Iec 60079 0 Pdf Freel
Jhuls Morgan
A good way to perform hazardous area classification is the application of the IEC 60079-10-1 standard. The latest version of this standard was issued in 2020. The standards has a few specific changes compared to the former version of the standard from 2015.
We will outline the general approach of the standard. This text can also be downloaded as a pdf here. There is also a link in the pdf for purchasing an official copy of the IEC 60079-10-1 Rev3.0 standard (check it, it saves a lot of money).
The Class / Division system, which is still used in Northern America, is not implemented in the IEC standard. A reference table between the zone and class/division system, can be used to switch between the two systems.
Zone 0: Place in which an explosive atmosphere consisting of a mixture with air of flammable substances in the form of gas, vapor or mist is present continuously, for long periods or repeatedly (consider more than 10% of the time or more than 1000 hours);
Zone 1: place in which an explosive atmosphere consisting of a mixture with air of flammable substances in the form of gas, vapour or mist is likely to be present occasionally under normal operating conditions (consider less than 10% of the time / 1000 hours but more than 0.1% of the time /10 hours);
Zone 2: Place in which an explosive atmosphere consisting of a mixture with air of flammable substances in the form of gas, vapour or mist is not likely to occur in normal operation and, if it does occur, will persist for a short period (less than 0.1% of the time / 10 hours).
This means, that the zone depends on the frequency, in which the concentration of gases, vapour or mist, is above the lower explosion limit. After all, only when the concentration of fuel is above the lower explosion limit, a mixture is explosive.
The grade of the release in, mass per second, can be calculated using the equations from the standard. The grade of the release stands for the evaporation rate (for liquids) or the gaseous release rate (for gases).
note: with the equation for the liquid release, an estimation must be made which part of the release evaporates immediatelly. When this is zero, the equation for the atmospheric pool release must be used.
When the grade of release is known, it is important to evaluate, how the concentration of flammable gases is dilluted. Dillution is achieved by ventilation and ventilation can be expressed as the air velocity around the source of release.
The model is based on the assumption that, the higher the air velocity near the source of release is, the higher the dillution is. of course the dillution must be in balance with the grade of the release.
On the x-axis, the calculated volumetric release characteristic of the source (m3/s) is plotted and on the y-axis the air velocity near the release source is plotted. Based on the values, the intersection of the corresponding lines, results in the dillution class.
For indoor situations the resulting dillution class from figure C.1. is a prelimenary dillution class. The dillutin class for indoor situations depends also on the average background concentration in the area.
The average background concentration in the area under consideration, must be lower than the critical concentration. The critical concentration is a certain percentage of the LEL of the substance. Mostly 25% of the LEL.
When the background concentration is lower than the critical concentration, than the check is "OK" and the dillution class remains the same as the prelimenary dillution class, based on figure C.1.
When the calculated background concentration is higher than the critical concentration, than the check is "Not OK" and the dillution class becomes low.
In order to simplify all the calculations and assessments, we developed Hazcalc. This is an online calculation model, which is based on scenarios, and fully compliant with the current European standard EN-IEC 60079-10-1.
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