4 1

The dust explosion severity test is performed to determine the degree of “explosibility’’ of a dust cloud characterized by the dust explosibility parameters, maximum explosion pressure, Pmax; maximum rate of pressure rise, (dP/dt) max; and explosibility index, Kst, under specified operating conditions. Kst is the rate of pressure increase during a dust explosion event. Pmax provides insight into the maximum achievable pressure generated during a dust explosion event.

Testing Principle and Methodology

The material to be tested is dispersed in a 20L Sphere pressurized with air and an ignition source, typically, 10KJ chemical ignitor is activated to attempt to ignite the material.  ASTM recommends the particles size of the material to be tested to be at least 95% less than 75 microns and less than 5% moisture. In certain unique cases where there is no chance of segregation of the material during normal operation, the material may be tested as received.

In case of uncertainty on how to perform the testing please contact Prime Process Safety Center for guidance. The test involves attempting to ignite the material to be tested in a 20L Sphere and activating the chemical ignitors situated at the center of the sphere. Once ignition occurs, the rate of deflagration resulting from the expansion of the fire ball of the sample in the sphere as well as the maximum pressure generated is recorded by pressure transducers. The testing continues with varying concentrations of the sample until the maximum of the maximal rate of pressure rise and the maximum of the maximal pressure are obtained. Three series of the test are performed and the (dP/dt)max and Pmax are averaged.

Applicable Standards

The Kst/Pmax test is conducted in accordance with the American Standard Testing Method (ASTM) E1226 and BS EN 14034 parts 1 & 2 

Data interpretation

The material is classified as St-1 (Kst between 1-200 bar.m/s), St-2 (Kst between 200-300 bar.m/s) and St-3 (Kst equal to or greater than 300 bar.m/s). St-1 rated materials have weak explosion characteristics while St-2 and St-3 rated materials have strong and very strong explosion characteristics respectively.  The significance or application of the Combustible Dust Cloud Explosion Severity Test lies in its crucial role in assessing and understanding the potential risks associated with combustible dust clouds. This test provides valuable information about the severity and explosibility of dust clouds, offering critical insights for industries dealing with combustible dust. The results of this test can be used to design deflagration containment, venting and suppression systems. These values are applicable to the design of protective measures, such as deflagration venting per NFPA 68, VDI Method 3673 or ISO Method 6184.

When to perform (Kst/Pmax/dP/dt)

When a material is determined to be explosible (Go), it must be subjected to the explosion severity test to determine the degree to which the material can explode as a dust cloud. Performing the Dust Explosion Severity Test at appropriate intervals, especially during material changes, process modifications, or as mandated by regulations, is crucial to ensure workplace safety and prevent potential dust-related incidents in industries where combustible dust is present. 

Why work with Prime Process Safety Center

  • Prime Process Safety Center is a leader in process safety testing with very experienced laboratory personnel. At Prime Process Safety Center our goal is to provide accurate, reliable and defensible data that meets industry and regulatory standards. We understand the need for the quality of your data, and we work assiduously to achieve just that.
  • We are knowledgeable and experienced in performing dust explosion severity testing, ensuring accurate and reliable results. 
  • We have state-of-the-art dust explosion severity testing equipment, providing precise and sensitive measurements. 
  • We follow strict testing protocols and quality control measures to ensure consistent and reliable test results. 
  • Our team can interpret and analyze the data obtained from the tests, providing valuable insights and recommendations for your specific application or research.


What is a Dust Cloud Explosion Severity Test?

The Dust Cloud Explosion Severity Test is a standardized procedure used to assess the severity and explosibility of combustible dust clouds. It involves creating a dust cloud in a controlled environment and measuring parameters like maximum explosion pressure (Pmax) and deflagration index (Kst) to evaluate the potential severity of a dust explosion.

Why is the Dust Cloud Explosion Severity Test important?

This test is important as it helps in assessing the severity and risks associated with potential dust explosions in industries dealing with combustible dust. It provides crucial data for risk assessment, safety measures, and regulatory compliance to prevent catastrophic incidents.

How is the Dust Cloud Explosion Severity Test conducted?

The test involves dispersing a dust sample into a test chamber to create a dust cloud. An ignition source is introduced to initiate an explosion. Pressure transducers installed within the chamber measure parameters such as maximum explosion pressure (Pmax), rate of pressure rise (dp/dt), and deflagration index (Kst).

What parameters does the test measure, and what do they indicate?

The test measures parameters like maximum explosion pressure (Pmax) and deflagration index (Kst). Pmax indicates the highest pressure reached during the explosion, while Kst represents the rate of pressure rise in a single explosion event.

How are the results of the Dust Cloud Explosion Severity Test used in industry?

Results from the test assist industries in evaluating the explosibility and severity of potential dust explosions. This information guides the development of safety protocols, risk assessment strategies, equipment design, and regulatory compliance measures to prevent dust-related incidents.