Like a powder keg: why the tragedy happened at the sugar factory in Skidel. Exploding Foods Is flour explosive?
It's just flour...
But there are cases when it explodes, detonates, for example, coal dust or even ordinary flour. This happens when they are dispersed in the air.
Under normal conditions, it is not at all easy to light coal, and flour is even more difficult. But when particles of coal and flour are sprayed into the air, they mix with the air. Each particle of coal or flour is surrounded by oxygen. Therefore, they combine with oxygen so easily, burn out at a tremendous speed - they detonate.
When does the dust explode? The fact that flour is explosive, people have known for a very long time. It is enough to drop a bag of flour so that the concentration of flour in the air is more than 50 g / m 3, and then “accidentally” light a match - and an explosion will inevitably be heard. Such explosions quite often occur at elevators and are often accompanied by casualties. This happens due to the fact that there is a lot of starch in flour, and starch is many, many sugar molecules connected to each other. Each of the sugar molecules "well" burns in the air, turning into carbon dioxide and water and releasing a large amount of heat. Under normal conditions, it is not at all easy to ignite flour. This only happens when the flour particles are suspended in the air, and each is surrounded by oxygen.
Under these conditions, it is easy for particles smaller than 0.1 mm to combine with oxygen, and they burn with great speed - they detonate. Explosive is a fine powder of very many substances that oxidize in the presence of oxygen.
And here is an example of how dry milk explodes:
Mixtures of certain types of dust with air are explosive. According to the degree of explosive danger, all dust is divided into four classes:
I - the most explosive dusts with a lower flammability (explosive) limit of up to 15 g / m3 (dust of starch, wheat flour, sulfur, peat, etc.);
II - explosive dusts with a lower flammability limit of 16 to 65 g / m3 (dust of aluminum, wood flour, coal, sugar, hay, shale, etc.);
III and IV - flammable dusts with a lower flammability limit above 65 g / m3 and an ignition temperature of up to 250 ° C and more than 250 ° C, respectively.
And here is the explosion at the mill:
So can sugar explode? Yes and no. Granulated sugar, refined sugar, brown sugar, sugar syrup do not pose such a danger under any circumstances. Everything burns, of course. But you won’t expect a real, loud “bang” from this sweet product. There is, however, the insidious "fifth element" - powdered sugar. All sorts of troubles are expected from her and only from her at the factories ... And not in vain. Sugar production is dusty. The smallest particles of powdered sugar hang in the air, accompanying the various stages of product readiness. It would seem that they hang and do not touch anyone. But this is for the time being. Imagine that somewhere in such a dusty workshop, faulty electrical wiring sparks.
The dust particles around her light up. The smallest size of powdered sugar grains (no more than 0.1 mm) provides them with the maximum surface area with which such a grain of dust reacts with oxygen. It oxidizes. Burns out very quickly. And nearby in suspension are myriads of the same dust particles, which at one moment pass each other a fiery baton. They burn together and almost simultaneously. It looks exactly like an explosion of great power. Such an explosion can even wipe the plant off the face of the earth. These are such "innocent" sweets. And if we hear that a sugar factory shop has exploded somewhere, it means that there have been violations of fire safety regulations: a large concentration of sugar dust in the air, and, of course, a spark source. Sugar dust in factories is successfully fought. First, through ventilation. In order not to emit dust into the atmosphere, it is captured using various filters: woolen, fabric and even resin. They also use special devices - cyclones. In the air turbulence that such an apparatus creates, centrifugal force begins to act.
It throws solid particles to the walls of the apparatus, they lose speed and settle into a special bunker. It should be noted that not only sugar dust is dangerous. Under similar conditions (concentrated dust suspension and spark source), any organic substance will explode with an almost 100% guarantee: flour, coal dust. However, this is by no means a reason to be afraid of packaged flour and deny yourself the pleasure of making homemade pies. No, you don't have to be afraid. Do not be afraid of sugar bags, sugar wagons, sugar trains. Be afraid of a disregard for fire safety in the workplace. I hope you will never have to face this in your life: everyone wants to live, and special services do not allow obvious disgrace. ]
And here is our first GIF in more detail:
wasserfall 24-10-2011 12:08
quote: Today, at about half past nine in the morning, at the Snezhka poultry farm, located on the outskirts of Bryansk, there was an explosion, the roar of which was heard even by those who live within a radius of two kilometers. Under the rubble of the destroyed feed shop, two dead workers were found, three more were injured.The economic situation of the factory, although it has a large area of land in a suburban area, has not been the best recently. According to several workers who fled after the explosion to the checkpoints, where the police took "defence", the feed shop corresponded in height to a seven-story residential building and was considered a place with very difficult working conditions. The day before, many residents of the surrounding houses paid attention to the stench coming from Snezhka. However, this was associated with some work at the factory.
After the explosion, a column of white smoke rose. The upper half of the feed shop, which is located in the middle of the enterprise, collapsed, burying two workers of fifty and sixty years old under the rubble - the body of one of them was found only in the evening, when part of the building structures was pulled apart with the help of heavy equipment. Three other people were slightly injured and needed medical attention.
According to the Ministry of Emergency Situations, the dust-air mixture could explode. The factory workers, who had already encountered the problem of dustiness in the production premises, told the RG correspondent the same thing. The Ministry of Internal Affairs reported that, according to the preliminary version, a violation of the technological process could become the cause of the tragedy. By evening, it became known that the investigating authorities of the Investigative Committee of the Russian Federation for the Bryansk region opened a criminal case on the grounds of a crime under the article "Violation of labor protection rules, resulting in the death of a person through negligence." Investigators and specialists continue to work at the poultry farm.
http://www.rg.ru/2011/10/23/reg-cfo/vzryv.html
Dr3-11 24-10-2011 03:19
GriboedovMC 24-10-2011 03:34
> And what does the air-dust mixture consist of?
*ominously*
This is a very terrible knowledge, I can reveal this secret only by taking it with me to your grave!!!
It is clear that a simple answer: "from dust and air" - how does the answer to the question not work?
Yes, it can explode.
But in such volumes, it is, of course, something.
This is how this factory killed the ecology around, if they "paid attention to the stench" only shortly before the explosion?
I just don't feel comfortable thinking that such an equivalent of dusty air has folded a building. How did they work there before?
Tataurof 24-10-2011 07:21
quote: if "pay attention to the stench" only shortly before the explosionthis is probably again the journalists distinguished themselves. for the first time they visited a poultry farm and found out that poultry farms smell))) apparently they didn’t really like the smell. about the sound of an explosion that was heard as far as 2 km away, they also powerfully pushed it. people could well be killed even with small pieces of slate from the roof if they fell from a height of the 7th floor
Maxim V 24-10-2011 07:38
Poultry farms use feed additives - permixes - if you take a handful of permix - throw it into the air and strike it with a lighter - you get a bright flash. If the permixes were unloaded at the factory in violation of technology, then the room(s) were dusty - an open source of flame was enough and an explosion occurred. (Such explosions were not uncommon in sugar factories.) In fact, it turned out to be a volume explosion ammunition.
quote: about the sound of an explosion that was heard as far as 2 km away, they also powerfully pushed it.
Absolutely normal - depending on the volume of the dust-air mixture - there could well be a TNT equivalent of several tens of kilograms.
MickyMouse 24-10-2011 07:47
Dust (flour, powdered sugar, etc. organic matter) at a certain concentration in the air, it explodes. From a spark, etc.
The Krasnodar Territory is full of elevators with "torn towers". And 2 km - not too far not to hear ..
Wolf5862007 24-10-2011 07:52
flour and coal dust is also dangerous, in the mines, after the first explosion of methane, coal suspension rises into the air and this is already worse than methane itself!
linkor9000 24-10-2011 07:56
quote: Dust (flour, powdered sugar, etc. organic matter) at a certain concentration in the air, it explodes.
yes, a hazardous production facility, safety rules and all that.
The question is, where did Rostekhnadzor look? The inspector must be told why he allowed the operation.
Maxim V 24-10-2011 08:03
quote:
Don't talk nonsense. The check takes place once a year - at the time of the check, everything is in order. A week after the check - during unloading - they violated the technology or someone - decided to joke and sent a stream of air (from the compressor) into a pile of feed. Yes, there are many options for how to form a dust-air mixture. And what about the inspector?
Ace_Odinn 24-10-2011 08:29
Previously, saltpeter for gunpowder was obtained from bird excrement, wasn't it?
Saltpeter is an oxidizing agent, coupled with dust, such a good gunpowder ...
naugrim2020 24-10-2011 09:26
Any more or less burning dust can explode. We had a case when, in Soviet times, the guys climbed into the air ventilation to the cinema to watch a film for free in the cinema. And there they either lit a cigarette, or they wanted to light it with a match. And they exploded.
Unforgiven 24-10-2011 10:26
Previously, he worked in an office that was engaged, among other things, in the packaging of food products. So the shop in which flour and sugar were packed was considered an explosive production.
Tataurof 24-10-2011 10:38
there could well be a TNT equivalent of several tens of kilograms.
Rusich 24-10-2011 10:49
quote: Originally posted by Maksim V:
permixes
PREmixes
Nebuchadnezzar 24-10-2011 11:03
In Soviet times, there were cases of explosions at sugar factories, sugar dust exploded at flour mills. Therefore, safety precautions were observed very strictly smoking in any case. It was like a massive explosion.
naugrim2020 24-10-2011 12:36
Here we make industrial floors - at flour mills and feed mills ONLY spark-free flooring.
v0land 24-10-2011 13:08
And not only.
still need explosion-proof lamps, engines and much more. For work in explosive zones and rooms.
Alex1952 24-10-2011 13:46
quote: The question is, where did Rostekhnadzor look? The inspector must be told why he allowed the operation.
What checks? Our current governor was the director of this poultry farm.
Fidoshnik 24-10-2011 17:18
quote: Originally posted by wasserfall:
although it has a large area of land in a suburban area
I think this is the answer.
Vasko26 24-10-2011 17:59
Alex1952 24-10-2011 18:23
quote: Explosive ANY dust
That's right. Explosives have such a permit - "Admitted to blasting in mines that are dangerous in terms of dust and gas." And not necessarily coal mines. It is considered one of the highest tolerances.
Everything is described in detail in the EPBVR-"Uniform Safety Rules for Explosive Operations".
demon 24-10-2011 18:51
At the mills, nameplates hung everywhere under the Soviets "EXPLOSIVE".
I remember in Rzhev a mill in the early 80s ipanula - a seven-story building - one box remained, and even then because the captured Germans built it, 28 200x - the explosion occurred exactly at the change of shifts.
At an increased concentration of organic suspension, dust particles rub against each other, pumping up static, so that no extraneous flash is required.
------------------
In Gun We Trust
linkor9000 24-10-2011 19:01
quote: Explosive ANY dust
well, try to blow up let's say chalk dust, or granite
explosion is combustion with a branching chain, only combustible
Alex1952 24-10-2011 19:21
I want to correct myself - any COMBUSTIBLE dust explodes ...
wla42 24-10-2011 19:33
Chelyabinsk, 1981: 
http://chelchel-ru.livejournal.com/306590.html
Everything was visible from the balcony of my room. I only saw the consequences. And my brother and mother heard the explosion and saw a cloud of smoke and ash rising into the sky. 18 dead. Explosion of air-flour mixture. It was a beautiful pre-revolutionary building.
MickyMouse 24-10-2011 20:06
"At an increased concentration of organic suspension, dust particles rub against each other, pumping up static, so no extraneous flash is required."
Why don't bears rubbing against an axle explode? :-))))
Athlon 24-10-2011 20:37
There was a precedent for the explosion of poplar fluff in the ventilation shaft at the Cosmos Hotel. There, her employees decided to clean the ventilation clogged with fluff with a burning match.
RICHTER73 24-10-2011 21:48
Now it's all the same for a safety engineer - "turma to sit."
Wolf5862007 24-10-2011 22:10
quote: Now it's all the same for a safety engineer - "turma to sit."
why would you?
The director is responsible for everything!
in my memory, even after the deaths at the mine, not a single one was planted !! even after the explosion on Raspadskaya, only the director was removed! (although he should have been in the turma), although he himself worked on Raspadskaya for 14 years and I know that they never spared money on TV there !! and the mine is really advanced in new technologies!
Nebuchadnezzar 24-10-2011 22:37
quote: It doesn't need combustible dust to explode. ANY dust that can form a suspension in the air is explosive. At the same elevators, it’s not flour that explodes there (it explodes at flour mills), but ordinary street dust that gets from dirty grain into the air during its cleaning.
I'll enlighten you a little, an explosion is burning at a very high speed. High explosives have a detonation velocity of 5-8 km/sec. Combustion requires a fuel and an oxidizing agent, oxygen. In explosives, both the combustible substance and the oxidizer are inside the explosive, so an explosion is possible both under water (as with depth charges) and underground, oxygen is not needed. And if there is dust from the road and from the fields, this is not a combustible substance, there is a sea of oxygen, but there will be no explosion in a dusty room, there is nothing to burn. If any dust is explosive, then strict security measures would be taken at any enterprise and even in residential buildings, and only at flour mills and sugar factories, although they say this can happen at spinning mills. Ordinary dust is particles of silicon oxide minerals and aluminum does not cause an explosion.
Sensitizer 24-10-2011 22:43
quote: Originally posted by Maksim V:
The check takes place once a year
once every three years.
Sensitizer 24-10-2011 22:51
I'll enlighten you a little, an explosion is burning at a very high speed. High explosives have a detonation velocity of 5-8 km/sec.
Wrong.
And the word "explosion" is a kind of generalization, it can be physical in general - without any combustion.
URSUS 24-10-2011 23:56
Why don't bears rubbing against an axle explode? :-))))
There are many fewer of them than dust and they rub against the axis, and not against each other, in short - the concentration of bears in the bear-air mixture is small! )))
Nebuchadnezzar 24-10-2011 23:59
quote: Wrong.
Do not confuse combustion, even high speed, with detonation.
During detonation, another propagation mechanism is shock-wave.
And the word "explosion" is a kind of generalization, it can be physical in general - without any combustion.
But in this case, combustion occurs. Sugar dust is a hydrocarbon that burns quickly when dispersed in the air.
Nebuchadnezzar 25-10-2011 12:06
http://ru.wikipedia.org/wiki/%C2%E7%F0%FB%E2
"Individual explosives, as a rule, contain oxygen as part of their own molecules, moreover, their molecules are essentially metastable formations. When sufficient energy (activation energy) is imparted to such a molecule, it spontaneously dissociates into constituent atoms, from which explosion products are formed, with the release molecules of nitroglycerin, trinitrotoluene, etc. have similar properties. detonations, but they are traditionally classified as explosives. See gunpowder." In general, oxygen is contained inside the explosive, as if burning occurs inside the substance itself, in its molecules, in contrast to black powder. And how fast the burning is going on is another question, write the reaction of the explosion of nitroglycerin and you will understand everything yourself.
Sensitizer 25-10-2011 12:25
quote: Originally posted by Nebuchadnezzar:
and you will understand everything.
I don’t need to understand anything, I have a specialized education and not only education, even scientific work was on VM, but I was not always a "law enforcer"
And the reaction of an explosion (by the way, google the difference between an “explosion” and detonation) of nitroglycerin you can’t just write (do not believe a school or even a university textbook), there are about 16-18 products in different%, and there are special methods for drawing up a transformation scheme.
quote: Originally posted by Nebuchadnezzar:
True, according to Wikipedia and chemistry http://ru.wikipedia.org/wiki/%C2%E7%F0%FB%E2
Do you want to find in one note on Wikipedia everything that I was probably taught for a year in my time?
The chemical reaction itself then, in fact, proceeds stupidly between atomic oxygen and atoms of carbon, hydrogen, much less nitrogen, but the mechanism of its propagation in this case differs significantly from the mechanism of layer-by-layer combustion.
Google "Chapman-Jouguet plane", etc.
Here's to you from the Soviet classics
Shagov Yu.V. Explosives and gunpowder. - M.: Military Publishing, 1976
According to existing views, all BBs, no matter how much they differ from one another in their chemical composition and physical properties, explode in essentially the same way. An explosion occurs as a result of a sharp compression of a small part of the BB. In this case, a compression wave is formed in the explosive - a shock wave. A sharp compression may be due to the impact of a fast moving object, a strong electrical discharge, or the explosion of another BB.
With rapid and strong compression, the BB heats up, as a result, a chemical reaction occurs, accompanied by the release of a large amount of energy and the formation of gaseous products.
The resulting gaseous products produce a sharp impact on the adjacent BB layers. These layers, in turn, are compressed, a shock wave is also formed in them and an intense chemical reaction occurs.
The shock wave propagates throughout the mass of the BB at a speed equal to several kilometers per second. The speed of propagation of the shock wave in the explosive determines the speed of the explosion. The shock wave has a sharply defined front ahead, on which a strong increase in pressure and temperature occurs. Directly behind the wave front, BB is converted into gaseous products and energy is released.
The explosion products are not removed from the reaction zone, but move in the direction of the process propagation following the shock wave. Due to the release of energy in the process of a chemical reaction and its constant replenishment, the speed of propagation of a shock wave in an explosive can remain constant. Such an explosion propagation is called BB detonation, and the wave is called detonation. The detonation velocity can be defined as the speed of propagation of the shock wave through the BB charge.
Detonation is the most perfect form of explosion, when the process proceeds at a constant and maximum possible speed for a given BB. Detonation velocity is one of the most important characteristics of a BB. It can be determined experimentally.
knkd 25-10-2011 01:11
in short - the concentration of bears in the bear-air mixture is small!
Now, if the bears are activated (like coal) and sprayed ...
kuzya 25-10-2011 01:50
In this case, a completely different distribution mechanism.
URSUS 25-10-2011 18:36
Rather, the surface of contact between the bears and the air is not large enough.
Now, if the bears are activated (like coal) and sprayed ...
I strongly disagree! I will continue to insist on my point of view! The surface of contact of each particular bear with the air is very large, due to the strongly developed surface of the bear (wool). And here, there are few bears, the distances between them are great and the detonation front cannot be transmitted from bear to bear. That is not enough bears in the bear-air mixture!
MickyMouse 25-10-2011 20:17
knkd 26-10-2011 12:07
quote: Originally posted by URSUS:
I will continue to insist on my point of view! ... That is, not enough bears in the bear-air mixture!
In my opinion, the concentration of bears in the bear-air mixture is even excessive. This prevents the penetration of the oxidant between the bears, which interferes with the normal course of the redox reaction.
linkor9000 26-10-2011 07:40
it is necessary to set up an experiment to determine the upper and lower explosive limits of the bear-air mixture, otherwise nothing
URSUS 26-10-2011 23:17
quote: Originally posted by MickyMouse:
So? 282? Ban bears? :-)))
In no case!!! Sugar or flour, sawdust is not forbidden !!!)))
URSUS 26-10-2011 23:32
quote: Originally posted by knkd:
Allow me to disagree with you!
In my opinion, the concentration of bears in the bear-air mixture is even excessive. This prevents the penetration of the oxidant between the bears, which interferes with the normal course of the redox reaction.
Dear colleague! In your reflections, you forget that it was only about those bears that rub against the earth's axis. Obviously, they thereby try to initiate spontaneous detonation by the occurrence of electrostatic forces, which is quite likely in conditions of low humidity. But as you know, in those latitudes in which the earth's axis passes, the concentration of bears per unit volume is extremely small. Otherwise, the bear-air mixture could have detonated long ago and displaced, or destroyed, the earth's axis. Which would inevitably lead to a global catastrophe (by the way, such a scenario of the development of events and the BP was not at all considered in the 151st chamber).
In addition, we are considering the case of a bear-air mixture, and not a mixture of bears with ammonium nitrate, hydrazine, or another oxidizing agent. Thus, the particle sizes of the oxidizing agent can be neglected, since they are obviously less than the interbear distance. This fully confirms my hypothesis about the practical impossibility of not only spontaneous, but also initiated detonation of the bear-air mixture in the zone of localization of the earth's axis solely because of the low concentration of bears.
URSUS 26-10-2011 23:37
quote: Originally posted by linkor9000:
it is necessary to set up an experiment to determine the upper and lower explosive limits of the bear-air mixture, otherwise nothing
Considering the mass of bears at a sufficient concentration of the mixture, I must say that this will be a very dangerous experiment!
URSUS 26-10-2011 23:40
quote: Originally posted by kuzya:
Don't talk about those explosions gentlemen
In this case, a completely different distribution mechanism.Let's imagine industrial premises, any.
There are so many nooks and crannies and nooks and crannies.
That's where the dust collects.
And explosions of this nature do not occur immediately.
The initiator of such an explosion is a small "pop".
It kicks up dust in one corner, a bigger one follows, and so on. along the chain.In simple terms, a fart, then bang, then dick-a-ak, and goodbye, darling, I won’t be back soon
The explosion is voluminous, because the dust-air mixture explodes.
Such an explosion is also called an aerosol.
The worst option, there are no witnesses after it.What is the mechanism of chemical transformations...
I, even as a chemist, deeply do not care
I only see what comes after
Although there were a couple of times, but not the volume, God was merciful. The dust will dissipate, bricks and latches will stop flying ... Well, you'll swear a little ... Forty minutes
Are you talking about ordinary house dust???
URSUS 26-10-2011 23:43
quote: Originally posted by Nebuchadnezzar:
I'll enlighten you a little, an explosion is burning at a very high speed. High explosives have a detonation velocity of 5-8 km/sec. Combustion requires a fuel and an oxidizing agent, oxygen. In explosives, both the combustible substance and the oxidizer are inside the explosive, so an explosion is possible both under water (as with depth charges) and underground, oxygen is not needed. And if there is dust from the road and from the fields, this is not a combustible substance, there is a sea of oxygen, but there will be no explosion in a dusty room, there is nothing to burn. If any dust is explosive, then strict security measures would be taken at any enterprise and even in residential buildings, and only at flour mills and sugar factories, although they say this can happen at spinning mills. Ordinary dust is particles of silicon oxide minerals and aluminum does not cause an explosion.
Why is combustion and an oxidizing agent necessary? And what about explosives that do not contain oxidizing agents - with azides, acetylides, etc.?
Maxim V 27-10-2011 07:24
The check takes place once a year
once every three years.
A neighbor works at Gorgaz - an inspector comes to check on them - every year.
Another neighbor works in MUP housing and communal services - the inspection of boiler houses - annually.
My wife works in an energy company - inspectors check them - annually - in the fall.
The disadvantage of pneumatic transport of flour is the occurrence of static electricity during the operation of the installation. Electric charges accumulate and are at rest on the bodies. In the nodes of the installation and on the surface of the flour, static electricity potentials arise, reaching up to several thousand volts. Spark charges of static electricity in flour dust of a certain critical concentration can cause explosions and fires.
Electrification of dispersed systems occurs under the mechanical effects of solid particles suspended in the air flow at a high speed of aerosols, with the isolation of material pipelines from the ground and low relative humidity of the environment. The quantitative side of the electrification process is influenced by the physicochemical properties of particles of suspended matter, their size, shape, concentration, state of their surface, speed of movement, temperature, air pressure, etc.
The surface of finer dust particles absorbs oxygen more easily and they ignite more easily. At a certain concentration, mixtures of dust of various substances with air become explosive. The minimum hazardous concentration for flour dust is 20.3 g/m3. This mixture can be ignited by an electrical spark, which can result from shock, when a grounded object approaches a charged object, or for other reasons. The very phenomenon of electrification of aerosols, material pipelines, the formation of explosive mixtures, the minimum amount of energy required for an explosion, have not yet been sufficiently studied.
An explosive concentration of flour dust in the air, a large potential difference in the flour and on the details of the installation pose a danger to personnel servicing flour storage and transportation equipment.
Rice. 1. Layout of the contact surface in the flour storage tank: 1 - contact surface; 2 - fastening rods; 3 - container cover.
A number of measures have been developed to prevent explosions and fires during the operation of aerosol transport systems for warehouses for bulk storage of flour. Neutralization of static electricity charges can be achieved by ensuring that all passing flour is in contact with conductive planes and reliably grounded, which is done by connecting them to the loop ground. The jumper resistance between any point of the pneumatic conveying unit and the protective earth loop must not exceed 0.1-0.2 Ohm. It is recommended to install inclined metal contact planes in the flour container (Fig. 1). They should be located in such a way that the free entry of flour into the container is ensured, the useful volume of the container does not decrease, and the possibility of sparking when metal impurities enter is excluded. Contact planes must be made of non-ferrous conductive metals (bronze, brass, aluminum, etc.). They are attached to the top cover of a metal container for storing flour, which must be connected to a protective earth. The cone-shaped structures of the contact surface are attached to the top cover of the metal container using fixing bolts.
The flour ducts must be connected to a protective ground, and the receiving shield must have independent grounding. The supporting metal structures on which the flour storage containers rest must be securely fastened to the protective ground. For reliable grounding of containers, a conductive circuit is required between the container and the protective earth loop. This circuit is achieved by blindly connecting the protective earth loop to support structures or other conductive structures that are in hard contact with the flour storage tanks.
When containers are installed on strain gauges, each container must be independently connected to the protective earth loop using an elastic conductor.
To increase the electrical conductivity of the walls of reinforced concrete containers for storing flour, it is recommended to cover them with vinyl acetate emulsions or paint them with conductive thefts. Each section of the flour pipeline or grounded group of equipment must have at least two connections to the protective ground loop.
Cloth filaments installed on tanks, augers, rotary feeders or other equipment must be sewn with copper wire and connected to protective ground.
Conductive rubber must be used as rubber gaskets to connect flour pipelines on flanges. When using gaskets made of ordinary rubber, there must be jumpers in the places of flange connections. Jumpers between pipes should be at the installation sites of fittings, rubber or other inserts that interrupt the current-carrying network. Using inserts made of conductive rubber, jumpers can be omitted.
It is necessary to monitor the temperature in lock and screw feeders during their operation. During their normal operation, the temperature of the rubbing parts does not rise to the self-ignition temperature of flour (200 ° C). When the covers of sluice feeders are tightly tightened, increased friction occurs between the covers and the rotating rotors, which contributes to their heating. In screw feeders, an excessive increase in temperature is observed with a high pressure of the air mixture in the mixing chamber and the installation of an electric motor with a power exceeding the calculated one. The pressure in the mixing chamber is high in the initial period of operation, when the flour line is not sufficiently cleaned, plugging in the flour lines, and the flour supply line is extended compared to the calculated one.
With the advance of oil vapors and oil condensate, a dielectric crust is formed on the pipe walls, on which it is possible
accumulation of static electricity. It is necessary to clean and flush the pipelines in a timely manner and take measures to reduce the ingress of oil impurities into the air ducts.
It is forbidden to carry out welding work in containers until they are completely cleaned of flour dust. It is impossible to carry out welding work in warehouses during the operation of the flour aerosol transport system.
Before putting into operation a warehouse for bulk storage of flour, it is necessary to identify and eliminate defects in the grounding system of the aerosol transport unit and flour storage tanks. Measure all transient resistances between the equipment, pipelines and the protective ground loop; if shortcomings are identified, they must be eliminated.
Some restaurant employees, when sifting flour, are seriously afraid that if they light a match, the building will fly into the air and they will fly with it. Tales that flour can explode have been known since Soviet times. But is it true? Can flour particles floating in the air form an explosion when interacting with fire? What kind of concentration is needed for this, is it really possible in a restaurant, or is it still about the scale of a bakery? With the help of experts, we find out how things really are.
Vladimir Pigor
chief engineer of the Ust-Labinsk elevator, which is part of the Kuban agricultural holding (Basic Element)
Flour can explode. However, for an explosion to occur, the presence of oxygen, open fire and a suspension of flour is necessary. In this case, an explosion can occur only at a concentration of flour of 50 grams per cubic meter in a confined space. If the concentration of flour exceeds the specified value, then the flour will burn.
Official requirements for the storage and processing of grain and flour are enshrined in the Federal Law "Safety Rules for Explosive and Fire Hazardous Production Facilities for Storage and Processing of Vegetable Raw Materials". Naturally, we strictly observe them, explosion prevention and explosion protection equipment undergoes weekly control.
When storing flour at home, an explosion is excluded.
Tales at the factory about explosions do not go. Everyone is well aware of how terrible the consequences of an explosion can be. At the mills of the holding, photographs are placed on special stands, which depict the consequences of explosions at grain storage and processing facilities.
I remember when we were shown a mini-explosion of flour during our lab refresher course. Flour was poured into a plastic square box, at the bottom of which there is a heating coil. The lid was changed to a paper sheet, which played the role of a discharge valve (otherwise it would have torn the box). The spiral was heated to red, then turned off and air was immediately forced through a specially located tube to form a suspension of flour. Immediately there was an explosion, the paper sheet was completely burned.
Boris Bulgakov
Senior Researcher, Department of Chemical Technology and New Materials, Lomonosov Moscow State University
Flour can really be explosive if small fractions form a thick suspension in the air (for example, when sifting on a vibrating screen) and there will be a spark.
An explosion is essentially a very fast burning. For combustion, an oxidizing agent is needed, in the role of which oxygen acts, and flour can be a reducing agent as well. Since the process is heterophase, that is, a solid substance and a gas interact, the reaction rate depends on the contact area. The smaller the particles, the larger the area and the faster the reaction, so an explosion occurs.
But not only flour can explode, but also coal or wood dust, powdered sugar. In Soviet times, research was conducted on this topic, I don’t know for what purpose. But the patents that have come out in recent years are mostly about safety in coal mines.
Illustration: Nastya Grigorieva
