How to calculate what kind of pump to use, how to calculate the flow rate of the pump

Select the "flow rate" of the pump based on the amount of water used per unit time during peak periods (or the maximum flow rate of water supply to the pool);

The "head" of the pump is selected according to the maximum height of the pump's water supply, the outlet pressure, the pressure drop of the pipeline, etc.

With these two main factors, you can basically select the type and specification of the pump, and then refer to the working mode and use conditions to determine other technical parameters.

Steps in pump selection.

Select the pump to list the basic data:

1. Characteristics of the medium: medium name, specific gravity, viscosity, corrosiveness, toxicity, etc.

2. The diameter and content of the solid particles contained in the medium.

3. Medium temperature: (

4. The required flow rate The leakage in the pipeline system can be ignored in the process of general industrial pumps, but the impact on the flow rate must be considered when the process changes. If the agricultural pump is used to transport water through open channels, leakage and evaporation must also be considered.

5. Pressure: suction pool pressure, drainage pool pressure, pressure drop (head loss) in the pipeline system.

6. Pipeline system data (pipe diameter, length, type and number of pipeline accessories, geometric elevation from suction tank to pressurized water tank, etc.).

If necessary, a characteristic curve of the device should also be made. When designing and arranging pipelines, the following matters should be noted:

1. Reasonable selection of pipeline diameter, large pipeline diameter, under the same flow rate, small liquid flow velocity, small resistance loss, but high **, small pipe diameter, will lead to a sharp increase in resistance loss, so that the head of the selected pump increases, the power of the belt increases, and the cost and operating expenses are increased. Therefore, it should be considered from a comprehensive technical and economic point of view.

2. The discharge pipe and its pipe joint should consider the maximum pressure that can be withstanded.

3. The pipeline layout should be arranged as a straight pipe as much as possible, try to reduce the accessories in the pipeline and minimize the length of the pipeline, when it must be turned, the bending radius of the elbow should be 3 5 times the diameter of the pipe, and the angle should be greater than 90 as much as possible.

4. The discharge side of the pump must be equipped with valves (ball valves or globe valves, etc.) and check valves. The valve is used to adjust the operating point of the pump, and the check valve prevents the pump from reversing when the liquid is flowing backwards and protects the pump from water hammer. (When the liquid flows backwards, a huge reverse pressure is generated, which damages the pump).

Pump selection to determine the flow head, the determination of the flow rate:

1. If the minimum, normal and maximum flow rate has been given in the production process, it should be considered according to the maximum flow rate.

2. If only the normal flow rate is given in the production process, a certain margin should be considered. For NS>100 high-flow low-head pumps, the flow margin is 5%, for NS<50 small-flow high-head pumps, the flow margin is 10%, for 50 NS100 pumps, the flow margin is also 5%, and for the pumps with poor quality and poor operating conditions, the flow margin should be 10%.

3. If the basic data is only given by weight, it should be converted into volumetric flow.

For novices, it is still difficult to choose the right water pump.

1.The efficiency of a pump, mainly a centrifugal pump, depends mainly on the specific speed ns and size. High specific speed, large volume (or power), high efficiency.

In addition, there is speed, machining accuracy, etc. In addition, the efficiency of the pump refers to the highest efficiency, and the efficiency of the specific operation is closely related to the pipe network. Therefore, efficiency must be given specific parameters, otherwise it is meaningless.

Most pumps have an efficiency between 50%-80%, with the highest pump efficiency reaching more than 90% and the low pump efficiency below 30%.

2.Pump efficiency is a technical and economic index to measure the efficiency of the pump, which refers to the ratio of the effective power of the pump (i.e., the output power of the pump) to the power of the pump shaft (i.e., the input power of the pump). The efficiency of the pump is generally more than 65% 90%, and the large pump can reach more than 90%.

The efficiency of a pump depends largely on the use of the pump. If not properly maintained and used, even if a high-efficiency pump is manufactured, it will not achieve the purpose of high-efficiency and low-consumption economical operation.

3.Due to the losses of the pump during operation, the actual (effective) head and flow of the pump are lower than the sum of the theoretical values, while the power values of the input pump are higher than the theoretical values.

1) the effective pressure head of the h pump, that is, the energy obtained from the pump by the unit amount of liquid in the gravity field, m; Q Actual flow rate of pump, m3 s; Liquid density, kg m3; The effective power of the NE pump, i.e., the mechanical energy obtained by the liquid from the pump per unit time, W.

2) The effective power of the pump can be written as ne = qh g

3) The power input to the centrifugal pump by the motor is called the shaft power of the pump, which is denoted by n. The ratio of effective power to shaft power is defined as the total efficiency of the pump, i.e. =ne n.

4) Pump efficiency: the ratio of the effective power of the pump to the shaft power. The efficiency on the pump nameplate refers to the maximum efficiency value that the pump can achieve at the rated speed.

The general pump efficiency is 60% to 85%. A high-efficiency pump means doing the same job with the lowest amount of energy and vice versa.

When calculating the efficiency of the pump, the relative value of the pump needs to be obtained from the parameters, and the accurate value of the parameter will also affect the efficiency value of the pump to a certain extent. The efficiency of the pump is an important reference data of the pump, which can reflect the relative work of the pump.

The volumetric efficiency of a hydraulic pump refers to the ratio of the actual output flow of the pump to the theoretical output flow.

In addition to volumetric efficiency, hydraulic pumps also have an efficiency index, mechanical efficiency. Mechanical efficiency is equal to the theoretical flow multiplied by the differential pressure of the fluid flow in and out of the pump body, divided by the input power.

Total efficiency is the ratio of actual output power to input power, and its magnitude is equal to the product of volumetric efficiency and mechanical efficiency.

Pump efficiency refers to the ratio of the effective power of the pump to the shaft power. =PE P The power of the pump usually refers to the input power, that is, the power transmitted by the prime mover to the pump shaft, so it is also called the shaft power, which is represented by P. The effective power of the belt is as follows:

The product of the pump's head and mass flow and gravitational acceleration. PE= G qh (W) or PE= QH 1000 (KW) Density of the liquid pumped (kg m3) Gravity of the liquid pumped =g (n m3) g: Acceleration due to gravity (m s) Mass flow qm= q (t h or kg s) Because the power of the pump n(kw) = head (m) Flow rate (m3 s) 1000 (gravity of water kg m3) 102 (power conversion coefficient) The efficiency of the pump can be obtained.

If the current and voltage can be measured (the power of the pump can be calculated), the efficiency of the pump can be obtained by measuring the flow rate and the efficiency of the pump, which is the formula for calculating the efficiency of the pump.

The pump flow rate is calculated as follows:

The flow rate q(m3 h) is calculated as 111111111111q=[(m q) t] k

i.e. maximum hourly flow rate (m3 h).

Hourly coefficient of variation.

k - coefficient of change (generally.

Q - water standard (South China generally uses 300 liters per person; The high-end house is 400 liters per day).

t - water use time (generally 12 hours a day).

m - the number of people who use water (generally 4-5 people per household).

1000 – unit conversion rate between liter and m3 h.

The calculation of pump parameters needs to be selected and calculated according to the specific situation and needs. Here are a few common references and how they are calculated:

Flow rate: The volume of liquid flowing through the pump per unit of time, measured in m h or l s. It can be measured or calculated, and it is usually necessary to consider factors such as the capacity of the water source, the flow limit of the pipeline, and the demand for equipment use.

Head: The difference in height of the liquid from the inlet to the outlet, in m. It needs to be selected and calculated according to specific needs and application scenarios, and it is usually necessary to consider factors such as conveying distance, conveying height, friction resistance, etc.

Power: The electric power required by the fuel pump, in kW. This can be calculated by flow rate and head, and often factors such as pump efficiency and power rating also need to be taken into account.

Pressure: This is the pressure of the liquid in the pipe, measured in pa or bar. Calculations need to be made based on specific scenarios and needs, and often need to consider factors such as flow rate, pipe cross-sectional area, pump head, etc.

Pump efficiency: This is the delivery efficiency of the pump, usually expressed as a percentage. It can be calculated by parameters such as flow, head, power, etc.

The above are only some common pump parameters and their calculation methods, and the specific calculation methods also need to be selected and calculated according to the specific situation and needs.

1. If the brand with the motor is there, you can get the power and speed of the pump. The maximum head of the pump can be estimated h=v 2 (2g), where v 2 is the square of the linear velocity of the outer edge of the impeller when it is running, v is equal to the diameter, n is the rotational speed); The g in the formula is the gravitational acceleration, because it is estimated, so it is calculated according to 10, and you can use the actual head of the pump with a 7% discount.

2. Flow rate Q=N (GH), (where N is the power of the matched motor kW). This calculation of the flow is on the large side, you can give a 5% discount (the result of the flow calculation is cubic meters per second).

3. If the motor is gone, the estimate can only be roughly guessed, you first assume that the speed of the pump is 1450 rpm or 2900 rpm (because most of the small and medium-sized pump speeds are these two, the motor is two poles or four poles, most small and medium-sized pumps will generally use high speed, which is conducive to reducing volume, controlling costs and improving efficiency, so most of them can be calculated at 2900 rpm), and then calculate the head and flow, Of course, in fact, you can use the speed of the motor you intend to use on hand to calculate it by substituting it into the above method.

There are several ways to estimate the flow rate of the pump, mainly to see the diameter of the pump inlet and outlet, the width and diameter of the outer edge of the impeller bridge. We use the inlet diameter to estimate it simply: the flow rate is generally 2-5 meters per second, then the flow rate can be as if Q = this pants posture D is the diameter of the pump inlet).

Of course, this result is safe, and you better use it with a 5% discount.

Pump efficiency is the ratio of the effective power of the pump to the shaft power. The effective power is the gravity of the medium (per cubic meter per cattle) multiplied by the head (per meter) multiplied by the flow rate (cubic meters per second) divided by 1000. Shaft power is the power that the motor transmits to the shaft of the pump.

The pump you are talking about can be calculated by itself: , converted to.

Pump efficiency (9761*.)

It's super inefficient.

Hello, the estimation of the weight of the pump mainly depends on the size and material of the pump. Generally speaking, the weight of a water pump is related to its size and material, and as the size of the large volume increases, the weight will also increase. First of all, to estimate the weight of a water pump, you need to know its dimensions, including its diameter and length.

Generally speaking, the weight of the pump is directly proportional to its size, i.e., as the size increases, the weight will also increase. Secondly, to estimate the weight of a water pump, you also need to know its material. Different posture materials have different weights, for example, cast iron pumps are much heavier than stainless steel pumps.

Therefore, if the material of the pump is different, its weight will also be different. In conclusion, the estimation of the weight of the pump mainly depends on the size and material of the pump. In general, the weight of a water pump is related to its size and material, and as the size increases, the weight also increases.