Operator Desks
The Hot Charge Cranes have both a manual and automatic control mode, determined by a 2-position selector switch on the control desk. With exception of emergency devices such as E-stop, pull wire and over-speed function, all logic as well as manual devices are directly connected as logic inputs to a controlling PLC.
Logic devices are the sensors along the gantry, track and shaft. Manual devices are the desk-mounted controls – namely master controllers for Hoist, CT and LT motions – to set speed and direction, within ranges permitted by the control logic. By safety requirements, the desk E-stop button will directly trip crane power, and all brakes will apply.
Desk controls and indicators are set out to represent the position of bins and shaft and movement of the crane motions between bins and shaft. Every sensor and position limit has a 22 mm cluster LED (zero wear) to show its status.
The top-mounted pilot controls enable manual operation within the limits determined by plant sensors, and PLC logic. There are times when the cranes need to be driven beyond the normal limit footprint, as well as when the container is not fully hoisted. It can even be lowered onto the furnace top.
Additional pilot controls enable out-of-norm manoeuvres, but they are concealed inside the desks. The selectors are spring-return. One operator must hold the bypass selector inside the desk for the selected crane function, and another drive the crane from the desktop. Two operators must collude to implement out-of-norm manoeuvres.
Desk controls and indications are wired directly to a PLC outstation, and this is connected by Profibus cable to the PLC in the main control suite. Overall, each crane system is a modern example of control technology combined with drive technology.