Abstract: The main standby switch of fire pump is the necessary condition to ensure the operation of fire reserve pump. The key to its switching method is the choice of control signal. In this paper, comparing the two main methods of switching between fire pump and standby, this paper puts forward the method that the pressure signal control method is better than the current signal in the fire water supply system and the pressure signal control method is suggested.
Key words: fire pump; fire standby pump; switching method; fire pump comparison is the heart of the water supply system. In the fire water system, the installation of fire reserve pump can increase the safety of the entire system, help to improve the reliability of the entire fire water system. According to the national standard "Code for fire protection of building design" (GBJ 16-87), except for factories, warehouses and units of seven to nine storeys with outdoor fire fighting water consumption not exceeding 25 L / s, fixed fire pumps shall be provided Spare pump, its working capacity should not be less than a main pump. 7.5.3 of "Code for Fire Protection of High-Rise Civil Buildings Design" (GB50045-95) also stipulates that fire-fighting water supply system shall be equipped with spare fire-fighting water pump. The main standby switch fire pump standby fire pump to achieve an important means of investment, but also fire water supply system, reliable, safe operation of an important part.
1. Fire pump standby switchover method From the fire pump start signal acquisition and control point of view, the design of fire pump standby switchover There are two main ways. The key is to control the choice of signal source, which can be divided into current signal control method and pressure signal control method. Usually fire pump main and backup pumps are required to be mutually alternative way to design.
Current signal control method is now the fire control design of fire pump standby switch the common method. It is through the pump motor current signal feedback to determine whether the fire pump is working. When the motor is short circuit (power off), the current is too large, the power automatically switches to another pump unit motor, stop the first fire pump, start another fire pump.
Pressure signal control method is set in the fire pump water outlet manifold node pressure gauge, as shown in Figure 1, the main fire pump standby switch is judged by the pressure gauge signal. When the fire pump control box received an action command, immediately start any fire pump, fire pump if the work of the electricity gauge pressure gauge indicates the pressure fails to reach the set pressure value, the control box will automatically switch to another Fire pump, start working.
Of course, the principle of electric fire pump control can be arbitrarily designated a fire pump as the main pump or spare pump. Current signal control method in the current domestic use of the earliest, most of the pressure signal control methods in foreign sprinkler system began to use, the pressure signal control method for automatic fire control system provides a reliable way.
2. The main standby switching method comparison
2.1 Analysis of the causes of fire pump failure Fire pump failure The final result is that the fire pump can not be normal water supply. Fire pump failure caused by the main reason can be divided into two categories, one is the motor failure, the other is the pump failure.
In the motor fault, there are power problems, such as power failure caused by abnormal power supply, the voltage is too high or too low; the motor itself, such as motor damage can not run; motor overload problem, motor driven pump shaft power is too large or Plumbing, the formation of the current is too large to stop working and so on.
In the pump failure, it may be due to pump bearings, impeller and other issues caused. According to the experience of engineering practice, the probability of motor failure than the probability of failure of the pump high.
2.2 fire pump standby switch method of analysis using current signal control method, which has the advantage of timely reflection of motor failure. The fault of the motor is also the main fault of the pump unit. However, this method does not explain whether the fire pump is actually out of water.
The use of pressure signal control method, you can truly reflect the actual working conditions of fire pump units, the switching signal credibility is high. Whether the motor failure or pump failure, as long as the fire pump outlet pressure does not reach a certain pressure value, you need to switch the main standby fire pump. However, the pressure signal control method also has its drawbacks. When the fire water system, the actual amount of water is large, the fire pump outlet pipe pressure drops, easy to cause the fire pump pressure switch signal malfunction, stop a fire pump switch to another fire pump start. Pump switching, restart need to have a certain amount of time. In this way, it is bound to cause fire water supply interruption, delay fire. In addition, the pressure signal control method can also be considered in the circuit design of the motor short circuit, overload, overvoltage, phase loss, undervoltage, overheating and other protection functions.
From the system point of view, the fire pump and motor as a whole fire pump unit point of view, to determine the final effect of its water supply that is whether the water pump unit, should be used to control the pressure signal of the main standby switching method is more reasonable. When the fire water supply system exceeds the design flow, it can be adjusted on the control circuit to expand the design of the fire pump capacity to ensure that all fire pumps work, and the fire pump power consumption during the fire only Is a part of the total fire power consumption, the entire fire power supply system will not cause a greater impact. In this way, the pressure drop in the outlet, the timely start of another fire pump, may need to consider the closure of the original fire pump.
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