Advantages and disadvantages of various pumps

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This post was last edited by yao_szzbC on 2024-3-4 13:51. 1. Centrifugal pumps: The pump casing is filled with liquid. The impeller rotates at high speed, causing the liquid to gain high velocity under the action of centrifugal force. This high-speed liquid flows through the gradually expanding passages in the pump casing, where its dynamic pressure head is converted into static pressure head. Care should be taken to prevent cavitation and air binding from occurring. Performance characteristics: Centrifugal pumps have a wide range of flow rates; both the flow rate and pressure remain stable, with no fluctuations. Centrifugal pumps operate at relatively high speeds and can be directly connected to electric motors and steam turbines; their drive mechanisms are simple and compact. It is easy and reliable to operate, simple to adjust and maintain, and readily amenable to automation and remote operation. Compared to reciprocating pumps with the same specifications, centrifugal pumps have a simple and compact structure, small size, light weight, fewer components, are easy to manufacture, and have low production costs. Additionally, they require less floor space; therefore, both their equipment and maintenance costs are relatively low. Centrifugal pumps have the following main drawbacks: Under normal circumstances, before starting a centrifugal pump, it is necessary to prime it or use a vacuum pump to remove the air from inside the pump. Although self-priming centrifugal pumps do not require priming before startup, their current applications still have certain limitations. The viscosity of the liquid has a significant effect on the pump’s performance. When the viscosity of the liquid increases, the pump’s flow rate, head, suction lift, and efficiency all decrease significantly. The application of centrifugal pumps under conditions of low flow rate and high head is somewhat limited. Due to the very narrow flow channels in the pump casing of small-flow centrifugal pumps, they are difficult to manufacture; moreover, their efficiency is quite low. II. Multi-stage centrifugal pumps are equivalent to multiple centrifugal pumps connected in series; each stage increases the pressure, thereby achieving a relatively high head. Performance characteristics: Compared to single-stage pumps, multi-stage centrifugal pumps have the distinction of possessing two or more impellers. They can draw in and discharge water in multiple stages, thereby pumping water to great heights. The head can be increased or decreased by adjusting the number of pump impellers as needed. Multistage pumps are mainly used for mine drainage and water supply in cities and factories; they are rarely used for agricultural irrigation. They are only suitable for pumping water in high-altitude mountainous areas where high head and low flow rates are required, thereby helping to alleviate difficulties in providing drinking water for humans and livestock. Multistage centrifugal pumps come in vertical and horizontal types. On the pump shaft of a multistage centrifugal pump, there are two or more impellers connected in series. Compared to ordinary single-stage centrifugal pumps, they can achieve a higher head ； Compared to reciprocating pumps such as piston pumps and diaphragm pumps, it can pump larger flow rates. Multi-stage centrifugal pumps feature high efficiency and can meet the requirements of operating conditions with high head and high flow rates. They are widely used in industries such as petrochemicals, chemicals, power generation, construction, and fire protection. Due to their inherent characteristics, compared to single-stage centrifugal pumps, multi-stage centrifugal pumps have different and more stringent technical requirements in terms of design, operation, maintenance, and repair. Often, it is people’s negligence or lack of thorough consideration regarding certain details that leads to frequent occurrences of abnormal wear, vibration, shaft seizure, and other malfunctions after multi-stage centrifugal pumps are put into service, ultimately resulting in shutdowns. III. Gear pump: The teeth of the two gears are separated from each other, creating a low-pressure area. The liquid is drawn in and then transported by the housing wall to the other side. On the other side, two gears come together to create high pressure that forces the liquid out. Performance features: Advantages: simple and compact structure, small size, light weight, good manufacturability, low cost, strong self-priming ability, insensitivity to oil contamination, wide speed range, capability to handle shock loads, easy maintenance, and reliable operation. Disadvantages: unbalanced radial forces, significant flow pulsation, high noise levels, low efficiency; poor interchangeability of parts; difficult to repair after wear; not suitable for use as a variable-displacement pump. IV. Screw pumps: Twin-screw pumps are very similar to gear pumps. One screw rotates, driving the other screw. The liquid is trapped in the meshing chamber, propelled along the axis of the screws, and then forced toward the center for discharge. Performance features: Advantages: 1) Wide range of pressure and flow rates ； 2) A wide range of liquid types and viscosities can be transported ； 3) Since the inertial forces of the rotating components inside the pump are low, very high rotational speeds can be used ； 4) Good suction performance, with self-priming capability ； 5) Uniform and continuous flow, minimal vibration, low noise ； 6) Compared to other rotary pumps, it is less sensitive to the gases and contaminants that enter ； 7) Sturdy structure; easy to install and maintain. Disadvantage: High requirements for the machining and assembly of the screw ； The performance of the pump is quite sensitive to changes in the viscosity of the liquid. V. Reciprocating pumps: Reciprocating pumps are positive displacement pumps. When the flow rate provided by the pump exceeds the demand of the pipeline, it is necessary to return a portion of it to the inlet of the reciprocating pump, as well as to use bypass regulation. Performance characteristics: Advantages: (1) It can achieve very high discharge pressures; the flow rate is independent of pressure. It has good suction capabilities and relatively high efficiency. In particular, steam reciprocating pumps can reach an efficiency of 80%–95% ； (2) In principle, it can transport any medium, with almost no limitations imposed by the physical or chemical properties of the medium ； (3) The performance of the pump does not change with variations in pressure or the viscosity of the fluid being transported. Other pumps do not possess the aforementioned advantages of reciprocating pumps, but they have a simpler structure, are easier to operate, and also offer the benefits of small size, light weight, uniform flow rate, as well as the possibility of mass production in series. Disadvantage: The data flow is not very stable. It is larger than centrifugal pumps at the same flow rate ； Complex structure ； High capital requirement ； Difficult to maintain, etc. VI. Double-acting reciprocating pump: The piston moves to the right; liquid is drawn in from the lower left, and discharged from the upper right. The piston moves left, drawing in liquid from the lower right and discharging it from the upper left. With one back-and-forth movement of the piston, there are two instances of liquid suction and discharge, resulting in a more uniform flow rate. VII. Pneumatic diaphragm pump: To prevent the plunger from coming into direct contact with corrosive liquids, the cylinder chamber is separated from the liquid by a diaphragm; this is essentially based on the principle of a reciprocating pump. Performance features: The pneumatic diaphragm pump is a new type of conveying machinery and represents the most innovative pump design available in China at present. Uses compressed air as a power source, suitable for various corrosive liquids. Pneumatic diaphragm pumps are available in four materials: engineering plastics, aluminum alloy, cast iron, and stainless steel. Pneumatic diaphragm pumps use nitrile rubber, neoprene, fluororubber, polytetrafluoroethylene, and polyhexafluoroethylene depending on the different liquid media. To meet the needs of different users. Installed in various special applications to pump fluids that conventional pumps cannot handle, it has achieved satisfactory results. (1) The pump will not overheat: Compressed air is used as the driving force, and the exhaust process is one of expansion and heat absorption; therefore, the temperature of the pneumatic pump decreases during operation, and no harmful gases are emitted. (2) No electric sparks are generated: Pneumatic diaphragm pumps do not rely on electricity for operation, and grounding prevents the occurrence of static sparks. (3) They can handle liquids containing particles: Due to their positive displacement operation and ball valves at the inlet, they are less likely to get clogged. (4) The shear force on the material is extremely low: it draws in and discharges the material as it operates, resulting in minimal disturbance to the material; this makes it suitable for transporting unstable substances. (5) The flow rate can be adjusted by installing a throttle valve at the material outlet. (6) It has a self-priming function. (7) It can run idle without any danger. (8) Can work underwater. (9) It can transport a very wide range of fluids, from those with low viscosity to those with high viscosity, and from corrosive ones to viscous ones. (10) There is no complex control system, no cables, fuses, etc. (11) Small in size and light in weight, making it easy to move. (12) No lubrication is required, so maintenance is simple, and it does not contaminate the working environment due to leaks. (13) The pump always maintains high efficiency and does not see a decrease due to wear. (14) 100% energy utilization: when the outlet is closed, the pump stops automatically; there is no risk of equipment movement, wear, overload, or overheating. (15) Without moving seals, maintenance is simple and leaks are avoided. There is no dead point during operation. VIII. Magnetic pump: A magnetic pump consists of three components: the pump itself, the magnetic coupling, and the drive motor. The left end of the pump shaft is equipped with an impeller, while the right end has an internal magnetic rotor; the pump shaft is supported by sliding bearings. The bracket connects the pump and the motor, ensuring the positional accuracy of the inner and outer magnetic rotors. When the motor drives the outer magnetic rotor to rotate, the magnetic field passes through the air gap and the isolation sleeve, causing the inner magnetic rotor to rotate synchronously, which in turn drives the impeller to rotate. Performance features: Compared with centrifugal pumps that use mechanical seals or packing seals, magnetic drive pumps have the following advantages: 1. The pump shaft is equipped with a sealed static seal instead of a dynamic seal, thereby completely preventing leakage of the medium. 2. No separate lubrication or cooling water is required, reducing energy consumption. 3. It changes from coupling-driven transmission to synchronous dragging, with no contact or friction. It features low power consumption and high efficiency, as well as damping vibration effects, which reduce the impact of motor vibrations on the pump and the impact of cavitation vibrations in the pump on the motor. 4. During overload, the inner and outer magnetic rotors slip relative to each other, providing protection for the motor and pump. IX. Water ring vacuum pump: The impeller is eccentric with respect to the pump casing, and a certain amount of water is filled inside the casing; as the impeller rotates, this water forms a water ring. As the adjacent blades (the red blades in the figure) rotate, the space formed with the water ring (the air chamber) expands, allowing air to enter; as the air chamber gradually shrinks, the air is compressed. Multiple sets of adjacent blades, that is, multiple sets of reciprocating compression. It features a compact structure, reliable and balanced operation, as well as uniform flow, which makes it commonly used in chemical production for transporting or pumping flammable, explosive, and corrosive gases. Water ring vacuum pumps have very low efficiency because the impeller stirs the liquid, resulting in significant energy loss. Performance features: Advantages: Simple structure, low requirements for manufacturing precision, easy to process. It has a compact structure, high pump speed, and can generally be connected directly to the motor without the need for a reduction gear. Therefore, a small structural size can yield a large displacement, while also requiring less floor space. Compressed gas is essentially isothermal, meaning that the temperature changes very little during the compression process. Since there are no metal friction surfaces inside the pump chamber, no lubrication is required for the pump, and wear is minimal. The sealing between the rotating part and the fixed part can be achieved directly by a water seal. It features even air intake, stable and reliable operation, simple handling, and easy maintenance. Disadvantages: Low efficiency, generally around 30%, with better cases reaching 50%. The low vacuum level is due not only to structural constraints but, more importantly, to the saturated vapor pressure of the working fluid. Using water as the working fluid, the ultimate pressure can only reach 2000~4000 Pa. Using oil as the working fluid, a pressure of 130 Pa can be achieved. In short, since the gas compression in a water ring pump is isothermal, it is possible to pump out flammable and explosive gases. Due to the absence of exhaust valves and friction surfaces, it is possible to extract gas containing dust, condensable gases, and gas-water mixtures. Thanks to these prominent features, it is still widely used despite its low efficiency. X. Vortex Pumps – Performance Characteristics: Advantages: The W-type single-stage direct-connected vortex pump is designed for pumping clean water or liquids with physical and chemical properties similar to water; the operating temperature of the liquid should not exceed 60 degrees. It is commonly used in boiler feed systems, and finds wide application in industries such as shipbuilding, light textiles, chemicals, metallurgy, machinery manufacturing, aquaculture, fixed fire protection systems for pressure stabilization, heat exchange units, and agricultural remote irrigation. The small size and light weight of vortex pumps offer great advantages in ship applications. It has self-priming capability or can achieve self-priming with the help of a simple device. It has a steep head curve, and therefore is insensitive to pressure fluctuations in the system. Certain vortex pumps can achieve gas-liquid transportation. This is of great significance for pumping volatile liquids containing gases and high-temperature liquids with very high vaporization pressures. Vortex pumps have a simple structure, and their casting and machining processes are easy to implement; moreover, certain components of vortex pumps can be made from non-metallic materials such as plastic or nylon molded impellers. Disadvantages: 1. It has low efficiency, which does not exceed 55%; the efficiency of most vortex pumps ranges from 20 to 40%, which hinders its development towards higher power levels. 2 The cavitation performance of the vortex pump is poor. 3 Vortex pumps cannot be used to pump media with high viscosity. As the viscosity of the liquid increases, the pump’s head and efficiency drop sharply; therefore, the viscosity of the medium must be kept below 114 centipoise. 4 The strict requirements for the radial and axial clearances between the impeller of the vortex pump and the pump body present certain difficulties in the machining and assembly processes. 5 The medium for pumping is limited to pure liquids only. When a liquid contains solid particles, wear causes an increase in the axial and radial clearances, which reduces the pump’s performance or even prevents the vortex pump from operating. XI. Vane pumps: Historically, vane pumps have been divided into two types depending on their category: 1) Referring specifically to slide vane pumps among positive displacement pumps. II) Refers to the three types of dynamic pumps (centrifugal pumps, mixed-flow pumps, axial-flow pumps) or other special pumps. Pump products of this type are generally not called vane pumps. However, as a monograph, vane pumps almost always refer to centrifugal pumps, mixed-flow pumps, axial flow pumps, etc. (In the 2014 exam material for first-level construction engineers on \"Mechanical and Electrical Engineering and Management Practice,\" these three types are referred to as impeller pumps). Based on whether their theoretical displacement per revolution is fixed or variable, they can be divided into vane variable pumps and vane fixed-displacement pumps. Performance features: Advantages: (1) The output flow rate is more uniform than that of gear pumps, with smooth operation and low noise. (2) The working pressure is high, and the volumetric efficiency is also high. (3) Single-acting vane pumps (Tokimec vane pumps) are easy to adjust for flow rate, while double-acting vane pumps have a long service life due to the radial hydraulic pressure balancing the rotor. (4) Compact structure, small footprint with high flow rate. Disadvantages: (1) Its self-priming capacity is inferior to that of gear pumps, and it has strict requirements regarding the oil suction conditions; its rotational speed must be within the range of 500–1500 r/min. (2) It is sensitive to oil contamination; the blades are prone to being damaged by impurities in the oil, resulting in poor operational reliability. (3) It has a more complex structure, requires high precision in component manufacturing, and is therefore more expensive. Vane pumps are generally used in medium-pressure (6.3 MPa) hydraulic systems, mainly for machine tool control. In particular, double-acting vane pumps (Tokyo Kikai SQP vane pumps) are widely used in precision machine tools due to their very low flow rate pulsation. XII. Steam jet pump: When steam enters the nozzle, it is ejected at high speed, creating a low pressure that draws in gas; the gases are mixed in a mixing chamber, and after passing through an expansion tube, their kinetic energy is converted into pressure energy. If the gas being drawn in comes from a container, and the pressure in that container is reduced, it can be called a jet vacuum pump. Performance features: (1) This pump has no mechanical moving parts, and it is not affected by factors such as friction, lubrication, or vibration; therefore, it can be designed to have a high pumping capacity. As long as the structural materials of the pump are chosen appropriately, it is highly advantageous for removing gases with corrosive properties, gases containing mechanical impurities, as well as water vapor. (2) Simple structure, light weight, and small footprint. (3) The working steam pressure is 4–9×105 Pa, and such a source of steam is available in most metallurgical, chemical, pharmaceutical, and other types of enterprises. Due to the aforementioned characteristics, steam jet pumps are widely used in industrial sectors such as metallurgy, chemicals, pharmaceuticals, petroleum, and food processing. 13. Axial flow pipeline pump: The impeller is designed in an axial flow configuration. The rotation speed is very high; if the motor power, impeller diameter, and pipe diameter are large enough, the flow rate can be high. Performance features: 1. The pipeline pump has a compact structure with the pump and motor integrated together, resulting in a small size. Its vertical design requires less space for installation, operates smoothly, and no adjustments are needed during installation. 2. The pump’s inlet and outlet are equipped with flanges of the same specification and are aligned on the same axis, allowing it to be installed directly on pipelines like a valve. Its low center height facilitates pipeline layout and simplifies installation. 3. The pump and motor are coaxial, resulting in a short axial dimension that enhances operational stability and reduces noise levels. 4. Traditional shaft sealing methods are not used, which prevents leakage of the transported medium; thus, it boasts the significant advantage of complete leaklessness. 14. Single-stage single-suction self-priming pump. The working principle of a self-priming pump is as follows: before the pump starts operating, the pump casing must be filled with water (or there must already be water inside the pump casing). Upon startup, the high-speed rotation of the impeller causes the water in the impeller channels to flow toward the volute; this creates a vacuum at the inlet, which opens the inlet check valve. Air from the suction pipe enters the pump and then reaches the outer edge via the impeller channels. Performance features: The self-priming pump is a type of self-priming centrifugal pump. It boasts advantages such as a compact structure, easy operation, stable performance, simple maintenance, high efficiency, long service life, and strong self-priming capability. There is no need to install a foot valve in the pipeline; before operation, it is sufficient to ensure that a certain amount of liquid is stored inside the pump. Different liquids can require self-priming pumps made of different materials. 1. Strong sewage discharge capacity: A special impeller design that prevents clogging ensures efficient operation of the pump with no blockages. 2. High efficiency and energy savings: Thanks to an excellent hydraulic design, its efficiency is 3–5% higher than that of ordinary self-priming pumps. 3. Good self-priming performance: The self-priming height is 1 meter higher than that of ordinary self-priming pumps, and the self-priming time is shorter. 15. Piston pump: It uses the reciprocating motion of a piston within a cylinder to change the volume inside the cylinder repeatedly, thereby sucking in and discharging fluid. Performance features: Piston pumps, also known as electric reciprocating pumps, are classified into single-cylinder and multi-cylinder types based on their structure, and they are characterized by a high head pressure. Suitable for transporting oil emulsions and similar substances at room temperature without solid particles. Used in oil fields, coal seam water injection, oil injection, and oil extraction ； Power pumps for chamber presses and hydraulic presses, hydraulic sand cleaning, transportation of ammonia liquid in fertilizer plants, etc. If the overcurrent component is made of stainless steel, it can transport corrosive liquids. Additionally, depending on the material of the structure, it can also transport high-temperature tar, sludge, highly concentrated grout, and highly viscous liquids. Piston pumps are suitable for applications requiring high pressure and low flow rates; especially when the flow rate is less than 100 m³/h and the discharge pressure is greater than 9.8 MPa, they exhibit high efficiency and excellent operating performance. It has good suction performance and can draw in liquids of various media and viscosities. Therefore, it is widely used in industries such as the petrochemical industry, machinery manufacturing, papermaking, food processing, and pharmaceutical production. Low- and medium-speed piston pumps have low speeds; they can be operated by hand or pulled by animals, and are suitable for rural water supply and small-scale irrigation. 16. Roots vacuum pump: The working principle of a Roots pump is similar to that of a Roots blower. Due to the continuous rotation of the rotor, the gas to be pumped is drawn in from the inlet into the space v0 between the rotor and the pump casing, and then discharged through the outlet. Since the v0 volume is completely sealed after inhalation, the gas in the pump chamber does not compress or expand. However, when the top of the rotor passes over the edge of the exhaust port and space v0 becomes connected to the exhaust side, the higher gas pressure on the exhaust side causes some gas to flow back into space v0, resulting in a sudden increase in gas pressure. As the rotor continues to rotate, the gas is expelled from the pump. Performance features: High pumping speed over a wide pressure range ； Starts quickly and can begin working immediately ； Not sensitive to dust and water vapor contained in the gas being drawn in ； The rotor does not require lubrication, and there is no oil in the pump chamber ； Low vibration, good rotor dynamic balance conditions, no exhaust valve ； Low driving power and low mechanical friction losses ； Compact structure with small footprint ； Operating and maintenance costs are low. Therefore, Roots pumps are widely used in the metallurgy, petrochemical, papermaking, food, and electronics industries. 17. Rotary vane vacuum pump: The vane of a rotary vane pump divides the crescent-shaped space enclosed by the rotor, the pump chamber, and the two end caps into three sections: A, B, and C. Performance features: The vane vacuum pump (abbreviated as vane pump) is a oil-sealed mechanical vacuum pump. Its operating pressure range is 101325~1.33×10-2 (Pa), classifying it as a low vacuum pump. It can be used alone or as a pre-pump for other high-vacuum pumps or ultra-high-vacuum pumps. It has been widely applied in production and research sectors such as metallurgy, machinery, military industry, electronics, chemicals, light industry, petroleum, and pharmaceuticals. 1. Small size, light weight, low noise ； 2. Equipped with a gas trap valve to remove a small amount of water vapor ； It can operate continuously for extended periods at ambient temperatures ranging from 5 degrees Celsius to 40 degrees Celsius, as long as the inlet pressure is below 1.3X103 Pascals; when the relative humidity of the gas being pumped is above 90 percent, the pressure relief valve should be activated. 3. Equipped with an automatic anti-backflow check valve for easy operation ； 4. The intake must remain unobstructed to allow normal operation for no more than one minute ； 5. Not suitable for pumping gases that are corrosive to metals, that react chemically with the pump oil, that contain particulate dust, as well as gases with high oxygen content, that are explosive, or that are toxic. 18. Mud Pump A mud pump is a machine that delivers fluids such as mud or water into the drill hole during drilling operations. Mud pumps are an important component of drilling equipment. In conventional rotary drilling, a flushing medium from the surface – such as clean water, mud, or polymer-based fluid – is forced under pressure through high-pressure hoses, faucets, and the central holes in the drill string, all the way to the bottom of the bit. This serves to cool the bit, remove the cut rock debris, and transport it to the surface. The commonly used mud pumps are piston-type or plunger-type; a power unit drives the crankshaft of the pump, and the crankshaft, in turn, drives the piston or plunger to move back and forth within the pump cylinder through a crosshead. Through the alternating action of the intake and discharge valves, pumping and circulating the flushing fluid is achieved. Performance features: 1. Capable of transporting high-concentration, high-viscosity fluids