Water expenses for external fire extinguishing at settlement
Number of habitants in settlement, thousands of persons |
Calculation amount of simultaneous fires |
Water expenses for external fire extinguishing, l/sec, with buildings |
|
up to 2 floors |
3 floors and more |
||
Up to 1 |
1 |
5 |
10 |
1-5 |
1 |
10 |
10 |
5-10 |
1 |
10 |
15 |
10-25 |
2 |
10 |
15 |
25-50 |
2 |
20 |
25 |
50-100 |
2 |
25 |
35 |
100-1000 |
3 |
- |
40-100 |
Fires at industrial enterprises, which are located inside boundaries of settlement, are included to the calculation amount of simultaneous fires. Water expenses on internal extinguishing of fires in dwelling, public and industrial buildings, which are equipped with internal fire faucets, should be taken into account additionally to the external fire extinguishing. List of such buildings and normative water expenses for internal fire extinguishing are given in СНіП 2.04.01-85. Calculation duration of fire extinguishing equals 3 hours. Serve of water calculation expendses for fire extinguishing should be provided during the highest hour’s water expenses on other needs. During these water expenses on watering, showers, cleaning of floor and technologic enterprises aren’t taken into account.
1.3 Water consumption mode, determination of calculation expenses and nesseccary pressure
Economic-drinkable water consumption mode during the day, month, year in the settlement cannot be uniform and depends on many factors (temp of people’ life and labor activity, year period, local conditions, etc.). It is usually accepted, that fluctuation of water consumption can be of summer and winter chart during the year. In calculations this fluctuations are evaluated by the coefficient of day’s ununiformity: the highest Kday max=1.3; Kday min=0.7.
Hour’s expends have considerable fluctuation during the day, which is taken into account by the coefficient of hours’ ununiformity:
the highest
(1.1)
the lowest
(1.2)
where αmax=1.2-1.4; αmin=0.4-0.6; - coefficients that take into account degree of equipping with modern amenities of houses, enterprises work mode and other local conditions (СНіП 2.04.02-84), β – coefficient, that takes into account number of habitants in the settlement (table 1.2).
Depending on value of Kh max the typical chart of day expends distribution by day’s hours is accepted (addition 1).
Table 1.2
Value of coefficient β [15]
Coefficient |
Number of habitants, thousands of persons |
||||||||||
up to 0.1 |
0.2 |
0.5 |
1.0 |
4 |
10 |
20 |
50 |
100 |
300 |
1000 and more |
|
βmax |
4.5 |
3.5 |
2.5 |
2 |
1.5 |
1.3 |
1.2 |
1.15 |
1.1 |
1.05 |
1 |
βmin |
0.01 |
0.02 |
0.05 |
0.1 |
0.2 |
0.4 |
0.5 |
0.6 |
0.7 |
0.85 |
1 |
For industrial enterprises hour’s water expends on technological needs are accepted as uniform by daily hours during the shift or by the technologists’ requirements, but distribution of daily or shift water expenses for economic-drinkable needs is worked out according to the addition 6. Water expenses on showers are distributed proportionally to daily expenses after each shift at enterprises.
Uniform water consumption is foreseen in the calculations during the hour. The hour, that takes the highest value of hour’s water expenses of the whole settlement, is the hour of the largest water consumption, and water expenses of each consumer for this hour are accepted as calculation.
Calculation (average in the year) daily water expenses, m3/day, on economic-drinkable needs of population are determined by the formula:
,
(1.3)
where gж-specific water expenses, l/day for person, Nж-calculation number of habitants, persons.
Calculation expenses per day of the highest and the lowest economic-drinkable water consumption are equal to:
;
(1.4)
;
(1.5)
where Kдоб max=1.3 and Kдоб min=0.7 – coefficients of day ununiformity.
Calculation (average in the year) daily water expenses, m3/day, on watering:
;
(1.6)
where gж.пол. - specific water expends, l/m2 on one watering, F1 – watering area, He.
Calculation (average in the year) daily water expenses, m3/day, on industrial needs, m3/day, are equal:
(1.7)
where gп, - specific water expenses, m3 on one unite of products, N2 – amount of products that are produced.
In the calculations of water-supply systems, as a rule, at first time, the hour’s water expenses for each category of water consumers are determined, and than this values are summarized, i.e. the hour’s water consumption of the whole settlement is determined. Hour’s water consumption by consumer, m3/hour, is equal:
(1.8)
where a – daily expenses’ distribution, Qдоб.max – for certain hour, %.
Maximal hour’s water consumption by one type of consumer, m3/hour, can be determined as:
(1.9)
Maximal hour’s water consumption in the settlement is determined by the chart of water consumption.
The highest expenses per second, l/sec:
(1.10)
where qhr.max – the highest hour’s water expenses, m3/hour, for the whole settlement or the separate water consumer.
There is can be a pressure in the water-plumbing network, that will ensure rising and outpouring of water at the highest water intake point. So that, free pressure (m) in the network is needed
(1.11)
where hr – geometrical height of water rising from the land surface to the point with the highest location, m; ∑hw – pressure looses from the connecting point of water-plumbing network to the water intake armature, m; hp – work pressure for outpouring from water intake armature, m, that is determined with СНіП 2.04.01-85.
According to СНіП 2.04.02-84, the necessary free pressure should be ensured in the external water-plumbing network
,
(1.12)
where n – quantity of building’s floors.
Local alluvial structures for pressure increase can be made for the separate multi-storey buildings, that are located among small buildings, or those, that are located at higher places. Free pressure at water intake gayser has to be not less than 10 m. Free pressure in the external industrial plumbing network is determined by technical data depending on accepted equipment.
Free pressure in economic-drinkable water-plumbing near the consumers hasn’t to be more than 60 m.
Free pressure at water-plumbing network during fire extinguishing depends on accepted fire extinguish system. There are systems of high and low pressure. In the high pressure system the fire is extinguished directly from the network with the help of fire sleeves that are connected to fire-cocks (fig. 1.5).
Fig.1.5. Schemes of fire extinguishing from the water-plumbing with high (a) and low (b) pressure
Free pressure in the high pressure water-plumbing network should be enough big to serve water to the highest point of building, that is burning, through fire sleeves with length 120 m, and to ensure compact stream from the barrel on height 10m. Approximately, this free pressure can be determined by the formula:
(1.13)
where Hб – height of building, m.
In the low pressure fire extinguishing system water is taken out by fire trucks pumps from water-plumbing network fire-cocks and is given to the place of fire with the same pressure by fire sleeves, as in the case with high pressure (fig.1.5b). In the water-plumbing network, in the case of fire, relatively low pressure is ensured, that equals to 10m.