Most of the fire-fighting water provided by fire-fighting water sources need to be pressurized by a fire-fighting pump to meet the requirements for water pressure and water volume during fire-fighting. The failure of the water pump due to improper installation and maintenance will inevitably affect the fire fighting and rescue and cause unnecessary losses.
↑Click on the pic above to learn 【fire pump】products, prices, parameters etc.↑
Compared with domestic water pumps and production water pumps, fire-fighting water pumps should have higher performance requirements. However, my country’s current regulations do not make detailed special regulations on the performance and test requirements of fire-fighting water pumps, resulting in no evidence to check when selecting fire-fighting water pumps. , A variety of problems have occurred.
NFPA20 stipulates the performance of fire pumps as follows: when the discharge flow of the water pump is 150% of the flow of the selected working point, its head shall not be less than 65% of the head of the selected working point, and the head when the pump is turned off shall not be greater than the selected working point 140% of the head. In fact, it stipulates that the performance curve of the pump is a smooth curve. There are no detailed regulations on fire-fighting water pumps in our country's standards, resulting in many discrepancies in the selection of fire-fighting water pumps. It is recommended that designers refer to NFPA20 regulations when designing.
The fire-fighting water supply system stabilizer is a water pump that maintains the pressure of the system at ordinary times, which monitors the system and enables the system to have the function of automatic control. The pressure of the stabilized pump can be determined according to the system pressure. The pressure of the general stabilized pump can be determined according to the system pressure. The pressure of the general stabilized pump is 0.1Mpa—0.2Mpa higher than the main pump, or the pressure of the stabilized pump is that of the main pump. 1.1 times-1.2 times. But there are different opinions on the determination of the flow rate of the stabilized pump. The flow setting requirement of the stabilized pump in our country is to meet the water consumption of one fire fighting unit.
The leakage of the automatic sprinkler system pipeline is in accordance with the national "Heating and Sanitary Engineering Construction and Acceptance Code" Article 3.15: During the hydraulic test, the pressure drop within 10 minutes should not exceed 0.05Mpa. Then the test pressure is reduced to the working pressure for visual inspection, and no leakage is considered qualified. Article 6.2.3 of "Specifications for Construction and Acceptance of Automatic Sprinkler Systems" stipulates that the test point of the water pressure test should be set at the lowest point of the pipe network of the system. Slowly increase the pressure, after reaching the test pressure, stabilize the pressure for 30 minutes, visually observe that the pipe network has no leakage, no deformation, and the pressure drop is not more than 0.05Mpa. Article 10.2.13 of "Code for Construction and Acceptance of Water Supply and Drainage Piping Engineering" GB50268-97 stipulates that the allowable water seepage volume of DN100 steel pipe is 0.28L (min•km), and the allowable water seepage volume of DN150 steel pipe is 0.3L (min•km). Obviously, if the pipeline construction reaches the national standard, the leakage of the system pipeline network is very small. The author himself has observed two completed projects. The leakage of indoor pipelines is mainly capillary leakage at the joints of the pipelines, and the leakage of the test drain valve and the pump outlet check valve that is in contact with the atmosphere at one end. The capillary leakage water at the pipe joints generally does not form water droplets, and mostly evaporates in the air. The valve whose one end is in contact with the atmosphere is easy to observe, and it is not a problem to close or replace the valve in time. The pump outlet check valve returns to the pool because it is not closed tightly. This phenomenon is not easy to observe and is a major hidden danger of water leakage in the system pipe network. For example, the flow rate of the stabilized pump used in a project is 1.33L/S, and the stabilized pump cannot reach the set pressure after long-term operation. After inspection, the pump outlet check valve is not tightly closed and water is leaking into the pool. Replace the check valve After that, the stabilized pump works normally and starts every few days. This shows that the leakage of the system is very small, almost negligible.
According to the investigation, the flow rate of the stabilized pump at home and abroad is mostly selected between 0.5L/S—2.0L/S. When the system has no air pressure tank, there will be water hammer when the pump is stopped. In view of the fact that the stabilized pump has requirements for monitoring and automatic control functions of the system. We recommend that the flow rate of the stabilized pump is 1.0L/S—2.0L/S, and the pressure is 0.1Mpa—2.0Mpa higher than the main pump or 1.1 times—1.2 times that of the main pump. The pressure-stabilizing pump is best equipped with an air pressure tank. If there is no pressure tank, it should be written on the controller of the pressure-stabilizing pump so that it will not start frequently due to the action of water hammer when the pump is stopped.
