Pump application basics

There is a certain interdependence and changing relationship between various performance parameters of the pump, which can be represented by drawing a curve, which is called the characteristic curve of the pump. Each pump has its own specific characteristic curve.
 Historical origins of pumps
 Machine that transports liquid or pressurizes liquid. A pump in a broad sense is a machine that transports fluid or pressurizes it, including some machines that transport gas. The pump transfers the mechanical energy of the prime mover or the energy of other energy sources to the liquid, thereby increasing the energy of the liquid.
 The improvement of water is very important for human life and production. There were various water-lifting devices in ancient times, such as the Egyptian chain pump (17th century BC), the Chinese tangerine (17th century BC), the windlass (11th century BC), the waterwheel (1st century AD), and the 3rd century BC The screw rod invented by Archimedes in ancient Greece. Around 200 BC, the ancient Greek craftsman Ctesibius invented the most primitive piston pump-the fire extinguishing pump. As early as 1588, there were records of a 4-blade sliding vane pump, and various other rotary pumps appeared one after another. In 1689, D. Papin of France invented the volute centrifugal pump with a 4-blade impeller. In 1818, a centrifugal pump with radial straight blades, semi-open double-suction impeller and volute appeared in the United States. From 1840 to 1850, H.R. Worthington of the United States invented a piston pump with direct steam action in which the pump cylinder and the steam cylinder faced each other, marking the formation of the modern piston pump. From 1851 to 1875, multi-stage centrifugal pumps with guide vanes were invented one after another, making it possible to develop high-lift centrifugal pumps. Subsequently, various pumps came out one after another. With the application of various advanced technologies, the efficiency of pumps has gradually improved, and the performance range and applications have also expanded.
 Pump classification basis
There are many types of pumps, which can be divided according to their working principles: ① Power pumps, also called impeller pumps or vane pumps, rely on the dynamic effect of the rotating impeller on the liquid to continuously transfer energy to the liquid, so that the kinetic energy of the liquid ( Mainly) and pressure energy increase, and then the kinetic energy is converted into pressure energy through the pressure chamber. It can be divided into centrifugal pumps, axial flow pumps, partial flow pumps and vortex pumps, etc. ② Positive displacement pumps rely on periodic changes in the volume of the sealed working space containing the liquid to periodically transfer energy to the liquid, increasing the pressure of the liquid to the point where the liquid is forcibly discharged. According to the movement form of the working components, it can be divided into reciprocating pumps and rotary pumps. ③Other types of pumps transfer energy in other forms. For example, the jet pump relies on the high-speed injection of working fluid to suck the fluid to be transported into the pump and mix it, and exchange momentum to transfer energy; the water hammer pump uses part of the flowing water to be raised to a certain height during braking to transfer energy; the electromagnetic pump uses The energized liquid metal flows under the action of electromagnetic force to achieve transportation. In addition, pumps can also be classified according to the properties of the transported liquid, driving method, structure, use, etc.
 Pump application fields
Judging from the performance range of the pumps, the flow rate of giant pumps can reach more than hundreds of thousands of cubic meters per hour, while the flow rate of micro pumps is less than tens of milliliters per hour; the pressure of the pump can range from normal pressure to as high as 19.61Mpa (200kgf/ cm2) or above; the temperature of the transported liquid can reach as low as -200 degrees Celsius and as high as over 800 degrees Celsius. Pumps transport a wide variety of liquids, such as water (clean water, sewage, etc.), oil, acid and alkali liquids, suspensions, and liquid metals.
 In agricultural production, pumps are the main drainage and irrigation machinery. my country's rural areas are vast and require a large number of pumps every year. Generally speaking, agricultural pumps account for more than half of the total pump output.
In the shipbuilding industry, there are generally more than a hundred pumps used on each ocean-going ship, and their types are also various. Others such as urban water supply and drainage, water for steam locomotives, lubrication and cooling in machine tools, conveying bleach and dyes in the textile industry, conveying pulp in the paper industry, and conveying milk and sugar foods in the food industry all require a large amount of of pump.
 Pump maintenance precautions
 The pump works by using two gears that mesh and rotate with each other, and does not have high requirements on the medium. The pump is equipped with a pair of rotary gears in the pump body, one active and one passive. Relying on the mutual meshing of the two gears, the entire working chamber in the pump is divided into two independent parts. When the pump is running, the driving gear drives the passive gear to rotate. When the gears enter mesh, the liquid is squeezed out, forming high-pressure liquid and discharged out of the pump through the pump discharge port.
  1. Add grease frequently. The electric oil drum pump operates at high speed, and the grease is easy to volatilize. Therefore, the lubrication at the bearing must be kept clean, and pay attention to replacement.
  2. Fiber formation and storage: The electric oil pump should be placed in a dry, clean and corrosive gas-free environment.
3. Pay attention to the insulation resistance of the pump. For electric liquid pumps that have been left unused for a long time or used in humid environments, the insulation resistance of the winding must be measured with a 500-volt megger before use. If the insulation resistance between the winding and the motor shell is less than 7 megohms, the winding must be dried.
4. The pump should be inspected and maintained frequently. Electric oil drum pumps should be inspected and repaired frequently. The power cord must be checked: internal wiring, plugs, switches are in good condition, insulation resistance is normal, the brush tailstock is loose, and the commutator is in contact with the brush. Good. Check whether the armature windings and stator windings are properly disconnected, whether the bearings and rotating parts are damaged, etc.
5. Preserve each part and replace the same part. When disassembling the pump, you should preserve each part. Pay special attention to the explosion-proof surface of the explosion-proof parts so that they cannot be damaged and roughened, including the insulating liner and casing. If there is any damage, , must be replaced with new identical parts. Substitute materials with lower performance than the raw materials or parts that do not meet the original specifications must not be used. During assembly, all parts should be installed in their original positions and no omissions can be allowed.
 Methods to improve pump efficiency
During the operation of the water pump, the water flowing in the pump is affected by the friction with the surface of the flow channel and the pump impeller, as well as the viscosity of the water itself. The energy consumed by the pump is mainly used to resist the flow friction and eddy resistance of the water surface. The energy consumed by water (head loss) during the flow process is used to overcome internal friction and friction at the interface between water and equipment. If the surface of the pump and impeller is smooth (this surface is called a hydraulically smooth surface), the surface resistance is small and the energy consumption is small. Polymer materials are sprayed on the flow surface and impeller of the water pump to form a hydraulically smooth surface. The surface finish of the ultra-smooth surface coating is 20 times that of polished stainless steel. This extremely smooth surface reduces the separation of the fluid in the pump. layer, thereby reducing the turbulence inside the pump, reducing the volume loss and hydraulic loss in the pump, reducing the power consumption, and achieving the purpose of reducing the water flow resistance loss, thus improving the hydraulic efficiency of the water pump and also improving the mechanical efficiency to a certain extent. and volumetric efficiency. The dense molecular structure of the coating can isolate the contact between air, water and other media and the base material of the water pump impeller, minimizing electrochemical corrosion and rust. In addition, polymer composite materials are essentially polymers and are resistant to chemical corrosion, which can improve the corrosion resistance of the pump and greatly enhance the pump's ability to resist erosion and corrosion. Due to its good wear resistance and impact resistance, it can play a very good anti-wear and buffering role when fine solid particle media come into contact and impact with the pump.
It is recommended that industrial enterprises apply this composite coating to cope with and extend the service life of pumps, achieve long-term pump efficiency, and avoid the many impacts on production, cost, labor, etc. caused by frequent replacement. To save energy and reduce consumption of water pumps, we should continue to explore under the conditions of combining theory and practice, boldly introduce new technologies, and find more reasonable and economical energy-saving measures. Polymer composite materials are simple and convenient to operate, have low requirements on the construction environment, and can be widely promoted and applied. The surface of this type of material is smoother than polished stainless steel, and it is hydrophobic and has waterproof algae adhesion. After completion, the surface of the equipment will form a hydraulically smooth surface, thereby improving the operating efficiency of the water pump and achieving significant energy saving effects. At the same time, it can also provide anti-corrosion protection to the inner surface of the water pump, which has the dual effects of energy saving and anti-corrosion. The use, repair and maintenance of water pumps will play a key role in saving energy, reducing consumption and improving economic benefits.
 Pump layout requirements
 There are certain technical requirements and technical indicators:
  1. Pump layout requirements
  (1) For pumps arranged in the open air or semi-open air, the pump is generally perpendicular to the axis of the prime mover and the axis of the pipe gallery.
(2) For pumps arranged indoors, when the temperature of the transported liquid is higher than the natural point or the transported liquid is liquid hydrocarbon, they should be arranged in separate rooms with other pumps and separated by firewalls.
 When the pump is arranged indoors, the traffic requirements for motorized maintenance vehicles are generally not considered.
 The clear distance between the pump end or pump side and the wall should not be less than 1.2~1.5m, and the clear distance between two rows of pumps should not be less than 2m. The power side and pump side of the steam reciprocating pump should have positions for extracting the piston and tie rod.
  When the vertical pump is arranged under the pipe gallery or under the frame, space required for the installation and maintenance of the pump body should be left above it.
 Space required for maintenance and inspection of various centrifugal pumps. When piping is laid out, at least one side on both sides of the pump must be reserved for maintenance.
 The space required for maintenance and inspection of other types of pumps.
  2. Pump layout
 (1) In open-air layout, pumps are generally arranged under or on the side of the pipe gallery, or near miscellaneous suction equipment. The main advantages are good ventilation and easy operation and maintenance. If the pump is arranged below the pipe gallery, the center line of the pump outlet should be aligned and 0.6m away from the center line of the pipe gallery column.
 (2) Semi-open-air arrangement Semi-open-air arrangement of pumps is suitable for rainy areas. Generally, the pump is arranged below the pipe gallery and a ceiling is provided on the upper part of the pipe. Or arrange the pump on the ground below the frame, using the frame platform as the ceiling. According to the pump layout requirements, the pumps can be arranged in single row, double row or multiple rows.
 (3) Indoor layout Pumps arranged indoors are suitable for cold or windy and sandy areas, as well as occasions with special process requirements.