Video demonstration of dust explosion and protective systems principles
Explosion with no protection
On these video shows we can demonstrate the dust explosion in closed vessel and it's spreading out of the vessel by the pipeline. On these video demonstration, there is no interference to the explosion (the action elements which can be seen on testing vessels are switched off, the explsion was made for calibration of the measuring).
For better comparison are all the tests made with the same coal dust of St 1 class (KST cca 130 bar*m/s, maximum explosion pressure cca 8 bar), unless stated different.
The following video shows closed, pressure sealed vessel, in which the explosion of coal dust is iniciated. Maximum explosion pressure is 8 bar and on the end of the demonstration, the pressure is still higher than 3 bar.
On the following two shows you can see what happens if the explosion spreads out of the vessel in which the ignition source occured. In small distance of pipeline the explosion spreads also in clean ducts and also the diameter of the pipeline makes no difference, when bigger than 80 mm. If there is flammable dust in the pipeline, the flame does not extinguishes in several meters, but the explosion accelerates, reaching higher pressures and speeds of spreading up to supersonic speeds of several hundreds meters per second (so called detonation). Also small amount of dust, not reaching the lower explosion limit, can cause this effect, although not in such destructive degree. This can cause so called secondary explosions, which have much more desctructive effects than the original explosion. This is the reason why explosion isolation should always be considered. This kinds of protective systems are mostly underrated.
First video shows the vessel of cca 2 m3 in which the dust is whirled and lately ignited. Dust is also whirled in the pipeline
which leads out of the vessel (red bottles on the pipeline are dust sprayers). Pipeline is DN 400.
Note the flame coming out of the pipeline and also the colour of the fume which is black - it is the ash of the burned dust.
Following video demonstrates even worse situation. The volume of the vessel is five times bigger (10 m3) and the diameter of the pipeline is DN 800 mm. In this demonstration, there is no dust whirled in the pipeline. It is clear even to unadept why not only the vessel itself should be protected, but also the pipeline going out of it.
Action element on the pipeline in this video is switched off. Red bottles on the vessel are dust sprayers.
Following video shows how big the safety zone of explosion is necessary. There is a vessel of the total volume of 2 m3, which has a hole in the top for explosion venting.
It is clearly visible that the pressure wave spreads first (and to the biggest distance), followed by the flame. Because the explosion happened under ideal circumstances (optimal concentration, good whirling of the dust and strong ignition source), the flame is long and narrow. If the conditions would not be optimal (lower or higher concentration for example, higher particle size), the flame would be in the typical shape of the classical fire ball. It is cause by burning of the dust relatively slowly thrown out of the vessel outside.
And the same situation in detail:
Demonstrations with applied explosion protective systems
Following videos show the same situations as above but with some kind of protective system (explosion venting, explosion suppression, explosion isolation). We recommend to see both demonstration (with and without protective system) one after another, so the difference is best visible.
Here is the cubic vessel of the volume 12 m3 with the explosion membrane on its rear side for explosion venting.
In this demonstration coal dust wasn't used. Instead of it polyesther dust with KST 300 bar*m/s and pmax cca 12 bar made the job.
... and the same situation from the side view in which you can notice the effect of pressure stroke coming out of vessel
faster than the flame.
Please remember this video next time you will see the membrane inside the building, aimed against the wall or directly to the stepwalk...
Following video shows the demonstration of explosion suppression system
ANTIDET SUPPRESSOR used
to protect 10 m3 vessel with coal dust air mixture. If you will watch the video carefully, you will notice 2 shots: First
one is activation of dust sprayers by pressurized air, second one is opening the action elements of explosion suppression system.
The initiation (explosio itself) cannot be heard because it took place about 5 miliseconds before opening the action elements' valves so both shots are heard as one.
Reduced pressure of the explosion when suppressed by ANTIDET SUPPRESSOR explosion suppression system never exceeds 35 kPa even if baking soda is used as the extinguish agent (used in food and pharmaceutical industry), although its extinguishing capabilities are worse than standard powder. This is the prove of excellent effectivity of the system, leading to the need of lower number of action elements for protecting the same volume and also to stressing the protected device by lower reduced pressure (saving money for the construction of such device).
In the last demonstration the system for suppression of the explosion flame
- ANTIDET BARRIER - in the pipeline is presented.
Other names used for such protective system are chemical barrier or HRD barrier.
The pipeline DN 800 leads out of the vessel of 10 m3 in which the coal dust-air mixture was ignited. System consists of one action element which extinguishes the flame coming out of the vessel and stop the pressure rising. The initial pressure caused by the explosion in the vessel would continue through the pipeline and descending as far as the pipeline goes. For total barrier (stopping flame AND all pressure) in the pipeline up to 500 mm (soon up to 630 mm), there are mechanical barrier systems - backflow valves ANTIDET DUMPER.
The main advantage of ANTIDET BARRIER system is that it can be applied also on the pipeline of higher diameter and also everytime the explosion can spread in both directions.
If you would have any questions regarding the demonstrations above or if you wish more information on explosion protection, please contact us and we can provide you more information right in your company in the form of lecture or demonstration. All free of charge.