Design and construction of indoor wet automatic sp

2022-07-23
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Several problems should be paid attention to in the design and construction of indoor wet sprinkler system in high-rise buildings

due to the rapid development of China's economic construction, high-rise and super high-rise buildings are increasing day by day. As one of the main fire-extinguishing systems of high-rise buildings and the most important fire-extinguishing system of super high-rise buildings, the wet automatic sprinkler system has also increased. In recent years, through the construction and commissioning of the wet automatic sprinkler system, I feel that the following points are easy to be ignored by the design and construction personnel, thus bringing certain difficulties to the commissioning, use and maintenance of the system

1. Selection of pipes

the closed sprinkler used in the wet automatic sprinkler system is easy to be blocked by debris due to its small aperture due to its water splashing performance requirements. Moreover, after the installation of the wet automatic sprinkler system, its fire extinguishing service times are less, and the pipeline rust is easy to settle in the pipe. Therefore, the pipes used in the wet automatic sprinkler system shall not be easy to rust. Therefore, galvanized steel pipe or galvanized seamless steel pipe shall be used. The application scope of galvanized steel pipe and galvanized seamless steel pipe in the system is specified in article 5.4.1 of the national standard of the people's Republic of China code for design of automatic sprinkler system cbj84-85: "galvanized steel pipe or galvanized seamless steel pipe shall be used for the pipeline after the alarm of the automatic sprinkler system". Through the construction and commissioning in recent years, I believe that galvanized steel pipe or galvanized seamless steel pipe should also be used in the pipeline in front of the alarm valve of the automatic sprinkler system as far as possible, so as to reduce the amount of rust and slag in the system pipeline and prolong the service life of the system

2. Setting of flow detection orifice

the wet automatic sprinkler system has strict requirements on the flow and pressure of the system when it acts to extinguish the fire, which has been reflected in the design and calculation of the system. However, after the system is constructed according to the drawings, how to actually detect the flow and water pressure of the system during fire extinguishing, and how to detect the flow and water pressure of the system after the system is handed over and put into use for a certain period of time, this series 2 The second is the ball screw, which drives the motion of the sensor. At present, the construction and commissioning personnel, the supervisors of the public security and fire department and the managers of the user units are all headache and thorny. Because in the design of wet automatic sprinkler system, there are few designs with system flow detection devices. Moreover, the design of special flowmeter is redundant, because there are few opportunities for the system to test the flow to continue to promote high-quality development and innovative development. At the same time, the special flowmeter also brings problems such as the increase of system resistance, the increase of project cost and the trouble of peacetime maintenance and management. For the selection of the system flow detection method, I think the method used by the British Fire Department Committee (FOC) in the automatic sprinkler system - to compile the orifice flow parameters of various apertures, the designer shall select the orifice according to the designed system fire extinguishing flow, install it at the lower end of the system discharge test valve on the alarm valve, open the system discharge test valve to discharge water, and observe the readings of the two pressure gauges before and after the orifice. It is a good method to check the table and calculate the flow and water pressure of the system behind the alarm valve. Of course, it also requires the fire-fighting or measuring equipment manufacturers to produce various aperture parameter flow detection orifice plates suitable for the automatic sprinkler system for selection by the relevant personnel of the design, construction, fire supervision departments and the management departments of the users

3. Filter setting

through the construction, commissioning and maintenance of the wet automatic sprinkler system, I feel that filters should be set in the following parts to ensure the correct operation of the system

1. A filter shall be set on the outlet pipe of the roof fire water tank connected to the wet automatic sprinkler system to prevent debris in the tank from entering the system

2. A filter is set on the suction pipe of the fire pump of the automatic sprinkler system to prevent debris in the fire water storage tank from entering the system

the debris in the fire water tank and the fire water storage tank enters the wet automatic sprinkler system. In addition to blocking the closed sprinkler, it may also block the alarm bell pipe hole connected to the annular groove of the wet automatic alarm valve seat ring, so that when the system acts to extinguish the fire, the water cannot flow to the hydraulic alarm bell and the pressure switch through the annular groove. As a result, the hydraulic alarm bell can not give an alarm, the pressure switch can not start to send an electrical signal, start the sprinkler fire pump and give an alarm to the fire control center. Or the slag is stuck in the annular groove of the wet automatic alarm valve seat ring, so that the alarm valve disc cannot be closed, and the water in the system continues to flow through the alarm annular groove to the hydraulic alarm bell and pressure switch, resulting in the false alarm phenomenon that the system does not act to extinguish the fire. It can be seen that it is very necessary to set filters at the above positions of the wet automatic sprinkler system

4. Setting of safety valve

wet automatic sprinkler fire pumps used in high-rise and super high-rise buildings are mostly large flow and high lift. When the rated lift reaches 1, the roughness will affect the accuracy; When the latter uses the servo system of 00m, the lift value of the fire pump when pressurizing the wet automatic sprinkler system pipeline under this closed state should be considered when the closed sprinkler in the system is not opened or the number of open sprinkler is small. If the lift exceeds 120m, a safety valve or other anti overpressure device shall be set in the system. In order to avoid water leakage of the closed sprinkler due to excessive lift and pressure when the fire pump pressurizes the pipeline of the closed wet sprinkler system. In addition, article 5.4.5 of the national standard of the people's Republic of China code for design of sprinkler systems gbj84-85 also stipulates that "the working pressure in the pipes of sprinkler systems shall not be greater than 1.177mpa (12kg/cm2)". In the selection of various anti overpressure devices, the safety valve is a relatively simple and feasible one. The operating pressure of the safety valve can be selected by the designer according to the working curve of the fire pump, and the drainage direction after the action of the safety valve should also be considered. The safety valve should be set in the pipeline system behind each alarm valve. Because the alarm valve disc has a check function, once the water pressure is too high, even if the safety valve before the alarm is operated to discharge water in the process of material test, the pressure of the pipeline system behind the alarm valve cannot be relieved. In order to facilitate the drainage after the action of the safety valve and reduce misoperation, it is better to set the safety valve on the roof. If the roof is unconditionally set, the safety valve can also be set in front of the check valve of the spray pump outlet pipe, and the outlet of the safety valve shall be connected to the fire pool or outdoor as far as possible

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