New Drives and Controls Integral to Crane Upgrade Project
QIT-Fer et Titane (QIT) plays a prime role in the Canadian mining and metallurgy sector. In operation in Quebec since 1950, the company is recognized as a world leader in the production of titanium dioxide and also has an enviable reputation world...
November 1, 2004 | By MRO Magazine
QIT-Fer et Titane (QIT) plays a prime role in the Canadian mining and metallurgy sector. In operation in Quebec since 1950, the company is recognized as a world leader in the production of titanium dioxide and also has an enviable reputation worldwide for the exceptional quality of its cast iron and steel.
With a workforce of close to 2,000, QIT operates an ilmenite deposit at Lake Tio near Havre-Saint-Pierre and a metallurgical complex at Sorel-Tracy, where ore is processed to produce high quality titanium dioxide, pig iron and steel.
Ilmenite, sold to steel mills throughout the world, is used to protect the crucibles of blast furnaces and thus extend their useful life. The titanium dioxide (TiO2) contained in the ilmenite helps prevent and repair premature erosion of the furnace refractory lining by forming a protective layer on the firebox lining.
Ore derived from QIT’s Havre-Saint-Pierre mine, titanium dioxide and other products destined for customers are typically transported by ship. The loading and unloading of these materials is carried out using two 25-tonne cranes, which have been in operation since the 1950s.
The electrical installations associated with the company’s two harbour cranes were showing a number of signs of aging, with the outmoded nature of the existing electrical systems and the high costs of annual maintenance having necessitated their replacement. Moreover, the required efficiency and operational security of the cranes demanded a high level of training and expertise, particularly related to the primitive control system.
Currently, each crane’s motors are run by relay and contactor mechanisms. In effect, these systems were installed in 1970, replacing the original devices, which were in operation for 20 years. As such, the existing control system is over 30 years old and is now obsolete, with replacement parts having become more and more expensive and difficult to find.
In addition, the external resistors used to control the speed of the motors dissipates a considerable amount of heat, while occupying a great amount of space in each harbour crane’s electrical room.
The crane upgrade solution required by QIT needed to resolve a number of specific problems:
The excessive demand on the Hold and Close brakes and the load trolley required frequent service and maintenance. With each change of direction, braking was systematically applied while the motor was turning at high speed.
When lifting a load, there was no mechanism to allow for equal distribution between the Hold and Close motors.
The brakes were experiencing specific operational problems due to damaged coils.
The motors used to move the cranes were constantly breaking down as a result of uneven load distribution.
The training period required for operators was excessively long because the control system featured no automation.
There was no even control of the lift speed on the Hold and Close motors for the handling of the tray or equipment.
There were no alarm indicators.
For over 20 years, the firm of Breton, Banville & Associs (BBA) of Mont-Saint-Hilaire, Qu., has maintained solid business relations with QIT, providing the metal producer with a variety of engineering services. ABB Canada of Montreal is also an important supplier of electrical equipment and systems to QIT, particularly AC drives.
QIT entrusted BBA with the mandate to implement the crane upgrade project in two separate phases. Phase I of the project consisted of replacing the 600-volt busbars with 15,000-volt reels with 600-volt transformation. This phase was completed by BBA in 1998-99.
Implemented in the winter of 2002 by BBA and ABB, Phase II of the project involved the replacement of the motor starters with AC drives, the addition of programmable robot technology (using PLCs) and a specialized crane control unit, as well as a new ergonomic control cab.
More specifically, Phase II of the project included the installation of ABB 630-kW ACS600 AC drives on the Hold and Close motors and another 200-kW drive on the trolley. A specialized ABB AC80 controller was also installed to automate Hold and Close operations in tandem. These three drives are powered by a 1,400-kW rectifier bridge with a capacity to regenerate power along the network.
BBA carried out the gauging of the Hold and Close drives by conducting a full dynamic analysis of all the mechanical components for different operating speeds.
The drives are configured so as to control activity sharing between the motors, to control the load speeds moving up and down, to optimize the load torque and speed ratio without causing any motor overheating (at low speed), to accurately diagnose alarms, and to integrally control the management of the clamp and tray.
The boom motor was replaced as well with a 60-kW ACS600 AC drive.
Furthermore, the starters for the four motors used to move the crane were replaced with four 60-kW ACS600 AC drives, allowing for sharing of the load in order to assure smooth and precise movement while distributing the torque evenly to all the motors. As well, the locking devices to avoid bad manoeuvres (anti-collision) and the anemometers were modernized.
Finally, all alarm signals and locking devices were automated and integrated with the operating interface to enable the rapid resolution of problems. Operations were also facilitated by replacing all the control arms and buttons with multi-functional automated levers. As such, commands can be transmitted to the various speed drives by way of Modbus+ and Profibus DP networks.
The first crane is currently in operation and the benefits with respect to maintenance and operational safety are tangible. The time required for learning to operate the crane and its systems has been shortened significantly. The cost of modernization has been greatly reduced by the reutilization of coiled rotor motors, and operating and maintenance costs will also decrease significantly.
In view of these concrete benefits, QIT planned the upgrade of its second crane for the following winter.