Industrial enterprises recognize the value of predictive maintenance as a core business strategy that improves process efficiency, reduces downtime and enhances return on assets. Manufacturers can predict the repair needs of critical components to maximize productivity and boost profits by preventing unexpected shutdowns.
After years of capital equipment investments and plant optimization, many manufacturers can't afford more major investment in new technology. Instead, they supplement equipment and processes as a way to bolster predictive maintenance efforts. Integrated condition monitoring systems meet these needs by opening access to process data from every corner of the plant floor. Leveraging existing networks to gather and share information, distributed solutions provide opportunities to monitor and protect the health of plant assets.
According to a Rockwell Automation survey conducted in May 2002, only 15 percent of companies use a predictive maintenance strategy to manage machinery. Still, the benefits can't be ignored. Research based on Industry Week's North American Best Plants program illustrates the value of predictive maintenance. Top-rated plants use reactive maintenance only 25 percent of the time, whereas predictive maintenance is used nearly 70 percent of the time. The average machine availability in these plants is 96 percent.
Until recently, such high levels of protection were reserved for the privileged few machines and components deemed most critical to production. The protective systems were centrally located in a control room and operated independently of the process control system. This required extensive wiring and valuable plant-floor real estate. Additionally, many systems were proprietary, so they didn't integrate easily with operator interfaces or factory networks. Not only was this approach costly to implement and difficult to troubleshoot, it gave plant managers a limited view of overall equipment availability and performance.
A distributed approach
Centralized controls and dedicated networks gave way to distributing protective devices close to the machines. With existing communication networks gathering information at the machines, companies improve system flexibility while achieving savings in wiring, material and labor. The key is combining machine monitoring and protection into one system that's less expensive and easier to use. With distributed monitoring, organizations have enjoyed savings from 20 percent to 60 percent
The ability to capture fault data across a network is something that interests companies keenly because the information is seen as a critical diagnostic tool for optimizing predictive maintenance procedures, reducing recurring faults and minimizing future downtime.
Integrated solutions reduce hardware cost and decrease the time spent troubleshooting, installing and upgrading equipment. Because measurement devices are placed alongside machinery and sensors, distributed systems cut the need for wiring dedicated exclusively to monitoring and protection by as much as 80 percent. Moreover, distributed systems expand by adding modules at the application without having to install new wiring. Other cost reductions are associated with documenting the system, verifying devices are connected correctly to the intended I/O module, and troubleshooting intermittent connections.
Modular and flexible
Because the available cabinet space close to machines and components is minimal, distributed protection devices must be smaller than conventional devices. The latest trend is small systems that feature DIN-rail mounted modules installed at the machine near the measurement locations. Reducing the control cabinet size reduces engineering costs and conserves valuable plant floor real estate.
The modular design matches the number of devices to the application requirements. The modules can be added to existing control panels or installed close to the machine without special enclosures, power or cooling requirements. Deploying the system across the bus architecture further reduces commissioning time.
Distributed monitoring systems protect critical equipment by sending real time alarm status data to master relays that shut down the equipment when necessary to prevent catastrophic damage. Because data analysis no longer occurs in a central control room, maintenance personnel can review important trend information, such as vibration and lubrication analysis, directly from the operator's consoles or portable HMI devices. That information allows operators to identify developing equipment faults and correct them before production or safety is compromised.
The rapid adoption of open networks maximizes the benefits of distributed monitoring and delivers instantaneous decision-making power across the enterprise. Suppliers of condition monitoring equipment now furnish products that communicate using open protocols. Industry standards published by groups such as OLE for process control (OPC) and the Machinery Information Management Open Systems Alliance (MIMOSA) are giving maintenance personnel open access to condition monitoring, diagnostic and asset management information from intelligent instruments and control systems.
Moreover, digital communication networks, such as DeviceNet, allow users to convey diagnostics not easily accessible through hardwired I/O interfaces, and to connect multiple devices to one wire. Benefits include real-time monitoring of critical machinery, as well as implementing corrective actions before a fault condition damages equipment.
Distributed protection devices communicate directly with programmable controllers or distributed control systems using the control network architecture. In addition, modules interface with condition monitoring software. This allows online and surveillance data to be stored in a common database and shared across enterprise asset management systems, as well as corporate and global information networks. Using a common platform to combine and compare data sources cost-effectively integrates data into one seamless source of concise information.
For a more detailed data analysis, online distributed protection and monitoring systems transfer data to internal or third party condition monitoring specialists via Ethernet or a wide area network. This remote monitoring approach shifts on-site maintenance engineers from a reactive to a proactive mode, freeing them to focus on optimizing the process rather than troubleshooting its problems.
These advances provide the elements that enable greater access to machine data, resulting in more informed decision-making. As manufacturers seek to integrate real-time asset maintenance more closely, open networks and software will play an ever-increasing role in interconnecting the disparate pieces of equipment.
Gaining an edge
Unplanned downtime need not cost companies millions of dollars each year. Distributed monitoring identifies developing faults in equipment and protects them before production or safety is compromised. Progressive companies realize capturing, analyzing and using machine condition information effectively provides them with a strategic and competitive advantage, allowing them to optimize production control, increase plant asset availability and improve plant uptime.
Rick Schiltz is Vice President of Marketing and Engineering for the Integrated Condition Monitoring business group of Rockwell Automation's Global Manufacturing Solutions division. He can be reached at 513-576-6151 or firstname.lastname@example.org.
Figures: Rockwell Automation