Presentation on theme: "Dredge Line Presentation"— Presentation transcript:
1Dredge Line Presentation SRS CrisafulliDredge Line Presentation
2Flump – Remote Controlled, Unmanned Electric Dredges
3Features and Capabilities Electric poweredDirect drive from motor to pump increases efficiencyElectricity from the grid eliminates refueling and is usually the cheapest source of powerRemote sites require a generator or installing electrical serviceAll power is transmitted to the dredge through a single cordWireless remote controlHandheld transmitter controls pump, speed, direction, and depthOperator does not need to be floating out in a lagoonLimit switches and automatic sequences are available, limiting the amount of supervision that is necessaryFLUMPFeatures and Capabilities
4Features and Capabilities Cable traverse onlySimple, straight, repeatable dredging passesLowest power requirementsTraverse distances over 500ft (150m) are not recommendedRequires more tension and stronger anchors to keep cable tightIf the cable droops below the water surface, the floating discharge line may float over it and get tangled as the dredge approachesSlack in the cable allows the dredge to drift side-to-side or twistFLUMPFeatures and Capabilities
6Features and Capabilities Diesel poweredSelf-contained power systemNo power cord to string out with the discharge lineSelf-propelled by hydraulic thrusterDischarge length not limited by traverse cable or power cord lengthsOptional cable traverse drive can supplement self-propulsionOperator on board for better situational awarenessOptional air conditioned cab enhances operator comfortFoam-filled aluminum (SD-110) or steel (6000) pontoonsVariable-speed pump powered by hydrostatic driveRotomite SD-110 and 6000Features and Capabilities
7Cable Traverse System – Drawing of a four-post layout ANCHOR POINTCable Traverse System – Drawing of a four-post layout
8Cable Traverse System Setup Considerations Figure out:Which direction to dredgeHow the discharge line should be routedHow the electrical power gets to the dredgeWhere to put the anchorsHow everything will adjust as the area is coveredCable Traverse SystemSetup Considerations
9Cable Traverse System Operation Begin dredgingAdjust speed and depth for optimum solids flowIdeally, those settings can be maintained and the dredge will not require further operator input until the end of the traverse is reachedCable Traverse SystemOperation
10Cable Traverse System Operation At the end of a dredging pass:Flush discharge line with waterTurn off pump and reverse dredgeAfter the dredge has returned to start:Lower cutterhead to new depth and resume dredging forward along the traverse cableAfter the desired depth has been reached:Adjust the lateral cables so the dredge follows a new path next to the previous oneCable Traverse SystemOperation
14Cable Traverse System Considerations Most effective and efficient system for rectangular lagoonsEffortlessly keeps the dredge going in a straight lineLess power required to keep the cutterhead pushing forwardAllows the dredge to travel back and forth in the same path, digging deeper with every passLess pronounced effects of wind/current pushing on the dredgeTraverse distances over 500ft (150m) are not recommendedRequires more tension and stronger anchors to keep cable tightSagging cable may get tangled with the discharge lineSlack in the cable allows the dredge to drift side-to-side or twistIt is MUCH easier to install and operate the dredge if the water is deep enough for it to float over the material.Cable Traverse SystemConsiderations
15Notice the traverse cable and dredge being pushed out of line. This happens when the dredge cut is not symmetrical.The effect is more pronounced as the traverse distance increases.
16Floating Discharge Line Rigid floating pipe with hose flex sections in between.Solid foam floats are pressed onto the pipe and extremely durable.
17Liner Protection System Removable wheels and cage keep the cutterhead from digging down through a solid lagoon bottom or snagging part of the liner.
26Dredge Performance: Budgetary Estimates Centrifugal pumps are limited to fluids with a specific gravity less than A dredge can usually be operated to maintain 1.3.Dredging at 15% solids is usually very good.Wastewater sludge is not just dirt mixed with water.There are other effects such as viscosity that are hard to account for.The same Flump that produced 20% solids has had trouble producing 6% solids in wastewater.Settled sludge usually can’t be pumped at its original consistencyThinning the sludge with water increases its volume1 cubic meter at a 1.5 specific gravity doubles in volume to 2 cubic meters of sludge after it is mixed with water to a specific gravity of 1.3Dredge Performance:Budgetary Estimates
28There are many different methods for dewatering There are many different methods for dewatering. Which is best depends on many factors and cannot be determined until all aspects of a system have been evaluated—which is a job for consulting engineers.Non-Mechanical: Geotextile Tubes, Drying BedsMore simple in nature, no moving partsRequires less energy, but more spaceMechanical: Filter Press, Belt Press, CentrifugeSmaller footprint, maybe less affected by rainSubject to breakdowns and maintenanceDewatering Methods
29Ecotube Geotextile Bags Geotextile fabrics are designed to filter water out of mud and other sludges.Pump the slurry into them and let water drain out.Dewatering:Ecotube Geotextile Bags
30Ecotube Geotextile Bags Flocculants and coagulants are usually added to the mixture to make the solid particles settle faster.Dewatering:Ecotube Geotextile Bags
31Ecotube Geotextile Bags The water that seeps out of the bags can be collected and pumped back into the lagoon.That extra water will keep the dredge floating and mixing the material to a proper pumping consistency.Dewatering:Ecotube Geotextile Bags
32Requires Further Research Geotextile bags are usually the best choice for dredging operations, as they are extremely easy to understand and use and are able to handle directly whatever flow the dredge can produce.This is the first (and currently only) method SRS Crisafulli evaluated for this project. Research into other possibilities is still underway.Preliminary Results:As reported to SRS Crisafulli, the total volume of all San Jose and Pampa de Perros primary, secondary, and tertiary lagoons equals well over 400,000 cubic meters of material.The bags alone to contain that volume will easily cost over $3 million. Hiring engineers to determine the best system would be a worthwhile investment!Dewatering Method:Requires Further Research
33Determine the acceptable balance of cost and speed for this project. How much funding is available for this project if it takes one year?What if it takes two years? Five years?How much of the project must be done right away?Will it be sufficient to dredge a portion of the lagoons immediately, then use a slower, smaller-scale method for the rest?Will these lagoons need to be cleaned again in 15 years?How will it be done then?Will a continuous dredging process and permanent dewatering facility be set up to keep this situation from happening again?What is the next step?
34For large projects like this, dewatering is always more costly than dredging. Geotextile tubes will cost the same whether the project takes one year or two because they hold a limited volume and cannot be reused.Drying beds will increase in size and cost as the rate of dewatering increases.Mechanical dewatering systems can be purchased in varying sizes and quantities to accommodate the desired dewatering rate.Mechanical dewatering systems are not one-time use and can be permanent installations or portable facilities.The optimum size and quantity of dredges can easily be matched to the dewatering system that is chosen.Deciding Factors