Explosion and fire hazard category of the parking lot. Fire hazard category of car park
Posted on 03/01/2012
This issue is one of the most pressing issues in the design of car storage facilities: parking lots, car parks, garages.
To begin with, you should answer the question: “Is it necessary to determine the fire hazard category of a car park or garage?”.
The answer is unequivocal - yes, it is necessary. If you look at the Technical Regulations on fire safety requirements (FZ No. 123), then in article 32 there is a clear classification for parking lots - functional fire hazard class F 5.2, as for storage facilities.
Those. the fire hazard category for a car park must be determined unambiguously, and the only document by which the fire hazard category of a parking lot or garage should be calculated is SP 12.13130.2009.
In accordance with clause 5.2 of SP 12.13130.2009, the category for explosion and fire hazard should be determined by successive testing from the most dangerous category (A) to the least dangerous (D).
In this regard, the calculation of the category of garages and parking lots with cars running on gaseous (propane) and liquid fuels (gasoline, diesel fuel) should begin with category A for fire and explosion hazard. Although many engineers and designers sin on this score and immediately put category B on fire danger, which is unacceptable and wrong.
So, we decided that it is necessary to determine the fire hazard category of the car park, we proceed to the calculations themselves.
An example of calculating the fire hazard category of car park No. 1
Underground car park for 90 cars, designed for temporary parking cars. The project does not define the type of fuel that will be used in cars. In principle, it is impossible to foresee, and then a security guard will not stand in the parking lot and check every arriving car.
The dimensions of the car park are 36X72 m, height 4 m.
Since it is impossible to know in advance the specific brands of cars, the type of fuel, we begin the calculation from category A for explosion and fire hazard, i.e. we use LPG (propane) as fuel.
Most often, gas cylinders with a volume of 50 liters are installed in cars. Since gas cylinders are filled with no more than 80% in accordance with safety requirements, we take 40 liters as the estimated volume.
When calculating, it is assumed that the entire mass of gas in the fuel system of the car will enter the parking lot.
The density of the liquid phase of propane is assumed to be 510 kg / m 3, design temperature equal to 25°C.
The total mass of gas released into the room will be:
m=ρV=510 0.04=20.4 kg.
The free volume of the room is taken equal to 80% of the volume of the room:
Vsv \u003d 0.8 36 72 4 \u003d 8294.4 m 3.
Propane vapor density at design temperature:
The average concentration of propane in the parking area will be:
Since the concentration of propane is less than half of the LEL (LEL of propane in air is 2.3% by volume), it is possible to use Appendix D of SP 12.13130.2009 to calculate the fuel participation factor in the explosion.
However, let's check whether the excess pressure will exceed the explosion if the coefficient of participation of fuel in the explosion is taken equal to the maximum value - 0.5.
Since the overpressure of the explosion does not exceed 5 kPa, the parking lot will not be classified as category A for fire and explosion hazard.
This conclusion is obtained under the condition that the volume of the gas cylinder does not exceed 50 liters.
We will make a calculation in the case of placing cars on liquid fuel - gasoline in the parking lot.
An example of calculating the fire hazard category of car park No. 2
The volume of the fuel tank of the car is assumed to be 60 liters, the degree of filling is 95%.
The area of the strait will be:
F \u003d 0.95 1 60 \u003d 57 m 2
To calculate the evaporation rate of gasoline, as reference data, you can use the data on AI-93 gasoline from the manual for NPB 105-95.
In the car park, general ventilation is always in operation, the operation of which must be taken into account in the calculation when determining the intensity of evaporation.
The air flow rate will be:
According to Table A.2 of SP 12.13130.2009, we find the value of the coefficient η for the air flow velocity in the parking room of 0.1 m/s and the air temperature of 25°C equal to 2.4.
Those. under these conditions, gasoline will evaporate almost two and a half times faster.
The evaporation rate W will be:
The mass of vapors entering the room will be:
Let's check if the calculated mass of gasoline does not exceed the total mass contained in the gas tank. The density of gasoline is taken according to GOST R 51105-97 equal to 780 kg / m 3:
m=ρV=780 0.057=44.46 kg.
Since the actual mass of gasoline in the gas tank is less than the calculated one, we take the latter value as a basis.
Gasoline is a mixture of hydrocarbons, and not an individual substance, therefore, when calculating the excess explosion pressure, formula A.4 should be used, and not A.1 of SP 12.13130.2009:
Since the excess pressure of the explosion is more than 5 kPa, the room should be classified as category A in terms of explosion and fire hazard.
In accordance with clause A.2.3 of SP 12.13130.2009, it is allowed to take into account the operation of emergency or general ventilation. In our case, the car park is equipped with general ventilation.
We will carry out the calculation subject to the placement of additional (backup) ones, which will be started when the main ones stop, the power supply of these fans must be carried out according to the 1st category of reliability (see PUE).
As mentioned earlier, the air exchange rate in the parking lot is 5 h -1 .
In accordance with paragraph A.2.3, the amount of gasoline vapors in the room can be reduced by an amount equal to:
Where A- multiplicity, T- the time of receipt of the combustible substance in the room.
Let's define the last value.
The time for complete evaporation of gasoline will be:
The coefficient K is equal to:
Those. the total mass of gasoline vapors located in the parking lot at the time of the explosion due to the operation of general ventilation, equipped with backup fans and power supply according to the 1st category, can be reduced by 2.7 times.
Consequently, the excess pressure of the explosion will also decrease by 2.7 times and will be 2.45 kPa, i.e. less than 5 kPa.
An example of calculating the category of a car park for fire danger No. 3
We will calculate the category of the parking lot by fire hazard if it belongs to the category B1-B4 by fire hazard. This calculation is applicable for any car storage room, including a garage.
To do this, we need to know the mass of each combustible material that is part of the car.
Such data, a break a lot of literature, I could not find, so I propose to do differently. It is known that the share of combustible materials in the total mass of the car is about 10%. The heat of combustion of automotive materials can be taken on the basis of a typical fire load (31.7 MJ / kg).
Once again I will make a reservation that it is impossible to know in advance which cars will be placed in the parking lot. But, as practice shows, you can limit yourself to a car weight of 3500 kg, which, by the way, is the boundary value when classifying a car as a passenger car, as well as a rather large margin. For example, the mass of most passenger cars is within 1500 kg, large SUVs in the region of 2500 kg.
So, the fire load of the car under the accepted conditions will be:
Q=m H=350 31.7=11095 MJ.
Now you need to determine the area of the fire load. It will be equal to the area of the car in horizontal projection. Conventionally, it can be taken equal to the area of a rectangle formed by two dimensions: the length and width of a vehicle unit.
As a rule, this area does not exceed 10 m 2, but sometimes it slightly exceeds it. However, in the case when the car area does not exceed 10 m 2, it must be taken equal to 10 m 2, otherwise the smallest value (again 10 m 2) should be taken as the worst option.
q \u003d Q / S \u003d 11095/10 \u003d 1109.5 MJ / m 2.
A room with a given specific fire load can be classified as category B3 in terms of fire hazard. We need to check the inequality. In this case, we need the third geometric dimension of the car - its height. The height can be taken with a sufficient margin equal to 2.5 m.
In this article, based on several examples, we will talk about how car park fire hazard category.
This issue, in my opinion, is one of the most pressing issues in the design of premises for car storage: parking lots, car parks, garages.
To begin with, you should answer the question: “Is it necessary classify fire hazard of a car park or garage?
The answer is unequivocal - yes, it is necessary. If you look at the Technical Regulations on fire safety requirements (FZ No. 123), then in article 32 there is a clear classification for parking lots - functional fire hazard class F 5.2, as for storage facilities.
Those. the fire hazard category for a car park must be determined unambiguously, and the only document by which the fire hazard category of a parking lot or garage should be calculated is SP 12.13130.2009.
In accordance with clause 5.2 of SP 12.13130.2009, the category for explosion and fire hazard should be determined by successive testing from the most dangerous category (A) to the least dangerous (D).
In this regard, the calculation of the category of garages and parking lots with cars running on gaseous (propane) and liquid fuels (gasoline, diesel fuel) should begin with category A for fire and explosion hazard. Although many engineers and designers sin on this score and immediately put category B on fire danger, which is unacceptable and wrong.
So, we decided that it is necessary to determine the fire hazard category of the car park, we proceed to the calculations themselves.
Underground parking for 90 cars, designed for temporary parking of cars. The project does not define the type of fuel that will be used in cars. In principle, it is impossible to foresee, and then there will not be a guard in the parking lot and checking every arriving car!
The dimensions of the car park are 36×72 m, the height is 4 m, the air exchange rate in the car park is 5 h -1 .
Since it is impossible to know in advance the specific brands of cars, the type of fuel, we begin the calculation from category A for explosion and fire hazard, i.e. we use LPG (propane) as fuel.
Most often, gas cylinders with a volume of 50 liters are installed in cars. Since gas cylinders are filled with no more than 80% in accordance with safety requirements, we take 40 liters as the estimated volume.
When calculating, it is assumed that the entire mass of gas in the fuel system of the car will enter the parking lot.
The density of the liquid phase of propane is assumed to be 510 kg / m 3 [we are looking for reference books, I took from here - Plant Engineer's Reference Book. Dennis A. Snow. Elsevier, 2002], the design temperature is 25°C.
The total mass of gas released into the room will be:
m=ρV=510 0.04=20.4 kg.
The free volume of the room is taken equal to 80% of the volume of the room:
Vsv \u003d 0.8 36 72 4 \u003d 8294.4 m 3.
Propane vapor density at design temperature:
The average concentration of propane in the parking area will be:
Since the concentration of propane is less than half of the LEL (LEL of propane in air is 2.3% by volume), it is possible to use Appendix D of SP 12.13130.2009 to calculate the fuel participation factor in the explosion.
However, let's check whether the excess pressure will exceed the explosion if the coefficient of participation of fuel in the explosion is taken equal to the maximum value - 0.5.
Since the overpressure of the explosion does not exceed 5 kPa, the parking lot will not be classified as category A for fire and explosion hazard.
This conclusion is obtained under the condition that the volume of the gas cylinder does not exceed 50 liters.
We will make a calculation in the case of placing cars on liquid fuel - gasoline in the parking lot.
The volume of the fuel tank of the car is assumed to be 60 liters, the degree of filling is 95%.
The area of the strait will be:
F=0.95 1 60=57 m2.
To calculate the evaporation rate of gasoline, as reference data, you can use the data on AI-93 gasoline from the manual for NPB 105-95.
In the car park, general ventilation is always in operation, the operation of which must be taken into account in the calculation when determining the intensity of evaporation.
The air flow rate will be: 
According to Table A.2 of SP 12.13130.2009, we find the value of the coefficient η for the air flow velocity in the parking room of 0.1 m/s and the air temperature of 25°C equal to 2.4.
Those. under these conditions, gasoline will evaporate almost two and a half times faster.
The evaporation rate W will be:
The mass of vapors entering the room will be:
Let's check if the calculated mass of gasoline does not exceed the total mass contained in the gas tank. The density of gasoline is taken according to GOST R 51105-97 equal to 780 kg/m3.
m=ρV=780 0.057=44.46 kg
Since the actual mass of gasoline in the gas tank is less than the calculated one, we take the latter value as a basis.
Gasoline is a mixture of hydrocarbons, and not an individual substance, therefore, when calculating the excess explosion pressure, formula A.4 should be used, and not A.1 of SP 12.13130.2009.
Since the overpressure of the explosion is more than 5 kPa, the room should be classified as And for explosion hazard .
In accordance with clause A.2.3 of SP 12.13130.2009, it is allowed to take into account the operation of emergency or general ventilation. In our case, the car park is equipped with general ventilation.
We will carry out the calculation subject to the placement of additional (backup) ones, which will be started when the main ones stop, the power supply of these fans must be carried out according to the 1st category of reliability (see PUE).
As mentioned earlier, the air exchange rate in the parking lot is 5 h -1 .
In accordance with paragraph A.2.3, the amount of gasoline vapors in the room can be reduced by an amount equal to:
where A is the multiplicity, T is the time the combustible substance enters the room.
Let's define the last value.
The time for complete evaporation of gasoline will be:
The coefficient K is equal to:
Those. the total mass of gasoline vapors located in the parking lot at the time of the explosion can be reduced by 2.7 times due to the operation of general ventilation, equipped with backup fans and power supply according to the 1st category!
Consequently, the excess pressure of the explosion will also decrease by 2.7 times and will be 2.45 kPa, i.e. less than 5 kPa.
We will calculate the category of the parking lot by fire hazard if it belongs to the category B1-B4 by fire hazard. This calculation is applicable for any car storage room, including a garage.
To do this, we need to know the mass of each combustible material that is part of the car.
Such data, a break a lot of literature, I could not find, so I propose to do differently. It is known that the share of combustible materials in the total mass of the car is about 10%. The heat of combustion of automotive materials can be taken on the basis of a typical fire load (31.7 MJ / kg).
Once again I will make a reservation that it is impossible to know in advance which cars will be placed in the parking lot. But, as practice shows, you can limit yourself to a car weight of 3500 kg, which, by the way, is the boundary value when classifying a car as a passenger car, as well as a rather large margin. For example, the mass of most passenger cars is within 1500 kg, large SUVs in the region of 2500 kg.
Posted on 02/10/2013
In this article I will tell you how to correctly calculate the fire hazard category of a room B1-B4. So, the premises of category B in terms of fire danger are divided depending on the specific fire load into the following groups: - B1, q over 2200 MJ / m 2; - B2, q from 1401 to 2200 MJ/m2; - B3, q from 181 to 1400 MJ/m 2 ; - B4, q from 1 to 180 MJ/m 2 .
Consider several examples of calculating the category of premises B1-B4.
1. An example of calculating the category of fire hazard No. 1
In the warehouse, non-combustible materials (metal products) are stored in boxes made of wood. The fire load is concentrated in the form of three racks 1 × 6 m in size. Between the racks there are passages 1.5 m wide. The minimum distance from the surface of the fire load to the lower belt of the floor trusses is 1 m. 10 wooden boxes weighing 3 kg each.
We will calculate the fire hazard category of the room. In the room, three areas for placing a fire load can be distinguished - racks. Let us determine the specific fire load for each of the sections.
The total mass of wood in each of the racks is equal to m=3·3·10=90 kg. The heat of combustion in the calculation is assumed to be 13.8 MJ/kg. The fire load will be: Q=m·Hc=90·13.8=1242 MJ. The area of the fire load is S=1·6=6 m 2 . Since the area does not exceed 10 m 2, then the area equal to 10 m 2 is taken as the calculated area for placing the fire load. The specific fire load will be: q=Q/S=1242/10=124.2 MJ/m 2 .
A room with a given specific fire load can be classified as category B4 in terms of fire hazard.
However, the distance between the fire load placement areas is less than the limit, defined in this case as follows: l= lpr+(11-H)=8+(11-1)=18 m, since the minimum distance from the fire load surface to the lower the floor truss belt is 1 m, i.e. less than 11 m. Therefore, the area for placing the fire load is summed up and will be 3 6 = 18 m 2.
Since the total area of the fire load exceeds 10 m 2, the room should be classified as category B3 for fire hazard.
2. An example of calculating the category of fire hazard No. 2
Production room for the production of non-combustible building materials. Indoors are located hydraulic presses, equipped with a lubrication system, carried out from oil stations. Oil stations are located in technological niches 3×3 m in size, capable of accommodating the entire volume of oil (ISO VG 460 oil, volume 1.5 m 3) located in the oil station (in the tank and pipelines).
Let's calculate the fire hazard category. The flash point of the oil is 246°C and the oil is not in a hot state. Therefore, we immediately proceed to the calculation of the category B1-B4. Since the niche under the oil station is able to accommodate the entire volume of oil, the area for placing the fire load is assumed to be equal to the filling area S=3 3=9 m 2 (10 m 2 is assumed in the calculation).
We do not know the heat of combustion of oil, therefore we will determine it by calculation using the Bass formula, knowing the density (900 kg / m 3): Hc \u003d 50460-8.545 900 \u003d 42769.5 kJ / kg \u003d 42.77 MJ / kg.
The total mass of oil will be: m=900 1.5=1350 kg.
The fire load will be: Q=m·Hс=1350·42.77=57739.5 MJ.
The specific fire load will be: q=Q/S=57739.5/10=5774 MJ/m 2 .
A room with a given specific fire load should be classified as category B1 for fire hazard.
Production area where metalworking machines are located various types in two spans. The width of the passage between the spans is 3 m. The distance between the machines in the span is 1.5 m. The machines have a lubrication system in which industrial oil I-20A is circulated in a volume of up to 15 liters in each machine. The machines are designed in such a way that the formation of an open mirror of spilled oil is possible only in the event of an emergency destruction of the machine. At the same time, under each machine there is a metal pallet with an area of 2 m 2, capable of containing the entire volume of oil in case of emergency depressurization.
Let's define the category of premises according to fire danger. Since the flash point of I-20A oil is more than 180 ° C, we immediately make a calculation according to whether the room belongs to B1-B4. The mass of oil will be m=0.015 890=13.35 kg.
We do not know the heat of combustion of oil, so we will determine it by calculation using the Bass formula, knowing the density (890 kg / m 3): Hc \u003d 50460-8.545 890 \u003d 42854.95 kJ / kg \u003d 42.85 MJ / kg. The fire load will be: Q=m·Hc=13.35·42.85= 572.05 MJ. The specific fire load will be: q=Q/S=572.05/10=57.2 MJ/m 2 . A room with a given specific fire load should be classified as category B4 for fire hazard.
4. Example #4
There are several areas of fire load in the room, conditionally designated as area Nos. 1-3.
On site No. 1 with an area of 30 m 2, organic glass (polymethyl methacrylate) with a total weight of not more than 2000 kg is located, the minimum height from the level of stacks to the ceiling is 12 m.
On plot No. 2 with an area of 20 m 2 there are wooden pallets with a total weight of 1700 kg, the distance to the ceiling is 11 m.
On site No. 3 with an area of 10 m 2, rubber products with a total weight of 300 kg are located.
Plot #1: q \u003d Q / S \u003d 2000 25.2 / 30 \u003d 1680 MJ / m 2.
Plot #2: q \u003d Q / S \u003d 1700 13.8 / 20 \u003d 1173 MJ / m 2.
Plot #3: q \u003d Q / S \u003d 300 33.52 / 10 \u003d 1005.6 MJ / m 2.
Since the maximum specific fire load is available in section No. 1, the category of the room will be determined for this section. The room can be classified as B2.
Let's check if the inequality holds: Q≥0.64qTH 2 , 50400≥0.64 2200 12 2 =202752. Since the condition is not met, the room should be classified as category B2 for fire hazard. For the rest of the segments, in this case, inequality verification is not required.
So, the room belongs to category B2 for fire hazard.
5. Example #5
There are several areas of fire load in the room, conditionally designated as area Nos. 1-3. The area of all sections does not exceed 10 m 2, the minimum distance from the fire load to the floors is 6 m. Polymethyl methacrylate with a total weight of not more than 70 kg is located in section No. 1, wood - no more than 120 kg in section No. 2, rubber - in section No. 3 no more than 50 kg. The distance between sections No. 1 and No. 2 is 14 m, between sections No. 2 and No. 3 - 7 m.
Let us determine the specific fire load for each of the sections.
Plot #1: q \u003d Q / S \u003d 70 25.2 / 30 \u003d 176.4 MJ / m 2.
Plot #2: q \u003d Q / S \u003d 120 13.8 / 20 \u003d 165.6 MJ / m 2.
Plot #3: q \u003d Q / S \u003d 50 33.52 / 10 \u003d 167.6 MJ / m 2.
A room with a given specific fire load can be classified as category B4. In this case, the distances between the sections should be more extreme. The critical density of incident radiant fluxes for polymethyl methacrylate, wood and rubber is 10, 11 and 14.8 kW/m 2 respectively.
The maximum distance between sections No. 1 and No. 2 will be: l=lpr+(11-6)=8+5=13 m 7 m.
Since the distance between sections No. 2 and No. 3 is less than the limit value, the room should be classified as category B3 for fire hazard.
So, in this article, we looked at several examples of calculating categories for fire hazard. These examples, for obvious reasons, do not claim to cover all options placement of fire load encountered in real premises, but, I hope, will be useful to you in practice.
PUE and joint ventures of various kinds do not tell us anything about how do-it-yourself wiring is done in the garage. Meanwhile, this is a room that, according to the fire hazard class, is in no way lower than P-IIA. In general, the beginning is carried out with the calculation of the class of the garage. And it will be different for everyone. A lot depends on the amount of fuel stored inside, including in the gas tank of the car. Let's take a look at the garage wiring requirements.
How to calculate the fire hazard class of your garage, and why you need it
All requirements for the manufacture of electrical wiring are standardized according to the hazard classes of the premises. Limiting factors include:
- Combustible materials: liquid, solid, explosive.
- The presence of conductive electricity ceilings, walls, floors.
- Wet work (a term from the standards), that is, laundry, washing, bathrooms.
- A separate category is work on the street.
In our case, there can be quite a lot of restrictions, but we will start with a fire hazard. According to SNiP 21-02 (clause 5.1.6), calculations should be carried out according to SP 12.13130. In turn, our garage falls under Appendix B of the mentioned document. Where it is written that sorting by fire hazard category from B1 to B4 is carried out according to the total heat released during the combustion of the amount of fuel available in the room. It is clear that a lot depends on the category of fuel. Because the specific heat is different. Here is the data from the table:
- Specific fire load up to 180 MJ/sq.m – fire hazard class B4.
- Specific fire load from 181 to 1400 MJ / sq.m - fire hazard class B3.
- Specific fire load from 1401 to 2200 MJ / sq.m - fire hazard class B2.
- Specific fire load from 2201 MJ / sq.m - fire hazard class B1.
The fire load is summed over all types of fuel available in the garage. For example, for AI-95 gasoline, the specific heat of combustion is about 32 MJ / l (at a temperature environment about 15 degrees Celsius). This means that the 98 Toyota Ipsum contains in its bowels (with a full supply) 60 x 32 = 1920 MJ of hypothetical problems. To obtain the specific fire load of the garage, you need to divide this figure by the floor area. You can see that with walls measuring 3 x 3 meters, the room clearly falls into category B3. But if the garage were a little larger (5 x 6 = 30 sq. M), the fire hazard class would immediately drop to B4.
Please note that according to SP 12.13130, you need to divide by at least 10. But even then it is not possible to place a supply of fuel everywhere. It directly follows from this that each reader must calculate the fire hazard class for himself.
Then apply specific rules and regulations. Moreover, for those who decide to switch to liquid (compressed) gas, there are instructions different from those indicated. In this case, an additional calculation is required, during which it may turn out that the fire hazard class of the room has increased to A or B. Cool formulas here are:
- The critical volume of the room is calculated: V = 1000 M / 2.886 = 346.5 M, where 2.886 is the mass in grams per meter, the maximum allowable for rooms without emergency ventilation. M is the mass of gas that will be thrown into the room. To do this, the amount of fuel filled is specified.
- It is allowed to take into account the work of emergency ventilation. In this case, the coefficient 2.886 is multiplied by K \u003d A T + 1. Where A is the frequency of air renewal in the garage due to the action of the emergency system, T is the period during which the leak will exist. You see that the allowable volume of the garage can be significantly reduced by moving it to a lower hazard class.
- The resulting value is compared with the free volume of the room. It is formed by subtracting the occupied space from the dimensions of the walls. If the calculation is difficult, then the free volume of the garage is allowed to be taken in the amount of 20% of the total.
- If it turns out that the minimum estimated safe volume of the garage is less than free, then the category automatically becomes the highest - A. Otherwise, only B2.
Rules for the placement of electrical equipment
We give head to the clipping that at least half of motorists are trying to use outlets on the street. In this case, there is an explicit instruction of PUE 7 to supply 220 V through a differential machine with an operating threshold not higher than 30 mA. The actual conditions of the street are equated to the bathroom in this regard. So, it does not hurt to know two more conditions: it is allowed to supply power at a reduced voltage (up to 50 V AC).
If the room falls into fire and explosion class A, then it is equipped in accordance with category B1a (clause 7.3.41 according to PUE 6) according to PUE 7 (protective shell). This imposes a whole bunch of additional requirements, for example:
- Installation of emergency ventilation with an exchange rate of at least 5. This equipment also applies to electrical equipment, therefore, it must be taken into account in the process of system design. Simultaneously with the activation of emergency ventilation, all other consumers are de-energized.
- Installation of sensors for monitoring the content of hazardous gas. It is clear that this equipment is also classified as electrical, therefore, should be taken into account. Control sensors and the emergency ventilation system are provided with wiring according to reliability category 1 in accordance with PUE 7.
- Part of the walls of the garage should be replaced with easily dropped structures according to SNiP 2.09.02.
- All electrical equipment is installed in an explosion-proof design. SP 31-110 tells us that in this case it is necessary to use fixtures according to PES 6, clauses 7.3 and 7.4 (excluded in the new edition).
Here is what they write in PUE 7 regarding electrical installations in explosive areas:
- Explosion-proof equipment is used in accordance with GOST 17494. The degree of protection of the housing in terms of IP is determined according to the table (see clause 7.3.66 PUE 6). Why do we need outdated standards, you ask? Because in the new ones, the issue of the explosiveness of gas is subtly bypassed. In class B1a rooms, installations with increased reliability against explosions (sparkling or heating above 80 degrees Celsius), or ordinary ones, but with an IP54 housing (and not heating above 80 degrees Celsius) are used.
- In the garage, stationary lamps with increased protection against explosions are used, and portable lamps must be explosion-proof. The problem is that such equipment is quite expensive. Therefore, you need to carefully evaluate the class of your premises in terms of fire hazard, so as not to give extra money. It is allowed to use devices with slotted light guides.
- Distribution devices (shields) must not be installed in explosive zones of any class. Installation must be carried out outside the garage. In some cases, it is allowed to install separate columns if their degree of protection is not lower than in table 7.3.11 of PUE 6.
- Do not use bare wires in hazardous areas. According to the classification, only cables with copper conductors are used on the territory of BI and BI-A facilities. Aluminum are prohibited (due to more heat dissipation). Including cables made of this metal.
- Ground conductors must have insulation similar to phase circuits.
- It is forbidden to use connecting and branching cable glands except for intrinsically safe circuits. We will not say exactly whether aspics are included here. Because there is no explanation as to what caused this requirement (heating or sparking). It is also not encouraged to create cable channels under the floor, which should be covered with sand after laying.
- All tires are insulated. One-piece connections are made by welding or crimping (silent about soldering). Of course, the tires must be made of copper. Bolted connections that do not allow self-unscrewing are allowed.
- Potential equalization is required. In theory, the body of the car should also be included in this circuit by a temporary connection. Any electrical equipment is not only grounded through a socket, but also grounded (by local wires). All lamps are also subject to this procedure (those that are expensive).
Until now, there have been requirements for explosive zones, and there are also fire hazardous garages. Their classification is given in clause 7.4 of the old PUE (sixth edition). From the foregoing, we must understand that the type of fuel, the size of the gas tank, spare canisters, the area and type of construction of the garage greatly affect the cost of the equipment. If there are no flammable substances inside the machines at all, then the measures are significantly softened. Those who wanted to put, roughly speaking, a gas tank inside the garage, will have to be quite tight.
In any case, it does not hurt to make a lightning rod, and to it - a ground loop. We have already told you how to do this, we recall that if you do not want to use the cable scheme, the peak is erected approximately in the center of the garage roof. See the corresponding review for formulas and links, it already indicates how to make a ground loop. The tire is made of a strip of steel with a thickness of at least 4 mm, or a rod with a diameter of 6 mm or more. underground part consists of at least two iron stakes, unpainted, with a length of 2.5 meters or more. The distance between them is selected from three meters.
It is logical to lay the ground loop even during the construction of the garage. In any case, this will be needed for the zeroing system (it is carried out with the same 6 mm wire rod if the zone is not explosive). Potential equalization is carried out separately from the power supply network. Grounding will also have to be brought from the ground loop, because - we bet - just a couple of old aluminum wires come into the garage. Thus, it will be necessary not only to ground the switchboard case, but also to bring the bus inside to connect all consumers.
Experienced people recommend taking a copper core of at least 4 square millimeters. This is probably in case of using welding, which - as our readers have already guessed - should not be close to the garage where fueled cars are parked. The wiring in the garage is carried out along the contours: separately lighting, sockets, hoods. If it is planned to consume at the distribution point from 6 kW (inclusive), then the core goes without branching and couplings directly to the shield. Only differential circuit breakers should be installed for wiring in the garage. Many will be against it, because their cost is an order of magnitude higher than conventional ones. Then make an exception for lighting.
Lamps are best taken at 12 V, LED, for pin or threaded cartridges. You can feed the local network through a special converter. Put it on a DIN rail in the switchboard right next to the machines. Making electrical wiring for the garage, start by carefully studying all the components of the local supply system. The scheme may vary significantly depending on the environment.
What happens to our garage?
You ask - why all these requirements? Well, if you are not going to comply with them, there was no need to ask such a question to the search engine! We talked about exactly how to conduct electrical wiring in the garage, how to determine the fire and explosion hazard class. Now you know where to look, where to look. And for sure laying electrical wiring in the garage will not seem as difficult as it was before reading this review.
But now you can easily put the hood on your cellar: 12 V systems are allowed even in wet rooms, so there will be no special problems. Before you make electrical wiring in the garage, break it into sections, see what devices and where you can apply. Maybe someone wants to get rid of condensate in the cellar, or dry vegetables and fruits in the garage. All this is real, you just need to take into account all the requirements, and then think about how you can save your money on reducing requirements by changing the conditions.
And we say goodbye to this. Ask questions, and we will try to answer them if there is time.
