Compared with constant speed operation, the constant speed water pump is notable for its obvious energy saving effect. However, speed governing pumps are used in water supply systems with different conditions, but there are obvious differences in energy saving effects. Energy consumption may even be obviously wasted and water supply safety is poor. In the water supply system with fire water supply, the use of speed pumps without water supply tank is an example. The Code for Fire Protection of Building Design (hereinafter referred to as "Construction Regulations") and "Code for Fire Protection Design of High-rise Civil Buildings" (hereinafter referred to as "High Regulation") stipulate that buildings with high pressure (normal high pressure) fire- Adverse points of fire hydrants and automatic sprinkler equipment such as the amount of water and water pressure, may not set fire water tank. The concept of a high-pressure (often high-pressure) fire-fighting water supply system has two implications: at firefighting, the water supply system can supply sufficient pressure and full firefighting water without restarting a dedicated firefighting pump, and the water supply is guaranteed at all times. Accordingly, to discuss the following types of water supply system is in line with fire safety requirements and must meet the requirements of fire conditions. 1 Currently a typical speed pump water tank fire water supply system The system is usually filled in the network to meet the fire requirements of the pressure value P1, in order to prevent loss of water due to pipe network pressure drop, the use of pressure pump 3, this The pump is a small constant pressure water pump running at full speed at any time in the governor operation to supply the amount of water loss to ensure that the pipe network pressure value P1 unchanged. Regulator pump flow is generally small, often 0.5-1.0L / s. Fire, fire hydrant due to the large amount of water, pipe network pressure dropped to a predetermined pressure value P2, start the main fire pump to meet the water requirements and fire safety requirements. Another form of regulator pump 3 does not use constant pressure speed pump, but a small constant pressure pump pressure, known as booster pump. At this point, the design pressure is greater than the pipeline pressure P1 pressure value of a certain value of P3, when the pipe network due to loss of water pressure dropped to P1, the booster pump to start the pipe network recharge, pipe network pressure rose to P3 Pump stopped working, fill pump for intermittent work. Fire, due to fire hydrant water, pipe network pressure dropped to P1 below a certain pressure value P4, start the main fire pump to meet the water requirements and fire safety requirements. Booster pump flow is generally about 5L / s. From the above we can see: Figure 1 fire water supply system in the fire need to start the main fire pump to provide fire-fighting water and pressure requirements of the whole is a temporary high-pressure water supply system does not meet fire safety requirements. A design example of a more fire water supply system The system is a mixture of life and fire pump water tank without water supply system. Speed ​​?? pump for constant pressure speed, intended to speed pump to meet the pressure of domestic water changes to adapt to changes in domestic water consumption in order to achieve energy-saving purposes. Fire start fire pump to meet fire water and water pressure requirements. Obviously a temporary high-pressure water supply system, does not meet the fire safety requirements. 3 speed pump without water tank constant pressure water supply system This system is speed water pump constant pressure fire water supply system. Working speed pump 2 (or 3) continuous operation over many years, not only in the speed range to ensure the fire when the pressure requirements, but also linear continuous supply of fire during some or all of the water. In the implementation of the fire fighting process, did not start the fire pump link, protection personnel as long as the hose connected to the fire hydrant, immediately put out the fire. The system is a high pressure (often high pressure) fire water supply system. 4 high-pressure (often high pressure) water supply system, there must be a reliable power supply to ensure the normal operation of fire pumps in order to ensure uninterrupted water supply. "Construction Regulations" and "high regulation" in their respective norms, according to different types of buildings, fire water supply and fire regulations consistent with the level of fire power. Such as "high regulation" provisions of the fire control room, fire pumps, fire extinguishing devices, valves and other fire power, a class of buildings should be designed according to the current power load requirements of a load requirements, that is, from two power supply. When the load is not large, the diesel generator set can be used as a backup power supply, and the special buildings should obtain the third power supply or self-powered power supply from the power system. Two types of buildings should be two secondary load requirements of the two power lines. Two power lines or two lines should be able to automatically switch, owned power generation equipment should have automatic start device. "Build Regulations" also according to different types of buildings, the provisions of its fire power supply were one, two, three load power requirements. This means that the design of high pressure (often high pressure) fire fighting water supply systems takes the type of building and its fire rating into account. Figure 3 Although a high-pressure (high pressure) fire fighting water supply system is understood in the water supply system, a sudden power failure in buildings with low fire power supply levels can cause serious consequences of fire extinguishing without water. Fire power rating is the design of high pressure (often high pressure) fire water supply system necessary conditions. 5 Combined Life and Fire Pumps Water tankless water systems are a waste of energy. The wasted energy is the work done to lift the full-life water consumption to the pressure needed by the hydrant. For example, it is an 8-storey residential building with a population of 10,000 and a daily maximum water standard of 130L / person · d. The maximum daily water consumption is 1300m3. The pump works 24 hours and the average hourly water consumption is 54m3. The required water supply pressure is 36m water column , Pump efficiency of 73%. When Figure 3 is only used as domestic water supply system in this residential area, the constant pressure value of the variable speed water pump is 36m water column, and the full power consumption of the water pump is (0.00272 * 54 * 36) -0.73 * 24 = 174KW · h. According to "Construction Regulations" requirements, 8-storey residential fire water should be designed to design fire hydrant diameter DN50mm, nozzle diameter 16mm, diameter DN50mm Ma twist hose length 20m, water gun full length 7m, calculate the fire hydrant port pressure 11.39m water column, Then the residential area in Figure 3 as the life and fire water system, the constant pressure pump speed value should be 36 +11.39 = 47.39m water column, usually no fire, the speed pump will still raise the total domestic water consumption to 47.39 (0.00272 × 54 × 47.39) ÷ 0.73 × 24 = 229kw / h, the water supply system consumes more electricity, (229-174) ÷ 174 = 0.316, which means 31.6% Water column length 10m, calculate more power consumption 50%. Then consider the speed of the pump under the operation of low-flow area of ​​?? low efficiency, the power consumption is much greater than the above value. 6 speed pump without water tank fire water supply system is a waste of energy in the device. Figure 3 only as a fire water supply system, the speed control pump running for many years, only to supplement the pipe network volume little leakage of water, or even to zero flow, resulting in long-term low-efficiency pump speed work area, only the pump zero flow power loss in vain Wasted about 40% of energy. Through the above discussion and analysis, speed control pumps used in fire water supply system, not only require a high level of fire power, but also in the long run more energy consumption, wear and tear fire engine maintenance and management caused inconvenience, it is not economical. Therefore, except in very special conditions, should not be used.