What Is The Heart Of A Fire Protection System - Fire Water Pump

Sep 14, 2024

Fire pumps are the heart of the fire water supply system. They not only provide necessary water source pressure and flow for firefighting, but also serve as the basic equipment to ensure the effective operation of the fire water system.

According to different working principles and application scenarios, fire pumps can be divided into multiple types, each designed to meet specific fire protection needs.

1, Classification of fire water pumps

According to different power sources, it is divided into diesel fire pumps and electric fire pumps.The type of fire pump should be determined based on comprehensive factors such as reliability, installation location, fire water source, fire water supply design flow rate, and head.

Fire water pump drivers should be directly driven by electric motors or diesel engines, and fire water pumps should not be driven by dual electric motors or dual power pumps based on diesel engines.

According to the design direction of the impeller, it is divided into centrifugal pumps and axial flow pumps. Generally, fire pumps belong to centrifugal pumps.

1. Diesel fire pumpThe power source of diesel fire pumps is more stable and reliable, suitable for use in places without power supply, especially for large-scale fires or long-term drainage tasks. When selecting a diesel fire pump, the following requirements should be noted:

(1) Diesel engine fire water pumps should use compression ignition diesel engines;

(2) The rated power of a diesel engine should be checked for the influence of altitude and ambient temperature on the power of the diesel engine;(3) The diesel engine fire water pump should have continuous working performance, and the test running time should not be less than 24 hours;

(4) The battery of the diesel engine fire pump should ensure that the fire pump can automatically start at any time;

(5) The fuel supply tank of the diesel engine fire pump should be determined based on the duration of the fire, and the minimum effective volume of the fuel tank should be configured at 1.5L/kW. The fuel stored in the fuel tank of the diesel engine fire pump should not be less than 50% of the reserve.

2. Electric fire pump

Electric fire pumps are environmentally friendly and have low noise, suitable for cities or industrial areas with stable power supply, and more suitable for small-scale fires or short-term drainage tasks.When using a fire pump driven by an electric motor, a dry-type fire pump with an electric motor should be selected.

3. Axial flow pump

Axial flow pumps are usually used for large flow requirements, but when axial flow deep well pumps are installed in wells, their submergence depth should meet the requirements for reliable operation. When the pump output flow rate is 150% of the design flow rate, the minimum submergence depth should be no less than 3.20m above the bottom water level of the first pump impeller, and for every 300m increase in altitude, the minimum submergence depth of the deep well pump should be increased by at least 0.30m;

2, Structure of fire water pump

The pump body is the main part of a fire pump, usually made of cast iron or stainless steel material.

There is a pump chamber inside the pump body, and water is sucked in from the pump chamber and pumped out through the hydraulic part.

There are inlet and outlet ports on the outside of the pump body, as well as necessary pipeline connection parts.

The casing of the water pump should be made of ductile iron.

The motor is the power source of the fire pump, with a power of over 5 kilowatts and a speed of approximately 2900 revolutions per minute.

The casing of the motor must have good insulation performance.

The impeller is the rotating part of the water pump, and its shape, quantity, size, and installation angle will directly affect the flow rate and head of the fire pump. The material should be bronze or stainless steel.

3, Performance parameters of fire water pump

(1) Traffic (Q):

The volume of liquid transported by a water pump per unit time is commonly measured in m ³/h or L/s. The flow rate determines how many liters of water a pump can deliver per second. The minimum rated flow rate should not be less than 10L/s, and the maximum rated flow rate should not exceed 320L/s.

(2) Head (H):

The energy increase per unit weight of liquid after passing through a water pump, measured in meters. The head determines the height at which the water pump can push water.

(3) Traffic performance curve

① The power of the driver equipped with the fire pump should meet the power requirements for operation at any point on the flow head performance curve of the selected pump.

② The flow head performance curve should be a smooth curve without humps or inflection points. The pressure at zero flow should not exceed 140% of the design working pressure, and should be greater than 120% of the design working pressure.

③ When the outlet flow rate is 150% of the design flow rate, the outlet pressure should not be lower than 65% of the design working pressure.

④ When the flow rate is at its lowest, the pressure is at its highest, and the sealing method and material of the pump shaft should meet the requirements for the operation of the fire pump at low flow rates.

4, Requirements for the installation of fire water pumps

(1) Requirements for the Setting of Fire Water Pump Sets

① Number of pumps in the workgroupThe model of fire water pumps in the same pump group for fire water supply should be consistent, and a group of working pumps should not exceed 3.

② Backup pumpFire pumps should be equipped with backup pumps, whose performance should be consistent with that of the working pump, except for the following buildings: residential buildings with a height of less than 54m and buildings with outdoor fire water supply design flow rate less than or equal to 25L/s; Buildings with indoor fire water supply design flow rate less than or equal to 10L/s.

(2) Series and parallel connection of fire water pumps

① Serial settingThe series connection of fire pumps is to directly connect the outlet of one pump to the suction pipe of another pump and operate both pumps simultaneously. The series connection of fire pumps can increase the head when the flow rate remains constant.

There are two situations for connecting fire pumps in series: one is to connect the fire pump in the fire room with a transfer water tank, and the other is to directly connect the fire pump in series.

② Parallel setting

When multiple fire pumps are connected in parallel, the parallel connection of fire pumps refers to the simultaneous supply of water to the fire water supply system by two or more fire pumps. The main function of parallel connection of fire pumps is to increase the flow rate, but when the flow rates are superimposed, the system's flow rate will decrease. Therefore, it is necessary to verify the impact of flow superposition on the outlet pressure of fire pumps.