Level 1 System
The IPACT Level 1 system controls all the equipment related to furnace charging - feeders, conveyors, weigh hoppers, skips, relief and equalizer valves, bells, stockrods, moveable armor, etc. All charging control functionality resides in Level 1, which means that the furnace can be charged with the Level 1 acting as a stand-alone system. In this mode, any "round" of up to forty steps (skips) can be run repeatedly, with each step containing up to four materials. An innovative scheduling function designed around modular "hopper tasks" is included in the Level 1 design. This scheduling function looks ahead in the schedule up to N steps (where N depends on stockhouse parameters) in order to insure that stockhouse delays are kept to the absolute minimum possible.
The scheduling function will schedule steps using either one or both sides of the stockhouse, thus, it will still support charging when one side of the stockhouse is down. If a material is scheduled that is not available, the scheduler will alert the operator via an alarm. If a step is scheduled for one side of the stockhouse but can only be gathered from the other side, the scheduler will automatically adjust the round to gather the material from the available side.
Variants of the IPACT Level 1 charging control system have been developed to work with a larry car/scale car, or to obtain all materials from a completely automated stockhouse. In the scale car system, coke was obtained from automated hoppers, while ores and fluxes were gathered by the scale car. IPACT developed the on-board Level 1 scale car logic as well as the communication interface in the main Level 1 system. The Level 1 system performs material overshoot prediction and compensation using digital filtering techniques. Overshoot is tracked on a per-bin basis. If the bin/conveyor belt configuration requires it, the system purges belts between material weigh-outs. In addition to overshoot compensation, material "makeups" are also calculated and allocated by Level 1, where a "makeup" is defined as the amount of a material that the furnace is short or ahead. Makeup values are maintained on a per-material basis, and are distributed over future scheduled steps. This insures that, over a period of several rounds, the burden ratio can be achieved with very high precision. Moisture compensation, not only for coke but potentially for other materials if desired, is included in Level 1. The IPACT Level 1 charging control system features innovative furnace startup, pausing, and halting functionality. On startup, the system will check the modes of all equipment necessary to charge the furnace, and alert the operator using very clear "pop-up" screens to conditions that will prevent the furnace from starting up. Once these conditions are rectified, the system will dump and hoist any material in hoppers that can contain more than one type of material (i.e. coke-only hoppers are not dumped), and then begin charging the requested round.
The IPACT Level 1 system contains two “pause” functions (pause at end of step, pause at end of round) that are operator selectable because furnace equipment sometimes needs minor work that doesn’t require a complete halt and restart of automatic charging. These will pause charging activity "gracefully", allowing maintenance functions to proceed, after which the operator can select "continue" from the HMI, and charging will proceed from the point at which it left off.
There are also two "halt" functions (halt immediate, halt at end of round) supported. Halt immediate will stop charging functions immediately, but in a manner that will require a full re-start. Halt at end of round will halt charging at the end of the current round such that the last material hoisted will get all the way into the furnace (i.e. not left on either bell), and all hoppers will be left empty.
In order to enable Level 1 to charge without Level 2, all furnace rounds are stored on Level 1. The size of available storage will depend on the type of PLC required by the customer; a typical size is forty rounds of up to forty steps each, with a maximum of four materials per step. The Level 1 charging system will recognize and alarm overweight and/or over-volume hoppers. As "splitting" a hopper’s contents between two skips is a procedure that typically requires manual intervention anyway, the system does not attempt to split the hopper automatically. However, the Level 1 system does help the operator by displaying a "pop-up" screen on the HMI to alert the operator to the condition, and interactively leading him through the manual split load procedure, one step at a time. The IPACT Level 1 charging control system can generate many hundreds of different alarm messages. The design criteria was "if charging halts for any reason, the operator should be given a clear indication of what is wrong, using preferably one but a maximum of two or three alarm messages". Thus, the system generates more than the typical equipment-oriented messages such as "hopper gate won’t open". Alarms are discussed further in the Level 1 HMI section.
Integrated Process Automation & Control Technologies