Dual Shredder Screen Diverter for Wastewater Jam Prevention
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Solution Overview
Problem
Municipal wastewater pump stations face blockages and costly, labor-intensive 'pump ragging' due to large solids that exceed the capacity of twin-shafted shredders, leading to potential overflow and environmental hazards when standard solids diverter technologies fail to manage tough materials effectively.
Innovation Solution
A system with dual shredding devices and a rotating screening drum, controlled by a logic controller that alternates the direction of rotation to distribute solids and manage jam conditions, ensuring continuous operation and reducing the risk of overflow by redirecting solids to alternate shredders with different capacities and operational modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single shredder is used to reduce solids, then the device complexity is reduced, but the reliability decreases due to jam conditions causing shutdowns and overflow
Solution Approach 1:
The single shredding function is segmented into two separate shredders working in parallel. Each shredder handles a portion of the solids load independently, so if one jams, the other can continue operating. This segmentation of the solids reduction function resolves the contradiction by distributing risk while maintaining overall system reliability.
Solution Approach 2:
The system changes the operational parameter of having one large shredder to two smaller shredders with different capacities and operational modes. This parameter change allows the system to maintain continuous operation by switching between or operating both shredders simultaneously, resolving the reliability issue without excessive complexity.
2Productivity
If a twin-shafted shredder is used, then the solids reduction capacity is improved, but the device becomes susceptible to ragging when solids exceed orifice capacity
Solution Approach 1:
The solids stream is segmented into two separate reduction paths with two independent shredders. This segmentation prevents any single shredder from being overwhelmed beyond its capacity, reducing the likelihood of ragging conditions that occur when solids exceed the orifice capacity of a single large shredder.
Solution Approach 2:
Instead of using one shredder with excessive capacity that can handle all solids, the system uses two shredders with partial capacities that together handle the total load. This partial action approach ensures each shredder operates within its optimal capacity range, preventing ragging while maintaining overall productivity.
3Reliability
If solids diverter technology is added to protect the shredder, then the reliability is improved, but the device complexity and cost increase
Solution Approach 1:
The two shredders serve multiple functions: they perform solids reduction during normal operation and act as a protective system against tough solids during abnormal conditions. This multi-functionality provides reliability protection without requiring separate dedicated protective devices, thereby limiting the increase in overall system complexity.
Solution Approach 2:
The dual-shredder system is self-protecting through its redundant configuration. When one shredder encounters tough solids that could cause damage, the system automatically shifts load to the other shredder, providing self-service protection without requiring external solids diverter technology or complex control systems.
4Strength
If the shredder shuts down to clear jams, then the motor and equipment are protected from damage, but the productivity decreases and overflow risk increases
Solution Approach 1:
The second shredder acts as an intermediary or backup system that takes over when the primary shredder jams. This intermediary capability allows the system to maintain productivity during jam conditions without compromising motor protection, as the jammed shredder can shut down safely while the other continues operating.
Solution Approach 2:
The system provides beforehand cushioning by having a second shredder ready to handle solids when the first one jams. This prior preparation ensures continuous productivity is maintained during jam events, preventing overflow while the jammed shredder is protected from damage through controlled shutdown.
Data Source
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AI summary
A system for comminuting solid waste material including a casing defining a comminution chamber having two side walls and adapted for connection in a solid waste disposal channel. The system includes a first shredding device and a second shredding device disposed along a line extending perpendicular to a flow direction in the channel to form a pair of interactive shredding members. A rotating screening drum disposed within the casing upstream of the first and second shredding devices and positioned between the first and second shredding devices, the rotating screening drum configured to permit fluid to pass therethrough and to move solids toward one of the shredding devices. The rotating screening drum is configured to rotate clockwise and counter clockwise to alternately distribute solids captured thereon to one of the first and second shredding devices.