Application conditions and energy consumption anal

2022-08-09
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Application conditions and energy consumption analysis of variable speed water pump in water supply system

compared with constant speed operation, constant speed water pump is remarkable for its obvious energy-saving effect. However, when the speed regulating pump is used in the water supply system under different conditions, the energy-saving effect is obviously different, and it may even waste energy obviously, and the safety of water supply is poor. When the water supply system is equipped with fire water supply, the use of speed regulating water pump without water tank is an example

the code for fire protection design of buildings (hereinafter referred to as the "building code") and the code for fire protection design of high rise civil buildings (hereinafter referred to as the "high code") stipulate that buildings equipped with high-pressure (normal high-pressure) fire water supply systems may not be equipped with fire water tanks if they can ensure the water volume and pressure of fire hydrants and automatic sprinkler fire extinguishing equipment at the most unfavorable points. The concept of high pressure (constant high pressure) fire water supply system includes two meanings: during fire fighting, the water supply system can supply sufficient pressure and all fire water consumption without starting the special fire pump, and ensure that the water supply is not interrupted at any time. Based on this, discuss whether the following water supply systems meet the requirements of the fire code and the conditions that must meet the requirements of the fire code

1 at present, it is a typical speed regulating water pump fire water supply system without water tank

the system usually fills the pipe with the pressure value P1 that meets the fire protection requirements. In order to prevent the pressure drop caused by the water leakage of the pipe, the stabilized pressure pump 3 is used. This pump is a small constant pressure speed regulating water pump that operates all day. It replenishes the water leakage at any time during the speed regulating operation to ensure that the pipe pressure value P1 remains unchanged. The flow of stabilized pressure pump is generally small, usually 0 0L/s。 During fire fighting, when the pipe pressure drops to a specified pressure P2 due to the large water output of the fire hydrant, start the main fire pump to supply the water consumption and pressure that meet the fire fighting requirements. Another form is that the pressure stabilizing pump 3 does not use a constant pressure speed regulating pump, but uses a small constant speed pump to supplement pressure, which is called a pressure supplementing pump. At this time, the design pipe pressure is greater than a certain pressure value P3 of the fire-fighting required pressure value P1. When the pressure of the pipe drops to P1 due to water leakage, the jockey pump starts to make up water to the pipe, so that when the pipe pressure rises to P3, the jockey pump stops working, and the jockey pump works intermittently. During fire fighting, when the pipe pressure drops to a pressure value P4 below P1 due to the large water output of the fire hydrant, start the main fire pump to supply the water consumption and pressure that meet the fire fighting requirements. The flow rate of pressure makeup pump is generally about 5L/s. It can be seen from the above that the fire water supply system needs to start the main fire pump to supply all the water consumption and pressure requirements for fire fighting during fire fighting. It is a temporary high-pressure water supply system, which does not meet the requirements of the fire code. A fire water supply system with many design examples for general flexible packaging manufacturers

2

this system is a water supply system without water tank of speed regulating pump combining life and fire protection. Speed regulating water pump! For constant pressure speed regulation, it is intended to make the speed regulating pump meet the pressure of domestic water unchanged and adapt to the change of domestic water consumption, so as to achieve the purpose of energy saving. During fire fighting, start the fire pump to meet the requirements of fire water consumption and water pressure. It is obviously a temporary high-pressure water supply system, which does not meet the requirements of the fire code

3 constant pressure water supply system without water tank of speed regulating pump

this system is a constant pressure fire water supply system without water tank of speed regulating pump. The working speed regulating pump 2 (or 3) operates continuously for many years. Within the speed regulating range, it can not only ensure the pressure requirements during fire fighting, but also linearly and continuously supply part or even all of the water consumption in the fire fighting process. In the process of fire fighting, there is no link to start the fire pump. As long as the protective personnel connect the hose to the fire hydrant, they will immediately put out the fire. This system is a high pressure (normal high pressure) fire water supply system

4 the high-pressure (normal high-pressure) water supply system must have a reliable power supply to ensure the normal operation of the fire pump, so as to ensure the uninterrupted water supply

in the respective specifications of the construction plan and the high plan, the fire power level consistent with the fire water supply is specified according to the category of different buildings. For example, the "high standard" stipulates that fire control rooms, fire pumps, automatic fire extinguishing devices, valves and other fire-fighting power, class I buildings should be powered by two power sources according to the current power design code. When the load is not large, the diesel generator set can be used as the standby power supply. For special buildings, the third power supply or self-contained power supply should be obtained from the power system. Class II buildings shall be powered by two circuits of secondary 5.7 startup and landing or emergency stop button load. Two power supplies or two circuit lines shall be able to switch automatically, and the self-contained power generation equipment shall be equipped with automatic starting device. According to different types of buildings, the building code also stipulates that the fire power supply is the power supply requirements of class I, II and III loads respectively. That is to say, the design of high-pressure (normal high-pressure) fire water supply system should consider the type of building and its fire power level. Although the water supply system is understood as a high-pressure (usually high-pressure) fire water supply system, for buildings with low fire power level, sudden power failure will cause serious consequences of water-free fire extinguishing. The grade of fire power supply is a necessary condition for the design of high voltage (normal high voltage) fire water supply system

5 the water supply system without water tank of the speed regulating pump combined with life and fire fighting is a waste of energy. The wasted energy is the work of raising the daily domestic water consumption to the pressure required by the fire hydrant. For example, the residential area of an 8-story residential building has a population of 10000 people, the maximum daily water consumption standard is 130l/person · D, the maximum daily water consumption is 1300m3, the water pump works 24 hours, the average hourly water consumption is 54m3, the required water supply pressure is 36m water column, and the working efficiency of the water pump is 73%. When it is only used as the domestic water supply system of the residential area, the constant pressure value of the speed regulating pump is 36m water column, and the full day power consumption of the pump is ((0.00272*54*36) -0.73) *24=174kw · H. According to the requirements of the building code, the 8-story residential building should be equipped with fire water supply. The designed diameter of the fire hydrant is dn50mm, the diameter of the water gun nozzle is 16mm, the diameter of the dn50mm hemp woven hose is 20m long, the length of the water gun is 7m, and the calculated pressure of the fire hydrant port is 11.39m water column. Then the constant pressure value of the speed regulating pump of the water supply system integrating life and fire protection in the residential area should be 36+11.39=47.39m water column. When there is no fire protection at ordinary times, The adjustable speed water pump still lifts all domestic water consumption to a height of 47.39m, and the full day power consumption is (0.00272 × fifty-four × 47.39)÷0.73 × 24=229kw/h, the water supply system consumes more power, () ÷ 174=0.316, that is, 31.6%. If the water gun is filled with water column length of 10m during fire fighting, the extra power consumption is 50%. Then consider the low efficiency area work under the small flow operation of the speed regulating pump, and its power consumption is far greater than the above value

6 the fire water supply system without water tank of speed regulating pump is a waste. First of all, we need to know that the main component of wood flour is a device of cellulose + lignin + hemicellulose energy. When it is only used as a fire water supply system, the variable-speed water pump operates for many years, only replenishing the pipe volume, with little leakage of water, or even zero flow, resulting in the long-term low efficiency area of the variable-speed water pump, and the power loss of the water pump at zero flow is a waste of about 40% of the energy

according to the above discussion and analysis, the application of variable-speed water pump in the fire water supply system not only requires high-level fire power supply, but also consumes more energy in long-term operation. The wear of fire-fighting machinery causes inconvenience in maintenance and management, which is very uneconomical. Therefore, it should not be used except under very special conditions

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