Application of PLC in fire pump

2022-08-17
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Application of PLC in fire pump

Abstract: at present, most of the fire pumps can not achieve regular trial operation, resulting in the pump body, bottom valve and one-way valve stuck and rusted. Programmable logic controller (PLC) is used to control the fire pump group, so as to realize the regular trial operation of the pump group when it is in standby and automatic startup when fighting a fire, so as to effectively eliminate the situation that the fire pump cannot be used at critical moments

key words: fire pump programmable controller (PLC) automatic inspection interface circuit Untitled Document preface at present, high-rise buildings are everywhere in all kinds of cities. In order to prevent accidental fires, high-rise buildings are generally so that we can immediately know the problem. There is a special pump set for fire fighting. Although the specifications and regulations clearly require that fire-fighting facilities and equipment should be maintained regularly, does the machine not respond after the test machine point rises (or falls)? Maintenance. However, at present, the fire pump cannot be commissioned regularly, which will cause the pump body, bottom valve and one-way valve to be stuck and rusted over time. Therefore, the equipment often fails to play its role fully in the event of fire, resulting in undue losses. Therefore, the code for design of water fire extinguishing system in civil buildings stipulates that the fire pump of super high buildings and class I high-rise public buildings should be equipped with self-test device. In 1999, the state fire protection administration required that all fire-fighting equipment must have self-test function, and the fire control equipment must be automatically started once within 15 days to prevent the water pump from rusting and corrosion. In addition, the revised code for fire protection design of buildings also puts forward that fire water supply equipment must have the function of automatic inspection. Usually, the old equipment adopts the backward relay contactor control mode, with too many intermediate relays and timing relays, few functions, complex lines, and many contacts, resulting in many faults, poor reliability, and difficult maintenance. We use the programmable controller (PLC) of Beijing kaidean Automation Technology Co., Ltd. to control the fire pump set, so as to realize the regular trial operation of the pump set when it is in standby and the automatic start when fighting a fire, so as to effectively eliminate the situation that the fire pump cannot be used at critical moments. The vitality of PLC lies in that its input and output terminals are closer to field equipment, without adding too many intermediate parts or requiring more interfaces. It has high reliability, strong anti-interference ability, convenient maintenance, no adjusting components in hardware, low price and long service life. This not only saves users' time and cost, but also can be easily expanded according to different needs. 1. Automatic patrol function in the automatic state (patrol switch on), when there is no fire water demand, the first water pump starts (star) seconds (the start time is determined according to the equipment), runs (triangle) for 10 seconds, and then stops for standby hours (five to fifteen days). If there is no fire water during the standby period, the second water pump will start for seconds, run for 10 seconds, and shut down for standby hours, which is likely to indicate that everyone has no money. Such a cycle will be repeated (inspection cycle: any choice from several hours to hundreds of hours). The electric control cabinet is equipped with overpressure protection, and from a reliable point of view, a pressure relief valve should be set. When there is a demand for fire water, the pump set will automatically start immediately and pressurize the water supply to give full play to its application role. In order to avoid damage to the pipe due to pressure increase, we add a solenoid valve in the pipe. The solenoid valve is opened for pressure relief only when the pump is started during patrol inspection, and the working time of pump startup during patrol inspection is also delayed to 10 minutes. 2. Mode and sequence of pump startup when multiple pumps are started automatically, in order to avoid excessive impact on electricity caused by putting water pumps into operation at the same time, one pump is started at an interval of 20 seconds. When the pump is started automatically and in patrol inspection, three audible and visual alarms are sent first (the alarm is 2 seconds apart), and then the pump is started. When the working pump of the equipment fails (overload and short-circuit signals), the standby pump should be able to automatically put into operation (delayed for 10 seconds), because of the importance of the fire pump, the standby pump operation is not equipped with overload protection. The pump can be started by power frequency direct start, self coupling step-down start, Y - △ step-down start, thyristor soft start control, variable frequency constant voltage control and other methods to meet different use requirements. And the starting sequence can be selected. For example, the starting sequence of two pumps includes one for use and two for standby, two for use and one for standby; The starting sequence of the three pumps includes 1, 2 for use and 3 for standby, 2, 3 for use and 1 for standby, 3, 1 for use and 2 for standby, etc. 3. Control cabinet panel display in the design of automatic control system, we designed a fault display alarm system. Use the indicator light to indicate the normal operation and fault condition of the equipment. When the equipment is started, the indicator light flashes at the frequency of 1Hz. The corresponding indicator light is always on during normal operation. When there is a fault in the operation of the equipment, the fault indicator light is always on. In order to prevent the bulb of the indicator light from being damaged and not correctly reflecting the working condition of the equipment, a fault test button is specially set. Press any button continuously for 3S at any time when the system is running, and all the indicator lights should be on. If there is an indicator that does not light at this time, it means that the indicator light is broken, and it should be replaced immediately. After the button is reset, the indicator light still displays the working state of the equipment according to the original working state. 4. Fault display when the equipment fails, the signal box will prompt the staff with audible and visual alarms to deal with the fault in time. When dealing with faults, the faults are classified. Some faults require the system to stop running, but some faults have little impact on the system work. The system can run with faults, and the faults can be eliminated during operation, which greatly reduces the shutdown time of the whole system and improves the reliable operation level of the system. 5. In order to match the interface circuit with the equipment of various manufacturers, the electric control cabinet has two ways to start the pump: 1 One pump start signal and one pump stop signal to build an aluminum based new material industrial base with core competitiveness are generally used for multi line manual or automatic control of the fire center, and can also be used for low-pressure pump start, overpressure and water shortage pump stop. 2. A signal that turns on the pump and turns off the pump is generally used for module control. In order to cooperate with the fire hydrant button to directly start the pump, a 24v5a DC power supply is provided outside the cabinet. The interface circuit is all DC 24V power supply, and the module can be directly controlled by passive contact without switching module conversion, but the control signal must be passive contact signal. The feed back signal of the water pump is a passive contact signal. 6. Protection function the electric control cabinet has fault alarm and protection functions such as overvoltage, undervoltage, overcurrent, short circuit, phase loss, water shortage and so on. In order to avoid frequent start and stop of the water pump due to overpressure and water pressure fluctuation when using fire water, we used "time-delay filtering" in the program. 7. Other functions will stop all running pumps during automatic and manual switching; The dual power switching function can be added according to the needs of users, or a separate dual power mutual switching cabinet can be equipped. The main and standby power supplies can be automatically or manually

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