An holistic approach to plant safety
01 February 2012
Manufacturers who seek to protect their people, assets and environment without compromising their productivity, need to manage a myriad of risks throughout their plants and factories. This is a tall order, so what better way than to leave it to one proven specialist
Some manufacturers take a ‘pieces-and-parts’ approach to risk management, which means dealing with multiple vendors, incompatible technologies, obsolete systems and competing standards. Others prefer to adopt risk management strategies and the safety technologies offered by a single vendor to help improve their safety and business performance.
Few companies are able to offer this broad-brush approach but one – Rockwell Automation - has demonstrated a comprehensive understanding of its customers’ risk management needs and is capable of delivering the full complement of hardware, software and safety-related knowledge to meet these needs, as these following case studies illustrate.
The body complete line at Kia Motors Corporation’s first-ever European facility in Zilina, Slovakia initially comprised Allen-Bradley CompactLogix, Allen-Bradley ControlLogix programmable automation controllers (PACs) with safety relays, scanners and their associated relays supplied by a second vendor.
The safety relays had complicated wiring and long conductor routing from the safety device to the relay in the main cabinet, without a bypass option from the scanners, which made troubleshooting difficult. The safety circuits and devices caused many small production line stops, and operators found troubleshooting difficult.
The solution to this problem came in the form of Allen-Bradley GuardLogix safety controllers (offering the benefits of a Logix platform, a common programming environment, common networks and a common control engine) with integrated safety control to Safety Integrity Level (SIL) 3 certification. Remote safety I/O modules were connected to an existing Allen-Bradley PanelView Plus HMI via EtherNet/IP, facilitating easy monitoring of safety conditions, alarms, and emergency events.
With the previous system, if a person entered a cell or one device failed during production, the entire line stopped, making it difficult to identify the failure. The new configuration divides the line into five zones, each with its own safety I/O and consequently reduced wiring requirement. Each safety I/O is connected to a GuardLogix controller via EtherNet/IP, while each scanner has a bypass function, allowing light signalling and switching. Now, if the line is interrupted, only the relevant zone is stopped, signalling its location.
Converting from a relay-based to a safety PAC configuration has improved flexibility and reliability, reduced maintenance and troubleshooting, as well as improving overall safety. Moreover, Kia Motors Slovakia claims to have achieved a 70% reduction in safety-related downtime since the installation. This integrated safety concept will now be transferred to other lines in the body and press shops.
Explosion prevention
A manufacturing procedure that involves the processing or use of fine powders presents a dust cloud explosion risk, and advanced monitoring systems are required to keep a close eye on atmospheric variables. The ACOM detection system from Germany-based ATEX Explosionsschutz GmbH monitors process air for the presence of volatile pyrolysis components, indicating the potential presence of thermal decomposition or smoulder spot development.
Capable of detecting levels of less than one part-per-million, the ACOM system detects self-ignition processes as soon as they start and can stop them by controlling process operations and advanced fire-fighting systems before the onset of deflagration. At its heart is a CompactLogix L32E PAC, with additional I/O providing connection of a carbon monoxide analyser, and PanelView Plus 600 HMI, which displays all necessary information to the process operator. ATEX Explosionsschutz’s Walter Kaars takes up the story:
“We chose Rockwell because the customer we supplied back in 1995 (when ACOM was first developed) happened to be using Rockwell systems throughout their plant. In 2008, however, we decided to implement Rockwell Automation-based architecture for a number of reasons. Firstly, our original supplier could not offer a safety-capable PAC; secondly, Rockwell Automation has a global presence, which is vital as far as our export markets are concerned. Thirdly, because Allen-Bradley equipment runs on standard Ethernet, we are able to offer a number of value-added capabilities without complicating the installation with extra protocols, programming languages and training.”
“We have already received feedback from customers who have both the old and new controller,” Mr Kaars adds, “The feedback is overwhelmingly more positive toward the machines with the new CompactLogix controller. We are now in a better position to serve a much broader range of customers across a greater geographical area, from both a technological and service perspective, knowing that a Rockwell Automation office or agent is just around the corner, no matter where our machines are installed.”
Protecting against arc flash
To mitigate electrical safety risks, manufacturers are increasingly looking beyond the use of personal protective clothing and equipment and instead are investing in arc-resistant technology. One such company is Delta, Ohio based North Star BlueScope Steel, which uses an electrical arc furnace to recycle scrap metal into hot-band steel. Past incidents at its facility, which were primarily caused by rodents, played a part in motivating the company to install arc flash equipment.
North Star partnered with Rockwell Automation and IDT Systems Inc., an electrical control systems integrator based in Cambridge, Ontario, to install an Allen-Bradley CENTERLINE ArcShield motor control centre (MCC) to improve employee safety. The MCC has a heavy-duty enclosure for containment, and a novel design that routes arc flash energy via top-mounted relief vents into an overhead plenum. With sealed low-voltage compartments, workers can now open the low-voltage section of the control cabinet and conduct maintenance and troubleshooting while still having full arc flash protection.
IDT Systems designed a control room for the ArcShield MCC to run large fans on an emission control system. The control room had only a 12-foot ceiling, so the team developed the overhead plenum to direct arc blasts outside of the building into a safer, fenced-off area. The ArcShield MCC design saved about seven to eight feet of control-room space, and Rockwell’s intelligent motor control system reduced overall engineering time. In addition, all control cables are covered, even in the high-voltage portion, so control cables are protected if an incident occurs.
According to North Star, the ArcShield MCC is “built like a tank”, and its systems integrator, IDT Systems is now recommending the system to other customers, the benefits of improved personnel safety, less damage to equipment and reduced downtime far outweighing the additional costs.
Expertise adds value
An experienced automation and safety component supplier who is well-versed in current safety regulations is undoubtedly a valuable asset for any company embarking on a safety system design exercise. Safety system suppliers like Rockwell Automation who take an holistic approach to safety, are able to provide not just the hardware and software, but the in-depth knowledge required to maintain and improve the safety function without compromising operational efficiency and productivity.
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