Study on Methods of Water Intake of Fire Pump in the Grid Water Tanks

Nanning Architecture Design Institute

Jiaxiu Lie, Feng Wei, Jianzhi Zhang
Add:No.159,Gonghe Rd, Nanning City, Guangxi Zip Code:530012
Tel:0771-2623556,0771-5887811 Fax:0771-2623519

Abstract: This paper makes an analysis and study of three methods of water intake of fire pump in the grid water tanks and the main advantage and disadvantage of these three methods are listed here
Keywords: Grid water tank Independent water intake Intake well public intake pipe

Since 1990‘s, with the further development of China‘s reform and openness and the increase of national economy, more and more synthetic buildings with all kinds of complex function gradually appear. However, due to the increase of the use of flammable renovating materials and decorations in the interior of buildings, it also leads to higher risk of the occurrence of building fire, and hence brings stricter requirements for the water supply design of buildings‘ fire-fighting system.

The lessons from many of national and international building fires indicate that if fire design in designing buildings (especially for the first-class high civil buildings)was not safe and considerate enough,it would lead to severedeath accidents and economic loss,more severely, it also brings negative political effects,
Fire pump and firewater tanks are the heart of fire water supply system, Its main designs include the following aspects:
1. Methods of water intake of fire pump
2. Water head ,flow and installation etc. of fire pump
3. The valid volume of firewater tank

This paper will focus on the discussion of methods on water intake of fire pump. In order to guarantee that fire pump station can normally work shile fire is in progress, the method of water intake of fire pump must be safe and reliable. Fire-fighting Specification of Building Design(FSBD)GBJ16-87( Revised version)and Fire-fighting Specification of High Civil Building Design(FSHCBD)GB50045-95 clearly specify: firewater tank should be divided into two grids when the storage of firewater tank is more than 1000 cubic meter(FSBD)or 500 cubic meter(Fshcbd).Its purpose is to make sure that a certain grid can still sork when another gird is under cleaning and maintenance.
For grid firewater tank, there are mainly three types of water intake as followings:

1) Each fire pump has an independent intake pipe into the firewater tank (See Figure 1)
2) By designing a public intake well, all fire pumps obtain water from the public intake well(See figure 2).
3) A linking pipe is set between the grids of firewater tank, and a control valve is designed on the linking pipe(See Figure 3)

Example Case Study: There is a first-class high civil building, which is designed with inside and outside fire hydrant system, automatic spraying system, and separated water-curtain protection system. Except the outside fire hydrant system , each system has independent pressure pump. Since the volume of firewater of the building is more than 500 cubic meter, its firewater tank is designed with two grids. There are three optional schemes for the water intake of fire pump.

Option 1:

As Figure 1 shows, fire pumps which are backup with each other intake water from No.1 firewater tank and No.2 firewater, respectively. This option is very pipular in current fire-fighting design.

Advantage:for each fire pump, independent intake pipe directly obtaining water from firewater tank. Simple intake pipe layout, easy construction and installation, and less cost.
Disadvantage:only one pressure pump is ready to work for each system, and other backup pump can not be used though it is idle. In case that a fire happens to occur, and the pump that is ready for working can not operate, the disastrous outcome is unexpected.

Option 2

All fire pumps intake water from public intake well as the Figure 2 shows.
Advantage: Independent intake pipe tank for each fire pump, simple intake pipe layout.
When a certain grid is under cleansing and maintenance, each pressure fire pump can be ready to work.
Disadvantage:Bigger diameter for linking pipe between firewater tank and intake well, If the intake well itself needed to be maintained, it will be less reliable.

Option 3:

As Figure 3 shows, all frie pumps intake water through the linking pipe between two grids. Runhua Mansion and Gonghua Mansion(both more than 100 meters high) designed by Nanning Architecture Design Institute in 1993 adopted the option. Based on the (FSHCBD)GB50045-82, in order to meet the requirement that each fire pump has an independent intake pipe, the linking pipe was designed as a part of firewater tank instead of adoption the common design of intake pipe in the option. And the design makes velocity of water intake inside the linkoing pipe lower(The flow is the one at the worst-case, and the situation where a grid is under maintenance).
Advantage:When a certain grid is under cleansing and maintenance, each pressure fire pump can be ready to work. And because the linking pipe can be stepwise maintained, it increases the reliability of the whole fire-fighting system.
Disadvantage:Since there are three control valves on the linking pipe, it increases the cost and the occupancy of space.
AAlthough FSHCBD(GB50045-95) doesn‘t have an explicit requirement for the working state of backup fire pump when a certain grid is under maintenance, the comparisons dons in this paper indicate that Option 3 is the most reliable and recommended by authors as a priority. Especially when there is no significant increase in cost(three valves and linking pump)and enough space in the room of pump station.

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