Automated Hot Metal Monorail System

Background

A joint venture was formed between an American and a Mexican firm to produce steel. The new mill needed a means of moving molten steel between the melt furnaces and the pour areas. It was decided that the best method for doing this was to install a monorail loop with three carriers. To help the operator with positioning the load, an auto-dispatch feature was added.

System Description

The hoist motion is controlled by an IMPULSE^® P3 Series 2 drive, and the trolley motion on the carrier is controlled by the V7 Yaskawa drive. The carrier operates the tilt mechanism for the bucket. The hoist is positioned using a four-position geared limit switch and the trolley is positioned using proximity sensors. An Allen-Bradley ControlLogix PLC controls the auto-dispatch operation. A Magnetek remote radio system allows any of six transmitters to control any of the three carriers based on a first-come first-serve method. A pendant can be plugged into any of the carriers to control them in the event that a radio fails. Photoelectric sensors are used to prevent carriers from running into each other.

System Operation

Before any steel is poured into the bucket, the bucket is coated at the alloy treatment area. After being treated, the operator manually moves the carrier and bucket to the melting area using the radio transmitter. When the carrier reaches the melting area the operator lowers the bucket to the low level to allow it to move under obstructions near the furnaces. Once positioned at one of the four pour locations, the bucket is manually filled, and then manually moved away from the area. When clear of the pour location, the operator places the radio in auto, toggles the dispatch to pour location #1 or #2, and turns off the transmitter. The transmitter must be turned off to allow the next operator to take control of the carrier with his transmitter. The hoist then rises to the full up position and starts traveling to the selected pour location. The carrier continues to the pour location, slowing down at the curve. When the carrier reaches its selected location it stops. The next operator then turns on his transmitter and puts it in manual to pour the molten steel. After the operator is finished pouring he puts the carrier in auto, presses the dispatch button, and turns off the transmitter. The hoist then raises to the full up position and proceeds to the alloy treatment area. While traveling in the curves and when nearing the alloy treatment area, the carrier runs in slow speed to provide an extra level of safety for moving with molten steel. When the carrier reaches the alloy treatment area, it stops and the next operator manually takes control of the carrier. The cycle then repeats itself.