Pressure terminology for fire water systems

There are several pressure terms for fire water systems, including static pressure, dynamic pressure, system working pressure, design pressure and working pressure. If you are not deeply involved in the field of fire protection, it is easy to be confused by these terms. Here is a simplified explanation of the differences between dynamic pressure, static pressure, system pressure, design pressure and working pressure, common requirements and simple test methods.

Static pressure: refers to the pressure when the water in the fire water system pipe network is stationary, mainly the vertical force exerted by the fluid on the pipe wall. Static pressure is the pressure measured when the fire water is not flowing. Therefore, this pressure value is generally used to check whether the system meets the requirements under quasi-working conditions. When using a high-level fire-fighting water tank to maintain a quasi-working pressure state, the static pressure at the most unfavorable point of the water fire-extinguishing facility served by the high-level water tank varies depending on the building type. If it is a Class I high-rise public building, it should not be lower than 0.10MPa (but when the building height exceeds 100m, it should not be less than 0.15MPa); if it is a high-rise residential building, a second-class high-rise public building, or a multi-story public building, it should not be less than 0.07MPa. Multi-story residential buildings should not be less than 0.07MPa. ; If it is an industrial building, it should not be less than 0.10MPa. When the building volume is less than 20,000m³, it should not be less than 0.07MPa; the minimum automatic water fire extinguishing system should not be less than 0.10MPa. If a pressure-stabilizing pump is used to stabilize the pressure, the hydrostatic pressure of the water fire-extinguishing facilities at the most unfavorable point should be greater than 0.15MPa when in quasi-working condition. You can check the static pressure value by checking the pressure gauge of the water test device at the end of the automatic sprinkler system when it is not turned on, and the pressure gauge of the test bolt at the end of the fire hydrant system (if the design does not have one, you can use a gun tip tool with a pressure gauge) to ensure that the system The quasi-working state functions normally.

Dynamic pressure: refers to the kinetic energy generated by the fire water fluid along the direction of movement. To put it bluntly, it is the pressure measured when the fire water flows in a certain place. Taking a fire hydrant as an example, when there is no fire hydrant, the dynamic pressure is the stable pressure value measured by the fire hydrant after the fire hydrant is opened. When there is a fire water pump, the dynamic pressure should be measured after the fire hydrant is opened and the water pump is started. obtained pressure value. The dynamic pressure of each fire hydrant should not be greater than 0.50MPa. When it is greater than 0.70MPa, a pressure reducing device must be installed. In places such as high-rise buildings, factories, warehouses, and civil buildings with indoor clearance heights exceeding 8m, the dynamic pressure of fire hydrants should not be less than 0.35MPa; in other places, the dynamic pressure at the fire hydrant opening should not be less than 0.25MPa. The working pressure of the sprinkler head at the most unfavorable point of the wet sprinkler system (the working pressure here refers to the pressure under working conditions, that is, the dynamic pressure) should not be less than 0.05MPa. Similar to the method of measuring static pressure, the dynamic pressure value can be detected by checking the pressure gauge of the water test device at the end of the automatic sprinkler system when it is turned on, and the pressure gauge of the test plug at the end of the fire hydrant system to ensure that the system is functioning normally.

System working pressure: refers to the maximum pressure that may be generated when the fire water supply system is operating. This pressure is mainly used to determine the pressure level of system pipes, valves and other related accessories. Only when the pressure level is higher than the system working pressure can the stability and reliability of these equipments be ensured. System working pressure requirements: ① The system working pressure of the low-pressure fire water supply system should be determined according to the system working pressure of the water supply pipe network, but should not be less than 0.60MPa; ② The system working pressure of the high-pressure and temporary high-pressure fire water supply system should be determined according to the system working pressure when the system is supplying water. , the maximum possible operating pressure is determined. The details can be determined as follows: a. The system working pressure of the high-pressure fire water supply system that supplies water to the high-level fire pool should be the maximum static pressure of the high-level fire pool, which is the static pressure at the lowest point (the highest pressure); b. Municipal water supply The system working pressure of the high-pressure fire water supply system that directly supplies water from the pipe network should be determined based on the working pressure of the municipal water supply pipe network; c. The system working pressure of the temporary high-pressure fire water supply system that uses a high-level water tank to stabilize the pressure should be the system working pressure when the fire water pump has zero flow. The sum of the pressure and the maximum hydrostatic pressure of the water pump suction port is simply the sum of the maximum pressure of the water pump + the static pressure contained in the position of the water pump suction port; d. The system working pressure of the temporary high-pressure fire water supply system stabilized by a pressure-stabilizing pump, The larger value of the sum of the pressure at zero flow of the waterproof pump, the maximum static pressure at the suction port of the fire water pump, and the pressure stabilizing pump maintaining the system pressure should be cancelled. Because the system working pressure is the maximum pressure that may exist in the system, the maximum value in the two situations is taken.

Design working pressure: refers to the pressure that the designer determines to meet the normal function of the fire protection facilities based on the conditions of the fire protection facilities downstream of the water supply system when designing. Taking downstream fire hydrants as an example, the design pressure must ensure that the end test fire hydrant pressure can meet regulations and actual needs. For systems using fire water pumps, the design working pressure of the system is usually the basis for determining the working pressure of the fire water pump.

Working pressure: refers to the actual pressure when the fire water system or equipment is working.