1. Land tube of cutter suction dredgers

 

  • According to the topographic conditions, natural conditions, engineering geology, project quality, and construction period, the pipeline scheme is determined, and the route, structure, and location of the mud discharge pipeline are arranged. If we analyze the long construction period of this project, which lasted for summer and winter, considering the material’s scalability under the influence of temperature, one rubber hose is connected every 200m or so to avoid the pipe flange connection pulling, expanding, and cracking, and mud leakage and water running during the construction of summer and winter festivals.

 

  • Set the routes straight and flat as possible, avoid sharp bends, uneven heights, and obstacles, and choose the economic route with slow slope and easy to install, dismantle and maintain pipelines; If the ship is shut down for a long time during the winter construction, it is necessary to release the water in the pipeline, otherwise the pipeline may be damaged, and consider the appropriate water release position in advance.

 

  • Simplify the construction plan, reduce the gate valve, 90°elbow, and other pipe accessories with high resistance, and reduce the hydraulic loss of the mud discharge pipe; For long discharge distance production, ship productivity is greatly affected by pipeline length (discharge distance), and some accessories can be reduced as far as possible, which can improve ship productivity and reduce cost. When laying the land pipeline, considering the filling quality’s smoothness’, many nozzles are laid out, and at least one gate valve is laid for each additional nozzles; In the implementation of this project, only two nozzles are provided during production. We placed the gate valve at the position of the first nozzle (the nearest nozzle, the transition nozzle). when the pipeline needs to extend or change to other position, first pour to the transition port and then make the nozzle temporarily, and then switch to the newly constructed nozzle, the middle of the pipeline is only a gate valve, and the nozzle can be arranged in any position needed to ensure the filling quality.

 

  • The location of the land joint should consider the influence of tidal range change to avoid excessive tension cracking and disconnection of low water level pipelines, and take precautions when connecting pipelines.

 

  • When making the nozzle, it is necessary to consider the design elevation of dredger filling, settlement and smoothness requirements, and do it well at one time, so as to avoid re-laying and affect the utilization rate of production time of ships.

 

  • The valve adopts a spiral gate valve or pinch valve. When the nozzle is switched, it is not necessary to remove the pump from cutter suction dredgers and stop production, which obviously improves the time utilization rate and production efficiency of the dredger.

 

  1. Underwater Pipe (Dive Pipe) of cutter suction dredgers

 

  • Measure the expanded range of the planned pipeline route location, find out the underwater terrain, so as to determine the arrangement of pipeline construction. For example, in the construction of Weifang Port, part of the pipeline is from shallow water depth in the area, after surveying, according to the tidal time, we dynamically adjust the operation sequence and arrange the operation to shorten the construction preparation time.

 

  • According to the surveying map, careful analysis is made to determine the specific route, structural form, and total length of the pipeline; in the early stage of port construction, the pipeline changed little from the upper water depth, and the slope was relatively slow. We used the 4+1 structure for the underwater pipe. In the later stage, considering back silting, We used a 4+1 structure for the underwater pipe. In the later stage, considering back silting,  The pipeline changes quickly and greatly from the upper water depth. Considering that the flexible pipe is more adaptable to the terrain, the underwater pipe adopts a 3+l structure, and some positions adopt a 2+1 or 1+1 structure.

 

  • Install blind plate for the pressure test to ensure water tightness; The maintenance of underwater pipe is more difficult than that of land pipe, so we should try to make full preparation in advance to reduce the rate of fault. After the assembly of the underwater pipe, we should conduct pressure tests to find and deal with problems in time, avoid finding problems in production, handle them, increase the difficulty and intensity, and delay production.

 

  • According to the specific situation, section or whole sink; It is necessary to consider the wind, water flow, and route topography to determine the way of sinking. Sea waves are big, the flow is fast, and the underwater pipeline is too long, so the working ship cannot control the pipeline ideally. The quality of the submerged pipeline is not good, regardless of the appropriate, not on the scheduled route. At this time, the subsection method is adopted to ensure the quality of the pipeline sinking. The segmental sinking pipeline is difficult to handle at the joint of the pipeline. Especially when it sinks at high tide, when it is not handled properly, the position of the hose is easy to be discounted and damaged.

 

  • A “pontoon bridge” is used for the line within a certain length. The pipeline may be damaged by wear or accident during construction. When the pontoon is set up, it can be repaired quickly to reduce the shutdown time of the ship. When sinking pipelines in sections, a pontoon bridge is used at the connection of sections, or to avoid bending and abrasion of rubber pipe at the connection. The two ends of the pontoon bridge enter the water. According to water depth and tidal variation, a semi-float tube or semi-float tube + zero buoyancy tube structure is adopted. When we construct the harbor project, we adopt the form of a pontoon bridge and get a good result.

 

  • Before pipeline floatation or at the end of dredging, clear water must be dredged to remove the mud in the pipeline, so as to avoid blockage or pipeline floatation during reproduction.

 

  1. Water Pipe (Floating Pipe) of cutter suction dredgers

 

  • In the construction, we basically adopt 1 + 1 structure, choose the rubber hose with good quality and high-pressure resistance. The float pipe itself is under great pressure during production, and it also withstands the stress of water flow and wind flow, choose a suitable hose is not easy to be damaged.

 

  • The three tapes on the pontoon are all clamped, and the tightness is checked regularly to avoid the misalignment of the pontoon and wearing the rubber hose.

 

  • The self-floating pipe with a strong ability to resist wind and waves is adopted for construction in the water area with heavy wind and waves can significantly increase the interest rate of ship production.

 

  • The float pipe anchor cable is tied to the pontoon bollard to avoid the wear of the pontoon and the anchor cable.

 

  • The anchor cable is directly wound around the discharge pipe, and the wear-resistant anchor chain is adopted for the part in contact with the pontoon, so as to avoid the breakage of the anchor cable with large wind flow, which may delay construction or cause safety hazards.