Characteristics Of Centrifugal Pumps And Submersible Pumps

Nov 07, 2024

Submersible pumps can be placed underwater, while centrifugal pumps can be placed on the ground, and the size should be the pipe diameter they are connected to.

1. Submersible pump

A widely used water treatment tool. Unlike ordinary water pumps, it works underwater, while most water pumps work on the ground.

Working principle of submersible pump

Before starting the pump, the suction pipe and pump must be filled with liquid. After turning on the pump, the impeller rotates at high speed, and the liquid inside rotates together with the blades. Under the action of centrifugal force, it flies away from the impeller and is ejected outward. The ejected liquid gradually slows down in the diffusion chamber of the pump casing, increases in pressure, and then flows out from the pump outlet and discharge pipe. At this time, a vacuum low-pressure zone is formed at the center of the blade due to the liquid being thrown towards the surroundings, which has neither air nor liquid. The liquid in the liquid pool flows into the pump through the suction pipe under the action of atmospheric pressure on the pool surface. The liquid is continuously sucked up from the liquid pool and continuously flows out from the discharge pipe.

Basic parameters of submersible pumps

Including flow rate, head, pump speed, matching power, rated current, efficiency, pipe diameter, etc

The main purpose and scope of application of submersible pumps

Including construction drainage, water agriculture irrigation, industrial water circulation, water supply for urban and rural residents, and even emergency rescue and disaster relief, etc

2. Centrifugal pump

First, let's talk about what centrifugation is

Centrifugation is actually a manifestation of the inertia of an object For example, water droplets on an umbrella will follow the slow rotation of the umbrella because the frictional force between the umbrella and the water droplets acts as a centripetal force for the water droplets But if the umbrella rotates faster and the frictional force is not enough to make the water droplet move in a circular motion, then the water droplet will detach from the umbrella and move towards the outer edge Just like using a rope to pull a stone in circular motion, if the speed is too fast, the rope will break and the stone will fly out This is called centrifugation

Centrifugal pumps are designed based on this principle The high-speed rotating impeller blades drive the water to rotate, throwing it out to achieve the purpose of transportation

There are many types of centrifugal pumps In terms of usage, it can be divided into civilian and industrial pumps, and in terms of conveying media, it can be divided into clean water pumps, impurity pumps, corrosion-resistant pumps, etc.

The basic structure of a centrifugal pump consists of six parts, namely: impeller, pump body, pump shaft, bearings, sealing ring, and packing box.

1. The impeller is the core part of a centrifugal pump, which has high speed and high output. The blades on the impeller play a major role, and the impeller needs to undergo a static balance test before assembly. The inner and outer surfaces of the impeller are required to be smooth to reduce frictional losses caused by water flow.

2. The pump body, also known as the pump casing, is the main body of the water pump. Plays a supporting and fixing role, and is connected to the bracket for installing bearings.

3. The function of the pump shaft is to connect with the motor through a coupling, transmitting the torque of the motor to the impeller, so it is the main component for transmitting mechanical energy.

4. Bearings are components that are fitted onto the pump shaft to support it. There are two types of bearings: rolling bearings and sliding bearings. When using butter as a lubricant for rolling bearings, it is recommended to add oil at a volume of 2/3 to 3/4. If the volume is too large, it will generate heat, while if it is too small, it will produce noise and heat up! Sliding bearings use transparent oil as a lubricant, add oil up to the oil level line. Too much oil will seep out along the pump shaft and float, and too little bearing will overheat and burn out, causing accidents! During the operation of the water pump, the maximum temperature of the bearing is around 85 degrees Celsius, usually around 60 degrees Celsius. If it is too high, the cause should be investigated (whether there are impurities, whether the oil quality is black, whether there is water ingress) and dealt with in a timely manner!

5. Sealing ring, also known as leak reducing ring. Excessive clearance between the impeller inlet and the pump casing can cause water from the high-pressure area inside the pump to flow through this clearance to the low-pressure area, affecting the pump's water output and reducing efficiency! A too small gap can cause friction and wear between the impeller and the pump casing. In order to increase reflux resistance, reduce internal leakage, and prolong the service life of the impeller and pump casing, a sealing ring is installed at the junction of the inner edge of the pump casing and the outer edge of the impeller, with a sealing gap maintained between 0.25 and 1.10mm.

6. The stuffing box is mainly composed of packing, water seal ring, packing cylinder, packing gland, and water seal pipe. The main function of the stuffing box is to seal the gap between the pump casing and the pump shaft, preventing the water flow inside the pump from flowing outside and preventing the air from entering the pump. Always maintain the vacuum inside the water pump! When the friction between the pump shaft and the packing generates heat, it relies on the water seal pipe to hold the water inside the water seal ring and cool the packing! Maintain the normal operation of the water pump. So special attention should be paid to the inspection of the packing box during the operation and inspection of the water pump! The packing needs to be replaced after about 600 hours of operation.

Working principle of centrifugal pump

The working principle of a centrifugal pump is that, relying on the high-speed rotating impeller, the liquid obtains energy under the action of inertial centrifugal force to increase pressure. Before the water pump starts working, the pump body and inlet pipe must be filled with water to prevent cavitation. When the impeller rotates rapidly, the blades cause the water to rotate quickly, and the rotating water flies away from the impeller under the action of centrifugal force. After the water in the pump is thrown out, a vacuum area is formed in the central part of the impeller. The water in Shuiyuan is pressurized into the inlet pipe through the pipeline network under the action of atmospheric pressure (or water pressure). By continuously cycling in this way, continuous pumping can be achieved. It is worth mentioning that before starting the centrifugal pump, it is necessary to fill the pump casing with water, otherwise it will cause the pump body to heat up, vibrate, reduce the water output, and damage the pump (referred to as "cavitation"), resulting in equipment accidents! The so-called cavitation refers to the phenomenon that when a centrifugal pump is started, if there is air inside the pump, due to the low density of the air, the centrifugal force generated after rotation is very small, and the low pressure formed in the center area of the impeller is not enough to suck the liquid below the pump inlet into the pump, and cannot transport the fluid.

There are many types of centrifugal pumps, and the common classification methods include the following:

1. Divided by impeller suction method: single suction centrifugal pump, double suction centrifugal pump;

2. Divided by the number of impellers: single-stage centrifugal pump, multi-stage centrifugal pump;

3. Divided by impeller structure: open impeller centrifugal pump, semi open impeller centrifugal pump, closed impeller centrifugal pump;

4. Divided by working pressure: low-pressure centrifugal pump, medium pressure centrifugal pump, high-pressure centrifugal pump;

5. Divided by pump shaft position: horizontal centrifugal pump, side vertical centrifugal pump.