Fire pump characteristics and technical selection and practical application

Fire water supplied by most fire sources requires a fire pump to pressurize it to meet the water pressure and water requirements of the fire. Pump set due to improper maintenance failure will inevitably affect the fire and rescue, causing unnecessary losses. Fire pumps and pump life and production of water pump performance should have higher requirements, but the current norms of our fire pump performance and test requirements did not make more detailed provisions, resulting in no choice when the fire pump check , There have been many problems. US NFPA20 fire pump performance requirements are: fire pump maximum flow should be 150% of the design value, the lift is not less than 65% of the selected working point lift, shut down the pump lift is not greater than 140% of the selected work point lift, , The regulator pump flow is 1-2L / S, lift for the fire pump head 1.1-1.2 times. At the same time the provisions of the fire pump outlet pipe should be set to measure the flow meter, the flow meter should be able to test the pump selected flow of 175%, the fire pump on the outlet pipe should be set diameter greater than 89mm pressure gauge. Suggest that the relevant departments of the reference to the United States standards for fire pump design, selection of more targeted, more specific requirements, so that the fire pump selection, testing is well documented. NFPA20 fire pump performance requirements are as follows: Pump out of the flow rate of 150% of the selected operating point, the lift is not less than 65% of the head of the selected operating point, shut down the pump lift is not greater than the selected operating point 140% of head. The fact is that the performance of the pump curve is a smooth curve. China's standard fire pump no detailed rules, resulting in the selection of fire pumps have a lot of discrepancies. It is recommended that designers refer to the NFPA20 regulations at design time. "High regulation" and "built rules" on the performance of the fire pump does not require testing, NFPA20 provides fire pumps in the outlet pipe set up with a flow meter. The flow meter should be able to test 175% of the selected flow of the pump. The fire pump should be equipped with a pressure gauge with a diameter greater than 89 mm on the outlet pipe so that the pump can fully test the performance of the pump after it has been installed to find out if it meets the design requirements. It is recommended that designers consider this issue in their design. Fire water supply system voltage regulator is usually to maintain pressure on the pump, the system plays a guardianship and the system has the function of automatic control. The pressure of the pump can be determined according to the system pressure. The pressure of the pump can be determined according to the system pressure. The pressure of the pump is higher than that of the main pump by 0.1Mpa-0.2Mpa, or the pressure of the pump is the main pump 1.1 times -1.2 times. But for the regulation of pump flow to have a different view. "High regulation" Article 7.4.8 supercharging facilities shall meet the following requirements: fire hydrant water supply system should not exceed 5L / S; for automatic sprinkler system should not exceed 1L / S. The United States NFPA20 "StandandfortheInstallationofCentrifugalFirePumps" (1996Edition) provides pressure pump (PressureMaintenanPumps / JoceyPumps / Make-UpPumps) flow of not less than the normal system of leakage, the pressure should be sufficient to maintain the system pressure. Obviously, our country has stipulated the upper limit of the flow of the steady pressure pump, and the United States has stipulated the lower limit of the steady pressure pump. The pressure setting of our country's regulated pump is to meet the water consumption of a fire fighting unit. The United States is the system's leakage water. Automatic Sprinkler System Pipeline Leakage According to the national "Heating and Sanitation Engineering Construction and Acceptance Code," Section 3.15: When the hydraulic test, the pressure drop within 10min is not greater than 0.05Mpa. Then the test pressure dropped to the working pressure for visual inspection, to not leak as qualified. "Automatic Sprinkler System Construction and Acceptance Code," the provisions of Article 6.2.3 hydrostatic test test point should be set at the lowest point of the system pipe network, the water pipe network, the net should be drained of air and should Slowly booster, to test pressure, the regulator 30min, visual pipeline without leakage, no deformation, and the pressure drop is not greater than 0.05Mpa. Water Supply and Drainage Pipeline Construction and Acceptance Code GB50268-97 Section 10.2.13 stipulates: DN100 steel pipe allows water leakage of 0.28L (min • km), DN150 steel pipe allows water leakage of 0.3L (min • km). Obviously, if pipeline construction meets the national standard, there will be little leakage of water in the system pipe network. The author himself has observed two completed projects. Leakage of indoor pipes is mainly caused by capillary seepage of water at the pipe interface and leakage of test drain valves and pump outlet check valves with one end exposed to the atmosphere. Pipeline capillary leakage at the interface generally can not form a drop of water, and more in the air evaporation. One end of the valve leakage contact with the atmosphere is easy to observe, promptly shut down or replace the valve is not a problem. Pump outlet check valve due to lax and back to the pool back to the water, this phenomenon is not easy to observe, is a major hidden pipe network leakage of water. For example, a project selected pump flow of 1.33L / S, the pump also failed to run a long time the set pressure, check the pump outlet check valve is not strict and leak to the pool, replace the check valve After the regulator pump work, and start a few days. This shows that the amount of system leakage is very small, almost negligible. According to the survey, the flow of pressure stabilizing pump at home and abroad was selected as 0.5L / S-2.0L / S. When there was no pressure tank in the system, the pump was stopped with water hammer. In view of the regulator pump system has the guardianship and automatic control requirements. We recommend that the regulator pump flow 1.0L / S-2.0L / S, the pressure is higher than the main pump 0.1Mpa-2.0Mpa or 1.1 times the main pump -1.2 times. Regulator pump is best equipped with pressure tank, if not set pressure tank, pump controller should be stamped on, so that when the pump is not stopped due to frequent water hammer and start.