How to Determine Basic Parameters of High Quality Dredge Pump

OCEAN Pump has been specializing in the research, development, production and sales of high quality dredge pump for many years. OCEAN Pump brand high quality dredge pumps have been widely used in domestic coastal areas, the Yellow River Basin, the Yangtze River Basin, inland river channels, dredging, mining, land reclamation and other fields. At the same time, the high quality dredge pump are exported to many countries and regions in the world and received good reviews. While OCEAN Pump continues to innovate and develop new products, it has also conducted in-depth research on how to choose the right high quality dredge pump for customers.  How to choose the basic parameters of the dredge pump is described as followed.

1. How to choose the inlet flow and pipe diameter of high quality dredge pump

Selecting a suitable high quality dredge pump should consider various factors. First, considering the inlet flow and pipe diameter: inlet flow = pipe cross-sectional area × flow velocity. Therefore, the inlet flow should be measured from the two aspects of pipeline and flow velocity.

When the water contains sand and mud, the slurry flow velocity in the pipeline must be guaranteed. Unlike the clean water pump, it is not good for high quality dredge pump if the slurry flow velocity in pipeline is too low or too high. If the flow velocity is too low, sedimentation and settling of sand will occur, and the concentration of sediment in the dredge pump chamber will increase sharply, causing the impeller to wear quickly. In serious cases, it will also cause pipe blockage and high quality dredge pump blockage. If the flow velocity is too high, it will lead to increasing pipeline loss, reducing flow rate, reducing drainage efficiency, and easy blockage of pipes and pumps. Therefore, when designing and selecting the high quality dredge pump model, the flow rate in actual work should match the diameter of the pipeline. In general, the flow velocity is 2 ~ 3m / s. When selecting the high quality dredge pump, if there is no special requirement, just select the corresponding pipe diameter according to the flow in the parameter table.

The design of complex working conditions requires checking the inlet flow velocity of the pipeline and selecting the best solution. For example, when transporting sediment at a long distance, check the flow velocity and control the pipeline loss. In addition, when water pumps are used for water draining in parallel, it is necessary to check the pipeline flow velocity when one pump works and multiple pumps work. This is the most possible design problems when high quality dredge pumps are used for drainage.

When the flow velocity is 2m / s, 3m / s, the comparison table of common pipe diameter and flow. (Flow unit: m3/h)

Comparison table of the minimum flow velocity of common materials

Basic principles for choosing inlet flow velocity：

• When the pipeline is short, the flow velocity is higher, and when the pipeline is longer, the flow velocity is lower.
• When the sand proportion is larger, the flow velocity is higher, and when the sand proportion is smaller, the flow velocity is lower.
• When the particle size of solid sand is larger, the flow velocity is higher, and when the particle size is smaller, the flow velocity is lower.
• When the slurry concentration is higher, the flow velocity is higher, and when the slurry concentration is lower, the flow velocity is lower.

2. How to choose the head of the high quality dredge pump

When selecting the head of the high quality dredge pump, three main parameters are considered such as drainage height, pipeline loss, and head reserve.

2.1 Drainage height

When the high quality dredge pump is used for diving, the drainage height is the height difference between the water surface and the pipe outlet(the height difference below the water surface to the dredge pump outlet is not counted as head). When the high quality dredge pump is used above the water surface (installed on a sand dredger or on land), the drainage height is the height difference between the high quality dredge pump outlet and the pipe outlet (the height difference between the sand pump machine suction port and the water surface is the suction stroke, not the head.)

If the drainage pipeline goes up to the highest point and then descends, forming a central bulge, the drainage height at this time is the height difference between the high quality dredge pump outlet and the highest point of the pipeline (can no longer be calculated based on the pipeline outlet).

2.2 Pipeline loss

Pipeline loss is greatly affected by the inner diameter of the pipe and the flow velocity of the medium. In addition, it is also affected by the pipe material (friction coefficient of the inner wall), slurry concentration, slurry viscosity, pipe length, pipe bending, and pipe fittings such as valves. Therefore, for drainage conditions of containing sediment in the water, the pipe loss is much larger than that in clear water, and the higher the slurry concentration and the greater the viscosity, the larger the pipe loss. When designing and selecting a high quality dredge pump model, the pipeline loss can be calculated according to the state of clean water, and then multiplied by 1.5 to 3 times as the pipeline loss for model selection. HDPE pipes are generally recommended for the drainage pipeline of high quality dredge pumps, the friction coefficient is relatively small, and the pipeline loss is also small.

Pipeline loss of a 100-meter-long straight cast iron pipe when pumping clean water at a flow rate of 2 m / s or 3 m / s (unit: m)

It can be seen from the table that the smaller the pipe diameter, the greater the pipeline loss; the greater the flow velocity, the greater the pipeline loss. Therefore, it is not advisable to use multiple thin pipes to replace thick pipes of equal area.

The pipeline loss when pumping mud and sand slurry has no theoretical calculation formula and reference chart, so the pipeline loss obtained by experience during design is not accurate. Especially when the pipeline is very long, there is a big gap between the design value and the actual value. The way to get the pipeline loss accurately is to actually measure. According to the existing drainage system, the user can use a pressure gauge to measure the actual working head (the pressure value at the sand pump outlet during normal drainage), and then subtract the drainage height to obtain the pipeline loss at the current flow rate. Based on this, accurate data will be available when the high quality dredge pump model is selected again, and it can also provide a basis for designing drainage systems under similar working conditions.

2.3 Head reserve

When the water contains sand, the water pump will wear for a long time, resulting in a decrease in flow rate and a decrease in head. When the maximum head of the high quality dredge pump is less than the working head, it cannot drain. Therefor, when selecting the dredge pump, the head reserve should be kept when selecting dredge pump model. In addition, since the high quality dredge pump pipe loss is calculated according to the 1.5-3 times of the pipe loss in clean water, which is a conclusion based on experience, therefore, for the design of uncertain conditions, it is also necessary to consider increasing the design head reserve. This is also one of the differences between the design and selection of clean water pumps and high quality dredge pumps. Based on past experience, the recommended head reserve:

Head 0-75m, head reserve 5-10m.

Head 75-160m, head reserve 10-20m.

Head 160-300m, head reserve 20-40m.

If the slurry concentration is high and the gravity ratio is greater than 30%, the head reserve needs to be increased by 1.5 to 2 times. Select the rated head of the high quality dredge pump according to the sum of drainage height, pipeline loss, and head reserve.

Design and selection personnel need to pay attention: the head of ordinary water pump has usage range. National standards and national quality inspection departments only require that the water pump should be used within the range of 0.7-1.2 times the rated flow(about 1.1 to 0.8 times of the rated head). High head water pump is not allowed to be used at low head. The rated head of high quality dredge pump selected according to the selection principle of this article, the head may exceed the usage range of the ordinary water pump in actual use(because the head reserve is large),so it is required to pay attention to the selected high quality dredge pump head.

After determining the rated head of the sand pump equipment, it is necessary to further check the rated flow of the dredging pump. Since the actual head is lower than the rated head in actual use, the actual flow is greater than the rated flow. It is necessary to check the rated flow and actual flow according to the performance curve of the sand pump. If the difference is not large, select the rated flow directly according to the design flow (as the sand pump wears, the actual flow will gradually decrease, so some reserve is also set aside.); If the difference is too large, the rated flow of the high quality dredge pump should be less than the design flow.

In addition, the OCEAN Pump dredging pump has the advantage of multiple units in series, which can reduce the cost of the drainage system. Users in need can consult our technical engineers.

3. Determine the slurry density and solid concentration, select the appropriate motor power

Water pump output power P = ρgQH

ρ——Density of slurry transported by pump

g——acceleration of gravity

Q——Flow of pump

H——Pump head

When choosing a high quality dredge pump, the slurry density must be considered. The slurry density is different and 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 also different. If the concentration is too high, the fluidity of the slurry is poor, and the power of the high quality dredge pump will increase significantly, which is easy to block the sand slurry pump and burn the motor. Therefore, the high quality dredge pumps stipulate the use conditions of the medium. For example: a kind of sewage pump, slurry density ≤1020 kg / m³, slurry concentration volume ratio ≤4%.

The user needs to check whether the allowable slurry density and slurry concentration of the high quality dredge pump meet the requirements of the working conditions. Not only is it easy to overload the motor when it is used over the range, but the life of the dredge pump will be greatly reduced.

There are two types of slurry concentration:

Solid volume ratio = total volume of solids in slurry ÷ total volume of slurry

Solid weight ratio = total weight of solids in slurry ÷ total weight of slurry

Solid weight ratio is a common way of expressing concentration. All data such as slurry research, calculation, design, type selection adopt weight ratio. The solid volume is relatively intuitive. Most users often talk about the solid volume ratio when describing the slurry concentration.

The method of accurately obtaining the slurry concentration is on-site measurement. The container can be sampled at the water outlet when the high quality dredge pump is working, and the solid weight ratio can be obtained by weighing and calculation, or the solid volume ratio can be checked after precipitation, and then calculated the solid weight ratio according to the solid specific gravity.

Comparison table of common material’s slurry density, solid volume ratio and weight ratio

Comparison table of common material’s solid weight ratio and slurry density (kg / m³)

As can be seen from the table above, the slurry density is closely related to the solid specific gravity and the slurry concentration (weight ratio and volume ratio).

It should be noted that the selection of high quality dredge pump must ensure the service life of the dredge pump under the premise of meeting the slurry density and slurry concentration. Even the clean water pump can extract mud and sand slurry, but the life is too short.

According to the maximum allowable value of the slurry density, the OCEAN Pump high quality dredge pump is divided into three grades, which are:

• Low concentration condition, density ≤1100kg / m³, all OCEAN Pump brand sand pump can be used, the main usage place: used in coal mining area, transport slurry containing coal slime and broken coal particles. The maximum allowable concentration (severity ratio): fine coal slime 29%, tailing slime 20%, quartz sand 15%, tailing sand 13%.
• High concentration working condition, density ≤1300kg / m³, some high quality dredge pumps belong to this category. Main use place: slurry transportation, or rock blasting construction drainage without specific measures to control the sediment content. Maximum allowable concentration (severe ratio): fine slime and tailing slime 40%, quartz sand 37%, tailing sand 33%.
• Ultra-high concentration working condition, density ≤1500kg / m³, some customized high quality dredge pumps are suitable. Main usage places: Professional sand mining, transportation of tailing sand, or thick slurry transportation without specific measures to control sediment content. The maximum allowable concentration (severity ratio): 60% fine slime and tailing slime, 40% yellow clay, 54% quartz sand, 48% tailing sand and 42% iron concentrate.

Remark:

• proportion value: fine iron ore 4.9, tailing sand 3.3, quartz sand 2.65, yellow clay 2.6, tailing slime 1.8, fine coal slime 1.45.
• The selection of high quality dredge pump suitable for other media is based on slurry density and solid proportion , referring to the above parameters.

Listed in the detailed list are A-grade and some B-grade dredge pump. C-grade dredge pump need to be customized by users. In addition, the motor power of the dredge pump in these three grades has sufficient surplus in design (1.3 to 1.5 times the affluence coefficient), so the anti-overload capability is strong during the sand discharge process. When the conventional sand pump work for a short period, the maximum allowable slurry density is ≤1300kg / m3, and the motor will not be burned. At this time, the service life of the impeller and other wearing parts is halved.

4. Confirm Voltage and Frequency

Domestic commonly used voltage: 380V, 660V, 1140V, 3000V, 6000V, 10000V.

Domestic frequency: 50Hz.

Commonly used voltages abroad: 220V, 400V, 440V, 550V, 690V, 1450V, 3000V, 6000V, 10000V.

Frequency in some foreign countries: 60Hz.

5. Determine the Maximum Particle Size to Prevent Clogging

5.1 Limited by the impeller flow channel and the blades numbers,the passability of each high quality dredge pump type is different, and the maximum pass diameter should be marked. When selecting the sand suction pump model, determine the maximum particle diameter before selecting the high quality dredge pump type or changing the number of blades. Make the suction salon head according to the determined dredging pump

5.2 OCEAN Pumpdesigns a large particle dredging pump, which is suitable for sand pumping conditions containing pebbles.

5.3 If the water contains impurities such as long fibers, you can take measures such as lengthening the filter or double-layer filter to prevent the filter from clogging so that the high quality dredge pumpdoes not pump water. If there are special requirements for the discharged medium, a separate customized plan is required.

Conclusion

These are to consider the solid passability, to avoid blocking pipes, blocking sand pumps, in order to maximize the advantages of dredge pumps, ensure the normal operation of sand dredging equipment, and allow users to get better results.

The above is how we choose and determine the parameters of the dredge pump from the aspects of flow, pipe diameter, head, supporting motor, and passability. Of course, to choose a suitable high quality dredge pump depends on the specific working conditions. The technical team of OCEAN Pump has more than 20 years of industry experience in designing and producing sand pump and sand dredger. W can inspect the construction environment on site, develop the construction plan and provide technical services in the whole process. Welcome to inquire us for more information!