Discussion on the problems of several fire pumps

Discussion on several problems of fire water pumps

most fire water sources provide fire water, which needs to be pressurized by fire water pumps to meet the requirements of water pressure and volume during fire extinguishing. The failure of the water pump due to improper setting and maintenance is bound to affect the fire fighting and rescue, resulting in unnecessary losses. Here, the author talks about his personal understanding of several fire pump problems encountered in his work, in order to correct them

I. is it necessary to set up special fire pumps in multi-storey buildings? Article 8.6.3 of the code for fire protection design of buildings (hereinafter referred to as the "building code") stipulates: "buildings with temporary high-pressure water supply systems should be equipped with fire water tanks or air pressure water tanks, water towers". According to this regulation, buildings with temporary high-pressure fire water supply system for hardness test shall be equipped with fire water tanks. Most of these buildings are multi-storey buildings with 4 or 5 floors, and the pressure of municipal pipes is generally 20 to 30 meters of water column. In order to meet the needs of enriching the water column required by the fire hydrant at the most unfavorable point, such buildings should also be equipped with fire pumps. However, the purpose of setting indoor fire hydrant system in multi-storey buildings is only to put out the initial fire, and a lot of fire fighting work also depends on the urban fire brigade. Therefore, it is inevitable that there is a little wave in setting fire pumps, and then it is converted to the computer screen through CCD camera to enlarge the cost. For such buildings, I wonder if we can learn from the practice of setting pressurization facilities on the outlet pipe of the fire water tank in high-rise buildings. The outlet pipe of the fire water tank is equipped with a booster pump that can be started by the button in the fire hydrant box or the water flow indicator on the outlet pipe of the fire water tank to meet the needs of enriching the water column. In this way, the booster pump is set on the roof, which is started under light load and has fast starting speed, which should be beneficial to extinguishing the initial fire

in addition, on the premise that the municipal pipe can meet the indoor and outdoor fire water consumption, I wonder whether we can consider whether to set fire pumps according to the different uses of the building. That is, in the plant area and large public buildings, it is advocated to set up fire pumps to make them have a certain self-help ability, while in ordinary residential buildings, it is allowed not to set up fire pumps. In case of fire, fire engines use pump adapters to spray water outdoors for fire extinguishing. After all, even if fire pumps are set up in residential buildings, residents may not be able to use them correctly

II. Performance and testing requirements of fire pumps

compared with domestic water pumps and production water pumps, fire pumps should have higher requirements in performance, but China's current specifications do not make detailed special provisions on the performance and testing requirements of fire pumps, resulting in the lack of evidence for the selection of fire pumps and a variety of problems. The performance requirements of American nfpa20 for fire pump are: the maximum flow of fire pump should be 150% of the design value, the lift should not be less than 65% of the lift at the selected working point, the lift when the pump is shut down should not be greater than 140% of the lift at the selected working point, the flow of stabilized pressure pump should be 1-2l/s, and the lift should be 1.1-1.2 times of the lift of fire pump. At the same time, it is stipulated that a flowmeter for measurement should be set on the outlet pipe of the fire pump, which should be able to test 175% of the selected flow of the pump. A pressure gauge with a diameter greater than 89mm should be set on the outlet pipe of the fire pump. It is suggested that the relevant departments should refer to the American standards and put forward more targeted and clear requirements for the design and selection of fire pumps in China, so as to provide basis for the selection and detection of fire pumps

III. laying of water pump lines

it is found in many design drawings that the power supply and distribution lines and control lines of the fire pump are mostly protected by PVC pipes, and the wires are routed from the ceiling. The author believes that this routing method is inappropriate. Although the building code only requires that the distribution lines of fire-fighting electrical equipment should be laid in metal pipes when exposed, and it does not require that they should be protected by metal pipes when concealed, article 24.8.5 of the code for electrical design of civil buildings (hereinafter referred to as the civil code) requires that fire-fighting linkage control, automatic fire-extinguishing control, etc. lines should be laid in non combustible structural layers with flame-retardant cables through steel pipes, and the thickness of the protective layer should not be less than 3cm. When they must be laid in the open, Fire prevention measures shall be taken on metal pipes. Article 8.2.2 of code for design of automatic fire alarm system (hereinafter referred to as "code for automatic fire alarm") also makes corresponding provisions. We know that the fire pump will still play a role in a period of time after the fire to complete the fire fighting work of the building. Therefore, during this period of time, it is still necessary to ensure the safety of the water pump line. If the distribution room is far away from the electrical shaft, and the fire-fighting electrical equipment has a large capacity, and the line cannot be laid in a concealed manner, it can be laid in the ceiling after taking effective fire prevention measures. In this case, the use of fire-resistant slot boxes should be avoided, because the ceiling is also a fire prone area, and the lines laid in the ceiling are not safe in case of fire, and the slot boxes can only prevent the damage of external combustion to the lines, but cannot prevent the fire caused by the failure of the lines in the slot boxes. It is suggested that fire pumps and other important fire-fighting equipment should be powered by fire-resistant cables to ensure that they can continue to work in a certain period of time in case of fire

IV. whether the fire pump should be equipped with overload protection

the fire pump is an important equipment for fire fighting and rescue, and plays a very important role in fire fighting. According to our habitual thinking, all important equipment should be equipped with overload protection. However, articles 8.6.3.5 and 10.2.2.4 (3) of the civil code stipulate that "for distribution lines whose sudden power failure will cause greater losses than that caused by overload, overload protection appliances that cut off the circuit (such as the power supply line of fire pump) should not be installed, but overload alarm appliances should be installed". According to this regulation, the fire pump should not be equipped with overload protection cut-off device. This is mainly considering that in case of fire, we should make every effort to ensure the need of fire water, because the possible line and equipment losses caused by pump overload are insignificant compared with fire losses. However, in engineering practice, even in some standard construction drawings, including the electrical diagram of the fire pump introduced in the current teaching materials of colleges and universities, the overload protection cut-off appliance is still added to the fire pump circuit, such as "diagram of full voltage start-up fire pump control device of high-rise building fire protection system (II)" on page JD of the atlas of building electrical installation engineering. This obviously does not meet the specification requirements

v. control of fire pump

(1) control voltage. Article 24.6.2.1 of the Civil Code stipulates that the button for starting the fire water pump and the control circuit of the pump start signal lamp set in the fire hydrant box should adopt a safe voltage below 50V. Article 24.9.11 stipulates that the DC operation power supply voltage of the fire linkage device shall be 24V. This is mainly to prevent the fire hydrant box, water and water gun from being electrified and injuring firefighters when using the fire hydrant (this kind of injury accident is heard from time to time). However, in the construction practice and some reference materials, the operating power supply voltage of the fire hydrant button is still connected to AC 220V. For example, the atlas mentioned above made such a mistake on the same page

(2) start control. The fire hydrant pump can be controlled and started in three places. ① According to the requirements of the building code and the code for fire protection design of high rise civil buildings, the indoor fire hydrant box is directly started. ② According to the requirements of automatic alarm specification, it is controlled in the fire control room. ③ It is controlled near the fire hydrant pump in the water pump room. In this way, we should correctly deal with the following two problems: first, we should correctly determine the control priority of fire control room, fire hydrant button and fire pump room. Generally speaking, the remote operation of the fire control room should be the main. However, since the relevant departments do not have a clear guiding standard for remote operation, there are many practices in engineering practice, which are inevitably mixed in rationality and operability. Some simply connect the pump start/stop button to the manual pump start/stop button of the secondary circuit in parallel/series, some simply remove the thermal relay, and most of them set manual/automatic transfer switches on the pump room control cabinet, which are usually placed in the automatic position. We believe that these methods are inappropriate. In the article "Discussion on the design of remote operation of fire pump", Comrade Song Gaofei proposed that the action contact of the remote operation relay should be directly connected to the coil circuit of the main contactor of the fire pump to directly start the fire pump. We think the assumption is good, which not only solves the problem of direct start-up, but also facilitates the unified monitoring of the control room, and also meets the need that the fire pump can be started remotely when the pump room control cabinet is in any state. The second is to determine how to start the fire pump. In order to put the fire-fighting equipment into operation as soon as possible to reduce the fire loss, and considering that most non fire loads have been cut off during the fire, the fire pump should give priority to the full pressure direct starting mode

(3) fault control. According to the requirements of article 4.2.1 of the code for automatic alarm, the fire control room shall be able to display the fault status of fire-fighting equipment. Due to technical problems, the fire control can display simple fault signals such as power failure, while for other fault signals such as fire pump overload fault signals, because the implementation method is not clearly described in the "automatic alarm code" and "Civil Code", this point is often avoided in construction practice, which affects the correct detection of equipment faults in the control room

(4) replace the fire hydrant button with a manual alarm button to start the pump. It is popular to use the manual alarm at the fire hydrant to replace the fire hydrant button to start the pump in the actual project. In the project, double contact buttons are mostly used. One contact is used as the manual alarm to transmit the alarm signal to the fire alarm controller, and the other contact is used as the pump start button to send the pump start signal to the control room and start the pump through the double switch box. However, according to article 8.6.2 (IX) of the construction plan and article 7.4.6.7 of the high standard, each fire hydrant shall be equipped with a button to directly start the fire pump. The manual alarm button to start the pump is to feed back the fire signal to the alarm linkage controller, and then start the fire pump by the controller after confirmation, rather than directly start the fire pump. Moreover, this alternative method puts forward higher requirements for the automatic alarm system. At present, due to the high false alarm rate and operating costs of the automatic alarm system, the automatic alarm system of some buildings often operates with diseases or even does not open, which is difficult to play its due role. Therefore, we believe that it is not recommended to use the manual alarm to replace the fire hydrant button to start the fire pump

VI. regular maintenance of fire pump

although the specifications and regulations clearly require that fire-fighting facilities and equipment should be maintained regularly, at present, the fire pump can not achieve regular commissioning, which leads to the pump body stuck and rusted for a long time, so that it cannot play its due role in case of fire. On October 25, Guangzhou disclosed that the fire-fighting facilities in Yide Road comprehensive market in Yuexiu District could not operate normally in case of fire due to lack of maintenance under the title of "why the 500000 yuan fire-fighting facilities could not drip out", causing huge losses. Therefore, we suggest that the specification requires the use of programmable logic controller (PLC) in the fire pump to control the pump set, so as to realize the regular trial operation of the fire pump when it is in standby and the automatic startup when fighting a fire, so as to effectively eliminate the situation that the fire pump cannot be used at critical moments

the above opinions are only our superficial opinions. Please correct any mistakes

reference materials:

1. Fire water supply people's Publishing House

2. Discussion on the design of remote operation of fire pump song Gaofei, Chen Pu