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Abstract—An innovative indigenous system for non-contact transmission of signals, to remotely control mudgun and drill machine at Blast furnace in Rourkela Steel Plant (RSP), has been designed and commissioned. Wired cable connections for equipment in hostile steel plant environment caused breakdowns, with associated productivity loss, due to damage to cables. Further, there are areas where cable laying or on-line fault rectification is extremely difficult. It is also common to encounter life threatening situations for the operators due to proximity of hot liquid iron coming out of tap holes of a Blast Furnace. Since modern steel plants are designed to deliver consistent productivity and quality, reliable wireless signal communication systems have to be aggressively developed and incorporated to avoid breakdowns and accidents for augmenting system output, efficiency and safety. Wireless transmission of signals the futuristic technology, enables sending and receiving of signals without any physical wires.
There was a threefold objective for this development: (1) enhance safety parameters for operator by providing flexibility to operate from safe distance (2) eliminate production loss due to breakdown of control cable and associated switchgear (3) Improve availability of mudgun and drill machine . The system comprises of radio remote control (RRC), hydraulic valve stand, Programmable Logic Controllers (PLC) and special dust proof panels. The application software has been developed in –house. The system, is in continuous operation since January 2015
I. SYSTEM DESCRIPTION
In any steel plant, Blast furnace is the most critical unit responsible for liquid iron production. Liquid iron from Blast Furnace is transferred to Steel Melting Shop for further processing. So the availability of Blast Furnace is the key factor for sustained productivity. The Blast Furnace # 4 of RSP has two tap holes from where liquid iron and slag come out, once the process of iron making is complete “Fig.1”
Mud gun and drill machine are considered as most important equipment of Blast furnace cast house. Mud gun is used to pack the tap hole with mud. Then burden is charged from the top and the process of iron making starts. Once the furnace is ready with the iron making, drill machine is used to drill through the tap hole and the liquid iron comes out. There are correspondingly two mud guns and one drill machine. The mud gun and drill machine are operated from two control
desks, one for tap hole # 1 and the other for tap hole # 2. Close proximity of the control desks from the tap hole caused dangerous situation to the operating personnel. Also, splinters from flowing metal caused damage to the associated cables of the control desk, which affected the machine availability, leading to reduced blast in Blast furnace subsequently leading to loss of productivity. Blast Furnace # 4 of RSP is one of the highest production furnaces with around 2400 Ton /day average production. With every tapping around 250 Ton metal comes out of the tap hole.
In the earlier scheme“Fig.2” two control desks were used to control operation of the two mud guns and one drill machine. Distance of the control desks were approximately 5 meters from the tap hole. A bunch of control cable approximately 200 meters, ran between the desk and the relay panel in the hydraulic room. Sequencing and interlocking for the mud gun and drill machine was realized by relay logic in the relay panel. Hydraulic and pneumatic valves were used for various operations of mud gun and drill machine. Valve stand for mud gun # 2 was mechanic-hydraulic type having control handles in the desk # 2. Valve stand for control of mud gun # 1 and drill machine was electrical proportional type. Earlier scheme was not PLC based, so any modification or trouble shooting was extremely difficult and time consuming.
Keeping above difficulties in view, a system of remote operation of mud gun and drill machine for the Blast Furnace # 4 has been developed and the system is in operation since January ‘2015
II. NEW SIGNAL CONFIGURATION
RRC based automation system has been designed, developed and implemented. Various technical papers / journals were referred to know more about industrial wireless applications, protocols, frequency hopping techniques, time division multiple accesses etc [1], [2], [3].A new system capable of transmitting all the digital and analog signals was developed jointly by Research & Development Centre for Iron and Steel (RDCIS) and RSP.
The prime objective was to get rid of the issues related with control of cast house equipment using, control cable, desk switch gear and intermediate junction boxes. Apart from equipment breakdown, operator safety was also a major issue. The existing system was thoroughly examined. It was concluded that one valve stand which was mounted with mechanical proportional valves also needs to be replaced with electrical proportional valve stand. Various issues were considered before the design was finalized, they are mentioned below.
Salient design development issues
• Design of a comprehensive schematic of wireless signal transmission system which includes extensive study of the subject, taking care of all possible factors affecting the signal transmission.
• Selection of proper equipment like radio modem, PLC, hydraulic valve stand equipment, after comprehensive survey of the site condition.
• Interfacing the old valve stand and relay panel with the new signal transmission system
• Installation of the system in phased manner with minimum shutdown of Blast Furnace.
• Integration of the new system with existing automation system
• In-house development of control software
IV. CHALLENGES FOR RESEARCH
Here we discuss some major issues that need to be addressed in order to achieve successful deployment of wireless in industrial ambience. [8]
A. Safety
Safety of man, machine, environment, and property [9] should always be the number one priority. Unsafe system can cause substantial production losses or damages to the property if the not designed properly. Equipments shall be able to go to safe mode on sensing a signal time out. Control system should be able to sense the loss of communication. Even if the wireless is used for process monitoring, utmost care should be taken to design the system so that it gives a real time picture of the process.
B. Availability
In large-scale industries like that of an integrated steel plant, availability of equipment is of great significance. Even short and transient communication errors can cause significant production outages. This is mainly due to the fact that process has to be stopped in a controlled manner in case of a single communication problem, and it can take up to several hours to achieve full production rate again, with production losses in the range of hundreds of thousands Rupees per hour. For several reasons self-healing mesh networks are appealing to use in industrial automation.
C. Security
Any complex process such as iron/steel making is controlled, based on vast numbers of collected real time measurements, generation of set points for actuators according to process algorithm, transmission of set points to actuators and response time of the actuators [10]. However, from a security perspective authentication, integrity, availability, and non-repudiation are important security objectives In reference to digital security, no repudiation means to ensure that a transferred message has been sent and received by the parties claiming to have sent and received the message. No repudiation is a way to guarantee that the sender of a message cannot later deny having sent the message and that the recipient cannot deny having received the message. To integrate the security mechanisms in the overall automation system in an efficient way with respect to key management and replacement of faulty field devices is an important issue.
D. Latency
In any real-time control system delivery of data has to be in time. Data delivered too late is of limited or no use. This is an important area of research, especially in industrial wireless where it can be mesh networks, frequency hopping situations, and synchronized communication in both directions between the nodes. Therefore new data should be propagated through the network instead of guaranteeing delivery of all transmissions. To decrease the number of retransmissions in the industrial wireless network one can use some error control techniques such as forward error correcting (FEC) codes. With respect to retransmissions in mesh networks and multi hop situations, it has to be guaranteed that data is delivered in the correct order.
E. System integration
Most critical aspect for expansion of industrial wireless network is integration into existing automation network. In most of our project which are brown-field in nature, we need to migrate from wired system to wireless, keeping existing automation backbone intact. System design has to be such that it is easily deployable, future expandable, having excellent trouble shooting feature, requiring low maintenance and maintainable by the available skill level of the plant.
F. Interference
Heavy industries often contain many sources of interference like, heavy electrical equipment and other communication equipment that operate in the same frequency band. Thus, it is very important that the implemented system can coexist in a radio environment with a large amount of interferences as well as limit its own disturbance. The obvious countermeasure for interference is the use of different diversity (time, frequency, and space) schemes , also some more fancy innovative techniques such as interference cancellation, effective radio resource management etc.
V. CONCLUSION
The successful use of wireless technology has immense potential in steel plant having harsh and dangerous operating environment that includes dust, molten metal, smoke, vibration, EMI/noise, and extremely high temperatures. The system developed has huge possibilities of technology transfer in areas like Raw Materials Handling Plant, Coke ovens, Sinter Plants and other Blast furnaces etc.
Wireless signal transmission has been successfully implemented in one of the most hazardous area of iron making namely cast house equipment of any Blast Furnace. The system comprises of RRC based signal transmitter & receiver, hydraulic valve stand, PLC system and special fire resistant panels. The application and control software has been developed in- house. The new scheme has demonstrated successful signal transmission without depending on the fixed control desk and control cable method. The implemented scheme has resulted in significant benefits including reduction in breakdown, increase in hot metal production, and elimination in machine damage.
Most significantly, this effort has helped to develop the necessary level of expertise in the field of wireless signal communication in steel plant operation, which can be gainfully extended in numerous other critical areas. Remarkable achievement of this innovation is enhancing human safety aspect.