Operating procedure of centrifugal pump

The operating principle of centrifugal pump is that swing water by taking advantage of centrifugal force produced by the rotation of pump impeller to increase the energy of water and then the water will deliver to the destination through pump case, pump outlet and pressure pipe.

1. Check-up before starting the pump

① Check if pump, valve and coupling screw of filter are fixed, if foundation bolt is loose and if motor grounding is connected securely.

② Check if shaft bolt is loose and rotate the pump 3 to 5 circles by hand to check if it rotates flexibly.

③ Check if there is oil at and if water is into the lubrication parts; add oil to the specified position if oil lacked.

④ Open pressure gauge and cooling water valve.

2. Stat the pump

Press the start button to open the pump and after pump pressure reaching the rated value, open outlet valve slowly until adjusting pump pressure to the specified value.

3. Check-up in the operation process

① Observe the fluctuation of pressure and current at any time in the operating process, which should be no more than specified value.

② In the operating process, listen to if the rotate sound of pump is normal; check if the seal oil leakage is in the allowed scope; if the amount of cooling water is proper; check if the temperature of parts is overheat.

③ Check the leakage of mechanical seal: light oil should be no more than 10 drips per minute and heavy oil should be no more than 5 drips per minute.

④ Adjust flow or head, which should be controlled through outlet valve.

4. Stop the pump

when stop the pump, close outlet valve firstly and then close inlet value.

How to reduce the power consumption of pipeline pump

Large power consumption of pipeline pump will cause unnecessary resource waste, sometimes even influencing the efficiency of the pump. Generally, the reason of large power consumption is caused by part damage and part structure of the pipeline pump.the following are the solutions for large power consumption of pipeline pump.

1. Check part size, clearance of pipeline pump and check if the parts are damaged. Clearance between parts will increase due to long wear, which will lead to friction between impeller and wearing ring and impeller and shell. Finally, the power consumption of pipeline pump will be large.

2. Check if the axial clearance of the coupling is too small.

3. Check if the density of liquid pumped by pipeline pump exceeds the specified scope. If the density of the medium is not in the scope of the pipeline pump, the model of the pump should be changed.

4. Check if the packing gland is too tight and if there is dry friction condition.

5. Check if the bearing pf pipeline pump is worn or damaged. Repair or change the bearing according to damaged condition of the bearing.

6. Check if the rotate speed of the motor is too high or power supply pressure is abnormal.

7. Check if the pump bearing is bent. Adjust or change the part according to the actual situation of the pump shaft bending.

Analysis common faults and solution of single-stage single-suction vertical centrifugal pump

ISG type single stage single suction vertical centrifugal pump barrier and elimination method:

1. ISG type vertical pipeline centrifugal pump installation is reasonable, the normal operation and service life of the pump has a very important influence, so the installation and correction must be carefully carried out.

2. Control installation size embedded anchor bolt, make concrete foundation work.

3. To be the basis of cement solidification after the pump is mounted on the basis, level of application level instrument to check the pump and motor shaft, such as level, application of adjusting pad iron is until levels and adjusted properly after tightening the foot nut.

4. Check the pump rotating parts is stuck in a collision phenomenon, should strictly check the pump shaft and motor coaxial degree and flakes available adjustment the concentric, finally hand rotation coupling, rotating easily even without brush touch phenomenon is normal.

5. The pump inhalation and spit out the line due to the respective support, does not allow the weight of the pipeline directly by the pump to bear, so as not to pump crushed,

6. The pump installation position above the liquid level in the pump suction within the allowable range) should be on the suction pipe end part is installed on the end of the valve and in the discharge pipeline set irrigation liquid hole or valve, pump for filling liquid before starting; pump installation position below the surface should be in the suction pipe installed by the control valve and filter device, to prevent debris into the pump, filter area should be 3-4 times larger than the area of the pipeline.

7. High lift pump in the outlet flow control valve on the outer end of the pipeline should also be installed check valve to prevent sudden stop when the water hammer damage.

8. Must ensure that the pump installation height is in line with the pump cavitation margin, and consider the pipeline loss and medium temperature.

Reasons for the damage of vertical and horizontal multistage centrifugal pump impeller

In the running process of the pump, impeller driven liquid rotation in the pump, impeller surface with a liquid, liquid and the pump shell, the liquid motion internal have friction loss, and liquid movement in the vortex loss, impact damage, the liquid in the pump circulation due to overcome the gap resistance to consume the volume loss. Due to various losses in the pump, the effective power of water is always less than the shaft power. Only as much as possible to reduce the loss of the pump, in order to improve the efficiency of the pump.

In the three loss of horizontal multistage centrifugal pump, the mechanical loss and hydraulic loss are directly related to the roughness of the pump flow surface, the more rough the flow surface, the greater the loss. For the centrifugal pump with low specific speed, the loss is more serious, when n1=30, the friction loss of the main part of the mechanical loss can be increased to nearly 30% of the effective power. The mechanical loss and hydraulic loss of the pump can be reduced significantly if the surface roughness of the transition surface and the outer surface of the impeller can be reduced directly. Based on the above principles, the use of super - sliding metal coatings, can achieve the purpose of reducing the surface roughness to reduce the power loss of pump.

Due to the erosion of sediment, water flow, the corrosion of the medium, horizontal multi-stage centrifugal pump impeller will gradually wear and corrosion. The blade surface often form grooves or striations, or by cavitation damage, blade honeycomb holes, and even perforation. If the blade casting with holes, sand holes or slag, running after the surface is easy to appear the blowhole, even cracks.

Horizontal multi-stage centrifugal pump impeller repair in a variety of ways, impeller cavitation repair, there are many kinds of methods, such as the use of arc macromolecular composite coating support, powder spraying (welding), epoxy resin coated lip and rubber, nylon composite repair etc., as well as the use of stainless steel mosaic, such as welding. The use of epoxy resin polymer material coating has the advantages of simple construction method, low cost, etc., and the effect is good. By optimizing the proportion, to adjust the material performance, showing that the toughness of high strength of adhesion and absorption of impact energy, with a high resistance to cavitation and abrasion damage strength and hardness

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How to reduce the pump cavitation of pipeline centrifugal pump

Improving the anti cavitation performance of the pump :

1. reduce the necessary cavitation margin:

1). The double suction impeller pump. The double suction pump NPSH delta HC than single stage single suction pump NPSH HC, N and Q for the same speed flow pump, adopt double suction impeller.

2). Appropriately increasing the inlet diameter of the impeller and increasing the inlet width of the blade. When the impeller inlet diameter and the inlet width increase, the absolute velocity and relative velocity of the impeller inlet are decreased, and the critical cavitation margin of the pump is decreased. However, at this time the impeller inlet area of the reduction of the area increases, leakage increased, the volume efficiency of the pump will be reduced.

3) impeller before the addition of inducer. Inducer before impeller of pipeline centrifugal pump impeller. The impeller and the pump vane pump, the pressure generated by the coaxial assembly of the wheel running together, the pressure generated by the impeller inlet pressure, improve pump cavitation performance. However, the addition of inducer, will make the pump performance is not stable, therefore, it is necessary to further explore and research.

2. Improve the anti cavitation ability of the flow component material in order to reduce the cavitation damage to the pump flow parts, to extend its service life, often choose the material with strong anti cavitation performance. Such as cast manganese, bronze, stainless steel and alloy steel casting impeller; or with polymer coating or laser spray plating parts surface to resist cavitation damage. In addition, on the surface of the flow parts finishing, improve its finish, but also to reduce the harm of cavitation.

Anti cavitation ability of the water inlet device:

The cavitation margin is closely related with the water inlet device and the pipeline system, so it should be designed to be a good water inlet device, so as to improve the pump inlet's cavitation margin, so as to meet the requirements of the dynamic pressure drop in the pump.

1. Reasonably determine the water absorption of the pump. The pumps are generally in non design condition, it should fully consider the various conditions that may be encountered in the work of the water pump, the determined height in any condition should meet the requirements of water pump performance.

2. Optional water inlet pipe. As far as possible to reduce the length of the inlet pipe and unnecessary pipe attachment, appropriate increase in the inlet pipe diameter, in order to reduce the hydraulic loss of the inlet pipe, improve the pump inlet cavitation. For large and medium axial flow pumps, the distribution of flow velocity and pressure in the inlet pipe can be evenly distributed, which will be beneficial to prevent the occurrence of cavitation.

3) well designed into the pool. Fall into the pool of good can not only reduce the water level in the pond, reduce the resistance coefficient of inlet, and the water in the pool is stable without swirl. Can avoid the air into the pump, to prevent the occurrence of cavitation premature.

Measures to be taken in operation management :

1. As far as possible to make the pump in the design of the operating conditions of the annex. According to the specific conditions of the pump station, the pump using variable valve, variable speed, variable angle and other regulatory measures to prevent pump operating conditions deviate from the design conditions too far.

2. The actual speed of the pump is higher than the design speed. Due to the need to be proportional to the square of the speed and the speed of the rotating speed is too high, not only to reduce the need for a substantial increase in cavitation margin, but also to reduce the effective cavitation margin.

3. Pump cavitation in the operation, the water inlet of the water pump filled with a small amount of air or high-pressure water way, to reduce or avoid cavitation damage.

Transmission principle of multi-stage pump

A proper amount of water is used as working fluid in the multistage pump body. When the impeller rotates in a clockwise direction, the water is thrown to the periphery of the impeller, because of the centrifugal force, the water forms a closed circular ring, which is determined by the shape of the pump cavity. The next part of the water ring coincided with the inner surface of the impeller hub tangent to the inner surface of the upper part of the water ring coincides with the leaves of the top contact (actually leaves into a certain depth in the water ring). At this time between the impeller wheel and the water ring to form a crescent shaped space, and this space has been divided into several small impeller blades and equal to the number of. 

If the lower impeller 0 degrees as the starting point, then the volume of the impeller rotating 180 degrees in front of the cavity from small to large, and communicated with the end face of the suction port, then the gas is inhaled, when the suction end of the cavity is isolated from the suction port; when the impeller continues to rotate, the cavity from big to small, make the gas is compressed; when the cavity communicates with the exhaust port, the gas will be discharged out of the pump. In summary, multistage pump is a pump chamber volume by the change to achieve soft pump suction, compression and exhaust, so it can change the size of the centrifugal pump. Multi stage pumps can be used in petroleum, chemical, machinery, mining, light industry, medicine and food and many other industrial sectors. In many industrial production processes, such as vacuum filter, vacuum water, vacuum feed, vacuum evaporation, vacuum evaporation, vacuum degassing and vacuum resurgence, etc., widely used in multistage pump. Can be pumped in addition to flammable, explosive gas, in addition to smoke and dust, water containing gas, therefore, the application of water ring pump is increasing.