1. Human factor. Due to the damage of the original motor, a considerable number of users randomly equipped the fire pump with another motor to drive it. As a result, the flow rate was low, the head was low, and even the water could not be pumped.

 

2. The transmission belt is worn. There are many large-scale isolated fire pumps that use belt transmission. Due to long-term use, the drive belt is worn and loosened, and slipping occurs, thereby reducing the speed of the fire pump.

 

3. Improper installation. The distance between the centers of the two pulleys is too small or the two shafts are not parallel, the fire pump transmission belt is installed on the tight side, resulting in too small wrap angle, the calculation error of the diameter of the two pulleys, and the large eccentricity of the two shafts of the fire pump driven by the shaft, etc. Both will cause changes in fire pump speed.

 

4. Mechanical failure of the fire pump itself. The fastening nut between the impeller and the pump shaft is loose or the pump shaft is deformed and bent, causing the impeller to move more, directly rubbing against the pump body, or the bearing is damaged, which may reduce the speed of the fire pump.

 

5. Improper maintenance of fire pump power machine. The motor loses its magnetism due to the burning of the windings, the number of winding turns, wire diameter, and wiring method changes during maintenance, and the failure of the fire pump or maintenance to completely eliminate factors will also change the speed of the fire pump.

 

Some users have measured that although the vertical distance from the water reservoir or water tower to the water surface of the fire pump is slightly smaller than the lift of the fire pump, the water capacity is still small or cannot be lifted. The reason for the fire pump is often that the pipeline is too long, there are many bends in the water pipe, and the resistance loss of the water flow in the pipeline is too large. The reason is often that the pipeline is too long, there are many bends in the water pipe, and the resistance loss of the water flow in the pipeline is too large. In general, the resistance of the 90-degree elbow is greater than that of the 120-degree elbow, and the head loss of each 90-degree elbow is about 0.5 to 1 meter, and the resistance of each 20-meter pipe can cause a head loss of about 1 meter. In addition, some users also choose the diameter of the inlet and outlet pipes of the fire pump at will, which also has a certain impact on the lift.

 

1. Some users do not fill enough water before starting the fire pump; sometimes it seems that the filled water has overflowed from the vent hole, but the air is completely discharged without turning the pump shaft, resulting in a little air remaining in the water inlet pipe or pump body middle.

 

2. The horizontal section of the inlet pipe that is in contact with the fire pump shall apply a descending slope of more than 0.5% against the direction of water flow, and the end connected to the inlet of the fire pump shall be the highest, and shall not be completely horizontal. If it is tilted up, air will remain in the water inlet pipe, which will reduce the vacuum in the water pipe and fire pump, and affect water absorption.

 

3. The packing of the fire pump has been worn out due to long-term use or the packing is too loose, causing a large amount of water to spray out from the gap between the packing and the pump shaft sleeve. As a result, the external air enters the fire pump from these gaps. The inside of the pump, which affects the pumping of water.

 

4. The water inlet pipe has been underwater for a long time, and the pipe wall has corroded holes. After the fire pump works, the water level continues to drop. When these holes are exposed to the water surface, air enters the water inlet pipe through the holes.