- Influence of short discharge distance construction on the dredge pump device
As we know, the design flow and design pressure of the single-speed dredge pump on the cutter suction dredger usually correspond to the characteristics of the pipeline under the design condition, that is, the rated discharge distance and height of the pipeline. At this point, the flow rate in the pipe is larger than the critical flow rate but less than the maximum allowable flow rate. The corresponding power of the diesel engine is the rated power. The normal and effective working range of the dredge pump device has been determined. When the project needs to be carried out under the condition of short discharge distance, the pipeline resistance becomes smaller, the total head required by the pipeline is low, the true suction cavity and the dredge pump flow become larger, and the slurry flow rate in the pipe will increase as the dredge pump flow increases. At this point, if the limit operating point of short discharge distance is exceeded, then the flow rate of the dredge pump, the velocity of slurry in the pipe, and the allowable suction vacuum of the dredge pump all exceed the limit value, the following situations will occur:
- The main engine of the dredge pump faces overload operation
The hazards are diesel engine speed decline, in the role of the governor, fuel injection reached the maximum, at this time the work cycle of the diesel engine is destroyed; Reduced efficiency; The combustion is not complete and the black smoke phenomenon is severe, resulting in the accumulation of carbon around the combustion chamber. The machine is subjected to excessive thermal load and mechanical stress, which causes accelerated fatigue of the stressed parts and causes various serious faults, even premature fatigue fracture of the crankshaft. Dredge pump transmission devices such as a clutch, gearbox, and coupling are also prone to failure.
- For the dredge pump, the flow is too large, the dredge pump may cause cavitation
Cavitation will not only make the dredge pump in the work of noise, but also cause violent vibration, displacement, head, and efficiency decline, dredge pump parts cavitation and damage, and serious will completely destroy the dredge pump, even stop discharging slurry.
- The velocity of the discharge pipe increases, and the wear of the pipeline increases
When cavitation occurs, the slurry concentration is usually very high. Once the discharge of slurry is interrupted suddenly, a large amount of high-concentration sediment deposits in the pipe, easily causing pipe blockage. The immediate effect is to stop dredging, delay construction, and pay for expensive repairs.
- Technical measures usually adopted for short discharge distance construction operations
In order to prevent the occurrence of the above situation, different technical measures are usually taken for different working conditions to adjust the dredge pump operating point, such as:
- A diesel engine with an improved fuel injector.
- Two dredge pumps with different heads, each of which has a diesel engine., work with a single pump, through the pipeline conversion, to adapt to short displacement work.
- The diesel engine is used at a reduced speed to reduce the driving power of the dredge pump.
- For the impeller with a small diameter, which is suitable for the construction of short discharge distance, the head and flow of the dredge pump are reduced accordingly.
- Use the following methods to increase the resistance of the discharge pipeline:
- Reduce the diameter of the discharge pipe.
- Increase the elbows in the pipeline.
- Install a throttle nozzle at the end of the pipeline.