XBD single-stage fire pump and multi-stage fire pump selection

Most fire-fighting water supplies for fire-fighting water and fire-fighting pumps need to be pressurized in order to meet the pressure and quantity of water required during fire extinguishing. Pump failure due to improper installation and maintenance will inevitably affect firefighting and rescue, resulting in unnecessary losses.

The performance of the fire pump should be higher than that of the domestic water pump and the production water pump. However, the current regulations of our country do not make specific requirements for the performance and test requirements of the fire pump, which results in the fire pump not being available for inspection. There have been many problems.

The performance requirements of the United States for fire pumps are: the maximum flow rate of the fire pump should be 150% of the design value, the lift should not be less than 65% of the head of the selected working point, and the lift when the pump is turned off should not be greater than 140% of the head of the selected operating point. The regulated pump flow is 1-2L/S, and the lift is 1.1-1.2 times the lift of the fire pump.

At the same time, it is stipulated that a flow meter for measurement should be installed on the fire pump outlet pipe. The flow meter should be able to test 175% of the selected flow rate of the pump. The fire pump should be equipped with a pressure gauge with a diameter greater than 89 mm on the outlet pipe. It is suggested that the customs authorities refer to US standards to provide more targeted and specific requirements for the design and selection of fire pumps in China so that they can be used in the selection and testing of fire pumps.

The performance of the fire pump is specified as follows: When the pump discharge flow is 150% of the flow at the selected operating point, the lift is not less than 65% of the head of the selected operating point, and the lift when the pump is turned off is not greater than the selected working point head. 140%. The reality is that the performance curve of the pump is a smooth curve. There are no detailed regulations on the fire pump in our country, resulting in a lot of access to the fire pump. Designers are advised to refer to NFPA20 when designing.

"High Regulations" and "Building Regulations" have no testing requirements for the performance of fire pump. NFPA20 stipulates that the fire pump shall have a measuring flow meter on the outlet pipe. The flowmeter should be able to test 175% of the selected flow rate of the pump. The fire pump should be equipped with a pressure gauge with a diameter greater than 89mm on the outlet pipe so that the pump can be fully tested after installation to see if it can meet the design requirements. Designers are advised to consider this issue in their design.

The fire water supply system voltage regulation is the water pump that the system usually maintains the pressure, plays the supervisory function to the system and causes the system to have the automatic control function. The pressure of the regulated pump can be determined according to the system pressure. The pressure of the general regulated pump can be determined according to the system pressure. The pressure of the general regulated pump is 0.1 Mpa-0.2 Mpa higher than that of the main pump, or the pressure of the regulated pump is the main pump. 1.1 times - 1.2 times. However, there are different opinions on the determination of the regulated pump flow rate. "High Regulations" Article 7.4.8 booster facilities should meet the following requirements: The fire hydrant water supply system should not be greater than 5L / S; for the automatic sprinkler system should not be greater than 1L / S. The United States NFPA20 "StandandfortheInstallationofCentrifugalFirePumps" (1996Edition) provides that the flow rate of the regulated pump (PressureMaintenanPumps/JoceyPumps/Make-UpPumps) is not less than the leakage under the normal conditions of the system, and the pressure should be sufficient to maintain the required pressure of the system. Obviously, China has stipulated the upper limit of the flow rate of the regulated pump, while the United States stipulates the lower limit of the regulated pump. China's regulator pump flow set requirements are to meet the water consumption of a fire unit, the United States is the system's leakage of water.

Automatic sprinkler system target = _blank> pipeline leakage according to the country "heating and sanitation construction and acceptance specifications" section 3.15: pressure test, pressure drop within 10min is less than 0.05Mpa. The test pressure was then reduced to the target=_blank> working pressure for visual inspection and passed as leak-proof. “Section 6.2.3 of the Code for the Construction and Acceptance of Automatic Sprinkler Systems” stipulates that the test points for the hydrostatic test shall be located at the lowest point of the system's pipe network. When water is injected into the pipe network, the air of the pipe network shall be drained, and Slowly increase the pressure, reach the test pressure, the voltage regulator for 30min, visual inspection of the pipe network without leakage, no deformation, and the pressure drop is not greater than 0.05Mpa. Regulation 10.2.13 of the “Code for Construction and Acceptance of Water Supply and Drainage Piping Projects” GB50268-97 stipulates that the permissible water infiltration of steel pipes of DN100 is 0.28L (min•km), and that of DN150 steel pipes is 0.3L (min•km). Obviously, if pipeline construction meets national regulations, there will be very little leakage of water in the system's pipe network. Atlantic pump installation and commissioning personnel had observed two projects that had been completed. Leakage of indoor pipes mainly caused capillary action to leak water at the interface of the pipeline, and leaks of test drainage valves and outlet check valves of the pumps that were in contact with the atmosphere at one end. The amount of water. The wicking of water at the interface of the pipeline generally does not form water droplets and evaporates in the air. The leakage of a valve that is in contact with the atmosphere at one end is very easy to observe. Closing or replacing the valve in time is not a problem. The water pump outlet check valve returns to the water in the pool because it is not closed. This phenomenon is not easy to observe, and it is a major hidden danger of leaking water in the system pipe network. For example, the flow rate of a steady-state pump selected for a project is 1.33L/S. The long-term operation of the stabilized pump can not reach the set pressure. After inspection, the pump outlet check valve is not strict enough to leak into the water tank. Replace the check valve. Afterwards, the regulated pump works normally and starts once every few days. This shows that the amount of leakage from the system is very small and almost negligible.

According to the investigation, the flow rate of the regulated pump at home and abroad is selected between 0.5L/S and 2.0L/S. When the system has no pressure tank, there is a water hammer phenomenon when the pump is stopped. In view of the regulated pump, the system has the monitoring and automatic control function requirements. We recommend that the regulator pump flow rate is 1.0L/S—2.0L/S, and the pressure is 0.1Mpa—2.0Mpa higher than the main pump or 1.1—1.2 times the main pump. The regulator pump is preferably provided with a pressure tank. If no pressure tank is provided, an article should be made on the controller of the regulated pump so that it will not frequently start due to the action of water hammer when the pump is stopped.