The mine hoisting fraternity in Canada is warming to the idea that micro-computers can control hoisting systems. Noranda has gone the computer control route at its Geco mine, and the company is in the process of doing the same at its partially-owned Hemlo Gold Mines operation. Asea Brown Boveri is supplying the computerized Asea Master Mine Hoist to the Hemlo mine. Inco Ltd. has installed a programmable logic controller (plc) at the North mine in the Sudbury area of northern Ontario. For the past nine months, it has controlled cage travel (20,000 miles in total) in the 22-level shaft. (Two, 18-ton skips operate on a separate plc system.) According to Everett Henderson, an Inco planner who led the company’s general engineering group on the project, the plc has performed admirably. “What I tried to do was make it comprehensive. It meets all the day- to-day requirements except slinging and shaft inspection,” Henderson told The Northern Miner Magazine. It is believed that the system is the first of its kind to be incorporated into the operation of a double drum hoist in North America. The hoist is a 12-ft Bertram Nordberg.
The heart of the Inco system is the plc, built by Gould Electronics of Mississauga (formerly Modicon). (The control panels at level call stations and at the shaft collar were designed and fabricated by Metalac Ltd. of Sudbury.) The plc has multi-level calling functions. Workers at different levels of the mine can call for the cage and punch in their destination at a local panel. The computer sorts the information and logically sets out an optimum travel route, picking up and dropping off people along the way. The plc can also perform local functions such as jogging and chairing the cage. A “dedicated” cage tender is not required. “Your average Joe can, just at will, move from point A to point B. You walk out to the station, 22 buttons are presented to you and you punch in where you want to go,” Henderson said. Workers are given a two-hour training program to learn how to run the system. More extensive training is given to service employees who use the cage frequently.
Scheduling lunch breaks and shift changes for the hoisting crew are a thing of the past. “This system is available 100% for users. It’s more responsive and, with its emergency functions, it can respond quickly,” Henderson said. Among the capabilities of the automated hoist, which were outlined in a paper Henderson recently prepared, are the following:
b The hoist’s current position is displayed at all station call panels. A green lamp shows the hoist is on automatic control. A yellow lamp indicates the hoist is moving up, while a blue lamp indicates down movement. (These lamps wink during express trips.)
b The next destination to be serviced is displayed on each panel with a solid lamp for the selected level.
b Outstanding work awaiting the hoist is shown on each panel as an intermittent lighting of the levels involved.
b Two large yellow lamps and two large green lamps, visible from the cage, are positioned in the shaft station area. The yellow lamps indicate that the hoist is in motion or ready to move. The green indicate that it is safe to enter or exit the cage.
b Each control panel has a selector switch for such local functions as chairing and jogging.
b In the event of failure or abnormal condition, brakes are actuated from a maintained-type emergency stop pushbutton installed on each control panel.
b The controls receive pick-up and drop-off requests in three different ways: The first is for normal movement and generates separate lists for ascent and descent moves; the second, which bypasses normal execution, is for “express service” to move equipment and the like; and the third is for emergency calls, which erases all other “work” and triggers an audible and visual alarm to alert others.
The system, which cost an approximate $150,000 for the hardware, can be installed on hoists arranged for single-stick control. Inco is considering installing it at its Crean Hill operation. The addition of the automatic control was the third step in an upgrading project at the North mine that also included a new brake system and the installation of a solid-state drive package that consisted of a CGE SilPac-600 thyristor armature supply.
At Hemlo Gold Mines’ Golden Giant mine, a decision has been made to convert the service cage from a motor generator set to a full reversing 6-pulse digital thyristor drive. The logic control will be a master programmable controller which, with peripheral devices coupled directly to the hoist drums, will supervise the hoist’s speed and position. For fully automatic control, station gate switches, in-position limit switches, destination control and indication lights will be installed at each underground level station. These remote inputs and outputs will be connected by a “bus link” cable to the master programmable controller. Asea Brown Boveri is supplying its Asea Master 240 computerized control. Asea is supplying the thyristor drive as well. The system is flexible in that new control functions or changes to existing functions can be done easily. The production skip hoist is already fully automatic.
Dan Nelson, the mine’s plant services co-ordinator, said converting to the new system with the thyristor and plc makes sense for long-life mines. “The system that’s on the cage right now is a 750Kw DC generator controlled by a 5Kw amplidyne generator with an amplistat control. That system is based on magnetic amplifier theory. The reason we got away from that is because that technology is about 40 years old, if not older. Nobody makes it anymore as original equipment. You’re trying to keep a system, that’s not modern anymore, going. It’s difficult to get spare parts and it’s not even taught at trade school. The other big problem is that you want to get away from rotating drives. They’re very maintenance intensive. If it’s got less moving parts, it’s got less of a chance of breaking down.
“Going to programmable control you get ease of troubleshooting. You don’t have to look after banks of relays. With the plc, push buttons and gate switches underground are considered to be remote inputs and outputs. When you want to run them, you just use the bus link. You don’t use the bulky multi-conductor cables. And besides, it’s a lot more precise.”
Nelson added that hoists can last a long time, mechanically. Today, old hoists are being refurbished and the old controls are being replaced with the new controls. — 30 —
Be the first to comment on "AUTOMATED HOISTS"