1.how to choose the flow rate of sand pump and pipe diameter
Selecting a suitable sediment pump should consider a variety of factors, first of all, consider the flow rate and pipeline diameter: flow rate = pipeline cross-sectional area * flow rate. So it is necessary to measure the flow rate from both the pipeline and the flow rate.
When the water contains sediment, the slurry flow rate in the pipeline must be ensured. Unlike clear water pumps, a flow rate that is too low or too high will not work. Too low a flow rate, sand settling back will occur, which will cause a sharp increase in the concentration of sediment in the pump chamber, making the impeller wear out quickly, and in serious cases, it will also lead to blocking the pipe and the pump. Flow rate is too high, will lead to increased pipeline loss, flow reduction, drainage efficiency is reduced, easy to plug the pipe, plug the pump. Therefore, when designing and selecting, the actual working flow should be matched with the diameter of the pipeline, and the flow rate is generally 2-3m/s. When choosing sediment pump, without special requirements, the corresponding pipe diameter can be selected according to the flow rate in the parameter table.
Complex conditions design need to check the pipeline flow rate, compare and select the best programme. For example, when transporting sediment over long distances, it is important to check the flow rate and control the pipeline loss. In addition to parallel drainage pumps, be sure to check a pump work and more than one pump work when the pipeline flow rate, which is the choice of sand pump drainage is most likely to appear in the design problems.
Common pipe diameters and flow rates for flow rates of 2m/s and 3m/s:
Note: Flow rate in m3/h.
Comparison table of minimum flow rates of common materials:
Basic principles for selecting flow rates:
Higher flow rates for shorter lines and lower flow rates for longer lines;
Higher flow rates when solid sand particles have a higher specific gravity and lower flow rates when they have a lower specific gravity;
The flow rate is higher when the solid sand particles are larger and lower when the particles are smaller;
higher flow rates at higher slurry consistencies and lower flow rates at lower slurry consistencies;
2.How to choose the head of sediment pump
Selection of sediment pump head, the main consideration of three parameters: drainage height, pipeline loss, head preparation.
a, drainage height
Pump submersible use, drainage height for the water surface and pipeline outlet between the height difference (below the surface of the water to the pump outlet height difference is not counted as head);
When the pump is used above the water surface (installed on board or on land), the drainage height is the height difference between the pump outlet and the pipeline outlet (the height difference between the pump suction outlet and the water surface is the suction range, not counted as the head).
If the drain line goes up to the highest point and then down, forming a central bulge, the drainage height is the height difference between the pump outlet and the highest point of the pipeline (can no longer be calculated on the basis of the pipeline outlet).
b, pipe loss
Pipeline loss by the inner diameter of the pipeline, the medium of the flow rate of the great influence, but also by the pipeline material (the friction coefficient of the inner wall), slurry concentration, viscosity of the slurry, the length of the pipeline, pipeline bending and the valve and other pipe fittings of the impact. Therefore, for the water containing sediment drainage conditions, the pipeline loss is much greater than when the water, and the higher the slurry concentration, the greater the viscosity, the greater the pipeline loss. When designing and selecting, the pipeline loss can be calculated according to the state of clear water first, and then multiplied by 1.5 to 3 times as the pipeline loss for selection. The drainage pipe of sand pump is generally recommended HDPE pipe, the friction coefficient is relatively small, and the pipeline loss is also small.
Pipe loss in 100 metres of straight cast iron pipe when pumping fresh water at flow rates of 2 m/s and 3 m/s (unit: metres):
From the table, it can be seen that the smaller the pipe diameter, the greater the piping loss; the greater the flow rate, the greater the piping loss. Therefore, the practice of replacing the thick pipe of equal area with several thin pipes is not desirable.
The piping loss when pumping mud and sand slurry is inaccurate due to the lack of theoretical calculation formula and charts for reference, and the piping loss obtained by experience during design is inaccurate. Especially when the pipeline is very long, the gap between the design value and the actual value is very large, the way to accurately derive the pipeline loss is the actual measurement. Users can be based on the existing drainage system, with a pressure gauge to measure the actual working head (normal drainage, the pump outlet at the pressure value), and then subtract the height of the drainage, you can get the current flow rate when the pipeline loss. This is the benchmark, and again when selecting an accurate data, but also for similar conditions to provide a basis for the design of the drainage system.
c, the amount of head preparation
When the water contains sand, the pump will wear out after long-term use, resulting in a decline in the flow rate, head reduction. When the maximum head of the sand pump is less than the working head, it can not drain. Therefore, sand pump selection head should be left according to the situation of wear allowance. In addition, due to the calculation of sand pump pipeline loss is in accordance with the clear water state pipeline loss doubled calculation, belongs to the empirical conclusion, therefore, for the design of the working conditions are not sure need to consider increasing the head of the design of the amount of reserves. This is also one of the differences between the design and selection of clear water pumps and sand pumps. Based on past experience, the recommended head capacity:
Head 0 ~ 75 m, head allowance of 5 ~ 10 m;
Head 75 ~ 160 metres, head allowance of 10 to 20 metres;
160-300 metres head, leave 20-40 metres head allowance;
If the slurry concentration is high and the weight ratio is more than 30%, the head allowance should be increased by 1.5 to 2 times.
Select the rated head of sediment pump according to the sum of drainage height, pipeline loss and head reserve.
Design and selection of personnel need to pay attention to: ordinary pump head is a range of use, the national standards and national quality inspection department of the pump test is only required in 0.7 ~ 1.2 times the rated flow range (about 1.1 ~ 0.8 times the rated head), high head of the pump is not allowed to be used in the low head. In accordance with the selection principles of this article selected rated head of the sediment pump, the actual use of the head may be beyond the use of ordinary pumps (because of the head of the amount of preparation is very large), so it is required to pay attention to the selected range of use of the head of the sediment pump.
After determining the rated head of the sand pump, there is a need to further check the rated flow rate of the sand pump. As the actual use of the head is lower than the rated head, so the actual flow rate is larger than the rated flow rate. Need to be based on the specifications of the product's performance curve, check the rated flow rate and the actual flow rate, if the difference is not large, directly according to the design flow rate selection of the rated flow rate (with the wear and tear of the sand pump, the actual flow rate will gradually decline, so there are also left some spare capacity.) If the difference is too big, the rated flow rate of sand pump should be less than the design flow rate.
3.Determine the density of slurry, solids concentration, select the appropriate motor power
Pump output power P = ρgQH: ρ - the density of the slurry conveyed by the pump; g - the acceleration of gravity; Q - the flow rate of the pump; H -head of the pump.
When choosing sand pump, it is necessary to consider the density of the slurry, the slurry density is different, the matching motor power is different.
When the slurry density is the same, due to the different specific gravity of the solid medium, the slurry concentration is different. Concentration is too high, the slurry fluidity is poor, the pump power will rise sharply, easy to plug the pump, easy to burn the motor. Therefore, impurities pumps are provided for the use of media conditions.
For example: a certain sewage pump, slurry density ≤ 1020 kg/m³, slurry concentration volume ratio ≤ 4%.
Users need to check whether the permissible slurry density and slurry concentration of the sediment pump meet the requirements of the working conditions. When the pump is used beyond the range, it is easy to overload and burn the motor, and the life of the pump will be greatly reduced.
There are two types of slurry concentration:
Solids volume ratio = total volume of solids in slurry ÷ total volume of slurry
Solids to weight ratio = Total weight of solids in the slurry ÷ Total weight of the slurry
Solids-to-weight ratio is the universal way to express consistency and is used in all slurry research, calculations, design, and sizing. Solids volume is more intuitive, and most users tend to say solids volume ratio when describing slurry consistency.
The concept must be clear when selecting the model. The practice of accurately obtaining the slurry concentration is on-site measurement, which can be done by taking samples with a container at the outlet when the sand pump is working, and by weighing and calculating the solids weight ratio, or checking the solids volumetric ratio after sedimentation, and then accounting for the solids weight ratio according to the solids specific gravity
Comparison table of common materials slurry density to solids volume ratio and weight ratio:
Comparison table of solids to weight ratio and slurry density (kg/m³) for common materials:
From the above table, it can be seen that the density of the slurry and the specific gravity of solids, slurry concentration (weight ratio and volume ratio) is closely linked.
It should be noted that: the choice of sand pump products, in its ability to meet the slurry density and slurry concentration of the premise, must be able to ensure the service life of the product. Both is the clear water pump can also pump sand slurry, is the life is too short.
Sino-Ocean sand pumps are divided into three grades according to the maximum permissible value of the slurry density of the transport medium, which are as follows.
A. Low concentration conditions, density ≤ 1100kg/m³, all sand pumps can be used, the main place of use: coal mining area, conveying slurry containing coal slurry, broken coal particles. Allowable maximum concentration (weight ratio): 29% fine coal slurry, 20% tailing coal slurry, 15% quartz sand, 13% tailing sand.
B. High concentration working condition, density ≤1300kg/m³, some products belong to this category. Mainly used in: slurry transport, or rock blasting construction drainage without specific measures to control sediment content. Allowable maximum concentration (weight ratio): 40% of fine coal slurry and tailing slurry, 37% of quartz sand, 33% of tailing sand.
C. Ultra-high concentration conditions, density ≤1500kg/m³, some customised products. Mainly used places: professional sand mining, conveying tailing sand, or thick slurry conveying without specific measures to control sediment content. Allowable maximum concentration (weight ratio): 60% of fine coal slurry and tailing slurry, 40% of yellow clay, 54% of quartz sand, 48% of tailing sand, 42% of iron ore concentrate.
Note: a) Specific gravity take: iron ore concentrate 4.9, tailing sand 3.3, quartz sand 2.65, yellow clay 2.6, tailing coal slurry 1.8, refined coal slurry 1.45.
b) Other media according to the slurry density and specific gravity of solids refer to the above parameters selection.
4.Confirm voltage, frequency
China common voltage: 380V, 660V, 1140V, 3000V, 6000V, 10000V
Frequency in China: 50Hz
Commonly used voltage abroad: 220V, 400V, 440V, 550V, 690V, 1450V, 3000V, 6000V, 10000V
Frequency in some foreign countries: 60Hz
5.Determine maximum particle size to prevent clogging
1, by the impeller channel and the number of blade limitations, each pump type through the sex is not the same, to indicate the maximum diameter through the mark. Selection, to determine the maximum particle diameter and then select the pump type or change the number of blades. Make suction salon head according to the determined pump type.
2, Ocean sand pump is specially designed with large particle sand suction pump, which is suitable for sand pumping environment containing pebbles.
3,If the water contains long fibres and other impurities, measures can be taken to prevent the screen from being clogged, so that the pump will not discharge water, such as extending the screen, or double screen. For the discharge of special requirements of the media, need to be individually tailored programme
These are to consider the passing ability of solids, to avoid plugging the pipe, plugging the pump, in order to maximise the advantages of the sand pump, to ensure that the equipment is normally used in operation, so that the user gets a better use of the results.
