Dust Explosion Severity (Kst/Pmax/dP/dt)

What Is a Dust Explosion Severity Test?

The dust explosion severity test determines how violently a dust cloud can explode under controlled conditions. The test measures three key dust explosibility parameters:

• Pmax – Maximum pressure generated during an explosion

• (dP/dt)max – Maximum rate of pressure rise

• Kst – Dust deflagration index, calculated from (dP/dt)max

Kst reflects the rate at which pressure increases during a dust explosion, while Pmax indicates the peak pressure achieved. These values are essential for classifying a dust’s explosion severity.

Testing Principle and Methodology

Technicians perform the test using a 20-liter explosion chamber (20L Sphere). Here’s how it works:

• The lab disperses the dust sample in the chamber and pressurizes it with air.

• A 10 kJ chemical ignitor at the center of the sphere attempts to ignite the material.

• Once ignition occurs, pressure transducers record the deflagration rate and the maximum pressure from the expanding fireball.

To ensure consistency, technicians test multiple dust concentrations until they identify the maximum values of both Pmax and (dP/dt)max. They repeat this process in three test series and average the results.

The dust sample must meet ASTM size and moisture standards:

• At least 95% of the sample should be smaller than 75 microns

• Moisture content should be less than 5%

In some cases, if there’s no risk of segregation during operation, the lab may test the sample as received. If you’re unsure how to prepare your sample, contact Prime Process Safety Center for guidance.

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Any questions or concerns? To learn more about our services, please call +1 (346) 462-3838 /+1 (346) 462-3816 or email info@primeprocesssafety.com.

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Applicable Standards

Prime Process Safety Center performs explosion severity testing in accordance with:

• ASTM E1226 – Standard Test Method for Explosibility of Dust Clouds

• BS EN 14034 Parts 1 & 2 – European standards for determining Pmax and (dP/dt)max

These standards ensure consistency, accuracy, and compliance for dust explosibility testing.

Data Interpretation

Based on Kst values, the material is classified into one of three dust explosion classes:

• St-1: Kst between 1–200 bar·m/s → Weak explosion

• St-2: Kst between 200–300 bar·m/s → Strong explosion

• St-3: Kst ≥ 300 bar·m/s → Very strong explosion

Understanding these parameters is essential for designing effective protective systems, such as:

• Deflagration venting systems (NFPA 68, VDI 3673, ISO 6184)

• Explosion suppression and containment solutions

This test provides vital information for process safety, risk mitigation, and regulatory compliance in any facility handling combustible dust.

When to Perform the Dust Explosion Severity Test

If a material is classified as explosible (Go) during initial screening, it must undergo the severity test to measure its explosion potential.

You should also perform this test:

• During material changes

• After process modifications

• When required by safety regulations

Regular testing helps prevent dust-related incidents and ensures a safe workplace in industries where combustible dust is present.

Why Choose Prime Process Safety Center

At Prime Process Safety Center, we bring precision and expertise to every test:

• Experienced personnel with deep knowledge in dust explosion severity testing

• State-of-the-art equipment for accurate, sensitive pressure and rate measurements

• Strict protocols and quality controls for consistent, defensible data

• Detailed interpretation and guidance based on your specific materials and processes

Our goal is to deliver dependable data that helps you protect your facility, comply with regulations, and make informed safety decisions.

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