It can be seen from the working principle of the marine centrifugal pump that the marine centrifugal pump has the following characteristics:

1. It does not have self-priming capability, so water diversion is required for work. For example, when the EMC marine seawater pump is used as the general fire pump on board, it is necessary to install an AELC self-priming device.
2. The normal working discharge pressure of the centrifugal pump is 10~40 meters. If the discharge pressure needs to be increased, the diameter of the impeller needs to be increased, or a centrifugal pump with multi-stage impellers in series, such as marine vertical multistage centrifugal pump.
3. The flow rate of the centrifugal pump is uniform, and its flow rate can be estimated according to the diameter of the suction pipe and the speed of the pump:
   Q=5D²
   The head of the marine centrifugal pump can also be estimated according to the empirical formula:
   H=Kn²D² (K is the empirical coefficient, n is the speed)
   When the rotational speed of the centrifugal pump is constant, if the head is large, the flow rate is small, and vice versa.
4. The marine centrifugal pump has axial thrust and balance when it works. The liquid pressure on both sides of the impeller is symmetrical and balanced. However, because there is a suction port with a certain diameter on the suction side, the hydraulic pressure is greatly reduced. The axial force in the direction of the suction port, the size of the axial thrust is related to the size of the asymmetrical area, and the more stages of the centrifugal pump, the greater the axial thrust generated.
   The axial thrust of the single-stage centrifugal pump is borne by the front support bearing. In order to avoid the axial displacement of the rotor of the centrifugal pump under the action of excessive axial thrust, which will increase the wear and tear of the impeller and the pump casing, a balance hole is often used. (opening holes on the impeller); symmetrical arrangement of two-stage impellers; or hydraulic automatic balancing device and other methods.
5. Suction height of marine centrifugal pump
   The vertical distance from the center of the pump to the suction liquid level is the suction height of the pump, also known as the geometric installation height of the pump.
   Under the condition of ensuring no cavitation, the smaller the pressure at the suction port, the better, the larger the diameter of the nozzle, the smaller the resistance, and the smaller the suction height of the pump, the better.
   Therefore, the diameter of the suction pipe of the marine centrifugal pump should be as large as possible, and the elbow should be reduced, and the inner wall of the pipe should be smooth. There are also requirements for the suction height of the pump: the suction pipe diameter is ≥80mm, and the geometric installation height is 3m; the suction pipe diameter is <80mm, and the geometric installation height is 4~6m.
6. Cavitation Phenomenon of Marine Centrifugal Pump
   The pressure at the suction port of the centrifugal pump can only suck liquid when it is lower than the external pressure. If the pressure at the suction port is less than or equal to the vaporization pressure of the liquid at the changed temperature, part of the liquid will vaporize, and the gas mixed in the water will also be precipitated, prompting the liquid entering the impeller to form a lot of bubbles, resulting in a local vacuum area, and it will be convenient for the liquid to replenish Impact, vibration and noise are generated, which reduce the pressure head, flow rate and efficiency of the pump. The surface of the blade produces pits under this impact, and the surface of the impeller is damaged. The above phenomenon is called cavitation. Therefore, effective measures should be taken in the work of centrifugal pumps to avoid cavitation.