Selection of pumps for water treatment equipment
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I would like to ask, in the process of designing water treatment equipment, what criteria are used to determine the choice of pump?
The selection of a pump begins with determining the required flow rate and head. Next, the performance parameter curve of the pump is examined to see at which point on that curve the desired flow rate and head correspond; this helps to initially select a suitable pump model. Then, the detailed performance parameter curve for that model is reviewed to determine exactly where the operating point falls within the high-efficiency range and whether it is suitable or not； Then, based on the flow rate and head, the shaft power of the water pump is calculated, and a corresponding motor is selected. It should be noted that in typical centrifugal pumps, speeds of 2900 rpm and 1450 rpm can both achieve the same operating point. If conditions permit, it is recommended to choose a pump with a lower speed, as it operates more stably.
It mainly depends on the required head and flow rate, as well as the medium it transports
The selection of a pump is primarily based on flow rate and head; it is also necessary to consider the medium being transported to prevent contamination of that medium.
The most important thing is to ensure his net positive suction head!
Determine the pump’s purpose and performance to select the appropriate pump type. This selection process begins with choosing the type and design of the pump. First, it is necessary to understand the principles for selecting pumps: 1. Ensure that the type and performance of the selected pump meet the requirements of the installation’s process parameters such as flow rate, head, pressure, temperature, cavitation threshold, and suction lift. 2. The requirements of the medium’s properties must be met. For pumps used to transport flammable, explosive, toxic, or valuable fluids, it is necessary to have reliable shaft seals or to use leak-free pumps such as magnetically driven pumps, diaphragm pumps, and shielded pumps. For pumps used to handle corrosive fluids, the moving parts must be made of corrosion-resistant materials, such as AFB stainless steel corrosion-resistant pumps or CQF engineering plastic magnetically driven pumps. For pumps that transport media containing solid particles, it is required that the convective components be made of wear-resistant materials, and where necessary, the shaft seals should be flushed with a clean liquid. 3. High reliability in terms of mechanics, low noise, and minimal vibration. 4. Economically, it is necessary to take into comprehensive account the total cost of equipment expenses, operating costs, maintenance costs, and management fees to minimize it. 5. Centrifugal pumps feature high speed, small size, light weight, high efficiency, large flow rate, simple structure, pulse-free fluid delivery, stable performance, ease of operation, and convenience in maintenance. Therefore, centrifugal pumps should be preferred as much as possible, except in the following cases: a) When metering is required, a metering pump should be used. b) When a very high head is needed along with a low flow rate, and no suitable centrifugal pump with a low flow rate but high head is available, a reciprocating pump can be used; a vortex pump can also be chosen if cavitation requirements are not high. c) When the head is very low but the flow rate is high, axial flow pumps and mixed-flow pumps can be used. d. When the viscosity of the medium is high (greater than 650–1000 mm2/s), rotary pumps or reciprocating pumps (gear pumps, screw pumps) can be considered.
e. When the medium contains 75% air, the flow rate is low, and the viscosity is less than 37.4 mm2/s, vortex pumps can be used. f. In situations where startup is frequent or pumping is difficult, pumps with self-priming capabilities should be used, such as self-priming centrifugal pumps, self-priming vortex pumps, and pneumatic (electric) diaphragm pumps. II. Understanding the basic criteria for pump selection. The criteria for selecting a pump should be considered from five aspects, based on the process flow and water supply/distribution requirements: fluid flow rate, head required by the system, properties of the fluid, piping layout, and operating conditions. 1. Flow rate is one of the important performance parameters when selecting a pump; it is directly related to the production capacity and transportation capacity of the entire system. In the process design of the design institute, it is possible to calculate the normal, minimum, and maximum flow rates of the pump. When selecting a pump, the maximum flow rate should be used as the basis, taking into account the normal flow rate as well. In the absence of a specified maximum flow rate, 1.1 times the normal flow rate can generally be taken as the maximum flow rate. 2. The head required by the installation system is another important performance parameter for selecting a pump; generally, the head value should be increased by 5%–10% as a safety margin when making the selection. 3. Properties of the liquid, including the name of the liquid medium, its physical properties, chemical properties, and other characteristics. Physical properties include temperature, density, viscosity, the diameter of solid particles present in the medium, and the gas content; these factors are relevant to calculating the system’s head, the effective net positive suction head, and determining the appropriate type of pump. Chemical properties refer mainly to the chemical corrosiveness and toxicity of the liquid medium, and they serve as important criteria for selecting the material for the pump as well as the type of shaft seal to use. 4. The pipeline layout conditions of the plant system refer to data such as the liquid delivery height, distance, and direction; the lowest liquid level on the suction side and the highest liquid level on the discharge side; as well as details regarding pipe specifications, their lengths, materials, fitting specifications, and quantities. These are necessary for calculating the system head and verifying the net positive suction head. 5. There are many aspects related to operating conditions, such as the operating temperature of the liquid, the saturated vapor pressure P, the suction side pressure PS (absolute), the pressure in the discharge side container PZ, altitude, ambient temperature, whether the operation is intermittent or continuous, and whether the pump’s location is fixed or movable. III. Specific procedures for selecting a pump In accordance with the principles and basic criteria for pump selection, the specific steps are as follows: 1. Based on the layout of the installation, terrain conditions, water level conditions, and operating conditions, determine whether to choose a horizontal, vertical, or other type of pump (such as pipeline-type, submersible, underwater, clog-free, self-priming, gear-driven, etc.). 2. 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-pump; or opt for a clog-free pump. Pumps installed in explosive areas should use appropriate explosion-proof motors based on the classification of the explosive area. 3. Determine whether to choose a single-suction pump or a double-suction pump based on the flow rate ； Depending on the required head, decide whether to use a single-stage pump or a multi-stage pump, as well as whether to choose a high-speed pump or a low-speed pump (such as an air-conditioning pump). Multi-stage pumps have lower efficiency than single-stage pumps; therefore, when both types of pumps are suitable for a given application, a single-stage pump should be preferred first. 4. Determine the specific model of the pump: After deciding on which series of pumps to use, it is possible to determine the specific model by using two key parameters – the maximum flow rate (if no such value is available, 1.1 times the normal flow rate can typically be used as an estimate for the maximum flow rate) and the head with a 5%–10% margin added to it. These parameters are then used to identify the appropriate model from the model chart or series performance curves. The procedure is as follows: Utilize the pump’s performance curve to find the desired flow rate value on the horizontal axis and the desired head value on the vertical axis. Draw vertical or horizontal lines from these two values respectively; if the intersection point falls exactly on the performance curve, then that pump is the one to be chosen. However, this ideal situation occurs rarely in practice. Usually, one of the following two situations arises: The first situation is when the intersection point is above the performance 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 selected. Or try to reduce the pipeline resistance loss. The second case: if the intersection point is below the characteristic curve, within the trapezoidal range of the pump’s characteristic curve, then this model can be initially selected. Subsequently, it is determined whether to adjust the diameter of the impeller based on the difference in head pressure. If the difference in head pressure is small, no adjustment is needed; if it is large, then 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, 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. 5. Once the pump model has been determined, for pumps that handle water-like physical and chemical media, it is necessary to consult relevant product catalogs or samples, and use the performance tables or curves associated with 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? 6. For pumps that transport liquids with a viscosity greater than 20 mm2/s (or a density greater than 1000 kg/m3), it is essential to convert the pump’s performance curve obtained from water-based tests into one that reflects its performance at such viscosity (or density). In particular, careful calculations or verifications must be carried out regarding the suction performance and input power. 7. Determine the number of pumps and the redundancy factor: 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 required flow rate is very high, and a single 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 certain 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 transportation requirements. 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. 8. Under normal circumstances, customers can submit their \"basic requirements for selecting a pump\", and our company will carry out model selection or recommend better pump products. If the design institute has already determined the pump model when designing the equipment, it should be configured in accordance with the institute’s requirements. 9. 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 appropriate 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 certain 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 transportation requirements. 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. This post was last edited by 11575276801 on 2009-2-16 09:48.]
e. When the medium contains 75% air, the flow rate is low, and the viscosity is less than 37.4 mm2/s, vortex pumps can be used. f. In situations where startup is frequent or pumping is difficult, pumps with self-priming capabilities should be used, such as self-priming centrifugal pumps, self-priming vortex pumps, and pneumatic (electric) diaphragm pumps. II. Understanding the basic criteria for pump selection. The criteria for selecting a pump should be considered from five aspects, based on the process flow and water supply/distribution requirements: fluid flow rate, head required by the system, properties of the fluid, piping layout, and operating conditions. 1. Flow rate is one of the important performance parameters when selecting a pump; it is directly related to the production capacity and transportation capacity of the entire system. In the process design of the design institute, it is possible to calculate the normal, minimum, and maximum flow rates of the pump. When selecting a pump, the maximum flow rate should be used as the basis, taking into account the normal flow rate as well. In the absence of a specified maximum flow rate, 1.1 times the normal flow rate can generally be taken as the maximum flow rate. 2. The head required by the installation system is another important performance parameter for selecting a pump; generally, the head value should be increased by 5%–10% as a safety margin when making the selection. 3. Properties of the liquid, including the name of the liquid medium, its physical properties, chemical properties, and other characteristics. Physical properties include temperature, density, viscosity, the diameter of solid particles present in the medium, and the gas content; these factors are relevant to calculating the system’s head, the effective net positive suction head, and determining the appropriate type of pump. Chemical properties refer mainly to the chemical corrosiveness and toxicity of the liquid medium, and they serve as important criteria for selecting the material for the pump as well as the type of shaft seal to use. 4. The pipeline layout conditions of the plant system refer to data such as the liquid delivery height, distance, and direction; the lowest liquid level on the suction side and the highest liquid level on the discharge side; as well as details regarding pipe specifications, their lengths, materials, fitting specifications, and quantities. These are necessary for calculating the system head and verifying the net positive suction head. 5. There are many aspects related to operating conditions, such as the operating temperature of the liquid, the saturated vapor pressure P, the suction side pressure PS (absolute), the pressure in the discharge side container PZ, altitude, ambient temperature, whether the operation is intermittent or continuous, and whether the pump’s location is fixed or movable. III. Specific procedures for selecting a pump In accordance with the principles and basic criteria for pump selection, the specific steps are as follows: 1. Based on the layout of the installation, terrain conditions, water level conditions, and operating conditions, determine whether to choose a horizontal, vertical, or other type of pump (such as pipeline-type, submersible, underwater, clog-free, self-priming, gear-driven, etc.). 2. 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-pump; or opt for a clog-free pump. Pumps installed in explosive areas should use appropriate explosion-proof motors based on the classification of the explosive area. 3. Determine whether to choose a single-suction pump or a double-suction pump based on the flow rate ； Depending on the required head, decide whether to use a single-stage pump or a multi-stage pump, as well as whether to choose a high-speed pump or a low-speed pump (such as an air-conditioning pump). Multi-stage pumps have lower efficiency than single-stage pumps; therefore, when both types of pumps are suitable for a given application, a single-stage pump should be preferred first. 4. Determine the specific model of the pump: After deciding on which series of pumps to use, it is possible to determine the specific model by using two key parameters – the maximum flow rate (if no such value is available, 1.1 times the normal flow rate can typically be used as an estimate for the maximum flow rate) and the head with a 5%–10% margin added to it. These parameters are then used to identify the appropriate model from the model chart or series performance curves. The procedure is as follows: Utilize the pump’s performance curve to find the desired flow rate value on the horizontal axis and the desired head value on the vertical axis. Draw vertical or horizontal lines from these two values respectively; if the intersection point falls exactly on the performance curve, then that pump is the one to be chosen. However, this ideal situation occurs rarely in practice. Usually, one of the following two situations arises: The first situation is when the intersection point is above the performance 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 selected. Or try to reduce the pipeline resistance loss. The second case: if the intersection point is below the characteristic curve, within the trapezoidal range of the pump’s characteristic curve, then this model can be initially selected. Subsequently, it is determined whether to adjust the diameter of the impeller based on the difference in head pressure. If the difference in head pressure is small, no adjustment is needed; if it is large, then 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, 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. 5. Once the pump model has been determined, for pumps that handle water-like physical and chemical media, it is necessary to consult relevant product catalogs or samples, and use the performance tables or curves associated with 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? 6. For pumps that transport liquids with a viscosity greater than 20 mm2/s (or a density greater than 1000 kg/m3), it is essential to convert the pump’s performance curve obtained from water-based tests into one that reflects its performance at such viscosity (or density). In particular, careful calculations or verifications must be carried out regarding the suction performance and input power. 7. Determine the number of pumps and the redundancy factor: 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 required flow rate is very high, and a single 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 certain 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 transportation requirements. 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. 8. Under normal circumstances, customers can submit their \"basic requirements for selecting a pump\", and our company will carry out model selection or recommend better pump products. If the design institute has already determined the pump model when designing the equipment, it should be configured in accordance with the institute’s requirements. 9. 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 appropriate 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 certain 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 transportation requirements. 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. This post was last edited by 11575276801 on 2009-2-16 09:48.]
The simplest way to choose a pump is: first, the medium to be transported； The second is the conveying flow rate ； Third is the elevation difference of the conveying medium, that is, the head ； Fourth is the power of the pump ； Fifth is the pump’s heat dissipation method.
There is also the flow head and its conveying medium.
Flow rate and head are the most important, right?
Floor 6 is more detailed. However, we can consult a design institute when making our selection choices, as their advice is often very valuable. :lol
1. First, determine the special properties and requirements of the medium to be transported, and then select the type and material of the pump； 2. Determine the conveying distance and height, and calculate the pump head using parameters such as the water suction height, frictional loss along the pipeline, and the head at the liquid outlet ； 3. Calculate the required power based on the medium, head, and pump efficiency, and select an electric motor accordingly ； 4. Determine the pipeline flow rate based on the different conveying media, and calculate the diameter of the conveying pipe. In one sentence: choose the model directly by looking at the various curves in the samples from reputable manufacturers.
Flow rate and head are the most important factors; whether it is used for transporting sewage or clean water, and also the solid content level. The poster gives me the parameters and basic conditions; I’ll pick a model for you
It also depends on the medium being transported; head and flow rate are very important
When selecting a pump, the installation method must be taken into consideration. If it is used alone, then it doesn’t matter as long as it meets the requirements regarding flow rate and head pressure. However, when pumps are used in parallel, it is necessary to consider whether the performance curve of the pumps is \"gentle\" or \"steep\"; otherwise, the selected pumps will not fulfill the design objectives. Furthermore, variable-frequency pumps are being used more and more; in essence, a variable frequency drive is added to the motor, with little increase in cost.