A mixture of natural gas with air can explode at a gas concentration in air of 5-15%.

A mixture of liquefied gas in air explodes at a concentration of 1.5-9.5%.

For an explosion, 3 conditions must be present simultaneously:

The gas-air mixture must be in a closed volume. In the open air, the mixture does not explode, but flares up.

The amount of gas in the natural mixture should be 5-15% for natural gas and 1.5-9.5% for liquefied gas. At a higher concentration, the sweep will light up and when the limit is reached, it will explode.

The mixture should be heated at one point to the flash point.

5 First aid for a victim of carbon monoxide poisoning

Symptoms:

There is muscle weakness

Dizziness

Noise in ears

Drowsiness

hallucinations

Loss of consciousness

convulsions

Assistance:

Stop the flow of carbon monoxide

Remove victim to fresh air

If the victim is conscious, lay down and provide rest and continuous access to fresh air

If there is no consciousness, it is necessary to start a closed heart massage and artificial respiration before the arrival of an ambulance or before regaining consciousness.

Ticket number 10

5 First aid for a burn victim

Thermal caused by fire, steam, hot objects and in-you. If the victim's clothes caught fire, you need to quickly throw on a coat, any dense fabric, or knock down the flame with water. You can not run in burning clothes, as the wind will fan the flames. When providing assistance in order to avoid infection, you should not touch the burned areas of the skin with your hands or lubricate with fats, oils, petroleum jelly, sprinkle with baking soda. It is necessary to apply a sterile bandage to the burnt area of ​​​​the skin. If pieces of clothing are stuck, then a bandage should follow over them, you can not tear it off.

Ticket number 11

5 Contents of the work permit for gas hazardous work.

Written permission, indicating the period of its validity, the start time of work, the end of work, their safety conditions, the composition of the team and persons responsible. for safety works. ND approved ch. engineer. List of persons entitled to issue ND approved. by order under predp. ND is issued in two copies. for one work foreman with one team; for one workplace. One copy is transferred to the manufacturer, the other remains with the person who issued the order. Accounting for ND is carried out according to the registration book; they enter: serial number, summary, position; FULL NAME. resp. guides; signature.

Ticket number 12

5 first aid to the victim of suffocation with natural gas

Remove victim to fresh air

In case of absence of consciousness and pulse on the carotid artery, proceed to the resuscitation complex

In case of loss of consciousness for more than 4 minutes - turn over on the stomach and apply cold to the head

In all cases, call an ambulance

Ticket number 13

1 classification of gas pipelines by pressure.

I- low (0-500 mm water column); (0.05 kg * s / cm 2)

II-medium (500-30,000 mm water column); (0.05-3 kg * s / cm 2)

Ticket number 14

3 requirement for lighting, ventilation and heating in hydraulic fracturing.

The need for heating the hydraulic fracturing room should be determined depending on climatic conditions.

In the premises of the GTP, natural and (or) artificial lighting and natural permanent ventilation should be provided, providing at least three air exchanges per hour.

For rooms with a volume of more than 200 m3, air exchange is carried out according to the calculation, but not less than a single air exchange in 1 hour.

The placement of equipment, gas pipelines, fittings and instruments should ensure their convenient maintenance and repair.

The width of the main passage in the premises should be at least 0.8 m.

June 3, 2011

–	Lower explosive limit	Upper explosion limit
Gasoline B-70	0,8	5,1
Tractor kerosene	1,4	7,5
Propane	2,1	9,5
n-butane	1,5	8,5
Methane	5	15
Ammonia	15	28
hydrogen sulfide	4,3	45,5
Carbon monoxide	12,5	75
Hydrogen	4	75
Acetylene	2	82

An explosion is an instantaneous chemical transformation, accompanied by the release of energy and the formation of compressed gases.

During explosions of gas-air mixtures, a large amount of heat is released and a large amount of gases is formed.

Due to the released heat, the gases are heated to a high temperature, sharply increase in volume and, expanding, press with great force on the building envelope or the walls of the apparatus in which the explosion occurs.

The pressure at the moment of explosion of gas mixtures reaches 10 kgf/cm 2 , the temperature fluctuates between 1500-2000°C, and the speed of propagation of the explosive wave reaches several hundred meters per second. Explosions tend to cause great destruction and fires.

The fire hazard properties of combustible substances are characterized by a number of indicators: flash point, ignition, self-ignition, etc.

Other properties of combustible substances include explosion pressure, the minimum explosive oxygen content, below which ignition and combustion of the mixture become impossible at any concentration of combustible substance in the mixture, the nature of interaction with fire extinguishing agents, etc.

"Occupational health and safety in gas industry»,
A.N. Yanovich, A.Ts. Astvatsaturov, A.A. Busurin

Indicators Methane Propane n-Butane Aviation gasoline Tractor kerosene Industrial oil Vapor flash point, °С —188 — —77 —34 27 200 Autoignition temperature, °С 537 600—588 490—569 300 250 380 .3-15 2.2-9.5 1.9-8.5 0.8-5.2 1.4-7.5 1-4 —(77/52) —(34/4) 27—69 146—191 Speed…

Explosive concentrations of liquefied and natural gases are formed during the shutdown of pipelines, tanks and apparatuses, when the gas is not completely removed and when it mixes with the incoming air, an explosive mixture is created. In this regard, before starting work, gas pipelines and tanks are washed with water, steamed, and purged with an inert gas. To prevent gas from other tanks or pipelines from being repaired ...

An analysis of fires that occurred at operated cluster bases of liquefied gas indicates that the main types of accidents are the following: the presence of gas leaks, ruptures in pipelines and flexible hoses, breakdowns flange connections and failures of plugs, breakdowns of stuffing box seals on shutoff valves, valves not tightly closed, destruction of liquefied gas tanks due to their overflow; various breakdowns on pipelines and tanks (destruction ...

When the gas evaporates, an explosive gas-air mixture is formed. In case of accidents in premises, explosive concentrations of gas occur first of all, near the place of gas leakage, and then spread throughout the premises. When gas evaporates in open areas near the leak, a gas contamination zone is formed that spreads throughout the warehouse. The size of the gas contamination zone during an emergency outflow of gas depends on many ...

The main difficulty in extinguishing gas fires is the fight against gas contamination and re-ignition after extinguishing a fire. No known extinguishing agent eliminates the risk of gassing and re-ignition. The main task in the fight against gas fires is the localization of the fire. It must be carried out by limiting the time of expiration and the volume of the escaping gas, as well as by thermal protection ...

General characteristics of the fuel. Compound. Heat of combustion of fuel.

Fuel are combustible substances integral part of which is carbon, used to obtain thermal energy by burning them.

As fuel use:

Natural gas extracted from gas fields;

Associated gas obtained during the development of oil fields;

Liquefied hydrocarbon gases obtained from the processing of associated oil fields and gases produced from gas condensate fields

The largest gas fields in Russia: Urengoy, Stavropol, Syzran, etc.

Natural gases are homogeneous in composition and consist mainly of methane. Associated gases from oil fields also contain ethane, propane and butane. Liquefied gases are a mixture of propane and butane, and gases obtained at oil refineries during the thermal processing of oil, in addition to propane and butane, contain ethylene, propylene and butylene.

In addition to combustible components, natural gases contain large amounts of hydrogen sulfide, oxygen, nitrogen, carbon dioxide, water vapor and mechanical impurities.

The normal operation of gas appliances depends on the constancy of the gas composition and the number harmful impurities contained in it.

According to GOST 5542-87, combustible substances of natural gases are characterized by the Wobbe number, which is the ratio of the heat of combustion to the square root of the relative (in air) gas density:

Basic properties of gases.

The specific gravity of air is 1.293 kg/m3.

Natural gas methane CH4, specific gravity 0.7 kg / m3, lighter than air by 1.85 times, so it accumulates in the upper part of the room or well.

Liquefied gas propane-butane mixture (propane С3Н8, butane С4Н10) has a specific gravity in the liquid state of 0.5 t / m3, in the gaseous state of 2.2 kg / m3.

Heating capacity.

At complete combustion one cubic meter of gas releases 8-8.5 thousand kilocalories;

Liquefied gas propane-butane 24-28 thousand kilocalories

The combustion temperature of gases is +2100 degrees C.

Natural and liquefied gases mixed with air are explosive.

Explosive limits of gas-air mixtures.

Up to 5% ignition does not occur

5% to 15% explosion occurs

Over 15% if there is a source of fire, it will ignite and burn

Sources of ignition of the gas-air mixture

● open fire (matches, cigarettes);

● Electric spark that occurs when turning on and off any electrical appliance;

● Spark generated by the friction of the tool on the workpiece gas equipment or when metal objects hit each other

natural and liquefied gases are colorless and odorless. Ethyl mercaptan, a substance that has the characteristic odor of sauerkraut, is added to make it easier to detect a gas leak.

1. The gas is colorless, tasteless and odorless. Non-poisonous, non-toxic. It has a suffocating effect, i.e. in case of leaks, it displaces oxygen from the volume of the premises.

2. Fire and explosion hazardous.

3. Approximately two times lighter than air, therefore, in case of leaks, it accumulates in the upper layers of the premises.

Air Density:rair.=1.29 kg/m 3 .

Gas Density:rgas.=0.72 kg/m 3 .

4. At a temperature of -162 ° C and atmospheric pressure(760 mmhg. Art.) natural gas turns into a liquid state.

5. The temperature developed during the combustion of gas is from +1600 to +2000 ° C.

6. Ignition temperature +645 ° C.

7. The combustion of one cubic meter of gas releases 8500 kcal of heat (calorific value of natural gas).

8. Gas explosion limits: 5% to 15% by volume.

If the concentration of gas in indoor air is less than 5% or more than 15%, there will be no explosion. There will be fire or fire. When less than 5% - there will be a lack of gas and less heat that supports combustion.

In the second case (concentration over 15%) there will be little air, i.e. oxidizer, and a small amount of heat to sustain combustion.

Basic physico-chemical concepts of explosions in blast-furnace and steel-smelting shops

Explosions in blast-furnace and open-hearth shops are caused by different reasons, but all of them are the result of a rapid transition (transformation) of a substance from one state to another, more stable, accompanied by the release of heat, gaseous products and an increase in pressure at the site of the explosion.

The main sign of an explosion is suddenness and a sharp increase in pressure in the environment surrounding the explosion site.

An external sign of an explosion is a sound, the strength of which depends on the speed of the transition of matter from one state to another. Depending on the strength of the sound, pops, explosions and detonation are distinguished. Claps are distinguished by a dull sound, a big noise or a characteristic crackle. The rate of transformations in the volume of matter during clapping does not exceed several tens of meters per second.

Explosions make a distinct sound; the rate of propagation of transformations in the bulk of the substance is much higher than with claps—several thousand meters per second.

The highest rate of transition of a substance from one state to another is obtained during detonation. This type of explosion is characterized by the simultaneous ignition of the substance in the entire volume, and instantly the largest number heat and gases and the maximum work of destruction is performed. Distinctive feature this type of explosions is the almost complete absence of a period of pressure build-up in the medium due to the enormous speed of transformations, reaching several tens of thousands of meters per second.

Explosions of gases

An explosion is a type of combustion process in which the combustion reaction proceeds violently and at high speeds.

Combustion of gases and vapors of combustible substances is possible only in a mixture with air or oxygen; the combustion time consists of two stages: the mixing of gas with air or oxygen and the actual combustion process. If the mixing of gas with air or oxygen occurs during the combustion process, then its speed is small and depends on the supply of oxygen and combustible gas to the combustion zone. If the gas and air are mixed in advance, then the combustion process of such a mixture proceeds rapidly and simultaneously in the entire volume of the mixture.

The first type of combustion, called diffusion, has become widespread in factory practice; it is used in various fireboxes, furnaces, devices where heat is used to heat materials, metals, semi-finished products or products.

The second type of combustion, when the mixture of gas with air occurs before the start of combustion, is called explosive, and mixtures are explosive. This type of combustion is rarely used in factory practice; it occurs sometimes spontaneously.

During quiet combustion, the resulting gaseous products, heated to a high temperature, freely increase in volume and give up their heat on the way from the furnace to the smoke devices.

In explosive combustion, the process proceeds "instantaneously"; completed in a fraction of a second in the entire volume of the mixture. The combustion products heated to a high temperature also “instantly” expand, form a shock wave, which spreads at high speed in all directions and causes mechanical damage.

The most dangerous are explosive mixtures that occur unexpectedly and spontaneously. Such mixtures are formed in dust collectors, gas channels, gas pipelines, burners and other gas devices ah blast furnace, open-hearth and other shops. They also form near gas devices in places where there is no air movement, and gases seep out through leaks. In such places, explosive mixtures ignite from constant or accidental sources of fire and then explosions suddenly occur, injuring people and causing great damage to production.

Explosive limits of gases

Explosions of gas-air mixtures occur only at certain concentrations of gas in air or oxygen, and each gas has its own, inherent to it alone, explosive limits - lower and upper. Between the lower and upper limits, all mixtures of gas with air or oxygen are explosive.

The lower explosive limit is characterized by the lowest gas content in the air at which the mixture begins to explode; upper - the highest content of gas in the air, above which the mixture loses its explosive properties. If the gas content in a mixture with air or oxygen is less than the lower limit or more than the upper limit, then such mixtures are not explosive.

For example, the lower explosive limit of hydrogen mixed with air is 4.1% and the upper 75% by volume. If hydrogen is less than 4.1%, then its mixture with air is not explosive; it is not explosive even if there is more than 75% hydrogen in the mixture. All mixtures of hydrogen with air become explosive if the hydrogen content in them is in the range from 4.1% to 75%.

A necessary condition for the formation of an explosion is also the ignition of the mixture. All combustible substances ignite only when they are heated to the ignition temperature, which is also a very important characteristic of any combustible substance.

For example, hydrogen in a mixture with air spontaneously ignites and an explosion occurs if the temperature of the mixture becomes greater than or equal to 510 ° C. However, it is not necessary that the entire volume of the mixture be heated to 510 ° C. An explosion will occur if at least a small amount of part of the mixture.

The process of self-ignition of the mixture from a fire source occurs in the following order. The introduction of a fire source (spark, flame of a burning tree, ejection of hot metal or slag from a furnace, etc.) into the gas-air mixture leads to heating of the particles of the mixture surrounding the fire source to the self-ignition temperature. As a result, an ignition process will occur in the adjacent layer of the mixture, heating and expansion of the layer will occur; heat is transferred to neighboring particles, they will also ignite and transfer their heat to particles located farther away, etc. In this case, self-ignition of the entire mixture occurs so quickly that one sound of popping or explosion is heard.

An indispensable condition for any combustion or explosion is that the amount of heat released is sufficient to heat the medium to the temperature of self-ignition. If there is not enough heat released, then combustion and, consequently, an explosion will not occur.

In thermal terms, the explosive limits are the limits when, during the combustion of the mixture, so little heat is released that it is not enough to heat the combustion medium to the autoignition temperature.

For example, when the hydrogen content in the mixture is less than 4.1%, so little heat is released during combustion that the medium does not heat up to a self-ignition temperature of 510 ° C. Such a mixture contains very little fuel (hydrogen) and a lot of air.

The same thing happens if the hydrogen content in the mixture is more than 75%. In such a mixture there is a lot of combustible substance (hydrogen), but very little air necessary for combustion.

If the entire gas-air mixture is heated to the self-ignition temperature, then the gas will ignite without ignition at any ratio of it with air.

In table. 1 shows the explosive limits of a number of gases and vapors, as well as their auto-ignition temperatures.

The explosive limits of gases in a mixture with air vary depending on the initial temperature of the mixture, its humidity, the power of the ignition source, etc.

Table 1. Explosive limits of some gases and vapors at a temperature of 20 ° and a pressure of 760 mm of mercury

As the temperature of the mixture rises, the explosive limits expand - the lower one decreases, and the upper one increases.

If the gas consists of several combustible gases (generator, coke, a mixture of coke and blast furnace, etc.), then the explosive limits of such mixtures are calculated using the Le Chatelier mixing rule formula:

where a is the lower or upper explosive limit of a mixture of gases with air in volume percent;

k1,k2,k3,kn is the content of gases in the mixture in volume percent;

n1,n2,n3,nn are the lower or upper explosive limits of the corresponding gases in volume percent.

Example. The gas mixture contains: hydrogen (H2) - 64%, methane (CH4) - 27.2%, carbon monoxide (CO) -6.45% and heavy hydrocarbon (propane) -2.35%, i.e. kx = 64; k2 = 27.2; k3 = 6.45 and k4 = 2.35.

Let us determine the lower and upper limits of the explosiveness of the gas mixture. In table. 1 we find the lower and upper explosive limits of hydrogen, methane, carbon monoxide and propane and substitute their values ​​into formula (1).

Lower explosive limits of gases:

n1 = 4.1%; n2 = 5.3%; n3= 12.5% ​​and n4 = 2.1%.

Lower limit an = 4.5%

Upper explosive limits of gases:

n1 = 75%; n2 = 15%; n3 = 75%; n4 = 9.5%.

Substituting these values ​​into formula (1), we find the upper limit av = 33%

The explosive limits of gases with a high content of inert non-combustible gases - carbon dioxide (CO2), nitrogen (N2) and water vapor (H20) - are conveniently found from the curves of the diagram built on the basis of experimental data (Fig. 1).

Example. Using the diagram in fig. 1, we find the explosive limits for the generator gas of the following composition: hydrogen (H2) 12.4%, carbon monoxide (CO) 27.3%, methane (CH4) 0.7%, carbon dioxide (CO2) 6.2% and nitrogen (N2) 53.4%.

Let us distribute the inert gases CO2 and N2 between the combustibles; we add carbon dioxide to hydrogen, then the total percentage of these two gases (H2 + CO2) will be 12.4 + 6.2 = 18.6%; we add nitrogen to carbon monoxide, their total percentage (CO + N2) will be 27.3 + + 53.4 = 80.7%. Methane will be taken into account separately.

Let us determine the ratio of inert gas to fuel in each sum of two gases. In a mixture of hydrogen and carbon dioxide, the ratio will be 6.2 / 12.4 \u003d 0.5, and in a mixture of carbon monoxide and nitrogen, the ratio will be 53.4 / 27.3 \u003d 1.96.

On the horizontal axis of the diagram in Fig. 1 we find the points corresponding to 0.5 and 1.96 and draw up the perpendiculars until they meet the curves (H2 + CO2) and (CO + N2).

Rice. 1. Diagram for finding the lower and upper explosive limits of combustible gases in a mixture with inert gases

The first intersection with curves will occur at points 1 and 2.

We draw horizontal straight lines from these points until they meet the vertical axis of the diagram and find: for a mixture of (H2 + CO2) the lower explosive limit an = 6%, and for a mixture of gases (CO + N2) an = 39.5%.

Continuing the perpendicular upwards, we cross the same curves at points 3 and 4. We draw horizontal lines from these points until they meet the vertical axis of the diagram and find the upper limits of the explosiveness of mixtures av, which are respectively equal to 70.6 and 73% .

According to the table 1 we find the explosive limits of methane an = 5.3% and av = 15%. Substituting the obtained upper and lower limits explosiveness of mixtures of combustible and inert gases and methane into the general formula of Le Chatelier, we find the limits of explosibility of generator gas.