CALCULATION OF THE AREA OF EASILY DISCHANGED STRUCTURES FOR ALCOHOL STORAGE

Z.R. Gainanova, student

Ufa State Aviation Technical University

The problems of preventing explosions in industrial buildings are solved during their design, when both the economic efficiency of the technological process and its safety are taken into account.

The protective effect of lightly dropped enclosing structures (LSC) is that they are destroyed in the initial stage of the explosion, when the pressure of gases - explosion products - has not yet reached a large value and is not dangerous for load-bearing structures. Through the openings, which were formed as a result of the destruction of easily dropped structures, excess volumes of gases - unburned mixture and explosion products - are displaced from the building to the outside. Due to the release of a certain part of the excess volumes of gas, the pressure and, consequently, the load on the main structures are reduced compared to the load that would occur if the same mixture exploded in a closed volume. When ensuring the explosion protection of buildings, it is necessary to strive to ensure that the overpressure does not exceed the allowable for structures. To reduce the pressure during explosions in industrial premises to values ​​that are safe for the strength and stability of the main load-bearing structures of buildings, the use of easily dropped structures allows. The scheme of pressure change during an explosion in a closed volume is shown in Figure 1.

Rice. 1. Calculation scheme of pressure change during explosion: 1 - in a closed volume;

2 - with easily dropped structures

The area of ​​LSC is determined in the following order. 1. We determine the initial data necessary for the calculation.

TV \u003d (1g + To) -0.9

TV \u003d (3216 + 293) 0.9 \u003d 3140.1 K.

The maximum degree of expansion of combustion products and the normal combustion rate, respectively, are taken from the tabular data (Appendix 3):

e = 7.5; V = 0.556 m/s.

2. Determine the estimated duration of the outflow of combustion products through the holes:

e- ^ = 7.5 2946.44 = 22098.3 m3 > ^ = 2946.44 m3,

We determine the temperature of the expiration of the explosion products:

TV + (0.8 - Shcm / ^ ohm) Tn

1.6 + (8 -2) Wcm/^ohm

t _: FZ: [adopted by the State. Duma July 4, 2008: approved. Federation Council on July 11, 2008]. - M.: Prospect, . - 144, p. - ISBN 978-5-392-01078-3.

2 SP 4.13130.2009. Set of rules. Fire protection systems. Limiting the spread of fire at protected facilities. Requirements for space planning solutions. - Input. 2009-05-01. - M.: Publishing house of standards, 2009. - 84 p.

3 Fire prevention in construction / B.V. Grushevsky [and others]; ed. Kudalenkina V.F. Higher Engineering Fire-Technical School of the Ministry of Internal Affairs of the USSR, 1985. 454 p.

3.5.2 Determining the area of ​​easily dropped structures

The calculated normal flame propagation speed is determined by the formula of the technical code:

where U n.max is the maximum normal speed of flame propagation, m/s.

The value of the lower concentration limit of flame propagation Snkp and the stoichiometric concentration Cmax in g / m 3 is determined by the formulas:

The coefficient that determines the degree of filling the volume of the room with an explosive mixture and its participation in the explosion is determined by the formula of the technical code:

where m is the mass of combustible gas or liquid vapor entering the room in emergency situations, or the amount of dust that can form an explosive mixture, kg. Determined according to [NPB 5-2005];

Z is the coefficient of participation of fuel in the explosion. Determined according to [NPB 5-2005];

C NKP - mass concentration of fuel in a combustible medium, corresponding to the lower concentration limit of flame propagation, g / m 3;

C max - mass concentration of fuel in a combustible medium, corresponding to the maximum normal flame propagation velocity U n.max, g / m 3.

The degree of filling the volume of the room with an explosive mixture is determined by the formula:

(3.17)

Estimated gas density in the explosive room before ignition

Window binding with dimensions 2110x2710 in accordance with P.A STB 939-93 Windows and balcony doors for buildings and structures will be used as LSC.

Flame volume

The volume V g.pom is determined based on the conditions:

V pl

The indicator of the intensity of explosive combustion is determined according to Table 3.2, depending on the size of the volume, occupying equipment and building structures in the volume of the room

Small equipment

Large Equipment

Accept 60% occupied by KG equipment and 40% occupied by MG equipment

The calculated degree of compression of combustion products during an explosion ε c is determined by formula (9):

where ε c.NKP is the degree of compression of combustion products during an explosion in a closed volume with a fuel concentration corresponding to the lower concentration limit of flame propagation;

ε c.max - the degree of compression of combustion products during an explosion in a closed volume of fuel concentration, which corresponds to the value of U н.max

The coefficient β μ , which takes into account the degree of filling the volume of the room with an explosive gas-air mixture, is determined by formulas (3.25-3.26) and table 3.5.

(3.26)

(3.27)

Since μ 1< μ ν <,μ 2 то β μ

. (3.28)

The coefficient taking into account the influence of the shape of an explosive room and the effect of the outflow of combustion products of an explosive vapor-air mixture K f is determined by the formula

(3.29)

if h p ≥ a p,

where a p is the length of the room, 76 m;

b p - the width of the room, 24 m;

h p - the height of the room, 3.5 m.

If μ ν ≤ 0.01, K f = 1 should be taken. For 0.01< μ ν < μ 2 величина К ф определяется линейной интерполяцией.

If the value of K f in the calculation is more than 1 or less than 0.35, then the value of the coefficient is 1 and 0.35, respectively.

This means that the minimum area of ​​easily dropped structures in the outer enclosure of the room is equal to:

(3.30)

The calculated flame propagation speed U p is determined by the formula

Since Ur is less than 65 m / s, it is possible to effectively use LSC to reduce the excess pressure in the room to a value of 5 kPa.

We accept that glass 5 mm thick is used for glazing window openings, single glazing

The design dimensions of glasses are determined by the formulas (24, 25) of this technical code:

Glass area S st is determined by the formula

The coefficient λ st is determined by the formula

. (3.35)

According to tables 4 and 5, the coefficients K SH and K λ are determined by linear interpolation:

The value of the reduced opening pressure of a double window glazing is determined by the formula

The coefficient of opening of glazing Kopen in the event of an explosion is determined according to Table 3 of this technical code by linear interpolation:

The LSC area in the outer enclosure of an explosive room when using double glazing is determined by the formula

(3.40)

In the absence of calculated data, the area of ​​easily dropped structures should be at least 0.05 m 2 per 1 m 3 of the volume of a room of category A for explosion and fire hazard and at least 0.03 m 2 - a room of category B for explosion and fire hazard p 5.6.6 TCP 45-2.02-92-2007

Table 3.5.

Pos	The name of a room	Category according to NPB 5-2005	premises, m 3	Transferable coefficient, m 3 / m 2	LSK area, m 2
3	Packing department	BUT	11753	0,05	167.9
7	Intermediate warehouse for finished products	B	5796	0.03	50
	Department of drawing up enamels	BUT	5967,36	-	414,25

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Is it reasonable for the expert's requirement, when passing the examination of project documentation, to confirm with a fire test report or fire certificate, explosion calculation, the use in the project of easily drop structures performed in accordance with GOST R 56288-2014

🔥LSC calculation example https://morozofkk.ru/?newsid=3299

At the moment, when designing, building, overhauling, reconstructing, technical re-equipment, changing the functional purpose of protection objects (territories, buildings, structures, outdoor installations, engineering systems, fire protection systems), the following are used:

Federal Law of July 22, 2008 N 123-FZ "Technical Regulations on Fire Safety Requirements" (as amended on July 3, 2016);

Regulatory documents included in the List of documents in the field of standardization, as a result of which, on a voluntary basis, compliance with the requirements of the Federal Law of July 22, 2008 N 123-FZ "Technical Regulations on Fire Safety Requirements" is ensured, approved by Order of Rosstandart of April 16, 2014 N 474 (as amended on February 25, 2016);

Regulatory documents included in the List of National Standards containing the rules and methods of research (testing) and measurements, including the sampling rules necessary for the application and execution of the Federal Law "Technical Regulations on Fire Safety Requirements" and the implementation of conformity assessment, approved by the Government RF dated March 10, 2009 N 304-r (as amended on June 11, 2015).

Currently, fire safety regulations include:

SP 4.13130.2013 "Fire protection systems. Limiting the spread of fire at protected facilities. Requirements for space-planning and design solutions" (as amended on July 18, 2013);

Explosion resistance of an object: the state of an object in which there is no possibility of damage to load-bearing building structures and equipment, injury to people by dangerous explosion factors, which can be achieved by relieving pressure (explosion energy) into the atmosphere to a safe level as a result of opening openings in the building envelope, blocked by safety anti-explosion devices (glazing, special windows or easily dropped structures) (clause 3.11 of SP 4.13130.2013).

Depressurization as a method of explosion protection: the most common method of fire and explosion protection of closed equipment and premises, which consists in equipping them with safety membranes and (or) other depressurizing devices with such a discharge section area that is sufficient to prevent the destruction of equipment or premises from an increase in excess pressure during combustion combustible mixtures (clause 3.23 GOST R 12.3.047-2012).

Safety anti-explosion device: a device in the form of special windows, glazing or easy-to-reset structures that open, at an early stage of the explosion of gas, steam, dust-air mixtures, discharge openings in the enclosing structures of the building and provide safe pressure inside the building (premises) and in the surrounding space (p. 3.30 SP 4.13130.2013).

In accordance with clause 4.16 of SP 4.13130.2013, at facilities of the functional fire hazard class F5 that are not explosion-proof, ensuring the explosion resistance of buildings and surrounding buildings in the event of an explosion of a gas, vapor, dust-air mixture must be accompanied by a calculation of loads depending on the parameters of the mixture, space-planning solution of the building, the presence of equipment in it, building structures (columns, trusses, cutting floors, partitions, etc.), characteristics of doors, characteristics of glazing and easily dropped structures.

At objects that are not explosion-proof, windows or other structures should be used that perform the function of a safety anti-explosion device that provides safe loads (5 kPa) in the event of an explosion of a gas, vapor, dust-air mixture.

In accordance with paragraph 6.2.5 of SP 4.13130.2013, in the premises of categories A and B, external easily dropped enclosing structures are provided.

Glazing of windows and lanterns is used as easy-to-reset structures. With insufficient glazing area, it is allowed to use coating structures made of steel, aluminum and asbestos-cement sheets and effective insulation as easy-to-reset structures. The area of ​​easily dropped structures is determined by calculation. In the absence of design data, the area of ​​easily dropped structures should be at least 0.05 m2 per 1 m3 of the volume of a room of category A and at least 0.03 m2 of a room of category B.

Window glass refers to easy-to-reset structures with a thickness of 3, 4 and 5 mm and an area of ​​at least (respectively) 0.8, 1 and 1.5 m2.

Armored glass does not apply to easily dropped structures.

The rolled carpet in areas of easy-to-reset coating structures is cut into cards with an area of ​​​​not more than 180 m2 each.

The calculated load from the mass of easily dropped pavement structures should be no more than 0.7 kPa (70 kgf / m2).

In accordance with clause 6.9.16 of SP 4.13130.2013, when using fuel capable of forming gas-, steam-, dust-air explosive mixtures, easy-drop enclosing structures should be provided in the fuel supply rooms, the area of ​​\u200b\u200bwhich is determined by calculation in accordance with GOST R 12.3.047, in the absence calculated data, the area of ​​easily dropped structures should be at least 0.05 m2 per 1 m3 of category A premises and at least 0.03 m2 - category B premises.

Window panes in buildings and fuel supply rooms should be provided as single panes and located in the same plane with the inner surface of the walls.

Calculations of the areas of easily dropped structures can be carried out on the basis of:

GOST R 12.3.047-2012 "National standard of the Russian Federation. System of labor safety standards. Fire safety of technological processes. General requirements. Control methods";

GOST 12.1.004-91 "Interstate standard. System of labor safety standards. Fire safety. General requirements" (as amended on 01.10.1993).

In accordance with clause 4.13 of GOST R 12.3.047-2012, measures to reduce the consequences of a fire or explosion should include the use of devices that reduce the pressure in the apparatus to a safe value during the combustion of gas, vapor and dust-air mixtures (Appendix H).

Annex "N" GOST R 12.3.047-2012 establishes a method for determining the required safe depressurization area for equipment and premises.

The method for determining the safe area of ​​equipment depressurization is also given in Appendix N 8 GOST 12.1.004-91.

At the moment, GOST R 56288-2014 "Window structures with double-glazed windows, easily dropped for buildings. Specifications" does not apply to regulatory documents on fire safety, since it does not include:

In the List of documents in the field of standardization, as a result of which, on a voluntary basis, compliance with the requirements of the Federal Law of July 22, 2008 N 123-FZ "Technical Regulations on Fire Safety Requirements" is ensured, approved by Order of Rosstandart of April 16, 2014 N 474 (as amended by February 25, 2016);

To the List of national standards containing the rules and methods of research (testing) and measurements, including the sampling rules necessary for the application and execution of the Federal Law "Technical Regulations on Fire Safety Requirements" and the implementation of conformity assessment, approved by order of the Government of the Russian Federation of March 10 2009 N 304-r (as amended on 06/11/2015).

At the moment, in accordance with Part 1 of Article 6 of the Federal Law of July 22, 2008 N 123-FZ "Technical Regulations on Fire Safety Requirements" (as amended on July 3, 2016), the fire safety of the protected object is considered to be ensured when one of the following is performed conditions:

1) the fire safety requirements established by the technical regulations adopted in accordance with the Federal Law "On Technical Regulation" are fully met, and the fire risk does not exceed the permissible values ​​established by this Federal Law;

2) the fire safety requirements established by the technical regulations adopted in accordance with the Federal Law "On Technical Regulation" and fire safety regulations are fully met.

Accordingly, at the moment, the requirements for easily dropped structures are established precisely in clause 4.16, clause 6.2.5, clause 6.9.16 of SP 4.13130.2013.

Calculations of the areas of easily dropped structures are carried out precisely on the basis of GOST R 12.3.047-2012 and GOST 12.1.004-91.

In the absence of design data, the area of ​​easily dropped structures should be at least 0.05 m2 per 1 m3 of the volume of category A premises and at least 0.03 m2 - category B premises.

The required area of ​​easily dropped elements of external enclosing structures per 1 m 3 of the volume of the room ( TO, m 2 / m 3) should be determined by the formula:

where TO indicated when determining the area: horizontal elements - TO d, vertical elements - TO c, sheet window glass - TO st; G- the normal burning rate of an explosive mixture, m / s, taken according to Table. eighteen; E R - calculated degree of expansion of combustion products; R R- the impact of the explosion on easily discharged elements: horizontal - , vertical - , window sheet glass
;R about- atmospheric pressure equal to 104 kgf / m 2; P- the volume of the room, m 3, determined within the internal surfaces of the enclosing structures (without deducting the volume of equipment and load-bearing structures - columns, beams, girders, pilasters, etc.).

Easily dropped elements of external enclosing structures, the surface of which deviates from the vertical by no more than 15º, are classified as vertical, with a greater deviation from the vertical - as horizontal.

In buildings with natural light (with windows, light or light-aeration lamps), sheet glass should be used first of all as easily dropped elements of external enclosing structures.

Estimated degree of expansion of combustion products E R should be determined by the formula:

, (8.2)

where E- the maximum degree of expansion of combustion products, taken according to table. 8.1; but- coefficient of filling the volume of the room with an explosive mixture, taken according to Table. 8.2, depending on the volume of the explosive mixture IN, m 3, determined by the formula:

B = E/ C, (8.3)

where E - the amount of substances entering the room, g; FROM- stoichiometric concentration of an explosive mixture, g / m 3, taken according to table. 8.1.

The impact of the explosion on horizontal easy-to-reset elements (except for sheet glass) of external enclosing structures (

where R g - the impact of an explosion on a horizontal surface, kgf / m 2, determined by adj. 1, and at normal burning rates ( G), not provided for in App. 1 is determined by the formula:

where G, D And P- the same as in formula 8.1 and adj. one; F- the area of ​​​​an easily dropped element of the enclosing structure, m 2, taken according to the drawings, and for elements with an area of ​​\u200b\u200bless than 1 m 2 - conditionally equal to 1 m 2.

Table 8.1

Characteristics of explosive substances

Substance name		The stoichiometric concentration of an explosive mixture ( FROM), g/m 3	The maximum degree of expansion of combustion products ( E)	The normal burning rate of an explosive mixture ( G), m/s
	Acetylene
	Diisopropyl
	Diethylene ether
	Isobutane
	Isobutylene
	Isooctane
	Isopropyl alcohol
	Methyl alcohol
	Ethylene oxide
	Propylene
	Cyclohexane
	Ethanol
* The degree of expansion is taken approximately equal to 8.
Note. Characteristics of substances not listed in Table. 8.1 should be taken from official reference books or data from ministries and departments.

Impact of an explosion on a horizontal surface ( R d) at a given value of the normal burning rate of an explosive mixture ( G) in the range from 0.3 to 1 m / s, but different from the indicated rounded values ​​\u200b\u200bof this speed in the drawings adj. 1 is determined by interpolation of the explosion impact values ​​obtained from the drawings for the two closest (to the given) rounded values ​​of the normal burning rate of an explosive mixture.

Table 8.2

The coefficients of filling the volume of the room with an explosive mixture

	The coefficients of filling the volume of the room with an explosive mixture ( but) at the maximum degree of expansion of combustion products ( E)

The impact of the explosion on vertical easy-to-reset elements (except for sheet glass) of external enclosing structures ( , kgf / m 2) is determined by the formula:

where R d and F- the same as in formula (8.4).

The impact of the explosion on sheet window glass (
, kgf / m 2) is determined regardless of the location of the glass in space (vertical, horizontal, inclined) by the formula:

, (8.7)

where R st - explosion impact, kgf / m 2, destroying sheet window glass (with double glazing) with a glass sheet aspect ratio of 1: 1 and taken according to table. 8.3, At- coefficient of working conditions, taken according to table. 8.4.

Table 8.3

Explosion impact breaking glass

Glass thickness, mm	The impact of the explosion, destroying glass, kgf / m 2, with the area of ​​\u200b\u200bone sheet F, m 2

Table 8.4

The value of the coefficient of working conditions

Notes: 1. The area of ​​one sheet of glass, taken as an easily dropped element, with a thickness of 3.4 and 5 mm must be at least 0.8, 1 and 1.5 m 2, respectively.

2. The impact of the explosion, destroying sheet window glass with single glazing, should be taken equal to 0.85 R Art.

The total area of ​​glazing (window sheet glass in windows and skylights)
, m 2, should be determined by the formula:

, (8.8)

where TO st - according to the formula (8.1); P- the same as in formula (8.1).

If the project cannot provide for the fully required glazing area, determined by formula (8.8), it is necessary to provide additionally horizontal (in the coating) or vertical (in the walls) easily dropped elements of external enclosing structures, the area of ​​\u200b\u200bwhich, respectively, or , m 2, should be determined by the formulas:

, (8.9)

, (8.10)

where
- according to the formula (8.8);
- glazing area in the enclosing structures provided for by the project, m 2. TO G, TO in and TO st by formula (8.1).

In buildings without natural light (without windows and lanterns), the area of ​​easily dropped elements of external enclosing structures - horizontal
or vertical
- is determined depending on the structural solution of the building according to the formulas (8.8, 8.9 and 8.10) with the corresponding replacement of the values ​​in them
,
And TO Art.