Combustible Dust Testing Lab

Preparation and modification of the object

Before starting the test, the object needs to be prepared according to the requirements of the relevant standards. This preparation includes drying, crushing, grinding and separation. Our laboratory has various types of grinders and drying equipment.

Sieve analysis (mean grain size)

The sieve analysis is used to determine the mean grain size. This parameter is required by test standards when determining other fire-technical parameters.

Basic chemical analysis

Basic chemical analysis includes determination of water content, volatile combustibles, ash and fixed carbon.

Screening test (GO/NO-GO TEST)

This is a flammability test in a Hartman tube in accordance with EN ISO/IEC 80079 - 20 - 2 or ASTM E1226. If ignition occurs, the material is combustible dust or combustible airborne particles and it is desirable to continue further procedures to determine the specific properties of the combustible dust or combustible airborne particles.

Weighing the prepared object before testing.

MIKE 3 - Determining the minimum ignition energy.

Minimum ignition temperature of dust layer (MIT_DL, MIT_D, LIT)

The minimum dust ignition temperature in the MIT_dl layer is defined as the minimum hot surface temperature at which a layer of dust of a specified thickness (usually 5 mm) on a hot surface ignites. The method is particularly apt for industrial equipment where a thin layer of dust is present, e.g. electric motors, luminaires, etc. The parameter evaluates the maximum permissible surface temperature to prevent dust fires on hot surfaces. Testing is carried out in accordance with the European standard EN ISO/IEC 80079 - 20 - 2 Methods for determining minimum ignition temperatures or ASTM E2021.

Minimum ignition temperature of dust cloud (MIT_DC, MIT_C, MIT)

The minimum ignition temperature of agitated dust MIT_dc is the lowest temperature of the hot inner wall of the furnace at which the agitated dust in the air inside this furnace ignites. The test is performed in accordance with EN ISO/IEC 80079 - 20 - 2 Methods for determining minimum ignition temperatures or ASTM E1491. Determining the minimum ignition temperature is important to prevent dust explosion.

Lower explosive limit (LEL, MEC)

The lower explosive limit is defined as the lowest concentration of a mixture of combustible dust with air at which this mixture becomes explosive. This value is very important for determining the environment in accordance with applicable standards and for protecting equipment from the danger of explosion by keeping the concentration of combustible dust in the air below the dangerous concentration. We set the lower explosive limit on the VA-20L explosion autoclave (manufactured by Kühner AG), which fully complies with the European standard EN 14034 - 3 + A1 or ASTM E1515.

Determination of explosion parameters

The maximum explosion parameters include the maximum explosion pressure p_max, the maximum rate of increase of the explosion pressure (dp/dt)_max of the agitated dust and the explosion constant K_St. Explosion tests with a defined mixture of dust and air are performed in accordance with European standards EN 14034 - 1 + A1 and EN 14034 - 2 + A1 and the international standard ASTM E1226. The burst pressure p_ex and burst rate (dp/dt)_ex are determined for each concentration, and the burst pressure and burst rate are plotted on a graph against the concentration until the maximum burst pressure value p_max and maximum burst rate value (dp/dt)_max are found. The values of explosion indicators are necessary to make qualified calculations and designs of explosion protection elements (membranes, valves, etc.).

Hot plate / hot surface - determining the minimum ignition temperature of settled dust.

Dosing the object before screening test..

Limiting oxygen concentration (LOC)

The limiting oxygen concentration LOC is the highest concentration of oxygen at which a dust-air mixture is no longer capable of an explosive reaction. We perform the test on the VA - 20L explosion autoclave (manufactured by Kühner AG) in accordance with the test standard EN 14034 - 4 + A1 or ASTM E2931. By gradually increasing the ratio of inert gas (nitrogen) to air and changing the dust concentration, the oxygen concentration is reduced to a level at which no explosion can occur at any dust concentration. This value is the oxygen concentration limit. Knowledge of this parameter is essential when designing technology inertization.

Minimum ignition energy of dust cloud (MIE)

The minimum ignition energy MIE is the spark energy required to ignite a dust/air mixture. A modified Hartman tube with a volume of 1.2 l with the designation of MIKE 3 (manufactured by Kühner AG) is used as the explosion vessel. The test is performed in accordance with the European standard EN 13821 or ASTM E2019. The value of the minimum ignition energy is used to exclude a possible source of ignition. In practice, this information is needed to protect equipment against electrostatic discharges.

Bulk density

Bulk density is the basic value for calculating weights in the inventory of sorted species at small-capacity landfills, for calculating tank volumes, etc. Our laboratory offers this test for both small and large containers.

Shakedown volume

This test is ideal for fuels and other solids in powder, granular or fibrous form. This involves determining the bulk density of the material poured into the vessel and subsequently compacted under clearly defined conditions. This parameter mimics the conditions of the long-term storage of material.

Velocity of fire spreading across a dust layer

The purpose of testing how fast fire spreads across a layer of settled dust is to determine the burning rate of the object in a layer of 1 mm and 5 mm. Determining this parameter requires test equipment, the main part of which consists of a special quartz glass tube with a supply of oxygen.

Positive result during the screening test.

VA-20l spreader.

Susceptibility to self-ignition using the isothermal method

This test reveals the susceptibility of material in powder form to self-ignition during storage. The purpose is to determine the induction time it takes a mass of powder to ignite spontaneously under certain conditions and to classify the materials into transport classes according to RID / ADR regulations and EN 15188.

Classification of dust layers into classes of flammability according to their flammability behavior

Determining the flammability behavior of a layer of dust makes it possible to assess whether that layer of material exhibits any reaction (e.g. ignition, smoldering) in contact with an external ignition source. It also measures the ability of a locally occurring reaction to spread further through a pile of dust or a layer of dust. The behavior exhibited during the test is then characterized by the class number (flammability class). This test is performed in accordance with EN 17077.

Dust resistivity

Determination of dust resistivity is performed according to EN ISO / IEC 80079 - 20 – 2. Dust samples are classified into group IIIC – conductive dusts or into group IIIB – non-conductive dusts. This is important for determination of combustible dust properties and its use in potentially explosive atmospheres.