Shipping two million tons of woodchips per annum from its plant and port facilities at Richards Bay, the Central Timber Co-operative (CTC) is one of the world’s biggest exporters of woodchips. When choosing a supervisory control and data acquisition (SCADA) system, systems integrators (SIs) Autotronix chose Adroit for its local support and reliability, thereby enabling CTC to meet its export demands. CTC purchases eucalyptus logs from local farmers and processes these into quality wood chips for the paper industry.
“Local support is very important for us and for our client. Because the plant is heavily involved in export, manufacturing downtime can cost the client heavily in demurrage charges [berthing costs]. We therefore needed a system that was highly reliable with uptime greater than 99,99999%, and chose Adroit because of its local support and because they deliver good value for money. We had already implemented Adroit on similar types of plants elsewhere making it re-usable software for us,” says Collin Chetty, project engineer for Autotronix.
“CTC was the first of three wood chipping plant projects that we undertook in that area. We have extensive knowledge and experience in this industry, and hence could complete the project timeously. We were called upon again for these reasons to do an expansion,” says Chetty.
“As project engineers, we must be able to expand the systems ‘as and when’ the plant expands and Adroit gave us that functionality. We also needed a good recording system for alarms and events that could be presented to CTC for swift problem reporting and maintenance scheduling.”
Autotronix is a leading system integrator in southern Africa, engineering small to multimillion rand projects for diverse industries in the region. Using a multidisciplinary approach and focusing on factory automation, energy management and telemetry/data acquisitions systems, the company has developed both proprietary and open solutions for many industrial applications.
CTC’s head office is based in Pietermaritzburg, KwaZulu-Natal. The plant, situated at Richards Bay, consists of a wood chipping line, a chip screening section and conveyor system to transport the chips to a storage area. The debarked logs are lifted onto a log deck conveyor and then onto a transfer belt conveyor, through a diverter and then fed rateably into two 96″ (2,4 m) chippers. The chips are then transported via conveyors to the screen. The function of the screen is to remove all the undesirable chips. The chips are then sent to a stock pile. A M6 conveyor was constructed to provide additional capacity to the existing C5 conveyor, and to enable the concurrent loading of two vessels.
The enclosed conveyor is 589 m long utilising a 1,5 m wide conveyor belt running at 3,9 m/s with a design capacity in excess of 1000 T.P.H. The concrete ‘U’ beams enclosure ensures that there is no adverse impact on the adjoining town of Byrne and local bird life. It also ensures longevity of the conveyor system in the corrosive Richards Bay atmosphere. The complex conveyor belt structure links directly into the port system.
A second 460 ton pneumatic ship loader was constructed by CTC in 2004. This loader moves on a 21 m rail span the length of the 300 m jetty. The 40 m loading boom has a telescopic pipe which is capable of spanning the width of the wood chip bulk carriers. Loading is achieved by means of a 54000 CFM Roots Single Stage Centrifugal Blower blowing chips into the ship’s hold – in this way, wood chip carriers can be loaded in 40 hours.
The automation consists of three Rockwell Control Logix PLC systems, server and Adroit SCADAs – one located at each of the two chippers, and the third at the export plant. The operators control the intake, chipping and transport via the Adroit human machine interface (HMI). The systems architecture is in hot standby configuration because of the high uptime required.
The two units are geographically separated by nearly 200 m, and the plant can be operated from either station, and the server was configured to hot standby using Adroit’s agent server and UI on same machine, eliminating the need for additional workstations.
The SIs implemented a standalone architectural configuration using Ethernet, ControlNet and DeviceNet systems. Autotronix constantly upgrades the SCADA system to ensure that CTC runs on the latest Adroit version.
The 1500 tag point SCADA has the crushing plant on remote I/O using ControlNet, with all the starters on Rockwell’s DeviceNet. Every starter brings back intelligent information, for example, current drawn and power consumed to the Adroit SCADA where it is trended. Autotronix did extensive scripting. Because of the nature of the plant they needed to display all sorts of faults and the status of the various intelligent drives, as well as the information that is filtered back in the form of state variables.
Rockwell Solution Control Logix programmable logic controllers (PLCs) talk to the Adroit SCADA via the Ethernet, and to each other at central processing unit (CPU) levels via ControlNet. Ethernet is used as a backup to maintain the network reliability providing Ethernet redundancy across the control network. Each of the drives had intelligent starters installed that were networked by DeviceNet.
The facilities are continuously manned. On-screen and audible alarm facilities have been implemented – with the audible alarm amplified electronically. Because these operations have two different operators, the alarm is filtered on two sides: wood chipping and export. The hot standby configuration of the system allows either operator to work both plants at anytime.
Instrumentation consists primarily of level transmitters, beltways, temperature transmitters for the chipper bearings, vibration transducers to monitor the health of the chippers and the chipper motor itself. CTC makes use of Adroit’s trending facility to monitor all motor currents, and to continuously trend all beltways to ensure accurate loading of the ships. This is particularly important as the company is billed on the tonnages that pass through. Adroit provides a mechanism for traceability.
Autotronix used standard Adroit graphics for quick loading. The SI will also investigate the use of Opus reporting software to enhance CTC’s access to shop floor information across the various levels of management and operation.
Article by: Adroit Technologies
Source: SA Instrumentation & Control, Dec 2006