Pump selection

This problem is too big! I’m not an expert in pumps, so I’ll give you a general idea based on my experience! First, the process determines the flow rate and head required for the pump to be selected, and based on these two parameters, the range of possible pumps is roughly established. Secondly, based on the properties of the medium being transported, such as whether it is corrosive or not, the type of pump to be selected is determined, such as corrosion-resistant pumps, shielded pumps, magnetic drive pumps, vacuum pumps, etc. In short, all various factors must be taken into account to select the optimal configuration! Generally, chemical plants provide the pump manufacturer with information such as the pump’s flow rate, head (or vacuum requirement), and the properties of the fluid (such as viscosity, density, toxicity, and corrosiveness). The pump manufacturer will then help select an appropriate model of pump for the purpose This post was last edited by lovingyou on 2009-4-7 22:37.]

This topic is too broad. Chemical pumps serve as essential auxiliary equipment in the petrochemical industry. Given the complex characteristics of chemical media, the continuous use of new materials, and the ongoing upgrading of pumps, how should chemical manufacturers select chemical pumps in a rational manner? What aspects should be given special attention? …Waiting, etc., is particularly important. Here, based on the characteristics of numerous chemical enterprises, a brief discussion on the selection of common chemical pumps is provided, in the hope of being beneficial to our clients. Corrosion resistance issue  Corrosion has always been one of the threats to chemical processing equipment. According to relevant statistics, about 60% of the damage to such equipment is caused by corrosion; therefore, when selecting chemical pumps, it is essential to pay attention to the scientific choice of materials. There used to be a misconception that stainless steel is a \"universal corrosion-resistant material,\" but this is not the case; its resistance to corrosion has significant limitations. Here are some key points to consider when selecting materials for use with common chemical agents: 1. Sulfuric acid, one of the highly corrosive agents, is an important industrial material with a wide range of applications. Sulfuric acid at different concentrations and temperatures causes varying degrees of corrosion to materials. For concentrated sulfuric acid with a concentration of over 80% and a temperature below 80°C, carbon steel and cast iron exhibit good corrosion resistance; however, it is not suitable for sulfuric acid that flows at high speeds, and thus cannot be used as material for pumps and valves ； Common stainless steels such as 304 (0Cr18Ni9), 321 (1Cr18Ni9Ti), and 316 (0Cr18Ni12Mo2Ti) also have limited utility in sulfuric acid media. Therefore, pump valves for transporting sulfuric acid are usually made of high-silicon cast iron (which is difficult to cast and process) or highly alloyed stainless steel (grade 20 alloy), but they are difficult to process and expensive. Fluoroplastic alloys exhibit excellent resistance to sulfuric acid. Experiments conducted by the Chinese Academy of Sciences have shown that no chemical medium is known to be capable of reacting with them; therefore, using fluoropolymer alloys and fluorine-lined pumps (F46) represents a more economical choice. 　　2. Hydrochloric acid: The vast majority of metal materials are not resistant to corrosion by hydrochloric acid (including various stainless steel materials); high-molybdenum high-silicon iron can only be used in hydrochloric acid at temperatures below 50°C and with a concentration of less than 30%. Unlike metal materials, the vast majority of non-metallic materials exhibit good corrosion resistance to hydrochloric acid; therefore, rubber-lined pumps and plastic pumps (such as engineering plastics and fluoroplastics) are the best choices for transporting hydrochloric acid. 　　3. Most common metals are rapidly corroded and damaged by nitric acid; stainless steel is the most widely used material resistant to nitric acid, exhibiting good corrosion resistance against nitric acid of all concentrations at room temperature. It is worth noting that stainless steels containing molybdenum (such as 316 and 316L) do not have better corrosion resistance to nitric acid than ordinary stainless steels (such as 304 and 321), and in some cases their resistance is even lower. For high-temperature nitric acid, fluoroplastic alloy materials are typically used. 　　4. Acetic acid is one of the most corrosive organic acids; ordinary steel suffers severe corrosion in acetic acid at all concentrations and temperatures. Stainless steel is an excellent material resistant to acetic acid, and 316 stainless steel containing molybdenum can also be used in high-temperature environments as well as with dilute acetic acid vapor. For demanding applications such as high-temperature, high-concentration acetic acid or environments containing other corrosive agents, high-alloy stainless steel or fluoroplastic pumps can be used. 　　5. Bases (sodium hydroxide) generally do not have strong corrosive properties, but most base solutions cause crystallization; therefore, centrifugal pumps equipped with mechanical seals made of siliconized graphite can be used. 6. Ammonia (ammonium hydroxide): Most metals and non-metals are only slightly corroded by liquid ammonia and ammonia water (ammonium hydroxide), with copper and its alloys being the exceptions that should not be used. Most of the company’s products are suitable for transporting ammonia and ammonia solutions. 　　7. Saltwater (seawater): Ordinary steel exhibits a low rate of corrosion in sodium chloride solutions as well as in seawater and brackish water; coating protection is generally required ； Various types of stainless steel also have very low uniform corrosion rates, but local corrosion may occur due to chloride ions; therefore, it is advisable to use 316 stainless steel or fluoropolymer pumps. 　　8. Alcohols, alkanes, esters, and ethers: Common alcohol-based media include methanol, ethanol, ethylene glycol, propanol, etc.; alkanes include propane, butane, etc.; ester-based media comprise various methyl esters, ethyl esters, etc.; ether-based media include dimethyl ether, diethyl ether, butyl ether, etc. These substances generally have low corrosivity, so ordinary stainless steel can be used for them. However, a proper choice should still be made based on the properties of the medium and relevant requirements. It is also worth noting that alcohols, esters, and ethers are soluble in various rubbers, which helps to avoid mistakes when selecting sealing materials. 　　There are many other media that cannot be listed here one by one. In short, when selecting materials, one should not act casually or blindly; it is necessary to consult relevant information and draw on proven experience. Feel free to call for inquiries! Sealing issues: Zero leakage is an eternal goal for chemical processing equipment, and it is precisely this requirement that has led to the increasing use of magnetic pumps. However, there is still a long way to go before true leaklessness can be achieved, such as the lifespan issue of magnetic pump isolation sleeves, the pitting problem of materials, and the reliability issues of static seals, among others. Here is a brief introduction to some basic aspects of sealing: 1. Sealing types: For static sealing, there are generally only two types – gaskets and seals; among these, O-rings are the most widely used ； For dynamic seals, chemical pumps rarely use packing seals; mechanical seals are preferred instead. Mechanical seals come in single-face and double-face types, as well as balanced and unbalanced versions. Balanced mechanical seals are suitable for sealing high-pressure media (typically those with pressures greater than 1.0 MPa). Double-face mechanical seals are used mainly for media that are high-temperature, prone to crystallization, viscous, contain particles, or are toxic and volatile. An isolation fluid must be injected into the sealing chamber using double-face mechanical seals, and its pressure is usually 0.07–0.1 MPa higher than the pressure of the medium. 　　2. Sealing materials: The static sealing material for chemical magnetic pumps is generally fluororubber; polytetrafluoroethylene is used only in special cases ； The material selection for the stationary and rotating rings of mechanical seals is quite important. It’s not true that one combination of cemented carbides with another is always the best; high costs are one issue, and it’s also unreasonable if there is no difference in hardness between the two materials. Therefore, it’s best to choose the appropriate materials based on the characteristics of the medium involved. (Note: Appendix D of API 610, eighth edition, provides detailed specifications for the typical configurations of mechanical seals and piping systems.) Viscosity issues The viscosity of the fluid has a significant impact on the performance of the pump. As viscosity increases, the pump’s head curve declines; both the head and flow rate at optimal operating conditions decrease, while power consumption increases, resulting in reduced efficiency. The parameters for standard samples represent the performance when transporting clean water; adjustments are necessary when transporting viscous media (the correction factors for different viscosities can be found in the relevant conversion tables). For transporting slurries, pastes, and viscous fluids with high viscosity, it is recommended to use mortar pumps; our company’s UHB-ZK corrosion- and wear-resistant mortar pump is suitable for media that are viscous or contain particles. Basic selection guidelines: When designing equipment, the design institute must determine the purpose and performance parameters of the pump and select the appropriate pump type. This choice starts with selecting the type and design of the pump. So, what principles should be used to choose a pump? What is the basis then? Principles for pump selection: 1. The type and performance of the selected pump must meet the requirements of process parameters such as flow rate, head, pressure, temperature, net positive suction head, and suction lift. 2. The pump must meet the requirements related to the properties of the medium being transported; for pumps used to transport flammable, explosive, toxic, or valuable materials, reliable shaft seals are required, or leak-free pumps should be used, such as magnetically driven pumps (which have no shaft seals and rely on indirect magnetic drive). For pumps used to transport corrosive media, the moving parts must be made of corrosion-resistant materials, such as those used in fluoroplastic corrosion-resistant pumps. For pumps used to transport media containing solid particles, the moving parts need to be made of wear-resistant materials, and where necessary, the shaft seals should be flushed with a clean liquid. 　　3. Mechanically, high reliability, low noise, and minimal vibration are required. 　　4. Correctly calculate the investment cost for purchasing pumps. Below are the basic guidelines for pump selection: 5. When transporting highly corrosive media (such as concentrated sulfuric acid or concentrated nitric acid), flammable and explosive materials, or in environments where there must be no contamination at all, magnetic pumps can be used, such as the CQB series of magnetic pumps and the IMD series. If self-priming is required, the ZMD series of magnetic pumps can be chosen. 6. IH, FIJ, and IHF centrifugal pumps offer advantages such as high speed, small size, light weight, high efficiency, large flow rate, simple structure, smooth flow, stable performance, ease of operation, and convenience in maintenance. When there are no special requirements regarding the operating conditions, centrifugal pumps are a good choice. 　　7. For pumps used to transport chemical media containing solid particles, where wear-resistant materials are required for the convective components, UHB mortar pumps are the best choice. The material used in UHB corrosion- and wear-resistant mortar pumps is a high-strength new type of engineering plastic called UHBWPE, which is a modified polyethylene with an ultra-high molecular weight of over 5 million. In plastics, it exhibits excellent wear resistance; experimental comparisons show that its wear resistance is far higher than that of stainless steel. It also features impact resistance, creep resistance, and outstanding corrosion resistance (comparable to F4), as well as unique properties such as non-adhesion. 　　8. When the liquid level of the medium is below the pump installation location, it is advisable to use a self-priming pump or an submersible pump. This post was last edited by *ebinan on 2009-4-8 08:51]

1. The density, viscosity, corrosivity, toxicity, temperature of the medium being transported, as well as other properties of the liquid being conveyed and the operating conditions (referring to the operating temperature of the liquid, saturated vapor pressure, pressure in the container on the suction side, pressure in the container on the discharge side, atmospheric pressure, and ambient temperature)； Is it batch operation or continuous operation? Is the pump’s position fixed or movable, or is it moved frequently?) 2. The production process regarding the flow rate of the liquid, and the requirements of the installation regarding the head pressure of the pump.

General procedure for pump selection: 1. Consider various factors such as the layout of the installation, topographical conditions (elevation), climate conditions, operating environment, operational conditions, and economic cost comparisons. 2. Decide whether to choose a horizontal, vertical, or other type of pump (piped type, right-angled type, angled type, curved type, parallel type, vertical type, upright type, submersible type, easily detachable type, underwater type, clog-free type, self-priming type, gear-driven type, oil-filled type, water-temperature regulated type). Horizontal pumps are easy to disassemble and assemble. (1) They are easy to manage, but they take up a lot of space; (2) they are relatively expensive; (3) they require a large area for installation ； Vertical pumps: (4) In many cases, the impeller is submerged in water; (5) They can be started at any time; (6) They are suitable for automatic or remote control; (7) They are compact; (8) They require little installation space; (9) They are relatively inexpensive. 3. Based on the properties of the liquid medium, determine whether to use a clean water pump, a hot water pump, an oil pump, a chemical pump, a corrosion-resistant pump, or a dirt-pumping pump; or opt for a pump that is not prone to clogging. 4. Pumps installed in explosive areas shall use explosion-proof motors, depending on the explosion area classification. 5. Selection of actuation motors: pneumatic, electric (electric types are available at 220V and 380V voltages). 6. Choose between a single-suction pump and a double-suction pump based on the flow rate; choose between a single-suction pump and a multi-suction pump, as well as between a high-speed pump and a low-speed pump (such as an air-conditioning pump), depending on the head required. Multi-stage pumps have lower efficiency than single-stage pumps, so when both types of pumps are suitable for a given application, it is preferable to choose a single-stage pump. 7. Determine the specific model of the pump. After selecting a pump from a particular series, the specific model can be identified using the two key performance parameters: the maximum flow rate and the head value, with an additional 5%–10% margin added to these values. This is done by referring to the model chart or the series-specific characteristic curves. Using the pump’s performance curve, locate the desired flow rate value on the horizontal axis and the desired head value on the vertical axis. Draw a vertical or horizontal line from each of these values; if the intersection point falls exactly on the curve, then that pump is the one to choose. However, this ideal situation rarely occurs in practice. Usually, one of the following situations arises: (1) The intersection point is above the curve, which indicates that the flow rate meets the requirements but the head is insufficient. In such cases, if the difference in head is small, around 5%, the pump can still be used; if the difference is significant, then a pump with a higher head should be chosen. Or try to reduce the pipeline resistance loss. (2) The second case: if the intersection point lies below the characteristic curve, within the trapezoidal range of the pump’s characteristic curve, then this model is initially selected. Subsequently, it is determined whether to adjust the diameter of the impeller based on the difference in head pressure; if the difference is small, no adjustment is needed, while if the difference is large, the impeller diameter is adjusted according to the required values of Q and H, using the corresponding formulas. If the intersection point does not fall within that trapezoidal range, then a pump with a lower head pressure should be chosen. When selecting a pump, it is sometimes necessary to take into account the requirements of the production process and choose Q-H characteristic curves of different shapes. For example: to transfer the liquid level to a container where a certain liquid level height must be maintained; at this point the liquid becomes thinner. A larger change in volume is desired, while the head change should be minimal. In such cases, a pump with a flat H-O curve is the appropriate choice. f is like: sending oil into a tubular heating furnace. If the flow rate remains stable during operation, coking is likely to occur in the furnace tubes. To avoid this situation, I hope that when the flow rate decreases slightly, the pressure of the oil in tube j increases significantly; this allows the newly formed scorch marks to be washed away by the higher liquid flow pressure. In such cases, it is advisable to use an oil pump whose Q-H curve shows a more steep decline. 8. After the pump model is determined, for water pumps or pumps that transport physical and chemical media similar to water, it is necessary to consult relevant product catalogs or samples, and use the performance table or performance curve corresponding to that model to make adjustments, in order to determine whether the normal operating point falls within the preferred operating range of the pump Is the effective NPSH greater than (NPSH)? Can the geometric installation height also be adjusted inversely using NPSH? 9. For pumps used to transport liquids with a viscosity greater than 20 mm2/s, it is essential to convert the pump’s performance curves obtained from water-based tests into curves corresponding to that viscosity; in particular, the suction performance must be carefully calculated or verified. 10. Determine the number of pumps and the redundancy rate: For pumps that are operating normally, usually only one pump is needed, as one large pump is equivalent to two smaller pumps working in parallel (in terms of head and flow rate). The efficiency of a large pump is higher than that of smaller pumps; therefore, from an energy-saving perspective, it is better to use one large pump rather than two smaller ones. However, in the following situations, it may be advisable to use two pumps in parallel: when the flow rate is very high and one pump is not sufficient to meet it. For large pumps that require a 50% backup rate, two smaller pumps can be used in operation with two as backups (a total of three). For some large pumps, pumps with a 70% flow capacity can be operated in parallel without the need for backups; when one pump is under maintenance, the other pump continues to handle 70% of the flow requirements for production. For pumps that need to operate continuously for 24 hours, three pumps should be kept in reserve: one is in operation, one is on standby, and one is under maintenance.