1. " Blast whilst being a very onerous study subject , is fraught with combinations, probabilities and becomes a true 'Weibull' consequential distribution dynamic."
Following is a basic range of comparisons and comment to assist in understanding and use as risk mitigation strategy during door selection.
BLAST DOORS
“An explosion is defined as a large-scale, rapid and sudden release of energy.”
Source: T. Ngo, P. Mendis, A. Gupta & J. Ramsay The University of Melbourne
Level of Force Level of Damage
Incident Overpressure Sudden Wind Speed Created Buildings in vicinity Humans in vicinity
PSI kPa MPH KPH Cyclone Category Equiv.
. 3 2 12 20 0 Windows & doors will move & shake Pressure is felt, but with no serious
minimal equipment impact consequence
1 7 40 64 0 Window glass can break Blown over fall /possible glass fragment
Moderate damage to unprotected equipment danger.
2 14 70 112 1 Moderate damage to residential prop Definite fragment injury to humans
Severe damage to unprotected equipment
3 21 102 164 4 Serious structural damage to buildings Serious human injury
5 35 163 262 5 Most none structurally reinforced Fatalities are probable
buildings collapse
10 70 294 473 Very Severe Damage to Concrete Disastrous consequences to
Reinforced buildings human life
BLAST INCIDENTS
Blast offcourse in most cases is accompanied or followed by Fire.
Whether internal or external - Size, Distance, Duration, Direction, Confinement This is due to the blast effect result on structures and the flammablity
or Dissipation are all factors that effect any blast event. result from sparking. Here again variables apply, just as in a blast, confinement,
vent or dissipation will along with the fuel element determine the ferocity of
'Reflected Peak Overpressure' is that momentary blast impact and it is the fire. Building material type fires generally result in temperatures around
generally referred to in milliseconds of duration. It is a positive dynamic 1000 deg. C. and have a general test method for materials known as the
pressure that is followed by a negative phase of approx. 15% to 20% bounce Cellulosic fire test. However Petroleum product, Fuel oil, Liquefied gases and
back and is in turn also effected by area etc. plastics when ignited can result in very high temperatures of some 1400 deg. C.
If one views the Boston Marathon bombing video's, and keeping in mind the area At these temperatures, radiated heat transfer can also be a significant
size and dissipation, the route flags do evidence this phenomena. additional factor of danger. These fires are known as Hydrocarbon Burn Fires
Whilst blast pressure can be redirected by shape ( aerofoil or angular bounce ) it is and have a different Fire Performance Test. Known as the Hydrocarbon Test.
not often practical to employ radical design for plant buildings, So a Structural Strength (HC Fires) have a very quick build to Peak temperatures within 3 to 4 minutes.
approach is the norm for materials and components of construction.
IN AUSTRALIA WE CAN BUILD EQUIPMENT & PERSONELL ACCESS
A concerning blast overpressure would be around 1.5kPa and it is the impulse duration BLAST DOORS WITH SPEC'S UP TO 150kPa REFLECTED BLAST
that does the damage. Designers need to have a safety margin approach of at least 20%. PRESSURES WITH A FIRE RESISTANCE LEVEL OF -/240/120
The equivalence statements and content is an approximate guide for assessing
Risk, and Mitigating same through design, by understanding possible incident events.