Classification and structure characteristics of multistage pump 

Multistage pump is a pump with two or more than two impeller. Usually the structure has the spiral case type multistage pump and the sectional type multistage pump.  

 The spiral case type multistage pump is generally used in the open type structure to facilitate the maintenance, and is advantageous for the symmetrical arrangement of the impeller, and reduces the axial force on the rotor. But the structure of technology and less: Series increasing, the shape of the pump body and cover more complex, pump dimensions is large, especially level and need to configure some level between channel, the pump complex shape. And when the series more, head higher, the opening of the sealing surface is more difficult. Based on these factors, the wide application of this structure is limited.  

 Segmented multi-stage pump compact structure, is conducive to improve the degree of standardization, generalization. Because of the structure of the pump head depends on the pump series, so the head of the pump range is wider.  

Power calculation formula of centrifugal pump

The characteristic curve of centrifugal pump is the inherent characteristic of the pump, it has nothing to do with the use of the outside world. However, once the pump is arranged in a certain pipeline system, the actual work is not only related to the characteristics of the centrifugal pump itself, but also depends on the working characteristics of the pipeline. Therefore, to select and make good use of centrifugal pump, it is also considered the characteristics of the pipeline at the same time. 

Because there are various losses in the operation of the centrifugal pump, the effective pressure head and flow rate of the pump are lower than the theoretical value, and the input pump power is higher than the theoretical value. 

H______ pump effective pressure head, that is, the unit volume of liquid in the gravity field from the pump to get the energy, m; 

Q ______ the actual flow ofpump, m3/s; 

P ______ liquid density, kg/ m3; 

Ne______ the effective power of the pump, that is, the mechanical energy of the liquid from the pump unit at the time of the unit, W. 

Effective power can be written as Ne = QH = g 

The power of the centrifugal pump is referred to as the pump shaft power, which is expressed by N. The effective power and shaft power is defined as the ratio of the total pump efficiency, namely =Ne/N according to the above analysis, we can understand the energy loss in the centrifugal pump to work, how to improve the power of centrifugal pump for efficient use of products of great significance. Each product has a shortage of places, these weaknesses may lead to a reduction in the use of the product performance. At this time the power is a very good test method, how to maximize the power of the product, the need for professionals to do more work and research. 

Cause and harm of centrifugal pump cavitation

The reason of low temperature centrifugal pump cavitation: pump through the rotation of the impeller on the liquid work, so that the liquid energy increases. In the interaction process, the velocity and pressure of the liquid changes. In general, the inlet of the impeller of the centrifugal pump is the place where the pressure is lowest. If the local pressure is equal to or lower than the temperature in the vapor pressure of liquid, gas and steam will be dissolved in the liquid from the liquid in a large number of escape, forming many mixed steam and gas bubbles. These small bubbles with the liquid flow to high pressure areas, due to air bubbles within and around the bubble is greater than the vaporization pressure, vaporization pressure, pressure difference. Under the pressure difference, the bubble burst and re condensed. In the condensation process, the liquid particles from all around to the bubble center to accelerate movement, in the condensation of the moment, the particles collide with each other, resulting in a high local pressure. These bubbles, if they break down near the metal surface, are condensed, and the liquid mass is like a myriad of small bullets, hitting on the surface of the metal. Under high pressure and high frequency, the surface of the metal is gradually destroyed by fatigue, which is often referred to as erosion. In the bubble generated by the inclusion of a number of active gases (such as oxygen, etc.), with the heat released by the bubble condensation, the metal from the chemical corrosion. Chemical corrosion and mechanical erosion of the common role, it is more accelerated the speed of metal damage, this phenomenon is the phenomenon of cavitation damage. 

At the beginning of the centrifugal pump cavitation, the cavitation area is small, the normal work of the pump has no obvious effect, and there is no obvious reflection of the pump performance curve. But when cavitation develops to a certain extent, the bubbles produced, affecting the normal flow of liquid, and even cause the liquid flow interruption, vibration and noise; at the same time, pump flow, head and efficiency decrease, is also apparent in the pump performance curve. Serious when the pump can not work. In order to avoid cavitation phenomenon, in the process of design, should make the liquid in the pump before the degree of cooling, at the same time the pump should be installed in the lower position, so that the liquid inlet has a certain static pressure head. In addition to pay attention to the cold, as far as possible to reduce the loss of cold. 

Installation instructions of horizontal centrifugal pump

1.In the installation, you need to check parts, such as motor, water pumps, etc., especially the pipeline, whether there are impurities affect the operation, to avoid damage to the parts when working. 

2.In order to maximize the performance of the equipment to play, and as far as possible to extend the use of equipment, installation of pipeline equipment should have different support. 

 

3.Due to the temperature limit, in the transmission of high temperature liquid, in order to ensure the pipeline with the force, in the early installation, the bottom bolt is not fixed, and then the pipeline with the temperature change and synchronous movement. 

 

4.Import and export flange specifications need to be consistent with the pipeline configuration specifications. 

 

5.The installation should be installed at the entrance of a filter to avoid the debris into the pump and affect the efficiency of the work or damage to the equipment. In addition, the outlet of the check valve should be installed outside. 

 

6.Due to the scope of application of the centrifugal pump may be in the suction range, so the import and export pipeline to minimize the twists and turns, to ensure that there will be no leakage of water vapor phenomenon. 

 

7.For the whole work and maintenance process can be carried out smoothly, at the time of installation, the inlet and outlet pipe to install a separate regulation and pressure testing equipment to ensure the timely detection and treatment of abnormal situation. 

 

8.A full set of installation is completed, start the test, check whether there is friction and the card dead phenomenon, OK no problem can be put into use. 

The reason and solution of the shortage of the centrifugal pump flow

1.Import and export pipeline, flow of centrifugal pump impeller partially blocked, the scale deposition in the pump inside. Check the pipe and pump cavity to remove the blockage, re adjust the valve size. 

2.The voltage is low. The solution to the problem of centrifugal pump flow: stable voltage. 

 

3.Centrifugal pump impeller wear. Solution: replace the new impeller. 

 

4.Is not the above several reasons please according to the following centrifugal pump does not water the reason comprehensive inspection. 

 

5.The centrifugal pump inlet or outlet valve is not open, the inlet pipe is blocked, the pump cavity impeller flow channel is blocked. Check whether the import and export of the valve is closed to open the closed valve, check the inlet and outlet pipes and pump impeller is a debris blockage removal. 

 

6.The motor's running direction is not right, the motor phase speed is very slow. Change the motor wiring to adjust the motor's turn, check the power supply into the wire fastening good motor wiring. 

 

7.The centrifugal pump inlet pipe leakage, leading to the centrifugal pump has been in the state of air suction. Check the leakage point of the imported pipeline leak to repair the leak, tighten the cover, remove the air. 

 

8.The centrifugal pump is not filled with liquid, the pump cavity has air. Unscrew the pump cover or open the exhaust valve and discharged into the air. 

 

9.The centrifugal pump inlet pipeline centrifugal pump water flow lack the required flow, or suction is too high, the inlet pipe valve centrifugal pump seal is not good Water Leakage. Check the pump (pipe network and the use of water pipe with the suction process is prone to this phenomenon), adjust the distance to shorten the distance, or replace the self suction pump. 10, pump outlet pipe resistance is too large, pump selection is not appropriate or the pump head can not reach. Reduce the pipe bend, bend too much can be installed on the automatic exhaust valve, exclude the pipeline corner of the condensation of air, or re election pump

How to solve the problem of horizontal multi-stage pump

1.Horizontal multi-stage pump does not absorb water or water. The cause of this failure is mostly due to the end of valve stuck, part of the blockage of water, high water or water pipe leakage is too high. Should be checked one by one, taken at the end of valve repair, clear the blockage and correct the steering and other processing. 

 

2.Pipeline leakage or leakage. No more than nuts tightened due. If the leakage is not serious, can be applied to cement slurry, mud or soft soap in the leakage; if the joints Water Leakage, tighten the nut wrench can be used. Serious leakage, leakage, must be re assembled. 

 

3.Multi-stage centrifugal pump severe vibration. May be the motor rotor is not balanced or shaft coupling. Sometimes bearing wear, bending, rotating parts of the relaxation, rupture, pipeline stent is not strong also cause vibration. Should be adjusted, reinforcement, inspection or replacement. 

 

4.The impeller is bad. When the damage is not large, can be repaired. Hard alloy should be replaced or plated when the damage is serious. Completely damaged, the impeller should be removed, the repair shop to repair. 

 

5.Horizontal multi-stage pump shaft bending. Is due to the impact load, belt pulled too tight, causing incorrect installation. If the bend is not serious, can be used manually screw to correct, but not too hard, in case of a complete break.

Structure of clean water horizontal centrifugal pump

1.Horizontal  centrifugal pump housing (that is, pump body and pump cover) to form a pump studio. Impeller, shaft and rolling bearings, etc. for the pump rotor. The suspension bearing part supports the rotor of the pump, and the radial force and axial force of the rolling bearing are affected by the pump. 

2.In order to balance the axial force of pump impeller, pump the most before and after is provided with a sealing ring, and a balance hole in the impeller hub, the axial force of pump impeller back some small, no sealing ring and balance hole. 

 

3.Axial horizontal centrifugal pump sealing ring is composed of packing gland, packing ring and packing etc., to prevent air or a large number of Water Leakage. The impeller of the pump if the balance cavity and impeller with soft packing suction port as the impeller inlet liquid in the vacuum state, it is very easy to intake along the surface of the shaft sleeve, the packing ring through the pump cover hole is arranged in the packing chamber, the pump room pressure water to fill material for sealing ring. If there is no balance hole of the impeller of the pump, the liquid pressure on the back side of the impeller is greater than the atmospheric pressure, so there is no leakage problem, therefore, the packing ring can not be filled. 

 

4.In order to avoid shaft wear, in the shaft through the packing chamber is equipped with protective sleeve. A quasi O type sealing ring between the shaft sleeve and the shaft, along with the surface to prevent intake or Water Leakage. 

 

5.Pump transmission is through the extension of the elastic coupling and motor coupling, the rotation direction of the pump, from the driver to see, for the clockwise rotation.