In the November 2015 issue of the Chemical Engineer I wrote an article (https://www.integpharma.com/white-papers) about the fatal flaws associated Hazardous Area Classification.
In this article I wrote the following with respect to equipment selection.
“Also, the logic behind this selection is that the event that causes a dust cloud to form is independent of the event that leads to an ignition source becoming active. This is probably true for electrical
equipment, less so for non-electrical equipment and could be completely wrong for an electrostatic spark where the creation of the dust cloud could also create the spark.”
The video at the link below shows a corn silo at White Farms Inc in Indiana, USA,toppling over and rupturing. This causes a large dust cloud to be dispersed which ignites immediately to give a flash fire. Possible sources of ignition include static electricity generated by the flow of corn and dust or a spark create by metal to metal contact as the silo ruptured.
This is an example of an event that simultaneously causes both the formation of a dust cloud and a source of ignition i.e. they are not independent.
Using the approach detailed in IEC 60079-10-2:2015 it is likely that the area outside the corn silo would be considered to be a Zone 2 since the likelihood of a dust cloud forming is low and certainly not expected during normal operation.
However, since the creation of the dust cloud and source of ignition are not independent the risk of an explosion (or at least a flash fire) are higher would be expected for a Zone 2. What the video illustrates is that in event of catastrophic failure of such silos there is a very high probability of a flash fire and this probability should be taken into account during any hazard analysis.
In my opinion, in any situation where the failure of mechanical equipment can lead simultaneously to both the creation of an explosive atmosphere in the form of a dust cloud and the creation of a source of ignition, the probability of an explosion occurring should be considered much greater than would be expected for a Zone 2 hazardous area.
Fire Triangle From Wikipedia, the free encyclopedia Jump to: navigation , search The fire triangle. The fire triangle or combustion triangle is a simple model for understanding the ingredients necessary for most fires . [1] It has been replaced in the fire fighting and protection industry partially by the fire tetrahedron (see below). The triangle illustrates a fire requires three elements: heat , fuel , and an oxidizing agent (usually oxygen ). The fire is prevented or extinguished by removing any one of them. A fire naturally occurs when the elements are combined in the right mixture. Without sufficient heat , a fire cannot begin, and it cannot continue. Heat can be removed by the application of a substance which reduces the amount of heat available to the fire reaction. This is often water, which requires heat for phase change from water to steam. Introducing sufficient quantities and types of powder or gas in the flame reduces the amount of heat available for t...
Is Cinnamon Flammable? - Science - ChefSteps Made from the dried bark of Cinnamomum verum , a tree indigenous to Sri Lanka, cinnamon's exotic perfume and subtle flavor come from its two major components: cinnamaldehyde and eugenol. These two chemicals are volatile, meaning they readily vaporize at temperatures comfortable to humans, which is in fact why cinnamon is so fragrant. But those same vapors are also highly combustible (indeed, combustion only happens in the presence of vapors), making cinnamon a highly flammable material under the right conditions. Now a cloud of cinnamon dust isn’t the kind of thing most people would consider dangerous, but add enough heat and you’ll quickly have an expanding ball of fire known as a dust explosion. For dealing with this situation, we can only recommend a good pair of running shoes. In fact, the federal Occupational Safety and Health Administration issues warnings about cinnamon explosions in food manufacturing plants....
From Chemical Processing Don’t Confuse a Functional Safety Audit with a Functional Safety Assessment Understand the critical differences between the two essential evaluations By John Walkington, ABB Safety Lead Competency Centre Apr 19, 2017 Many people working in safety instrumented system (SIS) project development, execution, operation and maintenance treat a functional safety audit (FS Audit) and a functional safety assessment (FSA) as one and the same. So, based on this assumption, they simply ensure that such an activity is undertaken and perhaps signify the need to perform this evaluation at some point when it appears as a milestone on the project schedule. Moreover, often they call upon someone working on the project, who may or may not have had some previous experience in quality auditing, to deliver this audit/assessment. However, this is not a reasonable approach because the concepts for the audit and assessment markedly differ. An FS Audit provides...
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