Manufacturing
Hydromet
Automation project resolves a pressing issue
In 2000 Hydromet, based at Unanderra on the NSW South Coast, were treating waste products discharged from the nearby BHP Billiton steelworks. As part of their process improvement strategy Hydromet acquired a filter press to commence a new waste treatment process for BHP. The success of the project was dependent upon the effective automation of the filter press and integration of its control system components. Local systems integrator Machinery Automation & Robotics Pty Ltd delivered a complete turnkey installation including all associated electrical work.
Hydromet’s new process requires use of the filter press to treat effluent from BHP’s nearby steel mill. Following treatment with an acid-based solution containing arsenic, cadmium and lead, the effluent is placed on the filter press where water is removed, leaving a powder residue. The residue is then shaken from the press plates onto a conveyor belt for stockpiling and loading on to the hopper for weighing, prior to shipment off site.
The effectiveness of the filter press process is largely dependent upon the efficiency of the variable speed pump controlling fluid entering the filter press, in this instance, one using a Taian inverter. For this reason MAR opted for the reliable Hitachi EH150 PLC to automate the process. The PLC provides the PID loop, which maintains constant pressure on the filter press via feedback from a pressure transducer. As more water is removed from the filter and residue deposits build up on the plates the Hitachi ensures constant pressure is applied until the residue is freed from the filter by a shaking and scraping action upon the plates. Load cells installed in the hopper have further automated the process as all residue loaded on to the hopper prior to shipment is now weighed and accurate records stored.
MAR integrated some of the best products available for the automation of Hydromet’s filter press. An ESA VT555 operator interface touch screen was chosen to monitor and control the entire operation and the integration of all auto- and manual control functions including fault displays and warning messages has proved popular with operators on site. All drives are started using Sprecher & Schuh motor circuit breakers and contactors and an Eldon cabinet with a forced cooling fan for the VVVF was identified as the most appropriate for the location. The unit is thermostatically controlled and the fan automatically cut out when the correct temperature is reached eliminating unnecessary dust and dirt being circulated.
Introducing a new process into a plant can be a challenge for any company. 'We wanted to deliver a total solution that minimised the effort required on our client’s part while still achieving an outstanding result’, MAR’s Managing Director Clyde Campbell explained. With this in mind MAR undertook the initial design, preparation of a functional description, electrical drawings, PLC- and operator interface touch screen programming, panel construction and wiring, on-site cable installation, testing and commissioning. In the process they delivered just the turnkey solution Hydromet were looking for.