Hydraulic calculation is the most difficult stage in creating an AUGPT. It is necessary to select the diameters of the pipelines, the number of nozzles and the outlet cross-sectional area, and calculate real time GOTV output.
How will we count?
First you need to decide where to get the methodology and formulas for hydraulic calculations. We open the set of rules SP 5.13130.2009, Appendix G and see there only the method for calculating carbon dioxide fire extinguishing low pressure, and where is the methodology for other gaseous fire extinguishing agents? We look at paragraph 8.4.2 and see: “For other installations, it is recommended to carry out calculations using methods agreed upon in the prescribed manner.”
Calculation programs
Let's turn to equipment manufacturers for help gas fire extinguishing. In Russia, there are two methods for hydraulic calculations. One developed and copied many times by leading Russian manufacturers equipment and approved by VNIIPO, on its basis created software"VALUE", "Salute". The other was developed by the TACT company and approved by the DND of the Ministry of Emergency Situations, on its basis the TACT-gaz software was created.
The techniques are closed to most design engineers and serve to internal use manufacturers automatic installations gas fire extinguishing. If you agree, they will show it to you, but without special knowledge and experience it will be difficult to perform hydraulic calculations.
E.1 The estimated mass of GFFS, which must be stored in the installation, is determined by the formula
where is the mass of fire extinguishing agent intended to create a fire extinguishing concentration in the volume of the room in the absence of artificial air ventilation, determined by the formulas:
For GOTV - liquefied gases, excluding carbon dioxide:
For GFFS - compressed gases and carbon dioxide
here - the calculated volume of the protected room, m. The calculated volume of the room includes its internal geometric volume, including the volume of the ventilation, air conditioning, air heating system (up to sealed valves or dampers). The volume of equipment located in the room is not deducted from it, with the exception of the volume of solid (impenetrable) building elements (columns, beams, foundations for equipment, etc.);
Coefficient taking into account leaks of gas extinguishing agent from vessels;
A coefficient that takes into account the loss of gas extinguishing agent through room openings;
Gas density fire extinguishing agent taking into account the height of the protected object relative to sea level for the minimum room temperature, kg/m, determined by the formula
here is the vapor density of the gas fire extinguishing agent at a temperature of 293 K (20 °C) and an atmospheric pressure of 101.3 kPa;
Minimum air temperature in the protected room, K;
A correction factor that takes into account the height of the object relative to sea level, the values of which are given in Table E.11 of Appendix E;
Standard volume concentration, % (vol.).
The values of standard fire extinguishing concentrations are given in Appendix D.
The mass of GFFS residue in pipelines, kg, is determined by the formula
where is the volume of the entire piping of the installation, m;
The density of the residual fire extinguishing agent at the pressure that exists in the pipeline after the end of the flow of the mass of gaseous fire extinguishing agent into the protected room;
The product of the remaining GFFS in the module, which is accepted according to the TD per module, kg, by the number of modules in the installation.
Note - For liquid flammable substances not listed in Appendix E, the standard volumetric fire extinguishing concentration of GFFS, all components of which are in the gas phase under normal conditions, can be determined as the product of the minimum volumetric fire extinguishing concentration by a safety factor equal to 1.2 for all GFFS , with the exception of carbon dioxide. For SO, the safety factor is 1.7.
For GFFS that are in the liquid phase under normal conditions, as well as mixtures of GFFS, at least one of the components of which is in the liquid phase under normal conditions, the standard fire extinguishing concentration is determined by multiplying the volumetric fire extinguishing concentration by a safety factor of 1.2.
Methods for determining the minimum volumetric fire extinguishing concentration and fire extinguishing concentration are set out in GOST R 53280.3.
E.2 The coefficients of equation (E.1) are determined as follows.
E.2.1 Coefficient taking into account leaks of gas extinguishing agent from vessels 1.05.
E.2.2 Coefficient taking into account the loss of gas extinguishing agent through room openings:
where is a parameter that takes into account the location of openings along the height of the protected room, m s.
The numerical values of the parameter are selected as follows:
0.65 - when openings are located simultaneously in the lower (0-0.2) and upper zones of the room (0.8-1.0) or simultaneously on the ceiling and floor of the room, and the areas of the openings in the lower and upper parts are approximately equal and constitute half of the total area of the openings; 0.1 - when the openings are located only in the upper zone (0.8-1.0) of the protected room (or on the ceiling); 0.25 - when the openings are located only in the lower zone (0-0, 2) the protected room (or on the floor); 0.4 - with an approximately uniform distribution of the area of openings over the entire height of the protected room and in all other cases;
Room leakage parameter, m,
where is the total area of openings, m;
Room height, m;
Standard time for supplying GFFS to the protected premises, s.
E.3 Extinguishing fires of subclass A (except for smoldering materials specified in 8.1.1) should be carried out in rooms with a leakage parameter of no more than 0.001 m.
The mass value for extinguishing fires of subclass A is determined by the formula
where is the mass value for the standard volumetric concentration when extinguishing n-heptane, calculated using formulas (2) or (3);
A coefficient that takes into account the type of combustible material.
The coefficient values are taken equal to: 1.3 - for extinguishing paper, corrugated paper, cardboard, fabrics, etc. in bales, rolls or folders; 2.25 - for premises with the same materials, to which access for firefighters after the end of the AUGP operation is excluded. For other fires of subclass A, except those specified in 8.1.1, the value is assumed to be 1.2.
In this case, it is allowed to increase the standard time for supplying GFFS by a factor.
If the estimated quantity of GFFS is determined using a factor of 2.25, the GFFS reserve can be reduced and determined by calculation using a factor of 1.3.
You should not open the protected room to which access is permitted, or break its tightness in any other way within 20 minutes after the activation of the AUGP (or until the fire department arrives).
Appendix G
Methodology for calculating the mass of gaseous fire extinguishing agent for mouthsnew gas fire extinguishing technology for extinguishing by volumetric method
1. The estimated mass of GFFS, which must be stored in the installation, is determined by the formula
Where 
- the mass of fire extinguishing agent intended to create a fire extinguishing concentration in the volume of the room in the absence of artificial air ventilation is determined by the formulas:
for GFFS - liquefied gases, with the exception of carbon dioxide
;
(2)
for GOTV - compressed gases and carbon dioxide
,
(3)
Where 
- estimated volume of the protected room, m3.
The calculated volume of the room includes its internal geometric volume, including the volume of the ventilation, air conditioning, and air heating systems (up to sealed valves or dampers). The volume of equipment located in the room is not deducted from it, with the exception of the volume of solid (impenetrable) building elements (columns, beams, foundations for equipment, etc.);
- coefficient taking into account leakage of gas extinguishing agent from vessels; 
- coefficient taking into account the loss of gas extinguishing agent through room openings; 
- density of the gas extinguishing agent, taking into account the height of the protected object relative to sea level for the minimum room temperature 
,
kg m -3, determined by the formula
,
(4)
Where 
- vapor density of gas extinguishing agent at temperature 
= 293 K (20 С) and atmospheric pressure 101.3 kPa; 
- minimum temperature air in the protected room, K; 
- correction factor taking into account the height of the object relative to sea level, the values of which are given in Table 11 of Appendix 5; 
- standard volume concentration, % (vol.).
The values of standard fire extinguishing concentrations () are given in Appendix 5.
Weight of GFFS residue in pipelines 
, kg, determined by the formula
,
(5)
where is the volume of the entire piping of the installation, m 3 ; 
- density of the fire extinguishing agent residue at the pressure that exists in the pipeline after the end of the flow of the mass of gaseous fire extinguishing agent into the protected room.
- product of the remainder of the GFFS in the module ( M b), which is accepted according to the TD per module, kg, per number of modules in the installation 
.
Note. For liquid flammable substances not listed in Appendix 5, the standard volumetric fire extinguishing concentration of GFFS, all components of which are in the gas phase under normal conditions, can be determined as the product of the minimum volumetric fire extinguishing concentration by a safety factor equal to 1.2 for all GFFS, for except for carbon dioxide. For CO 2 the safety factor is 1.7.
For GFFS that are in the liquid phase under normal conditions, as well as mixtures of GFFS, at least one of the components of which is in the liquid phase under normal conditions, the standard fire extinguishing concentration is determined by multiplying the volumetric fire extinguishing concentration by a safety factor of 1.2.
Methods for determining the minimum volumetric fire extinguishing concentration and fire extinguishing concentration are set out in NPB 51-96 *.
1.1. The coefficients of equation (1) are determined as follows.
1.1.1. Coefficient taking into account leaks of gas extinguishing agent from vessels:
.
1.1.2. Coefficient taking into account the loss of gas extinguishing agent through room openings:
,
(6)
Where 
- parameter that takes into account the location of openings along the height of the protected room, m 0.5 s -1.
The numerical values of the parameter are selected as follows:
0.65 - when openings are located simultaneously at the bottom (0 - 0.2) 
and the upper zone of the room (0.8 - 1.0) or simultaneously on the ceiling and on the floor of the room, and the areas of the openings in the lower and upper parts are approximately equal and constitute half of the total area of the openings; = 0.1 - when openings are located only in the upper zone (0.8 - 1.0) of the protected room (or on the ceiling); = 0.25 - when openings are located only in the lower zone (0 - 0.2) of the protected room (or on the floor); = 0.4 - with an approximately uniform distribution of the area of openings over the entire height of the protected room and in all other cases.
- room leakage parameter, m -1,
Where 
- total area of openings, m2.
Room height, m; 
- standard time for supplying GFFS to the protected premises.
1.1.3. Extinguishing fires of subclass A 1 (except for smoldering materials specified in clause 7.1) should be carried out in rooms with a leakage parameter of no more than 0.001 m -1.
The value of mass M p for extinguishing fires of subclass A 1 is determined by the formula
M p = K 4. M r-hept,
where M p-hept is the value of the mass M p for the standard volumetric concentration of CH when extinguishing n-heptane, calculated using formulas 2 or 3;
K 4 is a coefficient that takes into account the type of combustible material. The values of the K 4 coefficient are taken equal to: 1.3 – for extinguishing paper, corrugated paper, cardboard, fabrics, etc. in bales, rolls or folders; 2.25 - for premises with the same materials, to which access of firefighters is excluded after the end of the AUGP operation, while the reserve stock is calculated at a K 4 value equal to 1.3.
The supply time of the main stock of GFFS at a K 4 value of 2.25 can be increased by 2.25 times. For other fires of subclass A 1, the value of K 4 is taken equal to 1.2.
You should not open the protected room or break its tightness in any other way for at least 20 minutes (or until the fire department arrives).
When opening premises, primary fire extinguishing means must be available.
For premises in which access to fire departments is excluded after the end of the AUGP operation, CO 2 should be used as a fire extinguishing agent with a coefficient of 2.25.
1. Average pressure in an isothermal tank during the supply of carbon dioxide 
,MPa, is determined by the formula
,
(1)
Where 
- pressure in the tank during carbon dioxide storage, MPa; 
- pressure in the tank at the end of the release of the estimated amount of carbon dioxide, MPa, is determined according to Figure 1.
2. Average carbon dioxide consumption 
,
(2)
Where 
- estimated amount of carbon dioxide, kg; 
- standard carbon dioxide supply time, s.
3. The internal diameter of the supply (main) pipeline, m, is determined by the formula
Where k 4 - multiplier, determined according to table 1; l 1 - length of the supply (main) pipeline according to the project, m.
Table 1
|
Factor k 4 |
4. Average pressure in the supply (main) pipeline at the point of its entry into the protected room
,
(4)
Where l 2 - equivalent length of pipelines from the isothermal tank to the point at which the pressure is determined, m:
,
(5)
Where 
- the sum of the resistance coefficients of pipeline fittings.
5. Medium pressure
,
(6)
Where R 3 - pressure at the point of entry of the supply (main) pipeline into the protected room, MPa; R 4 - pressure at the end of the supply (main) pipeline, MPa.
6. Average flow rate through nozzles Q m, kg s -1, determined by the formula
Where 
- coefficient of flow through the nozzles; A 3
- area of the nozzle outlet, m2; k 5
- coefficient determined by the formula
. (8)
7. Number of nozzles 
determined by the formula
.
8. Inner diameter of distribution pipeline 
, m, is calculated from the condition
,
(9)
Where 
- diameter of the nozzle outlet, m.
R 
R 1 =2,4
Figure 1. Graph for determining pressure in isothermal
reservoir at the end of the release of the calculated amount of carbon dioxide
Note. Relative mass of carbon dioxide 
determined by the formula
,
Where 
- initial mass of carbon dioxide, kg.
Appendix 7
Methodology for calculating the opening area for releasing excess pressure in rooms protected by gas fire extinguishing installations
Opening area for releasing excess pressure 
, m 2, is determined by the formula
,
Where 
- maximum permissible excess pressure, which is determined from the condition of maintaining the strength of the building structures of the protected premises or the equipment placed in it, MPa; 
- atmospheric pressure, MPa; 
- air density under operating conditions of the protected premises, kg m -3;
-
safety factor taken equal to 1.2; 
- coefficient taking into account the change in pressure when it is supplied; 
- time of supply of GFFS, determined from hydraulic calculation, s; 
- area of permanently open openings (except for the discharge opening) in the enclosing structures of the room, m2.
Values 
,
, are determined in accordance with Appendix 6.
For GOTV - liquefied gases the coefficient TO 3 =1.
For GOTV - compressed gases the coefficient TO 3 is taken equal to:
for nitrogen - 2.4;
for argon - 2.66;
for the Inergen composition - 2.44.
If the value of the expression on the right side of the inequality is less than or equal to zero, then an opening (device) for relieving excess pressure is not required.
Note. The opening area value was calculated without taking into account the cooling effect of liquefied gas, which may lead to a slight reduction in the opening area.
General provisions for the calculation of modular type powder fire extinguishing installations.
1. The initial data for the calculation and design of installations are:
geometric dimensions of the room (volume, area of enclosing structures, height);
area of open openings in enclosing structures;
operating temperature, pressure and humidity in the protected area;
list of substances, materials located in the room, and their indicators fire danger, the corresponding fire class according to GOST 27331;
type, magnitude and fire load distribution scheme;
availability and characteristics of ventilation, air conditioning, air heating systems;
characteristics and arrangement of technological equipment;
the presence of people and their evacuation routes.
technical documentation for modules.
2. Installation calculation includes determining:
number of modules intended for fire extinguishing;
evacuation times, if any;
installation operating time;
the necessary supply of powder, modules, components;
type and required quantity detectors (if necessary) to ensure the operation of the installation, signaling and triggering devices, power supplies to start the installation (for cases according to clause 8.5).
Methodology for calculating the number of modules for modular powder fire extinguishing installations
1. Extinguishing the protected volume
1.1. Extinguishing the entire protected volume
The number of modules to protect the volume of the room is determined by the formula
, (1)
Where 
-
number of modules required to protect the premises, pcs.; 
- volume of the protected room, m 3 ; 
- the volume protected by one module of the selected type is determined by technical documentation(hereinafter referred to as the documentation application) per module, m 3 (taking into account the spray geometry - the shape and dimensions of the protected volume declared by the manufacturer); 
=
11.2 - coefficient of unevenness of powder spraying. When placing spray nozzles on the border of the maximum permissible (according to the documentation for the module) height To 
=
1.2 or determined from the documentation for the module.
- safety factor taking into account the shading of a possible source of fire, depending on the ratio of the area shaded by the equipment 
,
to the protected area S y, and is defined as:
at 
,
Shading area is defined as the area of the part of the protected area where the formation of a source of fire is possible, to which the movement of the powder from the spray nozzle in a straight line is blocked by structural elements impenetrable to the powder.
At 
It is recommended to install additional modules directly in a shaded area or in a position that eliminates shading; if this condition is met k 
is taken equal to 1.
-
coefficient that takes into account the change in the fire extinguishing efficiency of the powder used in relation to the flammable substance in the protected area in comparison with A-76 gasoline. Determined from Table 1. In the absence of data, determined experimentally using VNIIPO methods.
- coefficient taking into account the degree of leakage of the room. = 1 + V
F neg
,
Where F neg = F/F pom- ratio of the total leakage area (openings, cracks) F to the general surface of the room F pom, coefficient IN determined according to Figure 1.
IN
20
Fн/ F , Fв/ F
Figure 1 Graph for determining coefficient B when calculating the coefficient.
F n- area of leakage in the lower part of the room; F V- area of leakage in the upper part of the room, F - total area of leakage (openings, cracks).
For pulse fire extinguishing installations, the coefficient IN can be determined from the documentation for the modules.
1.2. Local fire extinguishing by volume
The calculation is carried out in the same way as when extinguishing throughout the entire volume, taking into account paragraphs. 8.12-8.14. Local volume V n, protected by one module, is determined according to the documentation for the modules (taking into account the spray geometry - the shape and dimensions of the local protected volume declared by the manufacturer), and the protected volume V h is defined as the volume of an object increased by 15%.
For local fire extinguishing by volume it is taken =1.3, it is allowed to take other values given in the documentation for the module.
2. Fire extinguishing by area
2.1. Extinguishing over the entire area
The number of modules required for fire extinguishing over the area of the protected premises is determined by the formula
- the local area protected by one module is determined according to the documentation for the module (taking into account the spray geometry - the shape and size of the local protected area declared by the manufacturer), and the protected area
is defined as the area of the object increased by 10%. For local extinguishing over an area, =1.3 is taken, other values are allowed To 4 given in the documentation for the module or justified in the project.
As S n the area of the maximum rank of a class B fire, the extinguishing of which is provided by this module, can be taken (determined according to the documentation for the module, m 2).
Note. If the number of modules of fractional numbers is obtained when calculating the number of modules, the next larger integer in order is taken as the final number.
When protecting by area, taking into account the design and technological features of the protected object (with justification in the design), it is allowed to launch modules using algorithms that provide area-by-area protection. In this case, the protected area is taken to be part of the area allocated by design (driveways, etc.) or structural non-combustible (walls, partitions, etc.) solutions. The operation of the installation must ensure that the fire does not spread beyond the protected area, calculated taking into account the inertia of the installation and the speed of fire spread (for a specific type of combustible materials).
Table 1.
Coefficient comparative effectiveness of fire extinguishing agents
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Currently, gas fire extinguishing is an effective, environmentally friendly and universal method of fighting fire at the early stage of a fire.
Calculation of installation of gas fire extinguishing systems is found wide application at facilities where it is undesirable to use other fire fighting systems - powder, water, etc.
Such objects include premises with electrical equipment, archives, museums, exhibition halls, warehouses with explosive substances located there, etc.
Gas fire extinguishing and its undeniable advantages
In the world, including Russia, gas fire extinguishing has become one of the widely used methods of eliminating the source of fire due to a number of undeniable advantages:
- minimization negative influence on the environment due to the release of gases;
- ease of removing gases from the room;
- precise distribution of gas over the entire area of the room;
- non-damage to property, valuables and equipment;
- functioning over a wide temperature range.
Why is a gas fire extinguishing calculation necessary?
To select a particular installation for a room or facility, a clear calculation of gas fire extinguishing is required. Thus, a distinction is made between centralized and modular complexes. The choice of one type or another depends on the number of premises that need to be protected from fire, the area of the facility and its type.
Taking these parameters into account, gas fire extinguishing is calculated, with mandatory consideration of the mass of gas required to eliminate the source of fire in certain area. For such calculations we use special techniques, taking into account the type of fire extinguishing agent, the area of the entire room and the type of fire-fighting installation.
For calculations, the following parameters must be taken into account:
- room area (length, ceiling height, width);
- object type (archive, server rooms, etc.);
- the presence of open openings;
- type of flammable substances;
- fire hazard class;
- degree of distance of the security console from the premises.
The need to calculate gas fire extinguishing
Fire extinguishing calculations – preliminary stage before installing a gas fire extinguishing system on site. To ensure the safety of people and the safety of property, it is necessary to carry out a clear calculation of the equipment.
The validity of the calculation of gas fire extinguishing and subsequent installation at the facility is determined regulatory documentation. The use of this system in server rooms, archives, museums and data centers is mandatory. In addition, such installations are installed in car parks closed type, in repair shops, warehouse-type premises. The calculation of fire extinguishing directly depends on the size of the room and the type of goods stored in it.
The undeniable advantage of gas fire extinguishing over powder or water installations is its lightning-fast response and operation in the event of a fire, while objects or materials in the room are reliably protected from the negative effects of fire extinguishing agents.
At the design stage, the amount of fire extinguishing agent required to extinguish the fire is calculated. The further functioning of the complex depends on this stage.
Firefighting
SELECTION AND CALCULATION OF GAS FIRE FIGHTING SYSTEM
A. V. Merkulov, V. A. Merkulov
CJSC "Artsok"
The main factors influencing optimal choice gas fire extinguishing installations (GFP): type of flammable load in the protected premises (archives, storage facilities, radio-electronic equipment, technological equipment etc.); the size of the protected volume and its leakage; type of gas fire extinguishing agent (GOTV); the type of equipment in which GFFS should be stored, and the type of UGP: centralized or modular.
The correct choice of gas fire extinguishing installation (GFP) depends on many factors. Therefore, the purpose of this work is to identify the main criteria that influence the optimal choice of gas fire extinguishing installation and the principle of its hydraulic calculation.
The main factors influencing the optimal choice of gas fire extinguishing installation. Firstly, the type of flammable load in the protected premises (archives, storage facilities, radio-electronic equipment, technological equipment, etc.). Secondly, the size of the protected volume and its leakage. Thirdly, the type of gas fire extinguishing agent. Fourth, the type of equipment in which the gas extinguishing agent should be stored. Fifthly, the type of gas fire extinguishing installation: centralized or modular. The last factor can only occur if there is a need for fire protection of two or more premises at one facility. Therefore, we will consider the mutual influence of only the four factors listed above, i.e. on the assumption that the facility requires fire protection for only one room.
Certainly, right choice gas fire extinguishing installations should be based on optimal technical and economic indicators.
It should be especially noted that any of the gas fire extinguishing agents approved for use will extinguish a fire, regardless of the type of combustible material, but only when the standard fire extinguishing concentration is created in the protected volume.
The mutual influence of the above factors on the technical and economic parameters of a gas fire extinguishing installation will be assessed.
Based on the condition that in Russia the following gas fire extinguishing agents are allowed for use: freon 125, freon 318C, freon 227ea, freon 23, CO2, K2, Ar and a mixture (No. 2, Ar and CO2) having trademark Inergen.
According to the method of storage and methods of control of gaseous fire extinguishing agents in gas fire extinguishing modules (GFM), all gaseous fire extinguishing agents can be divided into three groups.
The first group includes freon 125, 318C and 227ea. These refrigerants are stored in a gas fire extinguishing module in liquefied form under the pressure of a propellant gas, most often nitrogen. Modules with the listed refrigerants, as a rule, have operating pressure, not exceeding 6.4 MPa. The amount of refrigerant during operation of the installation is monitored using a pressure gauge installed on the gas fire extinguishing module.
Freon 23 and CO2 make up the second group. They are also stored in liquefied form, but are forced out of the gas fire extinguishing module under the pressure of their own saturated vapors. The working pressure of modules with the listed gas fire extinguishing agents must have a working pressure of at least 14.7 MPa. During operation, the modules must be installed on weighing devices that provide continuous monitoring of the mass of freon 23 or CO2.
The third group includes K2, Ag and Inergen. These gaseous fire extinguishing agents are stored in gaseous fire extinguishing modules in a gaseous state. Further, when we consider the advantages and disadvantages of gas fire extinguishing agents from this group, we will focus only on nitrogen.
This is due to the fact that N2 is the most effective (lowest extinguishing concentration) and has the lowest cost. The mass of the listed gas fire extinguishing agents is controlled using a pressure gauge. Lg or Inergen are stored in modules at a pressure of 14.7 MPa or more.
Gas fire extinguishing modules, as a rule, have a cylinder capacity not exceeding 100 liters. At the same time, modules with a capacity of more than 100 liters, according to PB 10-115, are subject to registration with the Gosgortekhnadzor of Russia, which entails quite a large number of restrictions on their use in accordance with the specified rules.
An exception is isothermal modules for liquid carbon dioxide (LMID) with a capacity from 3.0 to 25.0 m3. These modules are designed and manufactured to store carbon dioxide in quantities exceeding 2500 kg in gas fire extinguishing installations. Isothermal modules for liquid carbon dioxide are equipped with refrigeration units And heating elements, which allows you to maintain the pressure in the isothermal tank in the range of 2.0 - 2.1 MPa at temperature environment from minus 40 to plus 50 °C.
Let's look at examples of how each of the four factors influences the technical and economic indicators of a gas fire extinguishing installation. The mass of the gas fire extinguishing agent was calculated according to the method outlined in NPB 88-2001.
Example 1. It is required to protect radio-electronic equipment in a room with a volume of 60 m3. The room is conditionally sealed, i.e. K2 « 0. We summarize the calculation results in table. 1.
Economic justification table 1 in specific numbers has a certain difficulty. This is due to the fact that the cost of equipment and gas extinguishing agent from manufacturers and suppliers varies. However, there is a general tendency that as the cylinder capacity increases, the cost of the gas fire extinguishing module increases. 1 kg CO2 and 1 m3 N are close in price and two orders of magnitude less than the cost of refrigerants. Analysis of the table 1 shows that the cost of installing a gas fire extinguishing system with refrigerant 125 and CO2 is comparable in value. Despite the significantly higher cost of freon 125 compared to carbon dioxide, the total price of freon 125 - gas fire extinguishing module with a 40 liter cylinder will be comparable or even slightly lower than the carbon dioxide - gas fire extinguishing module with 80 liter cylinder - weighing device kit. We can definitely state that the cost of installing a gas fire extinguishing system with nitrogen is significantly higher compared to the two previously considered options, because Two modules with maximum capacity are required. Required more space for placement
TABLE 1
Freon 125 36 kg 40 1
CO2 51 kg 80 1
of two modules in a room and, naturally, the cost of two modules with a volume of 100 liters will always be higher than the cost of a module with a volume of 80 liters with a weighing device, which, as a rule, is 4 - 5 times cheaper than the module itself.
Example 2. The room parameters are similar to example 1, but it is not radio-electronic equipment that needs to be protected, but an archive. The calculation results are similar to the first example and are summarized in table. 2.
Based on the analysis of table. 2, we can clearly say that in this case, the cost of installing a gas fire extinguishing system with nitrogen is significantly higher than the cost of installing gas fire extinguishing systems with freon 125 and carbon dioxide. But unlike the first example, in this case it can be more clearly noted that the installation of gas fire extinguishing with carbon dioxide has the lowest cost, because with a relatively small difference in cost between a gas fire extinguishing module with a cylinder with a capacity of 80 and 100 liters, the price of 56 kg of freon 125 significantly exceeds the cost of a weighing device.
Similar dependencies will be traced if the volume of the protected premises increases and/or its leakage increases, because all this causes overall increase quantities of any type of gas extinguishing agent.
Thus, based on only two examples it is clear what to choose optimal installation gas fire extinguishing for fire protection of the premises is possible only after considering at least two options with various types gas fire extinguishing agents.
However, there are exceptions when a gas fire extinguishing installation with optimal technical and economic parameters cannot be used due to certain restrictions imposed on gas extinguishing agents.
TABLE 2
Name of GFSF Quantity of GFCF Cylinder capacity MGP, l Quantity of MGP, pcs.
Freon 125 56 kg 80 1
CO2 66 kg 100 1
Such restrictions primarily include the protection of particularly important objects in a seismic zone (for example, objects nuclear power etc.), where installation of modules in earthquake-resistant frames is required. In this case, the use of freon 23 and carbon dioxide is excluded, because modules with these gaseous fire extinguishing agents must be installed on weighing devices that prevent their rigid fastening.
TO fire protection premises with constantly present personnel (air traffic control rooms, rooms with control panels of nuclear power plants, etc.) are subject to restrictions on the toxicity of gaseous fire extinguishing agents. In this case, the use of carbon dioxide is excluded, because The volumetric fire extinguishing concentration of carbon dioxide in the air is lethal to humans.
When protecting volumes of more than 2000 m3, from an economic point of view, the most acceptable is the use of carbon dioxide filled in an isothermal module for liquid carbon dioxide, compared to all other gaseous fire extinguishing agents.
After a feasibility study, the amount of gas fire extinguishing agents required to extinguish the fire and the preliminary number of gas fire extinguishing modules become known.
Nozzles must be installed in accordance with the spray maps specified in the technical documentation of the nozzle manufacturer. Distance from nozzles to ceiling (ceiling, suspended ceiling) should not exceed 0.5 m when using all gas fire extinguishing agents, with the exception of K2.
Pipe distribution, as a rule, should be symmetrical, i.e. nozzles must be equally distant from the main pipeline. In this case, the flow of gaseous fire extinguishing agents through all nozzles will be the same, which will ensure the creation of a uniform fire extinguishing concentration in the protected volume. Typical examples symmetrical piping is shown in Fig. 1 and 2.
When designing piping, you should also take into account the correct connection of outlet pipelines (rows, bends) from the main one.
A cross-shaped connection is possible only if the flow rates of gas extinguishing agents 01 and 02 are equal in value (Fig. 3).
If 01 Ф 02, then opposite connections of rows and branches with the main pipeline must be spaced in the direction of movement of gaseous fire extinguishing agents at a distance b exceeding 10 D, as shown in Fig. 4, where D - inner diameter main pipeline.
When designing the piping of a gas fire extinguishing installation, no restrictions are imposed on the spatial connection of pipes when using gas fire extinguishing agents belonging to the second and third groups. And for the piping of a gas fire extinguishing installation with gaseous fire extinguishing agents of the first group, there are a number of restrictions. This is caused by the following.
When pressurizing freon 125, 318C or 227ea in the gas fire extinguishing module with nitrogen to the required pressure, nitrogen is partially dissolved in the listed freons, and the amount of dissolved nitrogen in the freons is proportional to the boost pressure.
b>10D ^ N Y
After opening the shut-off and starting device of the gas fire extinguishing module, under the pressure of the propellant gas, the refrigerant with partially dissolved nitrogen flows through the piping to the nozzles and through them exits into the protected volume. In this case, the pressure in the “modules - piping” system decreases as a result of the expansion of the volume occupied by nitrogen in the process of displacing the freon and the hydraulic resistance of the piping. Partial release of nitrogen from the liquid phase of the refrigerant occurs and a two-phase environment “mixture of the liquid phase of the refrigerant - gaseous nitrogen” is formed. Therefore, a number of restrictions are imposed on the piping of a gas fire extinguishing installation using the first group of gas fire extinguishing agents. The main purpose of these restrictions is aimed at preventing the separation of the two-phase medium inside the pipework.
When designing and installing, all piping connections of a gas fire extinguishing installation must be made as shown in Fig. 5, and it is prohibited to perform them in the form shown in Fig. 6. In the figures, arrows show the direction of flow of gas fire extinguishing agents through the pipes.
In the process of designing a gas fire extinguishing installation, the piping layout, pipe length, number of nozzles and their elevations are determined in axonometric form. To determine the internal diameter of the pipes and the total area of the outlet openings of each nozzle, it is necessary to perform a hydraulic calculation of the gas fire extinguishing installation.
The methodology for performing hydraulic calculations of a gas fire extinguishing installation with carbon dioxide is given in the work. Calculating a gas fire extinguishing installation with inert gases is not a problem, because in this case, the flow of inertia
gases occur in the form of a single-phase gaseous medium.
Hydraulic calculation of a gas fire extinguishing installation using freons 125, 318C and 227ea as a gas extinguishing agent is a complex process. The use of the hydraulic calculation technique created for freon 114B2 is unacceptable due to the fact that in this technique the flow of freon through pipes is considered as a homogeneous liquid.
As noted above, the flow of refrigerants 125, 318C and 227ea through pipes occurs in the form of a two-phase medium (gas - liquid), and with decreasing pressure in the system, the density of the gas-liquid medium decreases. Therefore, in order to maintain a constant mass flow of gaseous fire extinguishing agents, it is necessary to increase the speed of the gas-liquid medium or the internal diameter of the pipelines.
A comparison of the results of full-scale tests with the release of refrigerants 318Ts and 227ea from a gas fire extinguishing installation showed that the test data differed by more than 30% from the calculated values obtained using a method that does not take into account the solubility of nitrogen in the refrigerant.
The influence of the solubility of the propellant gas is taken into account in the methods of hydraulic calculation of a gas fire extinguishing installation, in which refrigerant 13B1 is used as a gas extinguishing agent. These methods are not general in nature. Designed for hydraulic calculation of a gas fire extinguishing installation with only 13B1 freon at two values of MHP nitrogen boost pressure - 4.2 and 2.5 MPa and; at four values in operation and six values in operation, the coefficient of filling of the modules with refrigerant.
Taking into account the above, a problem was set and a methodology was developed for the hydraulic calculation of a gas fire extinguishing installation with refrigerants 125, 318Ts and 227ea, namely: with a given total hydraulic resistance of the gas fire extinguishing module (entrance to the siphon tube, siphon tube and shut-off device) and the known pipe For the wiring of a gas fire extinguishing installation, find the distribution of the mass of refrigerant passing through the individual nozzles, and the time of expiration of the estimated mass of refrigerant from the nozzles into the protected volume after the simultaneous opening of the shut-off and starting device of all modules. When creating the methodology, we took into account the unsteady flow of a two-phase gas-liquid mixture "freon - nitrogen" in a system consisting of gas fire extinguishing modules, pipelines and nozzles, which required knowledge of the parameters of the gas-liquid mixture (pressure, density and velocity fields) at any point in the pipeline system at any time .
In this regard, the pipelines were divided into elementary cells in the direction of the axes by planes perpendicular to the axes. For each elementary volume, the equations of continuity, momentum and state were written.
In this case, the functional relationship between pressure and density in the equation of state of the gas-liquid mixture was related by a relationship using Henry's law under the assumption of homogeneity of the gas-liquid mixture. The nitrogen solubility coefficient for each of the freons under consideration was determined experimentally.
To perform hydraulic calculations of a gas fire extinguishing installation, a calculation program in Fortran language was developed, which was named "ZALP".
The hydraulic calculation program allows, for a given gas fire extinguishing installation scheme, which generally includes:
Gas fire extinguishing modules filled with gas extinguishing agents pressurized with nitrogen to pressure Рн;
Collector and main pipeline;
Distribution pipelines;
Nozzles on bends, determine:
Installation inertia;
Time of release of the estimated mass of gaseous fire extinguishing agents;
Time of release of the actual mass of gaseous fire extinguishing agents; - mass flow of gaseous fire extinguishing agents through each nozzle. The testing of the "2АЛР" hydraulic calculation method was carried out by triggering three existing gas fire extinguishing installations and on an experimental stand.
It was found that the calculation results using the developed method satisfactorily (with an accuracy of 15%) coincide with the experimental data.
Hydraulic calculations are performed in the following sequence.
According to NPB 88-2001, the calculated and actual mass of freon is determined. The type and number of gas fire extinguishing modules is determined from the condition of the maximum permissible module filling factor (freon 125 - 0.9 kg/l, freon 318C and 227ea - 1.1 kg/l).
The boost pressure pH of gaseous fire extinguishing agents is set. As a rule, pH is taken in the range from 3.0 to 4.5 MPa for modular and from 4.5 to 6.0 MPa for centralized installations.
A diagram of the piping of the gas fire extinguishing installation is drawn up, indicating the length of the pipes, elevations of the connection points of the piping and nozzles. The internal diameters of these pipes and the total area of the outlet openings of the nozzles are pre-set under the condition that this area should not exceed 80% of the area of the internal diameter of the main pipeline.
The listed parameters of the gas fire extinguishing installation are entered into the "2АЛР" program and a hydraulic calculation is performed. The calculation results may have several options. Below we will look at the most typical ones.
The release time of the estimated mass of gas extinguishing agent is Tr = 8-10 s for modular installation and Tr = 13 -15 s for centralized, and the difference in costs between nozzles does not exceed 20%. In this case, all parameters of the gas fire extinguishing installation are selected correctly.
If the release time of the estimated mass of gaseous fire extinguishing agent less values indicated above, then the internal diameter of the pipelines and the total area of the nozzle holes should be reduced.
If the standard release time for the calculated mass of the gas fire extinguishing agent is exceeded, the boost pressure of the gas fire extinguishing agent in the module should be increased. If this measure does not allow meeting regulatory requirements, then it is necessary to increase the volume of propellant gas in each module, i.e. reduce the filling factor of the gas extinguishing agent module, which entails an increase in the total number of modules in the gas fire extinguishing installation.
Performance regulatory requirements according to the difference in flow rates between nozzles, it is achieved by reducing the total area of the outlet openings of the nozzles.
LITERATURE
1. NPB 88-2001. Fire extinguishing and alarm systems. Design norms and rules.
2. SNiP 2.04.09-84. Fire automatics of buildings and structures.
3. Fire Protection Equipment - Automatic Fire Extinguishing Systems using Halogenated Hydrocarbns. Part I. Halon 1301 Total Flooding Systems. ISO/TS 21/SC 5 N 55E, 1984.