Introduction to Fire Safety Management

Explosion venting
is one of the most effective ways 
to relieve pressure; however, it is often diffi cult to size 
the vent correctly to ensure that suffi cient pressure relief 
is available as it must allow suffi cient outfl ow of the 
burnt fuel and air to relieve the pressure being generated 
by the heat of the explosion.
There are a wide variety of differing designs of 
venting dependent upon processes undertaken. These 
can be simple panels that are ejected, vent covers 
(attached to process vessels with clips and rubber 
seals), and hinged doors that can withstand explosions 
or where necessary redirect the explosion.
The vent area will depend upon the volume of the 
enclosure, the enclosure’s strength, the strength of the 
vent cover and burning rate of the dust cloud.
There are a number of hazards caused by venting 
which will need to be taken into consideration, these are:
➤
Emission of blast waves from the vent opening
➤
Ejection of fl ames from vent opening
➤
Fireballs can be ejected
➤
Emission of solid objects (parts of the vessel, vent 
covers, etc.)
➤
Reaction forces on the equipment, induced by the 
venting process
➤
Internal venting may also lead to secondary 
explosions.
Consideration must be given to the location of any 
explosion relief panel or venting, this must be con sidered 
at the design stage.
If venting an explosion cannot be achieved, 
explosion suppression
may be considered. Any 
suppression unit must be permanently pressurised, fi tted 
with a large diameter discharge orifi ce and any valve 
required to operate the discharge mechanism should be 
of high speed which is quite often achieved via a small 
detonation charge.
Dust
explosion
Figure 7.31
A vented dust explosion

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