What Is a Pumping Unit?

Water pump is also called "water pump". Centrifugal water pump is a hydraulic machine that uses the effect of atmospheric pressure to lift water from a low place to a high place. It consists of water pump, power machinery and transmission. It is widely used in farmland irrigation and drainage, as well as water supply and drainage in industrial and mining enterprises and towns. To meet different needs, there are many types.

Water pump introduction

Common pumps are piston, centrifugal and axial. Piston type water pump is the use of atmospheric pressure, such as common water pumps. The centrifugal pump uses the impeller to rotate to drive the water to obtain the centrifugal force, and the water is raised to a high place, but the height of the suction port of the centrifugal pump is still restricted by atmospheric pressure. Axial-flow water pumps, similar to the principle of electric fans, rotate the blades to push water to the rear of the pump shaft. The axial flow pump has a large flow, but the lifting height (lift) is not large.

Mechanical structure of pump

pump The basic structure of a centrifugal pump is composed of six parts, namely: impeller, pump body, pump shaft, bearing, seal ring, stuffing box.

1. The impeller is the core part of the centrifugal pump. It has a high speed and high output. The blades on the impeller play a major role. The impeller must pass the static balance test before assembly. The inner and outer surfaces of the impeller are required to be smooth to reduce the frictional loss of water flow.

2. The pump body is also called the pump casing, which is the main body of the water pump. It plays a supporting and fixing role and is connected with the bracket on which the bearing is installed.

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

4. The bearing is a component that is sleeved on the pump shaft to support the pump shaft. There are two types of rolling bearings and sliding bearings. The plain bearing uses transparent oil as a lubricant, and oil is added to the oil level line.

5. Sealing ring is also called leakage reducing ring.

6. The stuffing box is mainly composed of packing, water-sealing ring, packing tube, packing gland and water-sealing pipe. The function of the stuffing box is mainly to close the gap between the pump casing and the pump shaft, and to prevent the water in the pump from flowing to the outside and the outside air from entering the pump. Always keep the vacuum inside the pump! When the pump shaft and the filler produce friction to generate heat, it is necessary to rely on the water seal tube to hold the water into the water seal ring to cool the filler! Keep the pump running normally. Therefore, special attention must be paid to the inspection of the stuffing box during the running inspection of the pump! The packing needs to be replaced after about 600 hours of operation.

Introduction to the classification of pumps

Centrifugal pump

1. The pump body is also called the pump casing, which is the main body of the pump. It plays a supporting and fixing role and is connected with the bracket on which the bearing is installed.

2. The function of the pump shaft is to connect the motor and the motor by a coupling, and transmit the torque of the motor to the impeller, so it is the main component for transmitting mechanical energy.

3. The bearing is a component that is sleeved on the pump shaft to support the pump shaft. There are two types of rolling bearings and plain bearings. Rolling bearings use butter as a lubricant. It should be appropriate. Generally, the volume is 2/3 3/4. Too much volume will generate heat, too little and there will be noise and heat! The plain bearing uses transparent oil as the lubricant, and refuel to the oil level line. Too much oil will seep and drift along the pump shaft * too few bearings will overheat and burn out and cause an accident! During the operation of the pump, the temperature of the bearing is highest at 85 degrees and generally runs at about 60 degrees. If the temperature is high, find the cause (whether there are impurities, whether the oil is black, and whether water has entered) and handle it in time!

4. Sealing ring is also called leakage reducing ring. The excessive clearance between the impeller inlet and the pump casing causes water in the high-pressure area of the pump to flow to the low-pressure area through this clearance, affecting the water output of the pump and reducing the efficiency! Too little clearance will cause friction between the impeller and the pump casing and cause wear. In order to increase the backflow resistance and reduce the internal leakage, and delay the service life of the impeller and the pump casing, a seal ring is installed at the inner edge of the pump casing and the external assistance of the impeller, and the sealed gap is preferably maintained between 0.25 and 1.10mm.

How centrifugal pumps work

The working principle of a centrifugal pump is: relying on a high-speed rotating impeller, the liquid gains energy under the action of inertia centrifugal force to increase the pressure. Before the pump works, the pump body and the inlet pipe must be filled with water to prevent cavitation. When the impeller rotates rapidly, the blades cause the water to rotate quickly. The rotating water flies away from the impeller under the action of centrifugal force. After the water in the pump is thrown out, the central part of the impeller forms a vacuum area. The water from the water source is pressed into the inlet pipe through the pipe network under the effect of atmospheric pressure (or water pressure). In this way, continuous pumping can be achieved. It is worth mentioning that the centrifugal pump must be filled with water in the pump casing before starting. Otherwise, it will cause the pump body to heat up, vibrate, reduce the water output, and cause damage to the pump (referred to as "cavitation"). Cause equipment accident! The so-called cavitation refers to: When the centrifugal pump starts, if there is air in the pump, due to the low density of the air, the centrifugal force generated after rotation is very small, so the low pressure formed in the central area of the impeller is not enough to lower the liquid level below the pump inlet The phenomenon that the liquid is sucked into the pump, and the fluid cannot be delivered.

Classification of centrifugal pump

There are many types of centrifugal pumps, and the common classification methods are as follows

1. Divided by impeller suction mode: single suction centrifugal pump and double suction centrifugal pump;

2. According to the number of impellers: single-stage centrifugal pump and multi-stage centrifugal pump;

3. According to the impeller structure: open impeller centrifugal pump, semi-open impeller centrifugal pump, closed impeller centrifugal pump;

4. According to working pressure: low pressure centrifugal pump, medium pressure centrifugal pump, high pressure centrifugal pump;

5. According to the position of the pump shaft: horizontal centrifugal pump and vertical centrifugal pump.

Submersible pump

First, choose a standardized water pump

1. What is a standardized water pump? The standardized water pump is the latest model of water pump formulated and promoted by the country according to the requirements of ISO. Its main features are small size, light weight, excellent performance, easy operation, long life and low energy consumption. It represents the latest trend in the current pump industry.

Submersible pump

2. How to choose a water pump. When users choose a water pump, it is best to go to a sales point approved by the agricultural machinery department, and they must identify the manufacturer. It is recommended to give priority to the purchase of water-filled submersible pumps, and to clearly see the brand and product quality certificate. Do not buy "Three None" (ie, no manufacturer, no production date, no production license) products, otherwise there will be problems and users will be helpless.

3. What brand of water pump is good. As a user, due to the limitation of professional knowledge, it is difficult to determine the best way. The best way is to consult the experts in water pumps. If there is no one to consult, you may wish to consult some old pump users, especially those who are close to their own conditions of use. It is a wise choice to buy products that these users trust, reliable and mature. At the same time, the single-phase or three-phase pump should be decided according to the local power supply situation.

Second, choose the pump that meets the lift requirements.

1. Pump head selection. The so-called lift refers to the required lift, not the height of the pumped water, and it is particularly important to know this when choosing a pump. The pump lift is approximately 1.15 to 1.20 times the height of the lifted water. For example, if the vertical height from a water source to the water is 20 meters, the required head is about 23 to 24 meters. When selecting the pump, the head on the pump nameplate should be close to the required head. In this case, the pump has the highest efficiency and will be more economical to use. However, it is not necessary to be absolutely equal. Generally, as long as the deviation does not exceed 20%, the pump can work in a more energy-saving situation.

2. The nameplate lift is better. Choosing a pump with a lift on the nameplate that is much smaller than the required lift often fails to meet the user's wishes. Even if it can pump water, the amount of water will be pitifully small, and it will even become a useless "idle pump" . Do you buy a pump with a higher head? actually not. High head pumps are used for low heads, and the flow will be too large, which will cause the motor to be overloaded. If the motor runs for a long time, the temperature of the motor will rise, and the winding insulation will gradually deteriorate and even burn the motor.

Third, choose the right flow pump. The flow of the pump, that is, the amount of water output, should not be selected too large, otherwise it will increase the cost of purchasing the pump. It should be analyzed based on specific problems. For example, the self-priming water pump for the user's own draught should be selected as small as possible. For the submersible pump used for irrigation, the larger flow should be selected appropriately.

Piston type water pump

Also called "suction type pump". The water inlet pipe in the lower part of the body is inserted into the water. The pump is a cylinder. The cylinder is equipped with a piston that can slide up and down and closely matches the cylinder wall. There are valves v1 and v2 on the bottom of the cylinder and the piston that can only open upward. During use, if the piston moves upward, the valve v2 is closed by the effect of atmospheric pressure, so the air under the piston is thin and the air pressure is less than the outside atmospheric pressure. As a result, the water at the lower part is pushed by the atmospheric pressure to open the valve v1 and enter the cylinder. When the piston is depressed, the valve at the bottom of the cylinder v1 is closed by the pressure of the water, the water is blocked from flowing downward, so the valve v2 is opened upward, and the water enters the upper part of the cylinder. When the piston is lifted again, the water on the piston closes the valve v2, and the water flows out of the side pipe. At the same time, the water in the well pushes the valve v1 under the action of atmospheric pressure and enters the round pipe. In this way, the piston moves up and down continuously, and the water continuously flows out from the nozzle. The structure of this pump is simple and easy to operate, but the water output is small, the height of the water can only reach about eight meters, and the efficiency is low. 1. Before starting the pump, the suction pipe and the pump must be filled with liquid. After the pump is turned on, the impeller rotates at high speed, and the liquid in it rotates with the blades. Under the effect of centrifugal force, it leaves the impeller and shoots out. The ejected liquid gradually slows down in the pump casing diffusion chamber, and the pressure gradually increases. At the outlet, the discharge pipe flows out. At this time, at the center of the blade, the liquid is thrown to the surrounding area to form a vacuum low-pressure area with neither air nor liquid. The liquid in the liquid pool flows into the pump through the suction pipe under the effect of the atmospheric pressure on the surface of the pool. It is continuously sucked up from the liquid pool and continuously flows out of the discharge pipe.

Working principle of piston pump

Working principle of piston pump

The piston type pump is also called the pumping type, which uses the movement of the piston to discharge air, causing the internal and external air pressure difference to cause the water to rise under the action of air pressure. When the piston is depressed, the water inlet valve is closed and the exhaust valve is opened. When it is raised, the exhaust valve is closed and the water inlet valve is opened. Under the effect of external atmospheric pressure, water flows from the water inlet pipe through the water inlet valve through the water outlet above. In this way, the piston reciprocates up and down in the cylinder, constantly pumping water out.

Note: Both the piston type pump and the centrifugal pump use atmospheric pressure to pump water up. Because atmospheric pressure has a certain limit, the height of the pump's pumping height also has a certain limit, which does not exceed 10.3 meters.

Water pump mini circulating water pump

Miniature water pumps are often called micro-circulation water pumps because they have many functions and can be used for water circulation cooling. It has one inlet and one outlet for water inlet and one outlet, and can continuously form a vacuum or negative pressure at the inlet; a larger output pressure is formed at the outlet; the working medium is water or liquid; a compact instrument. There are also called micro liquid pumps, micro pumps, and micro pumps.

Features of various miniature water pumps

1.Miniature AC water pump

The commutation of the AC water pump is changed by the frequency of 50HZ of the commercial power. Its rotation speed is very low. There are no electronic components inside the AC water pump, which can withstand high temperatures. The volume and power of the same head AC water pump are 5- 10 times. Advantages: cheap, more manufacturers

2. Brushed DC water pump:

When the pump is working, the coil and commutator rotate, the magnetic steel and carbon brushes do not rotate, and the alternating current direction of the coil is completed by the commutator and brushes that rotate with the motor. As long as the motor rotates, the carbon brush will wear, When the computer water pump runs to a certain time, the carbon brush wear gap becomes larger, and the sound will increase accordingly. After several hundred hours of continuous operation, the carbon brush will not be able to perform the commutation function. Advantages: low price.

3. Brushless motor type DC water pump:

The motor-type brushless DC water pump is composed of a brushless DC motor and an impeller. The shaft of the motor and the impeller are connected together, and there is a gap between the stator and the rotor of the water pump. When the water is used for a long time, water will penetrate into the motor and increase the possibility of the motor burning out. Advantages: Brushless DC motors have been standardized and mass-produced by specialized manufacturers, with relatively low cost and high efficiency.

4. Brushless DC magnetic drive water pump:

Brushless DC water pump uses electronic component commutation, no carbon brush commutation is needed, high-performance wear-resistant ceramic shaft and ceramic bushing are used, and the bushing is integrated with the magnet through injection molding to avoid wear and tear, so brushless DC magnetic force The life of the water pump has been greatly enhanced. The stator and rotor parts of the magnetically isolated water pump are completely isolated. The stator and circuit board parts are encapsulated with epoxy resin and 100% waterproof. The rotor part is made of permanent magnets. The pump body is made of environmentally friendly materials, with low noise, small size and performance. stable. Various required parameters can be adjusted through the windings of the stator, allowing wide voltage operation. Advantages: long life, low noise up to 35dB, can be used for hot water circulation. The stator and circuit board of the motor are potted with epoxy resin and completely isolated from the rotor, which can be installed underwater and completely waterproof. The shaft of the pump uses a high-performance ceramic shaft with high accuracy and good shock resistance. ^[1]

Guide to the use of water pumps

Correctly mastering the use method is an important factor in extending the life of the pump and reducing economic losses.

Pumps for submersible pumps

Before starting, some necessary inspections should be done: whether the rotation of the pump shaft is normal and whether it is stuck; whether the position of the impeller is normal; whether the cable and cable plug are cracked, scratched, and broken. During the operation, pay attention to observe the change of voltage. Generally, it should be controlled within ± 5% of the rated voltage. In addition, the position of the pump in the water is very important. It should be selected as far as possible with plenty of water, no silt, and good water quality. It should be suspended vertically in the water, and it should not be placed horizontally to avoid sinking in the mud or being blocked by the suspended matter. As a result, the amount of water is drastically reduced or even not pumped.

Water pump for self-priming pump

It should be placed in a place with good ventilation as much as possible to facilitate rapid heat dissipation and reduce the motor temperature. Otherwise, it will be easy to burn the motor if it runs for a long time. For example, when a farmer uses a self-priming pump, because the plastic film covering the motor is not removed, the motor is overheated and the coil is burned. In addition, before starting, be sure to check the amount of water stored in the pump body, otherwise, it will not only affect the self-priming performance, but also easily burn the shaft seal components. Under normal circumstances, the water should be discharged 3 to 5 minutes after the pump is started, otherwise it should be stopped immediately for inspection.

Pump water pump repair

When the pump fails, do not disassemble it by yourself. When disassembling oneself, one is blindly dismantled without knowing where the fault is; the other is that there is no special tool and it often damages the original parts. The best way is to repair it at an experienced and large-scale repair point, and replace the "overage" parts and some wearing parts in time. Under normal circumstances, the pump should be repaired every six months to prevent work with "illness".

Storage of pumps during non-use period

In the non-use period, the pump should be lifted away from the water source in time, and the accumulated water in the pump should be drained, especially in the cold winter. Then place it in a dry place. Users with conditions can also apply butter to the key parts of the pump and add lubricating oil to the bearings to prevent parts from rusting. In addition, the non-use period of the pump is not as long as possible. If not used for a long time, it will not only easily corrode parts, but also reduce the service life of the pump.