Determination of
Dust Explosion Characteristics
Laboratory testing of dust explosion hazard
We have an accredited laboratory in which we can conduct the necessary laboratory tests to determine the explosive characteristics of dust:
- Determination of the fractional composition of the material
- Chemical analysis
- Screening test (EN 80079-20-2:2018)
- Minimum ignition temperature of dust MITDL and MITDC (EN 80079-20-2:2018)
- Minimum explosive concentration LEL (EN 14034-3:2017)
- Determination of explosion parameters PMAX, dp/dt, KST (EN 14034-1, 2:2017)
- Limit oxygen concentration LOC (EN 14034-4:2017)
- Minimum ignition energy of dust cloud MIE (EN 13821:2017)
- Fire propagation speed through dust layer BZ
- Spontaneous combustion (EN 15188:2021)
- Actual dust concentration measurements (EN 482:2016)
Stages of determining dust explosion hazard parameters
Dust Sample Preparation
Before testing begins, the material must be prepared in accordance with the requirements of the relevant standards. This preparation includes drying, crushing, grinding and separating.
Sieve analysis
Used to determine the average particle size. This parameter is required by test standards when determining other fire-technical parameters.
Basic chemical analysis
Basic chemical analysis includes determination of water, volatile flammable substances, ash and fixed carbon.
Screening test
This is a Hartmann tube flammability test in accordance with EN ISO/IEC 80079-20-2 or ASTM E1226. If a fire occurs, the material is combustible dust or combustible airborne particles, and it is advisable to continue further procedures to determine the specific properties of the combustible dust or flammable airborne particles.
Ignition temperature of dust layer MITdl, LIT
Minimum layer dust ignition temperature MITdl is defined as the minimum hot surface temperature at which a layer of dust of a given thickness (typically 5 mm) on a hot surface will ignite. This method is especially suitable for industrial equipment that contains a thin layer of dust, such as electric motors, lamps, etc. The parameter estimates the maximum permissible surface temperature to prevent dust from igniting on hot surfaces. Tests are carried out in accordance with EN ISO/IEC 80079 – 20 – 2 Methods for determining minimum ignition temperatures or ASTM E2021.
Dust cloud ignition temperature MITdc, LIT
Minimum dust cloud ignition temperature MITdc is the lowest hot surface temperature at which a dust cloud in the air inside the furnace will ignite. The test is carried out in accordance with EN ISO/IEC 80079-20-2 “Methods for determining minimum ignition temperature” or ASTM E1491. Determining the minimum ignition temperature is important to prevent dust explosions.
Explosive dust concentration LEL, MEC
The lower limit of explosive concentration is defined as the lowest concentration of a mixture of combustible dust and air at which this mixture becomes explosive. This value is very important for plant zoning and for protecting equipment from explosion hazards by keeping the concentration of combustible dust in the air below the hazardous concentration. We determine the lower explosion hazard limit using VA-20L (manufactured by Kühner AG), which fully complies with the European standard EN 14034 – 3+A1 and ASTM E1515.
Determination of explosion parameters
The maximum explosion parameters include the maximum explosion pressure Pmax, the maximum rate of increase in explosion pressure (dp/dt) max of the dust cloud and the explosion constant K St . Dust/air explosion tests are carried out in accordance with EN 14034-1+A1 and EN 14034-2+A1 and international standard ASTM E1226. The burst pressure Px and burst rate (dp/dt) ex are determined for each concentration, and the burst pressure and burst rate are plotted against concentration until the maximum burst pressure Pmax and the maximum burst rate (dp) are reached. /dt. Explosion hazard indicator values are necessary for qualified calculations and design of explosion protection systems (membranes, valves, etc.).
Limit oxygen concentration LOC
Limit oxygen concentration LOC is the highest oxygen concentration at which the dust-air mixture is no longer capable of an explosion reaction. The test is carried out on an explosion autoclave VA-20L (manufactured by Kühner AG) in accordance with test standard EN 14034-4+A1 or ASTM E2031. By gradually increasing the ratio of inert gas (nitrogen) to air and changing the dust concentration, the oxygen concentration is reduced to a level where an explosion cannot occur at any dust concentration. This value is the oxygen concentration limit. Knowledge of this parameter is necessary when designing inertia technology.
Minimum ignition energy MIE
Minimum ignition energy MIE is the spark energy required to ignite a dust-air mixture. The explosive vessel used is a modified 1.2 L Hartmann tube designated MIKE 3 (manufactured by Kühner AG). The test is carried out in accordance with the European standard EN 13821 or ASTM E2019. The minimum ignition energy value is used to eliminate a possible ignition source. In practice, this information is necessary to protect equipment from electrostatic discharge.
Bulk density
Bulk density is the main quantity for calculating dust concentration.
Density after vibration
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 then compacting it under well-defined conditions. This parameter simulates long-term storage conditions for the material.
Flammability
Determining the speed of fire spread through a layer of settled dust is determining the speed of dust burning in a layer of 1 mm and 5 mm. To determine this parameter, testing equipment is required, the main part of which consists of a special quartz glass tube with an oxygen supply.
Self-ignition
This test determines the tendency of a material in powder form to spontaneously combust during storage. The purpose of the test is to determine the induction time required for a mass of powder to spontaneously ignite under certain conditions and to classify materials into flammability classes in accordance with RID/ADR and EN 15188 rules.
Flammability class BZ
Determining the flammability of a dust layer allows one to evaluate whether that layer of material exhibits any reaction (e.g., combustion, smoldering) when in contact with an external ignition source. It also measures the ability of a local reaction to spread further through a dust pile or layer of dust. The behavior exhibited during the test is then characterized by a class number (flammability class). This test is carried out in accordance with the EN 17077 standard.
Dust conductivity
The determination of dust resistivity is carried out in accordance with EN ISO/IEC 80079-20-2. Dust samples are classified into group IIIC – conductive dust or group IIIB – non-conductive dust. This is important for determining the properties of combustible dust and its use in potentially explosive atmospheres.
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