Metals and minerals have been important resources for centuries, but the methods of mining those resources have drastically improved over the years. Today, mining companies use hoisting equipment to move materials and personnel from underground to the surface, typically from as far below the surface as a half mile to a mile deep.
As technological capabilities grow, mining companies look to become even more productive and competitive globally. They want to run hoists continuously without stopping for unplanned maintenance and increase the load size brought up by the hoists. However, safety and reliability are major concerns. A hoist’s skip can move up to 60 ft/s and needs to stop within a predetermined position without causing any issues.
Hoists can operate without any supervision. Operators can monitor the automatic operations from an on-site control cabin. However, more companies now see the value of remotely monitoring operations. Typical applications are in remote locations with weather extremes, and access to spare parts and equipment is limited. Response time is critical at these locations.
INCO Engineering designs and builds mining hoists and complete systems for vertical and inclined transport in mines (Figure 1). Established as CKD Prague in 1874, INCO Engineering emerged through a restructuring in 1994. From its remote-monitoring center in the Czech Republic, it can alert operators and supervisors in local mines when there’s an issue developing. The mining business is very competitive, dominated by INCO and two other major competitors.
“The equipment we supply is very robust and large,” says Vlad Hermann, representative, INCO Engineering North America. “We’re dealing with rather large and difficult-to-move equipment. Monitoring and controlling this kind of drum is critical for us. INCO developed a unique solution for customers. It’s a modular hoisting solution. Each module is built in a container. It can be tested on-site before it’s shipped (Figure 2). Another great benefit is it can be disassembled and shipped to another shaft when you’re done.”
INCO’s newest hoisting system, which includes remote operation and monitoring, is about two years old. It was developed working closely with ControlTech Industrial Automation, Rockwell Automation’s distributor in the Czech Republic. “There are more than 270 controls and checks being monitored,” says Hermann. “The system uses triple redundancy. We’ve sold about 10 systems. Five are in operation right now, installed and running in Europe. Another five are in the process of being implemented and commissioned. Two of those are in Europe, and three are in India. They are scheduled to be operational in April.”
The biggest advantages of the new system are its user-friendliness and the ability to operate and manage the hoisting system remotely when it’s in operation. “Everything is custom-made,” explains Hermann. “There are no identical systems. There will always be some minor differences. The drive and the PLCs and the communication equipment will always be there, but they will always be configured differently. This modular solution is something unique. Not all of our solutions are modular solutions. The ones going to India, for example, are not modular. They are custom-made though, and one of them will be positioned in a single building.”
The Czech Behemoth
INCO designs customized equipment for customers around the globe, including in Czech Republic, Poland, Slovakia, Russia, Kazakhstan, Turkey and India, and is growing in the United States and Canada. Customers’ targeted resources include coal, iron ore, uranium, copper, potash, silver and gold.
INCO’s hoists are technologically advanced behemoths, reaching up to two stories high. INCO works closely with customers to design and build the hoists to mine requirements. While the hoist specifics may change from customer to customer, the biggest constant is the need for safety and reliability. INCO builds layers of control redundancy into each hoist system to help minimize the risk of downtime.
An Allen-Bradley CompactLogix 1769-L33ER controller features an integrated platform for control and motion execution, communicates over an Ethernet network, and can be configured in a single programming environment. This provides INCO’s customers with fewer spare parts to maintain, while the control platform’s openness helps to ensure easy integration with third-party components.
The control system supports a device-level ring network topology, helping users to maintain communications if a fault occurs. Cabling is reduced due to an application of distributed inputs and outputs. An Allen Bradley PanelView Plus 6 human-machine interface (HMI) provides an interface between the machine and operator monitoring the hoisting process.
Additionally, INCO offers Transdatic, the advanced remote-monitoring system it developed. The system continuously monitors conditions of selected equipment, and data is securely transferred to INCO’s central service center. If an issue occurs, INCO staff can notify customers immediately, reducing the customer’s maintenance costs. Staff can also analyze the most frequent faults and help customers to make equipment and process adjustments to prevent further occurrences. The Transdatic system can be implemented with hoists anywhere in the world from the service center in the Czech Republic.
As part of the OEM Partner program with Rockwell Automation, INCO has reached new markets and customers in the mining industry. The INCO staff utilizes Rockwell Automation services for global equipment maintenance and support. “As we’ve expanded from building hoist equipment to providing services to maintain them, our collaboration with Rockwell Automation has grown,” says Dr. Jan Houdek, CEO and co-owner of INCO Engineering.
Control, regulation and safety
Safety and security of control and data is absolutely critical in mining applications, and INCO’s hoist system meets all challenges with triple redundancy. Control and security of the hoist is achieved through three PLCs and at least one drive. “If the size of the system is very large, we need to put drives in parallel,” explains Hermann. “The triple redundancy for the safety is important; it may have one drive, but the control system is triple-redundant, which provides power and control for the hoist motor.”
Programmable logic controllers designated as UB1, UB2 and UB3 perform logic functions of control, measurement and control programming in particular, which watches over the proper and safe operation of the hoist via the so-called Security file (Figure 3). And a backup program deals with the security file. A drive designated as UA regulates the motor of the hoist based on the commands received from the CompactLogix 1769 controllers.
All control systems— UB1, UB2, UB3—and the drive UA are connected to a redundant EtherNet/IP communication network to communicate with each other. This specifically means continuous data exchange and signals. Redundancy of the communication network is based on ring topology; in the event there is an interrupt of network cable or to any of the communication modules, communication continues from the opposite direction. Correct function and integrity of the communication network is continuously monitored, and, in the eventual break, the winding machine is safely stopped, and its continued operation is blocked. The communication network also includes a touchscreen to visualize the operating and fault conditions of the machine.
Power and drive
Rockwell Automation PowerFlex 755 drives with Revcon power feedback units or active front end (AFE) converters with controlled rectifiers or PowerFlex 7000 medium-voltage drives are used for power and regulation of INCO Engineering mining hoists. The drive uses feedback from an incremental encoder on the motor shaft and provides precise control of speed frequency based on the reference value of the desired speed of the hoist from master control system UB2.
In addition to speed control, which is used in most of the modes of operation of the hoist, it’s possible to select the drive mode torque control, when requested, instead of the speed torque. This control method is applied, for example, for the static brake testing. The torque is entered into the locked machine, and the drive communicates with a PLC UA2 via the network with FactoryTalk Historian DataLink.
Besides speed and possibly torque according to the set point in the inverter, the control circuit also performs a program of security checks for proper function and trouble-free status of the drive and motor protection.
The PLCs perform logic functions of management, measurement and control, called File Security of the hoisting machine. Rockwell Automation CompactLogix 1769-L33ER PLCs are used; these differ from each other only by the number and type of the input and output cards.
The position of individual PLCs is evident from the structural diagram in Figure 2. UB1 is located in the control desk, along with two touchscreens, or operating panels, to visualize operational status and any fault conditions of the machine. It also serves as a touchscreen for most controls. UB2 and UB3 are located in the control cabinet, along with machine safety circuitry and a number of auxiliary electrical equipment components such as power supplies, fuses, input-output relays and terminal blocks.
The PLC is located in the control desk. Typically you have the control cabinet, and then you have the control desk; that controller is located in that operator desk and carries out independent digital depth gauge for the position in the shaft and speedometer, a self-incremental encoder. It implements a series of logic signals and functions. In the control program, a system of security is implemented.
It will check a variety of items, such as the speed at the end of the transport path, fault of the speed controller, supply voltages, magnetic sensors in the shaft, end limit switches, isolation conditions and the operation of the braking system. “You can have four, six or 12 brakes on a hoist, depending on its size,” explains Hermann. “The braking of the system is one of the biggest safety features on the hoist; if a wire is cut in one area, that’s where the redundancy comes in.”
The third PLC is used to control the electrohydraulic braking system, HR23K Reprimatic, in all its operating modes. It implements logic control of the electrohydraulic valves, proportional pressure control, measurement and value functions. It also provides evaluation of the direction the load is moved, polarity and size of the load carried by the hoist and chooses one of two preset braking torque for safety braking. In addition it is realizing an extensive security set.