Fire – fighting water pump

Fire – fighting water pump

Function and Importance

Working Principle

• Centrifugal pump: It is driven by power equipment such as electric motors, diesel engines, or hydraulic machines to make the impeller rotate at high speed, generating centrifugal force. Under the action of centrifugal force, the liquid is thrown from the center of the impeller to the outer edge of the impeller, creating a low – pressure area at the center of the impeller. The water from the water source is sucked into the center of the impeller under the action of atmospheric pressure, and then is thrown out by the impeller, forming a water flow with a certain pressure and flow rate, thus realizing the transportation and pressurization of water.
• Positive – displacement pump: It realizes the suction and discharge of water by changing the volume of the pump chamber. When the volume of the pump chamber increases, a low – pressure is formed, and water is sucked into the pump chamber; when the volume of the pump chamber decreases, the water is compressed and discharged, so as to achieve the purpose of transporting and pressurizing water.

Performance Requirements

• Flow rate and head: The flow rate of the fire – fighting water pump should meet the water demand of the fire – fighting water supply system during a fire, and its head should be able to overcome the resistance of water flowing in the pipeline and lift the water to the required height. Generally, the maximum flow rate of the fire – fighting pump should be 150% of the design value, the head should not be less than 65% of the selected operating point head, and the head when the pump is closed should not be greater than 140% of the selected operating point head.
• Material requirements: The pump casing is preferably made of ductile iron, which has good strength and corrosion resistance; the impeller is preferably made of bronze or stainless steel to ensure that it is not easily damaged and corroded during high – speed rotation and long – term use.
• Zero – flow pressure: The flow – head performance curve should be a smooth curve without humps and inflection points. The pressure at zero flow should not be greater than 140% of the designed working pressure, and it is preferably greater than 120% of the designed working pressure.

Types

• Classification by mobility
  • Fixed fire – fighting water pump: Usually installed in the fire – fighting pump room of a building and fixedly connected to the fire – fighting pipeline system. It has a high flow rate and head and can meet the fire – fighting water demand of large buildings or building complexes.
  • Mobile fire – fighting water pump: Such as a portable motor – driven fire – fighting pump unit, which is assembled by a gasoline engine or diesel engine and a pump body. It can be carried by hand and is suitable for areas where fire trucks cannot pass, such as narrow streets and rural areas. It can also be used for other emergency operations such as drainage, drought – resistance, and greening irrigation.
• Classification by working principle
  • Centrifugal pump: It has the advantages of large flow rate, relatively high head, simple structure, and stable operation. It is the most commonly used type in fire – fighting water pumps and can quickly and effectively transport a large amount of water to the fire scene.
  • Positive – displacement pump: Including plunger pumps, gear pumps, etc. This type of pump has certain advantages in fire – fighting application scenarios with small flow rates and high heads, such as some special fire – fighting systems that require precise control of flow rate and pressure.

Installation and Setting Requirements

• Setting conditions: Fire – fighting water pumps need to be set in a temporary high – pressure fire – fighting water supply system. In a series – connected fire – fighting water supply system, a fire – fighting transfer pump also needs to be set. A standby pump should be set when setting a fire – fighting water pump and a fire – fighting transfer pump. However, for residential buildings with a building height less than 54m, buildings with an outdoor fire – fighting water supply design flow rate ≤ 25L/s, and buildings with an indoor fire – fighting water supply design flow rate ≤ 10L/s, a standby pump may not be required.
• Suction requirements: The fire – fighting water pump should adopt self – priming suction. For a fire – fighting water pump that directly sucks water from the municipal water supply network, an air – gap backflow preventer should be installed on its outlet pipe. When there is no suction well at the suction port, a vortex – preventing device should be installed at the suction port.

Maintenance and Management

• Regular inspection: Check whether the appearance of the water pump is damaged or corroded, whether the connecting parts are loose, and whether the pipeline is leaking. At the same time, check the lubricating oil quantity and quality of the water pump, as well as the temperature and wear of the bearing.
• Trial operation: Conduct a trial operation regularly to ensure that the water pump can start and operate normally when needed. The trial – operation time is generally not less than 15 minutes. Observe the operation status of the water pump, including whether parameters such as flow rate, head, and pressure are normal.
• Maintenance and repair: According to the water pump’s operation manual and actual operation conditions, maintain and repair the water pump regularly. Replace worn parts, clean the debris and dirt in the impeller and pump casing to ensure the good performance of the water pump.