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Our Solutions: Testing

Combustible Dust - Explosion & Ignition Testing

Our UK laboratory generates flammable & explosive test data for your combustible dusts and powders to aid in characterising, preventing, protecting and mitigating combustible dust explosions and fire hazards.

We undertake the following combustible dust tests:

  • Dust Combustibility (Group A/B)

  • Minimum Ignition Energy (MIE)

  • Minimum Ignition Temperature (MIT)

  • Layer Ignition Temperature (LIT)

  • Explosion Severity Test (Pmax/KST) ST Classification

  • Minimum Explosive Concentration (MEC)

  • Limiting Oxygen Concentration (LOC)

  • Burning Behaviour

Please contact us if you have any bespoke combustible dust or powder testing requirements or if you require consultancy services related to powder and combustible dust explosion safety.

COMBUSTIBLE DUST & POWDER FLAMMABILITY TESTING

Test your dusts & powders and prevent combustible dust explosions

Protecting your people, workplaces, business and the environment from an explosion hazard, fire or other combustible dust hazards rely on the awareness and maintenance of potentially combustible dust and powder materials. As part of your process, a thorough understanding of how to manage or eliminate these combustible dust dangers to avoid catastrophe is required.

Sigma-HSE’s combustible dust and powder testing laboratory offers comprehensive standard and custom combustible dust & powder testing packages to aid you in the identification and characterisation of these hazardous materials and their related risks to a dust explosion.

Discover our range of combustible dust tests

We offer a wide range of combustible dust & powder testing services accredited to UKAS ISO/IEC 17025:2017 standards. Learn more about our range of tests below and get in touch for a free no-obligation consultation today.

Dust Combustibility (Group A/B)

This test is conducted to assess whether dust or powder will form a flammable atmosphere or support flame propagation when dispersed as a dust cloud in the air. It’s a purely qualitative test that categorises a dust or powder into one of two groups:

Combustible (Group A) – Flammable or explosive

Non-Combustible (Group B) – Non-flammable or explosive

Varying concentrations of dust are dispersed into a 20L explosion vessel and exposed to a 2-kJ ignition source. Piezoelectric transducers then monitor a vessels atmosphere for ignition in the form of pressure rise.

Dust and powders that are found to be combustible (Group A) will present a flammable atmosphere when dispersed as a cloud. Therefore, if a sufficient ignition source is present then there is a serious risk of hazardous situations arising.

This can include combustible dust hazards, explosions or fires that may result in product loss and, potential operator injury or fatality. Further testing is required to establish a suitable basis of safety for each process or operation handling a combustible (Group A) dust and/or powder.

Dust particles that are found to be non-combustible (Group B) will not present a flammable atmosphere when dispersed as a cloud. As a result, dust and powders that are found to be Group B are not subject to the conditions stipulated in explosive atmosphere legislation DSEAR (Dangerous Substances and Explosive Atmospheres Regulations) or ATEX (Atmosphere Explosive) in regard to dust cloud explosion hazards*.

This screening approach can save the need to conduct further dust explosion dispersive testing to establish a suitable basis of safety for processing the substance.

* Ignition of a dust layer or bulk deposits through thermal decomposition may still present a risk and further dust testing should be considered. Discover more about our Air Over Layer, Bulk Powder (Diffusion Cell), Aerated Cell and LIT tests.

Minimum Ignition Energy (MIE)

BS EN ISO IEC 80079-20-2 / ASTM E2019 / BS EN 13821 (withdrawn)

The Minimum Ignition Energy (MIE) test is conducted to determine the lowest spark energy that can ignite a powder when dispersed in the air as a dust cloud. A purely capacitive generated spark is used to assess electrostatic discharges (brush, spark, transitional/propagating brush discharges).

An inductively generated spark is selected for mechanical (friction, impact and grinding) or electrical (wire short, electrical contact) spark incendivity analysis.

Working through a range of dust powder concentrations, potentially combustible dust is dispersed into a 1.2L litre glass vessel using dry compressed air. These momentarily suspended dust particles/clouds are then exposed to sparks of known energy for a selected duration. Following this, energy is then lowered, while dust powder concentration and time delay are varied until the ‘MIE’ is established.

MIE data is typically used to define the minimum spark energy needed to ignite a cloud of combustible process material in the working environment. MIE is one of three core tests where ‘Avoidance of Ignition Sources’ is the ‘basis of safety’ for the operation. This approach tests combustible dust or powders to determine how sensitive they are to ignition sources such as electrostatic discharge, mechanical & electrical sparks and hot surfaces.

The basis of safety is often used when charging vessels from sacks, IBCs or FIBCs, pneumatic conveying, milling and tabletting operations. Combustible dust that can create a flammable atmosphere is found to be insensitive to ignition and therefore, it is easy, practical and cost-effective to ensure that an ignition source capable of initiating a dust explosion is not present.

A sub-group of ‘Avoidance of Ignition Sources’ are the electrostatic properties of products and materials used in a process environment. This may include the electrostatic properties of materials being processed, electrostatic properties of containers or Personal Protection Equipment (PPE). This is particularly important where process materials are found to be very sensitive to ignition.

Minimum Ignition Temperature (MIT)

BS EN ISO IEC 80079-20-2” to the standards before BS EN 50281-2-1 / ASTM E1491

The Minimum Ignition Temperature (MIT) test is conducted to determine the lowest temperature at which a hot surface will ignite combustible dust or powders when dispersed in air.

Working through a range of combustible dust concentrations, powders are dispersed through a heated vertical ‘Godbert-Greenwald’ furnace using compressed air. Once an ignition temperature is observed, the furnace temperature is reduced. Dispersion pressure and combustible dust powder concentration are varied until an ‘MIT’ is established.

The MIT test is one of three core tests used to access combustible dust ignition sensitivity. It is generally used when the avoidance of ignition sources is the ‘basis of safety’. MIT test data is required for defining the maximum operating temperature for electrical and non-electrical equipment used in areas where test material is present.

Avoidance of ignition sources as the ‘basis of safety’, is often used for processes such as charging vessels from sacks, IBCs or FIBCs, pneumatic conveying, milling and tabletting operations. Materials that can create a flammable atmosphere are found to be insensitive to ignition and therefore, it is easy, practical and cost-effective to ensure that a source of ignition capable of initiating a dust explosion is not present.

Layer Ignition Temperature (LIT)

BS EN ISO IEC 80079-20-2 to the standards before BS EN 50281-2-1 / ASTM E1491

The Layer Ignition Temperature (LIT) test is conducted to determine the lowest temperature at which a hot surface will ignite combustible dust or powders when settled as a dust layer.

Potentially combustible dust is placed onto an isothermally heated hotplate and formed into a 5 mm layer. Once an ignition temperature is observed, the hotplate temperature is reduced and tested. This is then repeated with fresh combustible dust until the lowest ignition temperature is established.

The LIT test is one of the three core tests for accessing a material’s ignition sensitivity. It is generally used when the avoidance of ignition sources’ is the ‘basis of safety’ for an operation. This data is required for defining the maximum operating temperature for electrical and non-electrical equipment used in areas where test materials are present.

The avoidance of sources of ignition as the ‘basis of safety’, is often used for processes such as charging vessels from sacks, IBCs or FIBCs, pneumatic conveying, milling and tabletting operations. Many materials that can create a flammable atmosphere are found to be insensitive to ignition and therefore, it is easy, practical and cost-effective to ensure that an ignition source capable of initiating a dust explosion is not present.

Explosion Severity (Pmax & Kst)

BS EN 14034 parts 1 & 2 / ASTM E1226

The explosion severity test is conducted to determine the maximum pressure (Pmax), maximum rate of pressure rise (dP/dt)max and the dust constant Kst value of an ignited combustible dust, dispersed in the air, as a dust cloud.

Working through a range of potentially combustible dust concentrations, powders are dispersed into a 20L explosion vessel (sphere) using dry compressed air. These suspended dust clouds are then exposed to a large 10 kJ chemical source of ignition and the following dust explosion is monitored, measured, and recorded, using high-accuracy piezoelectric transducers. Testing is conducted over a wide range of combustible dust powder concentrations that enable flammability curves of Pm, dP/dt & Kst to be generated, along peak values. Data created via the 20-Litre demonstrates what the maximum dust explosion pressure would be under optimum concentration.

Data generated by the explosion severity test is predominantly used for either the design of dust explosion protection systems (venting, containment or suppression) or to confirm if a material is appropriate for processes within an established hazard protection system.

Minimum Explosion Concentration (MEC)

BS EN 14034 part 3 / ASTM E1515

 

The Minimum Explosive Concentration (MEC) or Lower Explosive Limit (LEL) test is conducted to determine the minimum quantity of combustible dust dispersed in the air, as a cloud that will form a flammable atmosphere.

Working through a range of decreasing combustible dust powder concentrations, a powder is dispersed into a 20L explosion vessel (sphere) using dry compressed air. The suspended potentially combustible dust cloud is then exposed to a large 2 kJ chemical ignition source and the following dust explosion is monitored, measured, and recorded, using high-accuracy piezoelectric transducers. Once ignition is achieved, the concentration of the combustible dust powder is then reduced until ignition is not possible and the ‘MEC’ is established.

Data generated by the minimum explosive concentration test is predominantly used to ensure that levels of airborne dust are kept below the minimum threshold by which a flammable atmosphere can be created and a combustible dust explosion could occur. It may also confirm if a material is appropriate for processes with an established LEV or set dust extraction rate.

Limited Oxygen Concentration (LOC)

The Limiting Oxygen Concentration (LOC) test is conducted to determine the minimum quantity of oxygen, within an atmosphere, that will enable combustible dust dispersed in the air to ignite when in contact with an ignition source.

Working through a range of combustible dust concentrations, a powder is dispersed into a 20L explosion vessel (sphere) using dry compressed air and nitrogen. Using partial pressures, oxygen content within the sphere at the time of ignition is controlled. These suspended dust clouds are then exposed to a large 2 kJ chemical ignition sources and the following dust explosions are monitored, measured, and recorded, using high-accuracy piezoelectric transducers. Once ignition is achieved at a specific oxygen concentration, oxygen concentration is then reduced, and powder concentration is varied, until ignition is not possible, and the ‘LOC’ is established.

Data generated by the Limited Oxygen Concentration test is predominantly used for either the design of nitrogen inerting systems or to confirm if combustible dust or powders are appropriate for processes with an established limited oxygen atmosphere. As many systems are set at a much lower oxygen level than required, this can result in large nitrogen costs. This can be avoided or reduced, by knowing a combustible dust’s specific LOC and setting oxygen levels accordingly.

Burning Behaviour

VDI 2263 and BS EN 17077

This combustible dusts test is conducted to assess the behaviour (severity) of combustion propagation through a material deposit when ignited by an external ignition source. A small powder strip is formed onto a heat-resistant, non-porous plate and ignition trials are performed using a hot (1000 °C) platinum wire. The burning behaviour is numerically rated from 1 (material does not ignite) to 6 (supports rapid combustion) in accordance with the test standards characterisation table. The rating is known as “CC” or Combustibility Class and testing is performed at ambient and elevated environmental temperature conditions.

 
Type of ReactionCCReference Product
No spreading
of fire
No ignition1Table Salt
Brief ignition and rapid extinction2Tartaric Acid
Localised combustion or glowing with practically no spreading3Lactose
Fire spreadsGlowing without sparks, (smouldering ) or slow decomposition without flame4Tobacco
Burning with flame or spark generation5Sulphur
Very rapid combustion with flame propagation or rapid decomposition without flame6Black Powder

When the burning behaviour of solid material is known, fires or explosion dust hazards caused because of the introduction of hot embers or friction heat (on bearing failure) can be predicted and then avoided or mitigated. It also can be used as a screening tool to highlight materials that should be classified as a ‘flammable solid’ for transportation.

CAN'T FIND THE COMBUSTIBLE DUST TESTS YOU NEED?

Get in touch with one of our experts to see how we can help

From wood dust to airborne dust particles, we can provide testing solutions for any material, product or chemical that may generate a fire or explosion hazard.

The Sigma-HSE Advantage

From the testing of a materials ignition sensitivity to explosion severity, Sigma-HSE is your single solution provider for a range of combustible dust & powder flammability testing. Our dedicated team of experts are committed to helping you ensure that your dusts or powders will not present a combustible dust explosion or hazard so you can maintain compliance with the regulators.

How to get your combustible dust & powders tested

Receive quick and accurate testing data in just a few simple steps

Contact us

Get in touch with one of our experts so we can learn more about your specific process and combustible dust testing requirements. We'll then generate and send you a customised quote.

Prepare & ship

Prepare your combustible dust samples and ship them to one of our laboratories (UK & India).

Dust Testing, Analysis & Reports

Once we've received your potentially combustible dust or powder samples, we'll begin testing and analysing. We'll then create and send you a custom in-depth report detailing the potentially hazardous properties of your materials.

Post-Project Support

If you need support after receiving your report, our after-project support team will be on hand to assist you with any questions you may have about your combustible dust or powders. We can also aid you in your understanding of what combustible dust explosion hazard prevention measures will be most suitable for your processes.

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Test your explosive dust and powders

Getting your combustible dust & powders tested is an important step to prevent a combustible dust explosion hazard. Learn more about how we can assist you to prevent a dust explosion, fire and other related hazards.