Engineering ships are mainly used in the construction of water conservancy projects, especially dredgers with dredgers as the main type. The dredging market meets the needs of the water transportation market. With the continuous expansion of international trade volume, the worldwide demand for large deep-water ports, wharfs and waterways continues to grow, thus promoting the development of the dredging industry. The development of the dredging industry has put forward new requirements for the design and development of dredgers. In the last few decades, the performance and function of dredgers have undergone tremendous changes. The design of dredgers is advocated to grow in large and huge sizes in order to pursue higher construction capacity and economic benefits.
The dredge design and development are much more complicated than those of ordinary ships. Because the dredger must not only have the necessary functions and necessary equipment for ordinary ships, but also have the functions of dredging construction, and need to be equipped with dredging equipment and other auxiliary equipment. The dredging equipment manufacturing industry itself belongs to the field of multidisciplinary and multi-industry specialized manufacturing. In addition. Modern dredgers have also widely used contemporary high-tech, such as DGPS, electronic chart, water level tele-reporting, various sensing technologies and computer technologies are fully utilized on the dredgers, the man-machine dialogue is becoming more and more perfect, and the dredging equipment is automated. Continuous improving. The development of modern high technology and its wide application on dredgers provide a wider space for the design and development of new dredgers, as well as for the selection of equipment for dredgers.
As a result, many new problems have been raised for the dredge design and development.
- Is the higher the technical performance of the dredger, the better?
- How to locate the specifications, performance and use of the dredger?
- How to balance the relationship between dredger specifications, performance and cost effectiveness?
1. How to locate the design goal of the dredger
Designing a dredger involves disciplines such as mechanical manufacturing, electrical and electronic, hydrodynamics, computer technology, automation science, materials science, marine meteorology and even nuclear physics, and belongs to the category of system engineering design. However, to determine the design and construction goals of the dredger, in fact, it is nothing more than two positioning methods.
- 1. Position the design goal of the dredger according to the specific project content.
In order to meet the needs of a specific project, specific performance indicators such as the dredging depth, soil-breaking capacity, and production capacity of the dredger are determined according to the dredging volume, digging depth index, and soil quality of the construction project. This design concept is not only widely used in general commercial dredging fields, but also in military, scientific research and engineering fields. The difference is that for dredgers that serve commercial projects, the goal of improving the performance of dredgers is to achieve higher production efficiency and conomic benefits, while dredgers used in military, scientific research and other fields meet the needs of specific projects. Relatively lower requirements for its economic performance.
- 2. The dredger is required to be able to undertake various types of projects around the world, and the specifications and performance indicators of the dredger are determined with the second goal.
Undoubtedly, the dredge design under the guidance of this concept inevitably requires the previous analysis of the aforementioned problems, and after balancing the pros and cons of various factors and obtaining reliable analysis data, the specific Design goals.
For a dredging company, it not only depends on its own ability to undertake dredging projects, but also tests the company’s investment and risk resistance capabilities. In fact, whether it is a dredge design and construction goal proposed for a specific project, or a dredge design and construction goal proposed for the purpose of being able to undertake various types of projects, the task should be proposed. Established after the dredger is built, there will be predictable engineering and market demand within a certain period of time.
Large cutter-suction dredgers built internationally are generally designed as self-propelled cutter-suction dredgers, while none of the previous cutter-suction dredgers have self-propelled functions. The purpose of designing the cutter suction dredger into a self-propelled cutter suction dredger with self-propelled capability is to pursue the ability of the cutter suction dredger to be able to achieve construction anywhere in the world. The cutter suction dredger is built as a self-propelled type, and sailing requires a huge price. To enable cutter suction dredgers to sail at sea, many problems need to be solved: such as strengthening the hull structure, increasing the hull size, increasing the propulsion system and other additional equipment required, all of which greatly increase the cost of ship construction and maintenance. . In terms of maneuvering, it also requires a high cost to equip qualified ship pilots. Even with the above disadvantages, the advantages of self-propelled cutter-suction dredgers are still very prominent compared with non-self-propelled cutter-suction dredgers. It can work independently, and can cross the ocean to carry out construction all over the world, which greatly reduces the time and cost required for dispatch. In addition, the self-propelled cutter suction dredger can also effectively avoid the huge risk of long-distance maneuvers of non-self-propelled cutter suction dredgers due to engineering needs.
2. Technical and performance indicators of the dredger
The performance index, work efficiency and economic efficiency of the dredger have been greatly improved than before. At the same time, the widespread use of high technology has greatly increased the construction cost of dredgers. This puts forward new requirements for the design work of the dredger to balance the reasonable unity of technical performance indicators and economic performance indicators, And pursue better dredge design effects.
- 1. Technical performance indicators
After the design specifications and use objectives of the dredger are determined, the specific performance indicators of the dredger need to be quantitatively determined. To determine specific technical performance quantitative indicators, the following issues should be focused on.
- 1) Navigation function
In theory, in addition to trailing suction dredgers that must have self-propelled capabilities, other types of dredgers (such as cutter suction, grab bucket, chain bucket, shovel) can be designed as self-propelled and Two forms of non-self-propelled.
A. Large dredgers requiring frequent long-distance dispatch should focus on their self-propelled capabilities.
B. Medium and small dredgers and dredgers that do not require frequent dispatch should not be designed as self-propelled dredgers.
- 2) Digging depth index
According to the purpose of the dredger, the digging depth index of the dredger is determined. Increasing the digging depth index of the dredger can expand the scope of use of the dredger. But it will inevitably increase the construction cost and production cost of the dredger. Take the cutter suction dredger as an example, analyze the following problems when determining its digging depth index.
A. The digging capacity of a cutter suction dredger depends on the characteristics of the equipped dredger. The digging depth index of cutter suction dredger is generally set at 18~20m. When the digging depth index is within 20m, no underwater pump is required, and when the digging depth index exceeds 20, an underwater pump must be equipped. This can be easily achieved by the design of the dredger.
B. The cutter suction dredger is equipped with underwater pumps, and many equipments need to be added, namely: the body of the underwater pump, the prime mover for driving the submerged pump, the connection between the prime mover and the underwater pump and the transmission device, and the need for additional Other equipment and materials. Under normal circumstances, for a cutter-suction dredger with the same clean water displacement (ie a cutter-suction dredger with the same row spacing and production capacity), the cost of equipping the underwater pump will account for three of the total equipment cost of the ship. More than one part.
C. In a project with a digging depth of no more than 20m, the construction cost of a dredger with a digging depth of more than 20m is much higher than that of a dredger with a digging depth of less than 20m.
- 3) Index of row spacing
Take the row spacing of cutter suction dredgers as an example (other types of dredgers generally operate by self-throwing or loading and throwing mud). The index and capacity of the cutter suction dredger’s row distance depend on the lift of the equipped dredger. At present, the head of the high-efficiency mud pump can reach 80-100m, and the maximum discharge distance can reach more than 2000m. To achieve a higher row pitch index, it is usually achieved by installing a series relay booster pump. If two in-cabin pumps are connected in series, the maximum row distance can reach 4000~5000m, while three in-cabin pumps are connected in series, the maximum row distance can reach 8000m. When the row distance is more than 5000~6000m, it can also be realized by using relay booster pump ship, pump station, etc. In the design of some large cutter-suction dredgers, the cutter-suction dredger is also designed to have the function of barge loading, which can achieve a longer row distance by loading and throwing mud.
- 1) Navigation function
4. Equipment selection principle
Generally, dredgers are under complex conditions with variable working conditions. Influenced by external factors, the frequency and amplitude of power fluctuations are large, and sometimes there are instantaneous impacts and stuffy vehicles. These factors have put forward harsh requirements on the main electromechanical equipment of the cutter suction dredger from different angles. In the dredge design process, great attention must be paid to whether the technical characteristics, performance, and technical parameters of the selected electromechanical equipment can meet the requirements of the dredger.
- 1) The concept of equipment applicability
In the dredge design work, it is a very important content to put forward the applicability requirements for the equipment equipped with the dredger. The applicability of the equipment means that the equipment fully meets the requirements of the dredger for its various technical indicators and performance parameters, while having good investment and economic efficiency. After determining the design and construction specifications and capabilities of the dredger, the equipment with better applicability is selected according to the dredger’s performance and capability characteristics.
- 2) Reliability requirements
Reliability is an inherent performance characteristic of equipment. Reliability refers to the ability of the equipment to work reliably within a given time under specified conditions and environments. Since dredgers are often operated under complex and variable working conditions, they have stricter requirements on the reliability of their equipment.
When selecting the main equipment of the dredger, the following characteristics of the selected equipment should be emphasized.
A. Whether the equipment can fully meet the technical performance requirements of the ship. When the dredger needs to work, can the equipment be put into construction work in a timely and reliable manner as required.
B. The pros and cons of the equipment’s uninterrupted continuous working time and performance changes.
C. It is estimated that the equipment can work satisfactorily without maintenance. D. Whether the selected equipment is a finalized product or a newly developed product. The finalized products generally have sufficient theoretical and empirical data, and the equipment ships are relatively reliable. However, products with an earlier finalization time may be technologically backward. The technical content of newly developed equipment is generally relatively high, but there is also the risk of immature technology. Therefore, when determining the specific target of the equipment, a comprehensive and sufficient balance argument should be made.
E. What are the consequences when the equipment fails? What is the price to pay to reduce or prevent failures?
F. What remedial measures can be taken after the fault occurs? How likely is the equipment to continue working in a malfunctioning state?
G. Under different working conditions and environmental conditions, such as the influence of temperature, weather, vibration, and shock on the equipment, how likely is it that the equipment can continue to work?
- 3) Maintainability requirements
The nature and working conditions of the dredger make the equipment equipped with it must deal with two problems. First, the equipment is often in a variable load and high impact working environment, which is more likely to fail and has a relatively short maintenance cycle. The second is that the dredging tool is basically in strong contact with the mud, sand and shimmering stones. The friction is strong and the wear is fast. It is necessary to replace the parts frequently, such as the dredger pump impeller, pump casing, liner, rake tooth, grab bucket Teeth, reamer teeth, etc. The above situation shows that the dredger also has high requirements on the maintenance performance of the equipment, and the equipped equipment should have good maintainability in order to pursue a long maintenance period and facilitate maintenance. Analyzing the pros and cons of equipment maintainability should focus on the following issues.
A. The maintenance cycle is the time the equipment can continue to work without maintenance.
B. The convenience of maintenance. It is the complexity of equipment disassembly and maintenance. This is also an important part of evaluating equipment technical performance.
C. The cost of equipment maintenance, that is, the expected indicator of the time and cost of equipment maintenance.
D. Solving the difficulty of repairing parts and accessories.
E. Service life, that is, the natural life of the equipment, that is, the number of years the equipment can work normally. For the dredger, the service life of the equipment should be more than 20 years.
F. Technical life span refers to the time concept during which the equipment does not lag behind in technical performance during its working period. Due to the rapid development of modern science and technology, it is more difficult in practice to maintain the equipment to be able to reach a relatively stable state in a relatively long period of time. As far as the dredger is concerned, its equipment should ensure that it will not lag behind for ten years, and that it can basically continue to work in a good technical state within twenty years.
G. Manipulative choice. It is to attach great importance to the simple, convenient and reliable performance indicators of equipment operation.
H. Pay attention to the standardization and generalization of equipment. In addition to special equipment, generally should pay attention to the selection of standardized, universal, and highly interchangeable equipment to facilitate equipment maintenance.
- 4) Selection principle of chain link type
The principle of chain link selection is to first determine the most important equipment, and select the matching equipment according to the technical requirements of the main equipment. From primary to secondary to secondary, the selection is performed level by level, forming a chain ring selection device mode.
4. The cost-effectiveness trade-off of dredge design
In the modern economic and social environment, it is almost impossible to have a design that only pays attention to technical performance without considering product economic indicators. The design of the dredger also exists on the basis of technical indicators such as applicability and reliability, fully considering the economic performance in use, and weighing the unified indicators of technical performance and economic performance, in order to achieve the goal of better design results.
For any engineering project design, a comprehensive and detailed cost-efficiency trade-off analysis and evaluation must be carried out. There are many types of cost effectiveness analysis and evaluation. This article does not introduce specific theoretical systems and analysis, evaluation, and calculation methods. In different designs, Leader Dredger can use specific analysis and evaluation methods according to actual conditions. Here, only the content that needs to be fully considered in the cost-effectiveness analysis during the design of the dredger is put forward to ensure the reliability and accuracy of the cost-effectiveness trade-off analysis.
The following tendencies exist in the design of dredgers:
- 1. Blindly pursue high specifications and performance indicators for dredgers, resulting in excessive investment costs and poor economic efficiency.
- 2. Pursuing low-cost investment in order to obtain higher economic returns, ignoring the basic level requirements of technical performance indicators, or even lowering safety indicators, the result is bound to be counterproductive.
- 3. In the selection and finalization of equipment, the lack of a full understanding of equipment technical performance and intrinsic quality and the basis for selecting the best products in the market makes the equipment selection unreasonable.
- 1. Investment scale
As mentioned earlier, the scale of investment (depending on the design and construction specifications of the dredger) depends on the foreseeable project, market demand, and the construction and economic capacity of the builder.
The investment scale should be carefully decided, and the specific design specifications and investment scale should be determined based on the market and the needs of the enterprise and the actual capabilities of the enterprise under the premise of full market research or greater confidence in obtaining market and project shares.
- 2. Cost efficiency trade-off analysis
The cost-efficiency and economic trade-off analysis of investment, design and construction of dredgers involves investment scale, expected report rate, investment payback period, risk index, etc.
5. Leader Dredger’s dredge design
- 1. The design tasks and objectives of the dredger itself are a systematic project that is related to multiple disciplines, new technologies, new processes, new materials, and the pursuit of new ideas. Therefore, Leader Dredger takes professionals with high theoretical quality, rich practical experience and a certain sense of innovation as the main body to make and make decisions on design specifications, tasks, and goals.
- 2. Based on the foreseeable project content, determine the specifications and goals of the design dredger.
- 3. High-performance and high-efficiency indicators are based on two factors, the function of the dredger itself and the performance indicators of the equipment. As far as the function of the dredger is concerned, we will adopt mature and advanced technology. For the selection of equipment, the correct design will be made after comprehensive evaluation of equipment reliability, maintainability, economy and applicability.
- 4. In the process of equipment selection, we will more accurately estimate the expected value of its natural life and technical life to avoid large deviations in equipment selection.
- 5. Cost-efficiency trade-off analysis and evaluation are extremely important content in the design work. The data used in the evaluation should be accurate and in line with reality in order to obtain the most reliable evaluation results.