Dynamic elaboration on the Art & Science of Hazardous Area Protection
Road Map to Safety
The structured road-map of EN1127
(A graphic appreciation of EN 1127)
EN 1127 is a fine example of the way the present-day Standard Documents, owned by IEC or EN are being written , compiled , presented & maintained.
Let us explore one of such documents and discover a structured perspective to the process of Hazardous Areas Analysis .
Our selected document is EN 1127
The outstanding feature of this document is its STRUCTURE .
The first pages are , of course , part of Introduction & other details.
Let us flip through these introduction-pages quickly and ….
stop at the doorsteps of SECTION 4.
The best way to analyze Hazardous area is to identify the Hazard itself. The main question is ” What is the cause of the Hazard ? “
The hazard lies in the properties of the materiel . The material can be in any state. (In our case the material is in the form of Vapours /Gas or Dust/Powder). Collectively these properties are termed as “COMBUSTION PROPERTIES”, and the materials are collectively termed as Flammable /Combustible
Let us move on to the next step.
Before we take any step forward, let us recall the concept of
The Combustion Properties of flammable material are directly exploited by the Ignition Sources such that the chain of events may lead to an EXPLOSION. These exploitable parameters are :-
Minimum Ignition Energy
Ignition temperature of the GAS Explosive Atmosphere
Minimum ignition temperature of a dust layer
(The flammable material is already in mixture with oxygen in the air )
At this stage….section 4 takes us a bit further in time , after the ignition….and continue the analysis of the AFTERMATH of IGNITION through the following parameters :-
a) Maximum explosion pressure (pmax);
b) Maximum rate of explosion pressure rise ((dp/dt)max);
c) Maximum experimental safe gap (MESG).
….let us step into SECTION 5
ELEMENTS Of RISK ASSESSMENT
Once we step-in , further details of the process of MAKING of An Explosive Atmosphere become obvious as depending upon :-
a) The presence of a flammable substance;
b) Degree of dispersion of the flammable substance (e.g. gases, vapours, mists, dusts);
c) Concentration of the flammable substance in air within the explosion range;
d) Amount of explosive atmosphere sufficient to cause injury or damage by ignition.
(EN 1127 -2007)
Steps to clarity are as follows:
The steps leads to the most informative part of EN 1127 , namely the list of
The details of this part of section 5 are at Ignition Sources
At this point …EN 1127 elaborates further on the thought-picture of AFTERMATHS of IGNITION in the form of following instructions :-
(The possible effects of the following shall be considered, e.g.:)
b) thermal radiation;
c) pressure waves;
d) flying debris;
e) hazardous releases of materials.
The consequences of the above are related to the:
f) chemical and physical properties of the flammable substances;
g) quantity and confinement of the explosive atmosphere;
h) geometry of the surroundings;
i) strength of enclosure and supporting structures;
j) protective equipment worn by the endangered personnel;
k) physical properties of the endangered objects.
The expected injury to persons, domestic animals or damage to objects and the size of the endangered place can thus be estimated only for each individual case.
Now that we have visited the avenues of “KNOW THY ENEMY” its time to devise a preventive strategy , by stepping into SECTION 6..and study the methods of …