Discuss the characteristics of the cutter suction dredger's dredge pump device

2021-12-06 13:59:13 Source: sand dredge pump-slurry pump parts-China Do Pump

News Digest:China Dredge Pump, Sand Pump China, CSD Pump, Discuss the characteristics of the cutter suction dredger's dredge pump device

Discuss the characteristics of the cutter suction dredger's dredge pump device. This article will determine the dredge pump and drive device by analyzing the characteristics of the dredge pump, the characteristics of the driving device, the characteristics of the pipeline, and the working point and range of the dredger pump device. The best matching working condition of pipeline and mud pump device. The discussion of the characteristics of the cutter suction dredger pump device is beneficial to greatly improve the working efficiency of the cutter suction dredger, thereby greatly increasing the efficiency of the enterprise and promoting economic development.

Keywords: cutter suction dredger; dredge pump; dredge pump characteristics; driving device characteristics; pipeline characteristics; working conditions

A dredge pump refers to an important equipment for continuous mud delivery through a pipeline on a cutter suction dredger. Mud pumps mainly include dredge pumps and driving devices (diesel engines that directly drive mud pumps), as well as clutches, high-speed gearboxes, and so on.

1. Features of dredge pump

The main dredging machinery of the cutter suction dredger is the dredge pump, therefore, the dredge pump plays an extremely important role in the muddy water dredging work. Cutter suction dredgers usually use centrifugal pumps as dredge pumps.

2. The main parameters of the dredge pump

The main parameters of the cutter suction dredger dredge pump include NPSH, power, flow, head, efficiency, speed, mud bulk density and slurry concentration, etc. Among them, the speed is a very key element that affects the performance of the mud pump. The cavitation margin is a parameter to measure the cavitation performance of the mud pump. Power refers to the input power of the mud pump, that is, the power transmitted to the shaft of the dredge pump by the driving device, and the output.
Power refers to the power delivered by the dredge pump to the mud pump when there is slurry flowing through it. It is usually represented by the letter Pe, then:
Pe=ρgQH/1 000 (kW) (1)
The power loss in the dredge pump refers to the difference between the input power and the output power, and the size of the loss is calculated by the efficiency η of the dredge pump. The shaft power at this time is:
P=Pe/η=ρg QH/1 000 η (2)

3. Mud characteristics

Those who have had practical experience all know clearly that in the actual dredging process, the dredge pump actually transports almost mud. In general, mud is a mixture of soil, water, and reamer. In addition, the distribution ratio among mud concentration, particle size, soil quality, and density all affect the characteristics of mud. Generally speaking, the various working parameters of mud and the relationship between them are consistent with the characteristic curve of clear water, but there are slight differences. The different degree ranges are related to the concentration, particle size, soil quality, etc. of the mud. The tendency of change is:
First, the particle size has a significant impact on the lift and efficiency of the dredge pump. When the delivered sand is coarser, the lift and efficiency decrease significantly. The particle size also affects the concentration on the performance of the mud pump. In the case of the same concentration, the coarser the sand, the greater the drop in lift and efficiency.
Second, with the same speed and flow rate of the dredge pump, the speed of conveying mud is slightly slower than the speed of conveying clean water; when the speed is the same, the pump lift and efficiency will decrease when the concentration is increased, and the rate of head drop is lower than The overall efficiency is that the higher the mud concentration and the coarser the particle size, the faster the lift efficiency will drop. The formula is as follows: H m =γm (1-k m P v) × H w (kPa) (H m and H w are the heads when the mud pump is pumping mud and clean water respectively) k m is the mud-sand coefficient (see Table 1).
Table 1 Numerical table of silt coefficient
Soil silt Fine sand Medium sand Coarse sand Gravel
k m 0 0.03 0.05 0.10 0.27 0.42 0.75
Third, when the mud is transported, since the mud mixture is more dense and its density is greater than that of clear water, it is assumed that the dredge pump rotates
With the same speed and flow rate, the shaft power of the dredge pump is greater than that in clean water, and it continues to increase with the increase of the slurry concentration, and the pump shaft power curve almost moves upward when the mud is being transported.
Fourth, the geometric parameters of the mud pump impeller will also have an impact on the performance of the mud pump. Under the same concentration, the performance of the mud pump with a larger outer diameter of the impeller decreases faster than a mud pump with a smaller outer diameter.

4. The characteristics of the drive unit

The driving mode of the mud pump is mainly diesel engine drive, electric drive, hydraulic drive and other forms. Among them, diesel engine driven dredge pump is the most common driving form of cutter suction dredger. For the diesel engine driven mud pump, the working conditions of the mud pump are closely related to the characteristics of the diesel engine: within the working range of the governor, when the load is decreasing, the diesel engine load will be below the rated torque point and the speed will remain constant status.
If the diesel engine works normally, it is generally in the governor working area, and its power is less than the rated power; if the diesel engine load changes in this area, the speed change of the diesel engine is relatively small, and the speed change of the diesel engine is mainly affected by the governor Impact.

5. Pipeline characteristics

The cutter suction dredger can only work safely when the pump device of the cutter suction dredger matches the characteristics of the conveying pipeline. The characteristics of the pipeline are related to the diameter of the mud pipe, the soil quality to be transported, the row spacing and row height, and various resistance losses, including the length of the pipeline.
The local resistance loss of the suction head, elbow, hose, valve, etc. There are many calculation formulas for the calculation of pipeline resistance. Due to limited space, I will not list them one by one here. The general formula used to calculate the total resistance loss of the pipeline is: H z =H s +H p (H s represents the resistance loss at the suction end; H p represents the resistance loss at the discharge end.

Working point of dredge pump

The working point of the dredge pump dredging device refers to the intersection of the characteristic curve of the mud pump driven by the diesel engine and the characteristic curve of the entire pipeline. Because how the working condition of the mud pump almost affects the overall dredging efficiency, it is important to choose a suitable and ideal working condition. Usually the steps to determine the best working conditions are: first draw the characteristic curve of the clean water of the dredge pump and the concentration of different mud at different speeds; then accurately calculate and draw the characteristic curve of the pipeline according to the actual situation of the pipeline; then the two Different curves overlap. The intersection point at each speed is the working condition point. Finally, select a more suitable working condition range from these working condition points and check whether there is overload in this range. The power of the diesel engine is corresponding to this Whether the range is fully utilized, so that the efficiency of the mud pump can reach a higher efficiency zone.

When discussing the characteristics of the cutter suction dredger's dredge pump device, full consideration should be given to the interrelationship between the dredge pump, dredge pump characteristics, driving device characteristics, pipeline characteristics and working conditions, so as to improve the work of the cutter suction dredger. Efficiency, improve the reliability of the cutter suction dredger device work. In actual dredging and dredging projects, with the continuous changes in row spacing, soil quality, and concentration, it should be possible to adjust the working range of the mud pump in time according to the matching of each curve to avoid adverse phenomena such as diesel overload and improve the efficiency of the dredge pump.

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