How do you classify combustible dust?
If the material will burn and contains a sufficient concentration of particles 420 microns or smaller to create a fire or deflagration hazard, it should be classified as a combustible dust.
What is the classification of dust?
A scheme for classification of dusts is illustrated which classifies dust into: oxidizers, explosives, and pyrophoric materials; noncombustible dusts; and combustible dusts with various ignition sensitivities that have either conductive or nonconductive resistivity.
What is ST1 combustible dust?
Ashok: Combustible dusts are ranked into one of four classes; ST0, ST1, ST2, ST3. The level of explosion violence increases with the class number. Even a St-1 dust generates sufficient power to cause a flash fire, compromise containment on a piece of equipment, or blow out the walls of a building.
What type of hazard is dust?
Exposure to dust can cause irritation to the eyes, skin and respiratory tract, and prolonged exposure can lead to a range of serious lung diseases including silicosis, coal workers’ pneumoconiosis (CWP), chronic obstructive pulmonary disease (COPD) and lung cancer.
How does OSHA define combustible dust?
Combustible dust is defined as a solid material. composed of distinct particles or pieces, regard- less of size, shape, or chemical composition, which presents a fire or deflagration hazard when. suspended in air or some other oxidizing medium.
What is KST and Pmax?
Kst value and Pmax are explosive properties measured in the laboratory to quantify the severity of a dust explosion. A weighed quantity of combustible dust is placed into the dust container. The main explosion chamber is then evacuated to 0.4 bar absolute.
How many group of classification is dust fire?
Combustible dusts are divided into three groups, depending on the nature of the dust: Group E, Group F, and Group G.
What are the characteristics of dust?
Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in homes is composed of about 20–50% dead skin cells.
What is PMAX and KST?
Kst value and Pmax are explosive properties measured in the laboratory to quantify the severity of a dust explosion. Explosion pressures are measured for a range of dust concentrations using piezo-electric pressure transducers.
What is Pmax in dust?
The Maximum Explosion Pressure (Pmax) and the Kst of the dust sample tested is defined as the mean of the maximum values of each test series (total of 3 series) over the concentration range close to the observed maxima.
How many types of dust are there?
Different types of dust also carry different risks to human health and can be classified into three types: L Class (Low Risk), M Class (Medium Risk) and H Class (High Risk). Each class has a maximum allowable concentration, which is essential for employers to understand.
What is the GHS classification for combustible dust?
However, the GHS does not contain a classification for combustible dust hazards, and to maintain coverage of this hazard under the HCS, OSHA amended the standard’s definition of “hazardous chemical” to include “combustible dust 2 .”
What is the particle size of combustible dust?
Dust Particle Size. For many years, NFPA 654 defined combustible dust as a “finely divided solid material 420 microns or smaller in diameter (material passing a U.S. No. 40 Standard Sieve) that presents a fire or explosion hazard when dispersed and ignited in air.”.
What is an explosible dust?
Overview Any combustible material can burn rapidly when in a finely divided form. If such a dust is suspended in air in the right concentration, under certain conditions, it can become explosible. Even materials that do not burn in larger pieces (such as aluminum or iron), given the proper conditions, can be explosible in dust form.
What is the NFPA standard for combustible dust?
Some NFPA standards still use a size criterion in defining combustible dust, such as NFPA 61 (2013) and NFPA 704 (2012) 10 . Other NFPA standards, however, have changed their combustible dust definition to remove the size criterion, but discuss size in their explanatory notes.