"A Winner of Elcina Award & Excellence in Electronics" from Govt. of India      Website Updated on 08 Nov 2008
 
 
Problem: How to transfer important signals from stacker/reclaimer to control room.

Background: Stacker/Reclaimers can be found in cement, power, steel industries where bulk movement/storage is needed. Stackers receive material from other stockyard equipment via a conveyor network and deposit it in a bunker or pile. Reclaimers remove the same material and deliver it to other stockyard equipment via a conveyor network.
It is very important to have information such as movement of stacker/reclaimer to control room while in operation. For example, if reclaimer is to be started, the reclaimer yard conveyor has to be started first and the same signal is to be given to the reclaimer. In the same way, the stacker yard conveyor has to be started after starting the stacker machine only.  So stacker running signal is sent to the Central Control Room (CCR), which in turn, sends signal to stacker yard conveyor. If there is a delay in these signals then tippler chute will get clogged. The main requirement of the signal interlocking is to prevent the clogging of both machine.

Generally, all industries like to go with the automation system for the machines, If stacker/Reclaimer is to be operated in auto mode, no. of inputs/outputs are required to be transferred from machine to CCR  (Example: - Travel Speed reference , Speed feedback, Machine position etc)
 
Stacker Reclaimers

Solution: There are two options to transfer the information (interlocks, signals etc). One option is Control Cable reeling drum (CCRD) used to transfer signals to CCR through slip-ring and carbon brushes. The problem of CCRD is that only limited signals can be transferred; signal loss and it breaks too often as these are moving machines. The second option is to have these machines communicate wirelessly with each other. Wireless technology is available for both VHF/UHF (licensed) and 2.4 GHz (unlicensed) bands. These can be connected directly with RS232/Ethernet ports of the PLC, which are installed at stacker/reclaimer and control room. The advantage being lot of signals can be transmitted which would have been impossible with a hardwire solution. The wireless approach not only avoids CCRD cable but also avoids CCRD drum and motor to run it. Furthermore, the signals can be easily expanded in future. If PLC's are not available, then hardwire I/O's can also be transferred wirelesses. These radios are also available as protocol transparent, which gives the System Integrator the freedom to use any PLC/IO module working on any of the serial protocols (Eg. MODBUS, DF1, DNP3.0 etc) or TCP/IP based protocols.