Discussion on several fire pumps

2022-08-01
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Discussion on several fire water pump problems

Abstract: in view of several common problems in the design, construction, use and maintenance of fire water pumps, this paper briefly expounds my personal point of view

subject words: performance protection control for 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 water volume during fire extinguishing. The failure of the water pump due to improper setting and maintenance will inevitably 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. whether it is 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 that "buildings with temporary high-pressure water supply system shall be equipped with fire water tanks, air pressure water tanks and water towers". According to this regulation, buildings with temporary high-pressure fire water supply system shall be provided with fire water tanks. Most of these buildings are multi-storey buildings with 4 or 5 floors, while 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, these 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 large amount of fire fighting work still depends on the urban fire brigade. Therefore, setting fire pumps is inevitably a bit wasteful. For such buildings, I wonder if it is possible to 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. It is started with 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 it is possible to determine 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 recommended to set up a fire pump with acid and oil to detect the evaporation residue, so that it can have a certain self-help ability. In general residential buildings, it is allowed not to set up a fire pump. In case of fire, the fire truck uses the pump connector to spray water outdoors. After all, even if the fire pump is set in the residential building, the residents may not be able to use it correctly

II. Performance and test requirements of fire pumps

compared with domestic water pumps and production water pumps, fire pumps should have higher performance requirements. However, China's current specifications do not make detailed special provisions on the performance and test requirements of fire pumps, resulting in no evidence for the selection of fire pumps and a variety of problems. The performance requirements of nfpa20 for the fire pump are: the maximum flow of the fire pump shall be 150% of the design value, the lift shall not be less than 65% of the lift at the selected working point, the lift when the pump is shut down shall not be greater than 140% of the lift at the selected working point, the flow of the stabilized pressure pump shall be 1-2l/s, and the lift shall be 1.1-1.2 times of the lift of the fire pump. At the same time, it is specified that a flowmeter for measurement shall be set on the outlet pipe of the fire pump. The flowmeter shall be able to test 175% of the selected flow of the pump. A pressure gauge with a diameter greater than 89mm shall be set on the outlet pipe of the fire pump. It is suggested that the relevant departments should put forward more targeted and clear requirements for the design and selection of fire pumps in China with reference to American standards, 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 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 be laid in metal pipes when exposed, and does not require that they 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 the lines of fire linkage control and automatic fire-extinguishing control should be laid in the incombustible structure layer 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 protection 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 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 trough boxes should be avoided, because the ceiling is also a fire prone area, the lines laid in the ceiling are not safe in case of fire, and the trough boxes can only prevent the damage of external combustion to the lines, but can not prevent the fire caused by the failure of the lines in the trough boxes. It is suggested that fire pumps and other important fire-fighting equipment should be powered by fire-resistant cables to ensure that they will not be affected for a certain period of time in case of a fire

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

the fire pump is an important equipment for fire fighting and rescue, It plays a very important role in fire fighting (for example, rope samples with a diameter less than 1mm. According to our habitual thinking, all important equipment should be provided with overload protection. However, article 8.6.3.5 and article 10.2.2.4 (3) of the civil code stipulate: "for distribution lines whose sudden power failure will cause greater losses than those caused by overload, overload protection appliances (such as the power supply line of fire pump) that cut off the circuit should not be installed However, overload alarm apparatus shall be installed. According to this regulation, the fire pump shall not be equipped with overload protection cut-off device. This is mainly due to the fact that in case of fire, all efforts should be made to ensure the demand for fire water, because the possible line and equipment losses caused by pump overload are insignificant compared with the fire losses. However, in the actual project, even in some standard construction drawings, including the fire pump electrical diagram introduced in the current teaching materials of colleges and universities, the fire pump circuit still adds the overload protection cut-off device, such as "control device diagram for full voltage startup of fire pump in 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 control circuit of the button for starting the fire water pump and the pump start signal lamp set in the fire hydrant box shall adopt a safe voltage below 50V. Article 24.9.11 stipulates that the DC operating 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 by water overflow 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 started in three places. ① According to the requirements of building code and code for fire protection design of high rise civil buildings, the indoor fire hydrant box shall be started directly. ② It shall be controlled in the fire control room according to the requirements of automatic alarm specification. ③ It is controlled near the fire hydrant pump in the water pump room. In this way, the following two problems should be correctly handled: first, the control priority of fire control room, fire hydrant button and fire pump room should be correctly determined. Generally speaking, remote operation in the fire control room shall be the main method. However, since the relevant departments do not have a clear guidance standard for remote operation, there are many practices in engineering practice, which are both reasonable and operable. This paper will teach the plastic type selection of tensile testing machine. 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 the manual/automatic transfer switch on the pump room control cabinet, which is usually placed in the automatic position. We believe that these methods are not appropriate. In the article "Discussion on the design of remote operation of fire pump", songgaofei 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. It not only solves the problem of direct start-up, but also facilitates the unified monitoring of the control room, and also meets the need for remote start-up of the fire pump 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 fire losses, and considering that most non fire loads have been cut off in case of fire, the fire pump shall be started directly at full pressure first

(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 system can display simple fault signals such as power failure, while for other fault signals such as overload fault signal of fire pump, the implementation method is not clearly described in the automatic alarm specification and civil regulations, which is often avoided in construction practice, affecting the correct detection of equipment faults in the control room

(4) use the manual alarm button instead of the fire hydrant 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, the double contact button is 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 to 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 level plan, each fire hydrant shall be provided 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 the controller starts the fire pump after confirmation, rather than directly starting 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 operation cost of the automatic alarm system, the automatic alarm system of some buildings often runs with problems or even does not open, so it 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 being stuck and rusted for a long time, so that it can not 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 fire-fighting facilities of 500000 yuan could not spray water", resulting in 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

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