Kruse Controls Inc. was contracted to automate a DredgeMasters International Inc. hydraulic cutter suction dredge for Phoenix Pinelands Corp. of Barnegat New Jersey. The customer was interested in building a dredge that would produce efficiently logically and automatically with little operator intervention.
Kruse Controls is a system integrator in Baltimore Maryland operating since 1991. They have been producing dredge automation systems since 1996.
Phoenix Pinelands Corporation in Barnegat New Jersey mines a product that is 90 percent sand and 10 percent gravel. The principal owner is David C. Denise president. Robert L. Woodington is vice president and part owner. The dredge with an 18×16 HydraMaster HDM 42 pump and total installed horsepower of approximately 1750 is named after Woodington. Ordered from DredgeMasters in March 2002 the dredge had been delivered and was operating by late February 2003.
The Kruse Controls engineers produced their system by watching experienced dredge operators at work.
“No sensors can duplicate the eyes and ears of an operator” said Jay Wise vice president of Kruse Controls. The operator can tell which vibrations or other situations can be ignored. He can listen feel and sense what response is needed said Wise.
Engineers from Kruse spent months watching dredge operators’ responses.
If the dredge hits a wall in the middle of a swing they observed the swing winch pressure goes up there is no density and the cutter pressure goes down. The operator moves the ladder up a bit to get over the wall then moves it back down at the end of the swing.
After logging the response to this and other situations Wise developed algorithms that mimic these responses.
“The system has a lot of code” he said.
The end product that he installed on Phoenix Pineands’ dredge included automatic production control automatic swing speed control automatic swing direction control automatic line plug detection and corrective action logic automatic step forward logic automatic wall detection and corrective action logic automatic back-up logic alarms interlocks trends of pressures temperatures and production remote shore control DGPS logging and control and automatic ladder descent logic. Additionally the automation will keep track of equipment usage and produce automatic daily reports of tonnage alarms operator selections downtime and cutter depth with locations.
The integrated automation system includes an Allen Bradley PLC (programmable logic controller) an on-board industrial computer workstation with the graphical operator interface software a duplicate graphical operator interface workstation for the remote office an on-board industrial computer workstation with DGPS software an industrial uninterruptible power supply for the PLC and workstations two DGPS receivers and antennas for dredge heading and cutter location hydraulic valve control interface modules and wireless Ethernet modems for dredge-to-office computer networking. Additionally this system includes all necessary hydraulic pressure transmitters mag flow meter densitometer ladder inclinometer level probes discharge and vacuum pressures fuel flow transmitters voltage monitor transmitter oil pressure transmitters and temperature transmitters to feed information to the PLC.
The PLC and supporting components are off-the-shelf common industrial controls devices found every day in the industrial field. There are no levers or knobs on this dredge. All automatic and manual settings are operated through the workstation’s touch screen or the hand-held game pad controller.
The on-board graphical operator interface allows the operator to enter operating parameters limits settings and automation selections. Descriptive text alarming individual alarm defeat selectors historical trend charts touch screen slider controls for setting cutter speed ladder speed flow velocity manual swing speed stern winch speeds swing winch mooring tensions and manual engine speed features are incorporated into the operator interface. A hand-held game pad controller was included to allow manual winch operation as an alternative to the touch screen. This has proven to be handy while setting anchors.
The dredge has a DGPS (differential Global Positioning System) integrated on board. This system uses two antennas and DGPS receivers interfaced to a standard computer workstation running DREDGEPACKTM software. Dredgepack indicates the heading and location of the dredge and cutter superimposed on the coordinates of the customer’s sand mine. The actual cutter depth and location is indicated and logged every five square feet as it moves about the pond by plotting representative colors of depth on the screen. Through the onboard Ethernet network the PLC sends depth and cutter offset information to Dredgepack and receives heading and location in return.
Kruse Controls developed a software interface to communicate with the main pump engine’s electronic status and diagnostics interface system. All of the engine’s vital information is displayed monitored and trended on the graphical operator interface workstation.
The patented PLC programming code is the heart of this system. The code was developed through years of experience on board cutterhead dredges and compiles the experience of the best dredge operators dredging engineers and the staff at Kruse Controls.
The operator controls the ladder and cutter manually with the buttons and a speed control slider on the graphical operator interface workstation. Using the touch screen buttons or the game pad controller the operator can run or jog the ladder in either direction. The ladder jog buttons do not use the slider speed setting as do the RAISE and LOWER run controls. The jog feature is meant to be a fine tuning of the cut depth and should therefore be controlled at a slower speed. The jog speed can be adjusted by an operator entry value on the graphical operator interface workstation maintenance screen.
The PLC program has ladder operation interlocks built in. The ladder will automatically stop when rising if it gets to the preset minimum cutter depth or hits the ladder upper limit switch. There is a float switch located on front of the dredge which will detect if the front of the dredge is pulled down by the ladder being stuck when rising. The float switch will disable the ladder-up motion. The ladder will automatically stop while lowering if it reaches the preset maximum cutter depth.
MANUAL WINCH OPERATION
The forward and stern winches can be manually operated with the buttons and a speed control slider on the “winches” screen. The winch payout and pull in speeds are set by a single slider control that will control the payout and pull in speed from 0 to 100 percent. The setting of the forward winch’s slider is ignored during swing mode. When the forward winches are being operated from the “winches” screen the swing control is disabled. This manual operation is for setting the anchor installing cable testing the winch or for maintenance purposes. If a winch is running in the manual mode all workstation screens will indicate in red that the operator has a winch running in manual mode. The winches can be jogged from the workstation or via the game pad controller.
Each of the winches has an operator entry setting for pressure limit and pressure alarm on the maintenance screen. The winch hydraulic pressure can be limited through the PLC program. Although the hydraulic system has physical limiting orifices it is possible to limit the hydraulic pressure to the winch via the pressure limit operator entry on the maintenance screen. As the indicated pressure approaches the set limit the PLC output is limited regardless of the winch slider speed control setting. If the hydraulic pressure exceeds the alarm setting an alarm will sound and the appropriate fault text will display on all of the alarm banners found on any of the screens.
The swing system can be operated in manual or automatic mode by the swing mode selector on the workstation main status screen. If the swing mode is in manual the swing direction is controlled by the dredge operator. Touching the swing port button on the screen will swing the dredge to port. Touching the swing starboard button will swing the dredge to starboard. An animated arrow will flash green on the button in the direction of the swing. The swing direction can also be controlled via the hand-held controller.
If automatic swing mode is selected the dredge will automatically reverse direction upon reaching the preset headings. While in the automatic swing mode it is still possible to use the swing direction buttons.
The swing speed can be operated manually or automatically. If the swing speed is in manual the speed is determined by the operator swing speed slider on the main status screen. If the swing speed is in automatic the speed is determined by the PLC program based on the operator-entered TPH (tons per hour) setting. As the actual TPH production (determined by the on board flow and density meter) drops below the operator setting the swing speed will increase to improve production. As the TPH production increases above the operator TPH setting the swing speed will reduce even stop to maintain production settings. When swinging the opposing swing winch will be in the mooring mode allowing it to pay out or pull in as needed to maintain the operator preset tension.
Because the cutter rotates forward in the port direction the PLC program monitors the hydraulic pressure of the forward port swing winch while swinging to port. If the pressure is below normal operating parameters the program assumes the cutter is “walking” the dredge to port and automatically increases the mooring tension on the starboard winch.
Each screen has an emergency backup button in the top left corner. When pressed the outer stern winch brakes are automatically released the forward winches are automatically set in the mooring mode and the center stern winch hauls in at the operator speed setting. This feature can be used to quickly back the dredge from a hazardous situation when necessary.
The PLC program incorporates an automatic feature to step the dredge forward following a sweep determining low production. Once the TPH production drops below the operator entered preset for an entire sweep the dredge will automatically step forward a preset distance and continue to swing the same arc and depth in the new location. This automation feature is selectable as an option to the automatic ladder descent feature which lowers the cutter a pre-set distance following low production recognition.
The PLC logic monitors the system to determine if the pipeline is in danger of plugging. If the parameters are beyond the pre-set values the dredge pauses swinging and the ladder rises several feet until the plug is cleared and the ladder will automatically descend to the original depth and continue swinging. If the original depth is not achieved due to sloughing of material the ladder will automatically settle at the new depth and continue to descend in the swing corner.
There is programming logic built in to determine if the ladder angle isn’t changing while it is rising. This scenario will assume that the ladder is stuck and will cease to raise the ladder while sounding an alarm. Additionally there is a tilt float switch located on the bow of the dredge to determine if the bow is being pulled under. Upon activation the automatic ladder raise is disabled.
A duplicate workstation in the office is used to monitor the operation or run the dredge remotely. It is also used to collect production data for daily reports of production downtime efficiency depths locations and operator entry changes.
DREDGE DESIGNED FOR EFFICIENCY
DMI designed this dredge with many special features to meet Phoenix Pinelands’ specifications for a high-powered efficient dredge able to accommodate an automated control and production monitoring system.
The 200 ton (dry weight) dredge is 145 feet long by 34 feet wide with a five-foot draught. Main power is by an electronically-controlled Caterpillar 3512 DITA SCAC marine auxiliary engine rated 1478 BHP @ 1200 RPM through a mechanical drive. The dredge is capable of dredging at ladder angles of up to 60 degrees. A Caterpillar 3306 DITA engine rated 275 BHP @1800rpm provides power for the cutter drive and all winches and for a 20 kW AC electric generator.
In addition to its automation features the dredge has a special noise control package which includes critical grade mufflers and acoustic insulation of the machinery house. The machinery house also features high temperature exhaust insulation spill containment dams and slip resistant rubber matting in walkways. The dredge operator control cabin has air conditioning and heating two consoles that house the computer and GPS equipment an adjustable operators chair carpeting insulation and tinted windows that allow 360 degree visibility. Noise levels inside the control cabin measure 65 decibels during dredging operations. A separate 12 kW gen-set with an automatic start timer is used to power the main engine coolant heaters so that the main engine is at a suitable starting temperature as soon as dredge operators arrive in the morning. The 12 kW generator also provides power for service work without having to start the auxiliary engine to power the main generator.
DMI is located in Hendersonville Tennessee.