Home / Industries / Pulp and Paper / Sample Project

Canadian Forest Products Limited
(Prince George Pulp and Paper Mills), Prince George, BC
Wireless Ethernet Network for Remote Control of Chip Receiving System

Background

Canadian Forest Products Ltd.'s Prince George Pulp and Paper Mill receives wood chips from suppliers by railcar and by truck. In 1999, a new railcar/truck dumper, chip conveyor and flinger system was built to replace the existing dumper and chip blow line. A chip receiver, who sat in the chip receiving office, controlled the system through an RSView interface to a PLC5/40. The RSView interface enabled the chip receiver to control the dumper and the chip delivery conveyors and flingers.

The dumper had three modes of operation: Rail Hand, Truck Hand, and Truck Auto. In rail mode, the railcars are pulled onto the dumper by one of two trackmobiles. Once the trackmobile has positioned the railcar to be dumped, the trackmobile driver must push a dump enable pushbutton that allows the chip receiver to take control. In either of the truck modes, the truck driver waited off of the dumper for the chip receiver to change the truck traffic light to green and then drove the truck onto the dumper. Once a truck had been driven onto the dumper, the driver gets out of his truck prepares it for dumping and then pushes a dump enable pushbutton that allows the chip receiver to take control of the dumper.

Part of the chip receiver's duties was to enter the railcar or truck gross and tare weights and the railcar or truck number into the Chip Receiving software (TOPS4). The TOPS4 software runs on a second PC that is attached to the mill network and communicates to the Fibre Supply Department's chip accounting database.

The chips are dumped from the railcar or truck into the chip dump pit. From the chip dump pit two reclaim chains move the chips onto a short conveyor that in turn dumps the chips onto the main conveyor that takes the chips to the plows and flingers that direct where they will be dumped on the chip pile.

A bulldozer is used to manage the chips while they are on the chip pile and to push the chips into the reclaim chutes. In order to control where the conveyor and flingers are dumping the chips, the bulldozer operator would talk to the chip receiver on the radio and let him know how the equipment should be set up.

Purpose

Canfor management decided to reduce the workforce in the chip handling area by getting rid of the chip receiver position. In order to get rid of this position, the method of controlling the system had to be modified to allow control by the trackmobile and bulldozer operators without them having to get out of their vehicles and go into the control room. Also, the system in the Chip Receiving office had to be modified so that the truck drivers could dump their trucks without any mill personnel being normally required. Andritz Automation was hired to design and implement a system to do this.

Functional Specifications

Through discussions with both mill operations and engineering personnel and by direct observations of the operations, we developed a list of points that would have to be addressed in order to allow the chip receiver's position to be eliminated.

• Give operators in the trackmobiles the ability to control the chip dumper.
• Add a Railcar Auto sequence to the PLC program.
• Allow the operators in the trackmobiles to view the camera feeds.
• Give the bulldozer operator the ability to control the main chip conveyor, flingers and plows.
• Have gross and tare weights automatically imported to the TOPS4 software.
• Have the railcar number automatically imported to the TOPS4 software.
• Set up a simplified control screen on the control computer for the truck driver to start and stop the chip dumper.
• Install a sensor to determine when a truck is waiting to move onto the dumper.
• Add a new camera to look into the chip dump pit.
• Install a level detector that can be used as an interlock to stop a railcar or truck from being dumped if there are already too many chips in the bin.
• Enable BC Rail to phone in and get on the chip receiving radio system to get hold of personnel working in the area.

System Configuration

Wireless Ethernet Network - In order to control the dumper and the conveyors from the trackmobiles and the bulldozer, Andritz Automation proposed to implement a wireless Ethernet network through which vehicle mounted computers running HMI software would communicate to the PLC, thus enabling control from the vehicles. In consultation with Canfor, Allen-Bradley RAC6182 touchscreen industrial computers were selected for the HMI unit because they are totally solid state and designed to withstand shocks and vibrations that they would likely experience being mounted in the vehicles. Since the RAC6182 runs under the Windows CE operating system, RSView32 Machine Edition was selected to be the HMI program to develop the control screens for the control from the vehicles. The main drawback with using the RSViewME from the mill's perspective was that the screens and database that had been previously developed on RSView32 for the control station in the chip receiver's office would not be able to be used since RSView32 and RSViewME are incompatible.

The RAC6182 computers only come in a 120 Vac version at this time, so to provide power for them a Xantrex Prosine inverter was specified and mounted in each trackmobile and the bulldozer. The unit was wired into the 12 Vdc power system on the vehicles with a relay in series that allows power to be applied to the inverter only when the ignition key is in the run or accessories positions. The RAC6182 computers are mounted in a custom-built aluminum boxes. The boxes are mounted in the vehicle cabs using rubber shock absorbers.

In order to implement an Ethernet network, the existing PLC5/40 was replaced with an Ethernet capable PLC5/40E. The Ethernet network was built around a main network cabinet located in the electrical room. A switching hub was located in the cabinet into which were plugged the master radio modem, the PLC5/40E, the Main control RSView32 computer, a computer for programming the PLC, and a video/network adapter. The remote units in the vehicles communicate to the PLC via slave radio modems located in each vehicle. The modems used were Datalinc SRM6210E modems configured for Point-to-Multipoint communications.

An external antenna was mounted on the chip dump building for the master radio modem and external antennas were mounted on each vehicle. Initially the whip antennas that were supplied with the radio modems were used on the vehicle units. They worked well close to the building but communications errors occurred when the vehicles got further away so the external antennas were installed on the vehicles and this cleared up the communications problems. Additionally, a repeater radio modem was installed on the main chip conveyor so that the bulldozer remains in communications when it goes over the back of the chip pile and has lost sight of the chip dump building.

Automatically Reading the Railcar Number - The railcars that the chips are delivered to the mill in all have Radio Frequency ID tags mounted on the side of them. Each railcar has two tags with the same information encoded on them. One tag is attached on each side of the car. Two Amtech Smartpass 1620 tag readers were installed on either side of the chip dumper. The readers interrogate the tag as the railcar is pulled onto the dumper. The Smartpass readers are connected to the computer in the chip receiving building that runs the RSView32 application by serial cables. A Visual Basic routine was written to take the raw data from the tag readers and strip out the extra data and get just the railcar number. The railcar number is then written to a string word in the PLC where the TOPS4 software can read it.

Chip Receiving Software/Dumper Control Integration - Canfor decided that rather than try to give the operators in the Trackmobile the responsibility for entering the data into the Chip Receiving software (TOPS4) that the data would be entered automatically and operator intervention would only be required if there was an unusual circumstance. To accomplish this the TOPS4 software had to be revised and the PLC program had to be revised to communicate the status of the dump cycle. A KT card was installed in the computer running the TOPS4 software and a DH+ link to the PLC was installed. The PLC sets bits to tell the TOPS software to take a gross weight, read the railcar number, and take a tare weight. The TOPS sends back bits to the PLC to tell it that a gross weight has been taken, the railcar number has been read, a tare weight has been taken, and that a sample is required. If a sample is required, then the PLC sends down the sample bucket at the correct time.

Remote Video Viewing - There were three cameras and associated monitors located in the chip receiving office. Since the operators are no longer sitting in the office where the video monitors are located, they needed the ability to see the camera views in the vehicles. In addition, they needed to be able to see into the chip dump pit. A fourth camera and monitor were installed to look into the chip dump pit. A Pelco Genex Video Multiplexer was installed in the network cabinet. The output of the multiplexer is connected to a PelcoNet Transmitter. The PelcoNet Transmitter takes the video signal and converts it to a JPEG image. The transmitter can be accessed from an Internet browser and control of the multiplexer can be accomplished through the browser. In this way, the operators in the vehicles can get the camera views on the RAC6182. One problem that has come up is that the version of Internet Explorer that runs on the Windows CE operating system does not support streaming JPEGs, so in order to see updates of the video the operator must refresh the screen every so often. There are a number of ways that are being explored to get around this problem.

Chip Level Detection - A number of methods of measuring Chip Level in the dump pit were investigated. A microwave barrier system from Endress + Hauser was selected and installed. This system has a receiver and a transmitter and is mounted on the steel walls at the bottom part of the dump pit. Blocks of non-conductive plastic are positioned between the face of the instrument and the dump pit so there should be little chance of wear or damage. The plastic blocks are cut to match the inside contour of the dump pit wall so there is nowhere for chips to hang up.

Truck Dumping - A loop detector was installed in the ground to detect when a truck is waiting to be dumped. If the system is in Truck Auto mode, then when the loop detector is activated and all the permissives for letting a truck into the system are met the truck control traffic light will turn automatically turn green. The truck will drive onto the dumper, the driver will get out and prepare his truck for dumping, he will push the dump enable pushbutton, he will go into the chip receiving office and using the simplified screen will start the truck dump cycle. He will then enter all his pertinent data into the TOPS4 system. Once the truck is empty, he will push the down pushbutton on the screen and bring the dumper down. He will drive off of the dumper and the system will wait for the next truck to come to the truck dumper system entrance to start the cycle over again. This will all be done without the direct involvement of Canfor personnel unless a problem occurs.

Project Status

The project is substantially complete now and the system has been running since the beginning of July. Andritz Automation personnel provided the training for the operators on the new screens are using the system and it is working well. The Railcar Auto sequence has been implemented so that the trackmobile operator positions the car for dumping, moves off of the dumper, pushes the hardwired dumper enable pushbutton, and pushes a start dump cycle pushbutton on the RAC6182 screen. The railcar raises up and dumps its load of chips. The operator then pushes the lower dumper pushbutton to bring the car down and then once all the permissives are met the next trackmobile pushes the empty railcar off of the dumper and the positions the next full one for dumping so the cycle starts over.