1.1 Basic requirements for dredge pump selection
In general, the design of dredge pump must take the needs of dredging market into account , and it must have a large range of application, and it will not be designed for specific environment.
In the design of the dredge pump, the maximum flow rate, head and stability of operation of the dredge pump should be considered firstly, economic factors should also be considered. the material of pump body parts should be reasonably selected, At the same time, the maintenance and management should be convenient. Dredge pump without hump operation characteristic curve should be selected as far as possible.
With the development of dredging market, the requirements for dredging equipment are becoming higher and higher, and the suction resistance and vacuum of dredging pump are also increasing, which has a great impact on the working efficiency of dredging pump, and the probability of cavitation corrosion of dredging pump is also increasing. Especially when the dredging depth reaches more than 20m, the above situation will be more obvious. The use of underwater pump can effectively improve the above situation, the lower the installation position of underwater pump, the less the suction resistance and vacuum, which can obviously reduce the loss in the working process, improve the working efficiency. The installation of underwater pump can effectively increase the depth of dredging and improve the capacity of transporting sediment. By cooperating with the dredging pump in the ship, it can improve the intake of soil, expand the use range of dredge pump and reduce the power loss of the primary engine.
In the construction process, if the flow rate and indenter of the dredge pump exceed the actual needs, it may cause the overload of the primary mover. For short discharge length, although the flow can be limited by installing a nozzle in the pipe head, it will affect the throttling energy of the pipeline and cause more unnecessary waste. The characteristic parameters of the dredge pump can be changed by cutting the outer diameter of the impeller of the dredge pump, which can expand the range of use of the dredge pump. In order to avoid too much influence on the efficiency of the pump after cutting the impeller, the permissible cutting amount of the impeller varies with its specific revolutions. The impeller with low and medium specific revolution should be cut with equal outer diameter, and the impeller with high specific revolution should be turned obliquely, so that the outer diameter at the front of the blade is larger than that at the back cover. The diameter must meet the requirements for the amount of turning.
1.2 Multiple Pumps in Series
When the discharge length increases, the resistance of the pipeline will increase continuously. A single dredge pump cannot meet the requirements of construction, so the series operation of multiple pumps is required. When multi-pump series operation is carried out, each dredge pump must be consistent. It is better to choose the same type of dredge pump for series operation. If the same type of dredge pump cannot be selected, it is also necessary to choose one with similar performance. When the dredge pump with similar performance is connected in series, its flow must be equal. The theoretical indenter is also equal to the sum of the indenters of the grounded green pumps in series, but in fact, the indenters are too small. If multiple pumps are used in series, it is possible to operate one or several dredge pumps with different performance under excessive load, while other dredge pumps are not fully loaded. Thus, the power of all mud pumps cannot be fully utilized. During the series operation of multiple pumps, areas with high pressure may cause the dredge pump to bear mechanical stress and load beyond the upper limit, and cause different degrees of wear of the dredge pump’s original parts, so as to damage the dredge pump in advance and increase the engineering cost.
1.3 Working Conditions of Series Pumps
For the condition with long discharge length, the best construction plan is to install multiple oil pumps in series in the mud pipeline to form relay pump. A certain distance must be maintained between the mud pump and the series pump. When installing relay pumps, the compatibility of each pump should be guaranteed, mainly considering the characteristics of dredging pumps and the connection of mud pipes. The relay pump should be installed at an inlet pressure of around lkg/cm2. Normally, the discharge length is not always fixed in one position, but needs to be constantly adjusted according to the needs of the project. Relay pump installation position will generally choose the smallest discharge distance, in order to install with the relay pump. If the selected relay pump is too small, it will increase the resistance in the cabin, affecting the efficiency of dredging. If the relay pump is too large, it will become a suction pump, which will have a certain impact on the safety of the project.