Liquid Waste Technology (LWT) specializes in the design and manufacture of custom solutions for the dredging industry. LWT builds high quality computer and remote controlled portable dredges uniquely equipped for a variety of applications including:
- Wastewater lagoon dredging
- Water treatment plant maintenance
- Mine tailings
- Canal dredging
- Dredging w/ geo tubes
- Lake and pond dredging
- Marina maintenance
- Sand dredging
- Dredging mud and silt
Remote Control Dredges
Concept for Automated Solids Control Dredging
Totally automated and remote operations are achieved with low voltage electronic controls. A PLC (programmable logic controller) is programmed to provide control over the dredges automated functions and control loops, minimizing labor and maximizing production of solids at the set flow rate. This system is ideally suited for providing material to both de-watering and continuous process systems. LWT supplies components and will provide customized operational features to meet your specific operational needs.
Automatic Remote Control Dredging
Settled solids are excavated from the lagoon bottom by the LWT dredging unit which may be operated either remotely on shore and/or manually on board. The unit’s forward and reverse travel as well as its side to side lateral movements are totally automated by a steel rail system located on the ends of the lagoon.
Display and Controls
With a lap top computer or desk top computer, the owner can observe a visual graphical image of the system's entire operations while working, and record operating data. Controlled by the PLC, the electronic control system directs the dredge to make "sweeps" covering the entire lagoon, automatically without an operator. The dredge is programmed to travel forward at a controlled speed, taking eight foot wide passes through the solids bed. When the dredge comes to the end of the run it automatically goes into high speed reverse, slows the pumping rate, and travels until it reaches the initial starting point for that pass. The dredge then raises the auger head, shifts laterally to the starting point of the next pass, lowers the auger head, restores the slurry pump speed and moves forward to continue dredging. Incorporation of LWT's BOTTOM SENSE™ will "float" the auger head and allow it to follow the bottom contour or stay a set depth off the bottom.
Automatic Solids and Flow Control
The solids/flow control system is also controlled by the PLC. The dredge travel function is electronically linked to the density meter providing an electronic signal proportional to the density of the slurry, to the PLC. The PLC control look compares the incoming signal to the adjustable solids set point and continuously regulates the solids delivered by the dredge. The same principle is used to regulate the flow volume. An electronic magnetic induction flow meter provides feedback to the PLC control look which, in turn, regulates the flow delivered from the dredge slurry pump.
The NEMA rated control panel for the Automated Rail Lateral Move System has displays and input controls for the speed and direction of the slurry pump, auger and the traverse system. An alpha-numeric readout displays slurry density, slurry flow rate, and shutdown fault messages. The display may optionally show the location of dredge in the pond, depth of operations, slurry pump pressure or other required functional feedback data. This system is compatible for a continuous process system or supplying material to a tank for batch feeding a dewatering system.
Manned Dredges
Built for powerful, easy to control, effective dredging. The unit includes an industrial diesel powered hydraulic power unit, throttle controlled, hydrostatic high pressure circuit driving a submersible hydro-solids pump.
LWT LLC manufactures horizontal dredges for effective dredging and performance. These are versatile systems for fast, efficient, cost effective removal of sludge, sediment, residuals, silt, and sand.
Power Transmission
The transmission converts power to hydraulic flow for use by the hydraulic motor on the slurry pump and for the auxiliary systems. The power transmission is sophisticated, powerful and designed to maximum efficiency and performance.
To assure continuous dependable performance, LWT incorporates a direct drive, dual pump circuit hydraulic system with one pump serving the slurry pump, and another serving the auger and the auxiliary functions (i.e. pump elevation, auger, and travel). The slurry pump drive features a high pressure (4,000 psi), 90% efficient, dedicated hydrostatic transmission. The engine also direct drives a pressure compensated hydraulic piston pump which is continually matching the power available to the functions requiring it. The valving system allows the speeds of the auger, slurry pump and traverse system to be independently controlled with the speed pots mounted in the control panel so that operating one function will not have an adverse effect on another and require continuous resetting and adjusting of the controls. LWT has designed and placed pressure relief valves and pressure gauges on the circuits with dual oil cooling systems and separate oil reservoirs.
Control System
The PIT HOG™ hydraulic auxiliary functions are controlled utilizing an electronic proportional valve bank. The controlling switches and speed pots are reliable, simple to operate and eliminate potentially leaky hydraulic valves from the heated operator cab.
Operational circuits may have digital pressure gauge read outs on the operator control panel. The pump speed is throttle controlled, while the auger and travel speeds are controlled with speed potentiometer type dial throttles which are easily reset to previous operational values.
Slurry Pump
The working heart of any dredge is the power transmission and the slurry pump. The recessed impeller, cast iron pump with a minimum 6" solids handling capacity, provides efficiency, lower maintenance costs, superior performance and excellent wear characteristics for long life. LWT incorporates a flex coupler between the pump and hydraulic drive motor to assure that shocks on the drive system are minimized. Placing the pump immediately behind the variable speed auger head enables the PIT HOG™ dredge to remove maximum solids concentrations with a minimum of dilution. In operation, the removable cutter teeth loosens the material and the auger flighting conveys it directly to the pump suction. The auger shroud totally surrounds the auger and may be tilted to meet the sludge bank. The pump speed is easily controlled with a marine type throttle.
Click to view our LWT Brochure 2007.
ENEL Launches a New Automated PLC Controlled Dredge in Guatemala – Click here to view the case study.
