First, single-stage single-suction chemical centrifugal pump product overview:
1. Single-stage single-suction chemical centrifugal pump is a nationally designed energy-saving pump. It is an updated type of BA type, B type and other single-stage clean water centrifugal pumps. The advantages are as follows: the whole series of hydraulic performance layout is reasonable, the user has a wide selection range, and the maintenance is convenient; the efficiency and the suction stroke reach the international average advanced level. IH type single-stage single-suction chemical pump is suitable for industrial and urban water supply and drainage. It can also be used for agricultural drainage and for the transportation of clean water or other liquids with physical and chemical properties similar to clean water. The temperature is not higher than 80 °C.
2, single-stage single-suction chemical centrifugal pump implementation standards:
The single-stage single-suction chemical centrifugal pump is a single-stage single-suction cantilever centrifugal pump, which is an energy-saving and replacement product that replaces the F-type corrosion-resistant centrifugal pump. Used in petroleum, chemical, synthetic fiber, fertilizer, power station, metallurgy, food and pharmaceutical industries to transport corrosive liquids without suspended particles or media that are not allowed to be contaminated. The temperature of the transport medium is generally -20 ° C ~ 105 ° C. Special measures can be used up to 180 °C.
The single-stage single-suction chemical centrifugal pump is generally driven by an electric motor, and the pump body and the suction line are filled with liquid before starting the pump. When the impeller rotates at a high speed, the impeller drives the liquid between the blades to rotate. Due to the centrifugal force, the liquid is swept from the center of the impeller to the outer edge of the impeller (the flow rate can be increased to 15-25 m/s), and the kinetic energy is also increased. When the liquid enters the pump casing, the flow velocity gradually decreases as the flow path in the volute casing is gradually reduced, and a part of the kinetic energy is converted into static pressure energy, so that the liquid flows out along the discharge port with a higher pressure. At the same time, the center of the impeller forms a certain vacuum due to the liquid being pumped out, and the pressure Pa at the liquid level is higher than the center of the impeller. Therefore, the liquid in the suction line enters the pump under the pressure difference. The impeller rotates continuously, and the liquid is continuously sucked in and out. Because the centrifugal pump can transport liquid, mainly by the action of centrifugal force, it is called IH type single-stage single-suction chemical centrifugal pump.
Centrifugal pumps are the most widely used in chemical production because of their wide range of properties (including flow, pressure head and adaptability to media properties), small size, simple structure, easy operation, uniform flow, low failure, and long life. Long, low purchase and operating costs are outstanding advantages. Therefore, this chapter focuses on the centrifugal pump as a typical example of the application of fluid mechanics.
I. Basic structure and working principle of single-stage single-suction chemical centrifugal pump. Discuss the basic structure and working principle of centrifugal pump, and firmly hold the theme of effectively converting kinetic energy into static pressure energy.
(1) The basic structure of a single-stage single-suction chemical centrifugal pump
The basic components of a single-stage, single-suction chemical centrifugal pump are a high-speed rotating impeller and a fixed snail-shaped pump casing. An impeller having a plurality of (usually 4 to 12) back-curved blades is fastened to the pump shaft and is driven by the motor to rotate at a high speed with the pump shaft. The impeller is a component that directly works on the liquid in the pump and is an energy supply device for the centrifugal pump. The suction port in the center of the pump casing is connected to the suction pipe, and the bottom of the suction pipe is provided with a one-way bottom valve. The discharge port on the side of the pump casing is connected to a discharge line equipped with a regulating valve.
(2) Working principle of single-stage single-suction chemical centrifugal pump
When the IH type single-stage single-suction chemical centrifugal pump is started, the pump shaft drives the impeller to rotate together at high speed, forcing the pre-filling liquid to rotate between the blades. Under the action of inertial centrifugal force, the liquid moves radially from the center of the impeller to the outer circumference. . The liquid gains energy during the movement through the impeller, the static pressure energy increases, and the flow rate increases. When the liquid leaves the impeller and enters the pump casing, some of the kinetic energy is converted into static pressure energy due to the gradual expansion of the flow passage in the casing, and finally flows into the discharge pipe tangentially. Therefore, the volute pump casing is not only a component that collects the liquid flowing from the impeller, but also a transducing device. When the liquid is from the center of the impeller to the outer circumference, the center of the impeller forms a low pressure zone, and the liquid is sucked into the center of the impeller under the action of the total potential energy difference between the liquid level of the sump and the center of the impeller. The liquid is continuously sucked in and discharged by the continuous operation of the impeller. The mechanical energy obtained by the liquid in the centrifugal pump ultimately manifests as an increase in static pressure energy.
[Animation] The basic structure and working principle of the single-stage single-suction chemical centrifugal pump need to be emphasized that if the pumped liquid is not filled into the pump casing before the centrifugal pump starts, the air density is low and the impeller rotates. The centrifugal force is small, and the central region of the impeller is insufficient to form a low pressure of the liquid in the suction sump. Therefore, the liquid can not be transported by the IH type single-stage single-suction chemical centrifugal pump. This indicates that the IH type single-stage single-suction chemical centrifugal pump has no self-priming ability, and this phenomenon is called air binding. The suction line is equipped with a one-way bottom valve to prevent the liquid poured into the pump casing from flowing out of the casing before starting. Air is trapped from the suction line into the pump casing.
(3) Impellers and other components of single-stage single-suction chemical centrifugal pumps
1. The impeller of a single-stage single-suction chemical centrifugal pump is a key component of a single-stage single-suction chemical centrifugal pump.
(1) According to its mechanical structure, it can be divided into three types: closed type, semi-closed type and open type. Closed impellers are suitable for conveying cleaning fluids; semi-closed and open impellers are suitable for conveying suspensions containing solid particles, which are inefficient. When the closed and semi-closed impellers are in operation, a part of the high-pressure liquid leaving the impeller can leak into the cavity between the impeller and the pump casing. Since the pressure at the liquid suction port on the front side of the impeller is low, the liquid acts on the front and rear of the impeller. The pressure on the sides is not equal, and an axial thrust directed to the suction side of the impeller is generated. This force pushes the impeller to move toward the suction side, causing friction at the contact between the impeller and the pump casing, causing vibration of the pump in severe cases and damaging the normal operation of the pump. Drilling a number of small holes in the rear cover of the impeller reduces the pressure difference across the impeller, thereby reducing the adverse effects of axial thrust, but at the same time reducing the efficiency of the pump. These small holes are called balance holes.
(2) According to different liquid absorption methods, the impeller can be divided into single suction type and double suction type. The single suction type impeller has a simple structure, and the liquid can only be sucked from one side. The double suction impeller can simultaneously draw liquid symmetrically from both sides of the impeller, which not only has a large liquid absorption capacity, but also substantially eliminates the axial thrust.
(3) According to the geometry on the blade on the impeller, the blade can be divided into three types: back bend, radial and forward bend. Because the back bend blade is beneficial to the conversion of kinetic energy of liquid into static pressure energy, it is widely used.
2. Guide wheel of single-stage single-suction chemical centrifugal pump
In order to reduce the energy loss caused by the impact when the liquid leaving the impeller directly enters the pump casing, a fixed and vaned guide wheel is sometimes arranged between the impeller and the pump casing. The vanes in the guide wheel gradually turn the liquid entering the pump casing and the flow passage continuously expands, so that part of the kinetic energy is effectively converted into static pressure energy. Multistage centrifugal pumps are usually equipped with guide wheels.
The snail-shaped pump casing, the back-bending blade on the impeller and the guide wheel can all improve the conversion rate of kinetic energy to static pressure energy, so they can all be regarded as energy-transfer devices.
3. Shaft sealing device
Since the pump casing is fixed and the pump casing is fixed, there must be a certain gap at the contact between the shaft and the pump casing. In order to avoid leakage of high pressure liquid in the pump along the gap or to prevent outside air from entering the pump from the opposite direction, a shaft seal device must be provided. The shaft seal of the centrifugal pump has a stuffing box and a mechanical (end) seal. The stuffing box is used to seal the pump shaft through the annular gap of the pump casing, and a soft packing (such as oil-impregnated or graphite-coated asbestos rope) is placed therein. The mechanical seal consists of a moving ring mounted on the rotating shaft and another stationary ring fixed to the pump casing. The end faces of the two rings are relatively rotated by the spring force to act as a seal. Mechanical seals are suitable for applications where the seal is high, such as the transport of acids, bases, flammable, explosive and toxic liquids. When the centrifugal pump is started, the pump shaft drives the impeller to rotate at a high speed, forcing the pre-filling liquid to rotate between the blades. Under the action of the inertial centrifugal force, the liquid moves radially from the center of the impeller to the outer circumference. The liquid gains energy during the movement through the impeller, the static pressure energy increases, and the flow rate increases. When the liquid leaves the impeller and enters the centrifugal pump casing, some of the kinetic energy is converted into static pressure energy due to the gradual expansion of the flow passage in the casing, and finally flows into the discharge pipe tangentially. Therefore, the volute pump casing is not only a component that collects the liquid flowing from the impeller, but also a transducing device. When the liquid is from the center of the impeller to the outer circumference, the center of the impeller forms a low pressure zone, and the liquid is sucked into the center of the impeller under the action of the total potential energy difference between the liquid level of the sump and the center of the impeller. The liquid is continuously sucked in and discharged by the continuous operation of the impeller. The mechanical energy obtained by the liquid in the centrifugal pump ultimately manifests as an increase in static pressure energy. The role of the impeller is to transfer the mechanical energy of the prime mover directly to the liquid to increase the static pressure and kinetic energy of the liquid (mainly increasing the static pressure energy).
1. Impeller The role of the impeller is to transfer the mechanical energy of the prime mover directly to the liquid to increase the static pressure and kinetic energy of the liquid (mainly increasing the static pressure energy). The impeller has three types: open type, semi-closed type and closed type. The open impeller has no cover on both sides of the blade, which is simple to manufacture and convenient to clean. It is suitable for conveying materials containing a large amount of suspended solids. The efficiency is low and the liquid pressure is not high. The semi-closed impeller has no cover on the suction side. The plate has a cover plate on the other side, which is suitable for conveying materials that are easy to precipitate or contain particles, and the efficiency is also low; the closed impeller has a front and rear cover plate on both sides of the blade, and the efficiency is high, and is suitable for conveying impurities. Cleaning liquid. The general centrifugal pump impeller is mostly of this type.
2. Pump casing The function is to close the impeller in a certain space so that the liquid can be sucked in and out by the action of the impeller. The centrifugal pump casing is often made into a volute shape, so it is also called a volute. Since the cross-sectional area of ​​the flow passage is gradually enlarged, the high-speed liquid drawn from the periphery of the impeller gradually reduces the flow velocity, so that part of the kinetic energy is effectively converted into static pressure energy. The pump casing not only collects the liquid that is pumped out by the impeller, but is also an energy conversion device.
Second, single-stage single-suction chemical centrifugal pump Product use:
The IH type single-stage single-suction chemical centrifugal pump is designed according to the performance and size specified by the international standard ISO2858, and is mainly composed of the pump body, the pump cover, the impeller, the shaft, the sealing ring, the bushing and the suspension bearing.
2. The pump body and pump cover part of the single-stage single-suction chemical centrifugal pump are divided from the back of the impeller, which is commonly referred to as the rear opening structure. The utility model has the advantages that the maintenance is convenient, the pump body is not moved during the maintenance, the suction pipeline, the discharge pipeline and the electric motor are removed, and only the intermediate coupling member of the extension coupling is removed, and the rotor portion can be taken out for maintenance.
3. The housing of the single-stage single-suction chemical centrifugal pump (ie pump body and pump cover) constitutes the working chamber of the pump. The impeller, shaft and rolling bearing are the rotor of the pump. The suspension bearing component supports the rotor portion of the pump, which is subjected to the radial and axial forces of the pump.
4. Single-stage single-suction chemical centrifugal pump In order to balance the axial force of the pump, most of the pump impellers are provided with a sealing ring before and after, and a balance hole is arranged on the rear cover of the impeller. Large, there is no seal ring and balance hole on the back of the impeller.
5. The axial seal ring of the single-stage single-suction chemical centrifugal pump is composed of packing gland, packing ring and packing to prevent air intake or a large amount of water leakage. If the impeller of the pump is balanced, the cavity with the soft packing is connected to the suction port of the impeller. If the liquid at the inlet of the impeller is in a vacuum state, it is easy to enter the air along the surface of the sleeve. Therefore, a packing ring is inserted in the filling chamber. A small hole in the pump cover guides the pressurized water in the pump chamber to the packing ring for sealing. If there is no balance hole in the impeller of the pump, since the liquid pressure on the back of the impeller is greater than atmospheric pressure, there is no gas leakage problem, so the packing ring may not be installed.
6. In order to avoid shaft wear, bushing protection is provided at the part of the shaft passing through the packing cavity. An O-ring seal is provided between the sleeve and the shaft to prevent air intake or water leakage along the mating surface.
7. The transmission mode of the single-stage single-suction chemical centrifugal pump is connected with the motor by lengthening the elastic coupling. The rotation direction of the pump is rotated clockwise from the driving end.
Third, the single-stage single-suction chemical centrifugal pump model meaning:
IH50-32-160A-302
IH-International Standard Chemical Centrifugal Pump
50-pump suction port diameter is 50mm
32-pump outlet diameter is 32mm
160-impeller nominal diameter 160mm
A-impeller outer diameter cutting code (A and B respectively indicate the first and second cutting)
Material code of 302-pump contact parts Professional production, quality service. Factory direct sales, pump accessories Daquan IH single-stage single-suction cantilever chemical centrifugal pump
Fourth, the single-stage single-suction chemical centrifugal pump common chemical medium talk about the main points of material selection:
1. Sulfuric acid: As one of the strong corrosive media, sulfuric acid is an important industrial raw material with a wide range of uses. Different concentrations and temperatures of sulfuric acid have a great difference in corrosion of materials. For concentrated sulfuric acid with a concentration above 80% and temperature less than 80 °C, carbon steel and cast iron have good corrosion resistance, but it is not suitable for high-speed flowing sulfuric acid. It is not suitable as a material for pump valves; ordinary stainless steels such as 304 (0Cr18Ni9) and 316 (0Cr18Ni12Mo2Ti) are also limited in their use for sulfuric acid media. Therefore, the pump valve for conveying sulfuric acid is usually made of high-silicon cast iron (difficult to cast and process) and high-alloy stainless steel (20 alloy). Fluoroplastics have better sulfuric acid resistance, and a fluorine-lined pump (F46) is a more economical option. The company's applicable products are: IHF fluorine plastic chemical centrifugal pump. IH type single stage single suction chemical centrifugal pump
2. Hydrochloric acid: Most metal materials are not resistant to hydrochloric acid corrosion (including various stainless steel materials), and molybdenum-containing high silicon iron can also be used only for 50 ° C, 30% hydrochloric acid. Contrary to metal materials, most non-metallic materials have good corrosion resistance to hydrochloric acid, so rubber pumps and plastic pumps (such as polypropylene, fluoroplastics, etc.) are the best choice for transporting hydrochloric acid. The company's applicable products are: IHF fluorine plastic chemical centrifugal pump, PF (FS) strong corrosion resistant centrifugal pump, CQ polypropylene magnetic pump (or fluoroplastic magnetic pump).
3. Nitric acid: Most metals are quickly corroded and destroyed in nitric acid. Stainless steel is the most widely used nitric acid-resistant material. It has good corrosion resistance to all concentrations of nitric acid at normal temperature. It is worth mentioning that it contains molybdenum-containing stainless steel. Such as 316, 316L) corrosion resistance of nitric acid is not only better than ordinary stainless steel (such as 304, 321), and sometimes even worse. For high temperature nitric acid, titanium and titanium alloy materials are usually used. The company's applicable products are: DFL (W) H chemical centrifugal pump, DFL (W) PH shielding chemical centrifugal pump, DFCZ process pump, DFLZP self-priming chemical centrifugal pump, IH type chemical centrifugal pump, CQB magnetic pump, etc., the material is 304.
4. Acetic acid: It is one of the most corrosive substances in organic acids. Ordinary steel will be severely corroded in acetic acid of all concentrations and temperatures. Stainless steel is an excellent acetic acid resistant material. Molybdenum-containing 316 stainless steel can also be used for high temperature. And dilute acetic acid vapor. For high temperature, high concentration acetic acid or other corrosive media, high alloy stainless steel pumps or fluoroplastic pumps are available.
5. Alkali (sodium hydroxide): Steel is widely used in sodium hydroxide solution below 30 °C and 30% concentration. Many factories still use ordinary steel at 100 ° C and below 75%, although the corrosion increases, but the economy it is good. The corrosion resistance of ordinary stainless steel to lye has no obvious advantages compared with cast iron. Stainless steel is not recommended as long as a small amount of iron is allowed in the medium. For high-temperature alkaline liquids, titanium and titanium alloys or high-alloy stainless steels are often used. The company's general cast iron pumps can be used for low-concentration lye at room temperature. For special requirements, all kinds of stainless steel pumps or fluoroplastic pumps can be used.
6. Ammonia (ammonium hydroxide): Most metals and non-metals are slightly corrosive in liquid ammonia and ammonia (ammonium hydroxide). Only copper and copper alloys should not be used. Most of the company's products are suitable for the transport of ammonia and ammonia.
7. Brine (seawater): The corrosion rate of ordinary steel in sodium chloride solution and seawater and salt water is not too high, generally it needs to be protected by paint; all kinds of stainless steel also have a low uniform corrosion rate, but may be caused by chloride ions. Sexual corrosion, usually 316 stainless steel is better. The company's various chemical pumps have 316 material configurations.
8. Alcohols, ketones, esters, ethers: Common alcohols are methanol, ethanol, ethylene glycol, propanol, etc., ketone media are acetone, methyl ethyl ketone, etc., ester media have various methyl esters. Ether, ethyl ester, etc., ether medium is methyl ether, ***, butyl ether, etc., they are basically non-corrosive, common materials can be applied, and specific selection should also make reasonable choice according to the properties of the medium and related requirements. It is also worth noting that ketones, esters, and ethers are soluble in a variety of rubbers and avoid errors when selecting sealing materials.
There are many other media that can't be introduced here. In short, you should not be random and blind when selecting materials. You should consult relevant materials or learn from mature experience.
Five, single-stage single-suction chemical centrifugal pump structural features:
The main components of the single-stage single-suction chemical centrifugal pump are pump body, impeller, seal ring, impeller nut, pump cover, sealing parts, intermediate bracket, shaft and suspension components.
The pump cover is fixed to the intermediate bracket through the stop, and then the pump body is connected to the intermediate bracket by the pump body, and the pump cover is clamped in the middle. The pump body is axially sucked, radially discharged, and supported by the foot, and can be directly fixed to the base. The suspension member is fixed to the intermediate bracket by a stop and supported on the base by a suspension bracket. During the inspection, the inlet and outlet connecting pipes, the pump body and the motor can be removed. Simply remove the intermediate coupling of the extension coupling to exit the rotor parts for maintenance.
The shaft seal has a packing seal and a mechanical seal form, which can be selected according to the nature of the transport medium and the requirements of the production process.
The pump is coupled to the motor via an extended coupling, and the pump rotates clockwise as viewed from the drive end.
Sixth, the material selection of single-stage single-suction chemical centrifugal pump How to choose the appropriate chemical pump material:
Mechanical products, material is very important, especially the chemical centrifugal pump is quite strict in material requirements. When buying a chemical pump, it is the material of the pump. If the material does not meet the requirements, it will not be worth the loss, so it is various for the chemical industry. The corrosion performance of liquid quality should be clear in order to prescribe the right medicine. Corrosion has always been one of the most headaches of chemical equipment. If it is slightly careless, it will damage the equipment and cause accidents and even disasters. According to relevant statistics, about 60% of the destruction of chemical equipment is caused by corrosion. Therefore, in the selection of chemical pumps, we must first pay attention to the scientific nature of material selection. There is usually a misunderstanding that stainless steel is a “universal material†and it is dangerous to hold a stainless steel pump regardless of the medium and environmental conditions.
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