 litre-sphere, a value for the minimum ignition energy can be estimated. (more info)

6. Determination of the limiting oxygen concentration by means of a 20 litre-sphere
VDI 2263, Blatt 1, 2.4.

The limiting oxygen concentration (LOC) is the experimentally determined oxygen concentration which will just not allow an explosion of a dust/air/inert gas mixture. It is a compound and inert gas specific characteristic. (more info)

7. Determination of the explosion characteristics of combustible dusts

This is a combination of tests 5 and 6.

8. Determination of the minimum ignition energy (MIE) by means of the modified Hartmann-apparatus

The minimum ignition energy (MIE) of a dust cloud is the lowest energy value of a high-voltage capacitor discharge required to ignite the most readily ignitable dust/air mixture at atmospheric pressure and room temperature. The dust concentration and the ignition delay are systematically varied until a minimum value of the ignition energy is found. The tested energy levels are 1000, 300, 100, 30, 10, 3 en 1 mJ. (more info)

9. Determination of the electrical resistivity of a powder
VDE 0170/0171

To determine the likelihood of electrostatic discharges in installations, it is necessary to know the resistivity of the powder used in the installation. The applied test equipment and procedure are in concordance with the draft code DIN VDE 0170/0171. (more info)

10. Determination of explosibility by means of a 20 litre-sphere
VDI 2263, Blatt 1, 2.1.2.

In a standardised test apparatus with a contents of 20 litre, a small number of tests is performed over a wide range of concentrations to determine whether or not the dust is explosible. (more info)

Additional information

A sample of 3 kg of dust is necessary to do the experiments. The codes prescribe a distribution of the dust particle size smaller than 250 µm for dust layer tests and smaller than 63 µm for dispersed dust tests. In specific cases, the tests can be performed on other size distributions. The powder samples must be accompanied by safety data, prescribing the precautions to be taken when handling the powder (e.g. Material Safety Data Sheet).

All tests will be performed in a period of 2 weeks after delivery of the dust sample, Material Safety Data sheets, and the purchase order (3 weeks for tests 6 and 7). Lead time may vary due to work load. The results of the tests are treated in a confidential way and are exclusively available to the contractor.

If the material requires special methods of disposal, additional charges may apply, or arrangements may be made to return the unused portion of the dust sample to the customer.

For more information please contact Adinex.
tel.: +32(0)14/27.03.90
fax.: +32(0)14/27.03.99