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Comprehensive guide to key points regarding fire pumps. I. Installation requirements: Fire pumps must be installed in both temporary high-pressure and stable high-pressure fire water supply systems. In series fire water supply systems and gravity-based fire water supply systems, in addition to fire pumps, fire transfer pumps are also required. Fire pump systems should be provided separately for the fire hydrant water supply system and the automatic sprinkler system. Fire pump systems should be equipped with backup pumps, whose performance should be identical to that of the main pumps. However, backup pumps are not required in the following types of buildings: 1) Residential buildings with a height of less than 54 meters, and buildings where the designed outdoor fire water supply flow rate is 25 L/s or less. 2. Buildings with an indoor fire protection water supply design flow rate of less than or equal to 10 L/s. II. Series and parallel connections of fire pumps
In a series connection of fire pumps, the discharge outlet of one pump is directly connected to the suction pipe of another pump, with both pumps operating simultaneously. A series connection of fire pumps can increase the head while maintaining the same flow rate. The parallel operation of fire pumps involves two or more fire pumps supplying water to the fire protection water supply system simultaneously; the purpose of this parallel operation is mainly to increase the flow rate. III. Requirements for the installation of fire pumps and their piping systems 1. Fire pumps should be capable of drawing water in a self-priming manner. 2. When the fire pump draws water directly from the municipal water supply network, a check valve with an air separator should be installed on the outlet pipe of the fire pump. 3. When there is no water intake well at the water intake, a swirl preventer should be installed there. 4. For a set of fire pump systems, there should be no fewer than two suction pipes; when one of them is damaged or under maintenance, the remaining suction pipes should still be able to handle the entire designed flow rate of the fire water supply. 5. The layout of the suction pipes for fire pumps should avoid the formation of air pockets. 6. A set of fire pump systems shall be equipped with no less than two main water supply pipes to connect to the fire water supply ring network; when one of these pipes is under maintenance, the remaining pipes shall still be able to supply the entire designed flow rate of fire water supply. 7. The submersion depth of the suction inlet of the fire pump shall meet the requirements for safe operation of the fire pump at the lowest water level. The submersion depth of the suction pipe nozzle below the lowest effective water level of the fire tank shall be determined based on the flow velocity and hydraulic conditions of the suction pipe nozzle, but it shall not be less than 600 mm. When a swirl preventer is used, the submersion depth should not be less than 200 mm. 8. A rising-stem gate valve or a butterfly valve with a self-locking device shall be installed on the suction pipe of fire pumps; however, when a non-rising-stem valve is used, it must be equipped with opening scales and markings ； When the pipe diameter exceeds DN300, it is advisable to install electric valves. 9. A check valve and a rising-stem gate valve shall be installed on the discharge pipe of the fire pump ； When butterfly valves are used, they should be equipped with a self-locking device ； When the pipe diameter is greater than DN300, electric valves should be installed. 10. When the diameter of the suction pipe of the fire pump is less than DN250, its flow velocity should be between 1.0 and 1.2 m/s ； When the diameter is greater than DN250, it should be 1.2–1.6 m/s. 11. When the diameter of the discharge pipe of a fire pump is less than DN250, the flow velocity should be 1.5–2.0 m/s ； When the diameter is greater than DN250, it should be 2.0–2.5 m/s. 12. The layout of the water intake wells should ensure smooth water flow within the wells, uniform flow velocity, and the absence of vortices, while also facilitating installation and construction. 13. When the suction pipes and discharge pipes of fire pump systems pass through exterior walls, waterproof sleeves should be used ； When passing through walls and floors, the relevant regulations must be complied with. 14. When the suction pipe of the fire pump passes through the fire water tank, a flexible sleeve should be used ； When using rigid waterproof sleeves, a flexible joint should be installed on the water pump suction pipe, and the pipe diameter should not exceed DN150. IV. Starting device for fire pump 1. The fire pump should be capable of being started and stopped manually as well as automatically, and it must be ensured that the automatic start-up time from receiving the start signal to the pump beginning to operate properly is no more than 2 minutes. Fire pump systems should not be equipped with an automatic shutdown function; the shutdown of the pumps should be decided by personnel with authority, based on the progress of fire fighting efforts. 2. The fire pump should be able to start automatically upon receipt of signal from switches such as the pressure switch installed on the fire pump’s discharge main, the flow switch on the outlet pipe of the elevated fire water tank, or the pressure switch of the alarm valve. The pressure switch in the fire pump room should be incorporated into the fire pump control cabinet. 3. Fire hydrant buttons should not be used as switches to directly start fire pumps, but they can be used as switches to send alarm signals or to activate rapid opening and closing devices for dry fire hydrant systems. 4. The pressure-stabilizing pump should be controlled by a pressure switch or pressure transmitter installed on the fire water supply network or air tank, which is used to automatically start and stop the pump. V. Requirements for the commissioning of fire pump systems 1. When the fire pump is started automatically or manually, it should begin operating properly within 55 seconds, without any abnormal noise or vibration. 2. When fire pumps are started by means of switching to a standby power source or switching to a standby pump, they shall be brought into normal operation within 1 minute or 2 minutes, respectively. 3. After installation, the fire pump shall undergo on-site performance testing; its performance shall be consistent with the data provided by the manufacturer, and it shall meet the requirements regarding the design flow rate and pressure for fire water supply. 4. The pressure of the fire pump at zero flow rate shall not exceed 140% of the designed operating pressure ； When the discharge flow is 150% of the design operating flow, its outlet pressure shall not be lower than 65% of the design operating pressure. VI. Maintenance and Management of Fire Pumps
1. The fire pump should be manually started once a month, and the status of the power supply should be checked. 2. Once a week, the fire pump should be started automatically under conditions simulating its automatic control, and the results of these automatic inspections should be recorded automatically; such records should be checked and kept on a monthly basis. 3. The voltage of the starting battery for the diesel fire pump should be checked daily; the amount of fuel in the fuel tank should be inspected weekly, and the diesel fire pump should be started manually once a month. 4. The flow rate and pressure of the fire pumps shall be tested once every quarter. VII. Review of Past Exam Questions 【2015 Technical Practice 51】A building is equipped with a temporary high-pressure fire water supply system; calculations show that the designed head for the fire pump is 0.90 MPa. When selecting a fire pump, the pressure of the fire pump at zero flow rate should be between ( ) MPa. A. 0.90~1.08 B. 1.26~1.35 C. 1.26~1.44 D. 1.08~1.26 【Answer】D 【Explanation】According to Article 5.1.6 of the Code, the flow-head performance curve should be a smooth curve without humps or corners; the pressure at zero flow rate should not exceed 140% of the design operating pressure, and it is preferable that it be greater than 120% of the design operating pressure ； When the discharge flow is 150% of the design flow, its outlet pressure should not be lower than 65% of the design operating pressure. The answer to this question is D. Note: The fire pump can operate at any point on its performance curve; therefore, it is required that its flow and head performance curve be smooth without any peaks, so as to avoid surge operation of the pump. The pressure at zero flow rate in fire pumps should not exceed 140% of the rated design pressure. This is to prevent excessively high pressures during operation at low flow rates, which could lead to excessive costs associated with the system’s piping network or to overpressure conditions within the system. The pressure at zero flow rate should not be less than 120% of the rated pressure. This is because the control and prevention of overpressure in fire protection water supply systems are both achieved through pressure regulation. If the performance curve of a fire pump lacks a certain slope, it becomes difficult to achieve proper pressure and hydraulic control. Therefore, upper and lower limits for the pressure at zero flow rate have been established for fire pumps. 【2016 Technical Practice 63】Which of the following statements regarding fire water supply systems is incorrect? （） A. Connecting fire pumps in series can increase the head while keeping the flow rate constant, whereas connecting them in parallel can increase the flow rate. B. The control cabinet for fire pumps should ensure that they start automatically under normal conditions. C. The indoor fire hydrant supply network should be separated from the networks of other fire suppression systems such as sprinkler systems; when the same fire pumps are used, the supply pipes should be divided after passing through the alarm valves, in accordance with the direction of water flow. D. Outdoor fire water supply pipes should be divided into several separate sections using valves, with no more than 5 outdoor fire hydrants in each section. 【Answer】C 【Explanation】Connecting fire pumps in series involves directly linking the outlet of one pump to the inlet pipe of another pump, with both pumps operating simultaneously. Connecting fire pumps in series can increase the head while keeping the flow rate constant. The parallel operation of fire pumps involves two or more fire pumps supplying water to the fire protection water supply system simultaneously. The main purpose of paralleling fire pumps is to increase the flow rate; option A is correct ； The fire pump control cabinet should be installed in the fire pump room or a dedicated fire pump control room, and it must ensure that the fire pumps are in an automatic start mode under normal conditions; option B is correct ； According to Article 8.1.7 of the Fire Protection Code, the indoor fire hydrant supply network should be installed separately from the networks of other water-based fire suppression systems such as automatic sprinkler systems ； When fire pumps are used together, the water supply pipes should be separated in the direction of water flow in front of the alarm valve. According to 8.1.4-3, fire supply pipes should be divided into several separate sections using valves; the number of outdoor fire hydrants in each section should not exceed 5, so option D is correct. The answer to this question is C. [2016 Comprehensive Ability 72] A fire protection testing agency conducted tests on the fire water supply system of a high-rise office building classified as Category II. Outside the building, there are two fire water inlets. The designed flow rate of the automatic sprinkler system is 27 L/s, and the designed head is 1.0 MPa ； The design flow rate for the indoor fire hydrant system is 20 L/s, and the design head is 0.98 MPa ； The effective distance from the minimum effective water level of the elevated fire water tank to the sprinklers on the highest floor is 10 m. Upon checking the inspection and acceptance report, all tests for the system have passed. To test the performance and operating conditions of fire pumps, among the following test results, which one complies with the current **fire protection technical standards?** A. The pressure of the automatic sprinkler pump at zero flow rate is 1.50 MPa. B. After the test device at the most unfavorable point in the automatic sprinkler system is opened for 5 seconds, the flow switch sends a signal to start the automatic sprinkler pump. C. The motor stops operating when the flow rate of the fire pump reaches 25 L/s. D. When the flow rate from the test fire hydrant in the indoor fire hydrant system is 3 L/s, the fire pump does not start. [Answer] Controversial [Explanation] According to Article 5.1.6-4 of the Fire Protection Code, the pressure of the fire pump at zero flow rate should not exceed 140% of the designed operating pressure, and it should be greater than 120% of that designed operating pressure ； For this project, the design head of the automatic sprinkler system is 1.0 MPa; therefore, the pressure at zero flow rate should not exceed 1×1.4=1.4 MPa, so option A is incorrect ； In a fire hydrant system without a pressure-stabilizing pump, the fire hydrant pump should be activated by a flow switch located on the outlet pipe of the high-level fire water tank. The fire pump should start when the flow rate exceeds 1% to 3% of the designed flow rate for the fire supply system; in other words, when it is greater than 0.6 L/s. The sprinkler pump should be activated when the flow rate is greater than 0.81 L/s, and the fire hydrant pump should be activated at even higher flow rates. Option B is correct ； According to 11.0.2, fire pump systems should not be equipped with an automatic shutdown function; the decision to stop the pump should be made by personnel with appropriate authority based on the circumstances of the fire fight. Option C, which states that the motor stops automatically when the flow rate of the fire pump reaches 25 L/s, is incorrect. As stated in the problem, the static water pressure at the most unfavorable point of the automatic sprinkler system is 0.1 MPa, so it is not necessary to install a pressure stabilizing pump. In a fire hydrant water supply system that is directly supplied by a high-level fire water tank, the automatic start-up flow rate is 1.0–2.0 L/s; that is, when a fire hydrant at the most unfavorable location is used (the system flow rate exceeds 1.0–2.0 L/s), the flow switch sends a signal to start the pump. The fire hydrant pump should be able to start when the flow rate from the test fire hydrant is 3 L/s, so option D is incorrect. The answer to this question is B. 【2016 Technical Practice 99】Which of the following statements regarding the selection of fire pump are correct? （） A. Diesel fire pumps should use diesel engines with compression ignition; option A is incorrect. B. The flow-rate versus head performance curve of fire pumps should be smooth, without any corners or peaks. C. The models of fire pumps within the same pump set for fire water supply should be identical, and the number of operating pumps should not exceed 5. D. The sealing method and material used for the pump shafts of fire pumps must meet the requirements for operation at the lowest flow rates. E. In the case of fire pumps driven by electric motors, it is necessary to choose those with electric motors that are installed in a dry manner. 【Answers】BDE 【Explanation】Diesel fire pumps should use diesel engines with compression ignition; therefore, option A is wrong ； The flow-head performance curve of fire pumps should be a smooth curve without any inflection points or humps; option B is correct ； The fire pump models within the same fire water supply pump set should be identical, and the number of operating pumps should not exceed 3; therefore, option C is incorrect ； The sealing method and material of the fire pump shaft must meet the requirements for the operation of the fire pump at its minimum flow rate; option D is correct ； When using an electric motor to drive a fire pump, a fire pump with a dry-installed motor should be selected; option E is correct. The answer to this question is BDE. 【2016 Comprehensive Ability 99】An industrial complex in the south, with an area of 180,000 m² and a rectangular shape; its width is 1,000 meters. The fire pump room is a separate building located at the center of the site. The fire water supply system uses a temporary high-pressure system that can be used both indoors and outdoors, with a designed flow rate of 120 L/s and a pressure of 1.0 MPa. The walking distance from the plant’s fire control room to the fire pump room is 800 meters. At the time of acceptance, among the following test results, those that comply with the current **fire protection technical standards are (). A. The height difference between the floor of the fire pump room and the outdoor ground is 50 mm, with no water barrier in place. B. The walking distance from the most remote outdoor fire hydrant to the fire pump room is 1350 m. C. The designed flow rate of the pressure stabilizing pump is 3 L/s. D. There are five fire pumps in operation with one as a backup. E. There is no duty room in the fire pump room. [Answer] CE [Explanation] According to Article 5.5.14 of the Fire Protection Code, technical measures must be taken to prevent the fire pump room from being flooded; therefore, option A is incorrect ； According to the problem description, the pump house is located at the center of the industrial complex, which has a rectangular shape. Therefore, the distance from the pump house to the least favorable point (the farthest point) within the complex is approximately 1,030 meters. Consequently, the distance from the least favorable outdoor fire hydrant to the edge of the complex is 320 meters. Given that the protection radius of an outdoor fire hydrant is 150 meters, it is evident that the placement of this outdoor fire hydrant is inappropriate. Hence, option B is incorrect ； According to 5.3.2-2, the normal leakage rate of a fire water supply network shall be determined based on the pipe material and joint type. In the absence of any data regarding the network’s leakage rate, the design flow rate of the pressure stabilizing pump should be set at 1%–3% of the designed fire water supply flow rate; this value should not be less than 1 L/s ； The designed flow rate for this application is 120 L/s; therefore, the designed flow rate of the pressure stabilizing pump should be between 1.2 and 3.6 L/s, so option C is correct ； In accordance with the principles of \"one in use and one as backup\" and \"two in use and one as backup\", it is not acceptable to have only one fire pump among the five fire pumps; therefore, option D is incorrect ； A duty room is not required to be installed in the fire pump room; option E is correct, so the answer to this question is CE.