If a control system is nearing the end of its life cycle and the company cannot afford the time or cost of upgrading the entire system, then certain measures need to be taken during the transition period to extend the life of the aging system.
In most cases, a control system consists of many programmable logic controllers ( PLCs ). These include controllers, input/output (I/O) cards, network infrastructure, gateways, or interface devices to allow data transfer between systems, human-machine interface (HMI) software applications, or proprietary consoles.
To maximize the lifecycle of a system, it is crucial to have a sound preventative maintenance plan and a plan to manage dependencies on aging components and software, which are essential for operational activities.
7 Tips for Control System Maintenance
Maintaining consistency with the control system version and properly maintaining the system throughout its lifecycle are essential for ensuring its reliability and continuous operation. This practice may impact time, manufacturing, and production schedule requirements.
1. Control System Power Supply: A good, reliable, and independent power supply is essential for maintaining the system's longevity. Uninterruptible power supplies (UPS) can be used to power critical components.
2. Environment: Listing the environment separately means taking factors such as temperature, humidity, and dust into account. The temperature and humidity around system components are crucial. Higher cabinet temperatures shorten the lifespan of components inside (above threshold temperatures). This also applies to computers. Accumulated dust acts as an insulating layer, significantly reducing the ability of cooling air to remove heat.
3. Network Updates: The network is the backbone of the control system, but it is often the most easily overlooked part. Data must be transmitted from the processor to the server/human-machine interface in order to apply control.
More and more systems are choosing Ethernet as the preferred method for controlling distributed components. Inverters, valve assemblies, remote I/O, and other systems all rely on a stable and reliable network. In most cases, it should be made as robust as possible. Users should explore the topology of the layout, using multiple links and switches to achieve distributed load and fault tolerance.
4. Keep it up-to-date: Every control system has a lifespan. Typically, the computer should be replaced every 5 to 6 years, and the controller/hardware should be replaced as needed. Keeping it up-to-date may involve upgrading the computer and control software. Companies that upgrade to the latest software versions provided by the supplier may face the problem of frequent PC upgrades, because upgrades and features offered on newer operating systems are often not supported by older hardware.
5. Virtualization: In most cases, legacy systems can be virtualized, allowing users to "make do" until the final solution is in place. This is useful, for example, if you have the latest control hardware and need to immediately replace your HMI PC.
6. Phased Replacement: Replacement typically involves updating the human-machine interface (HMI) software to a package compatible with both existing and new hardware. Users can replace their hardware in phases, running the new and old systems side-by-side on the new HMI software until the upgrade is complete and they have brand-new hardware. This eliminates the vulnerabilities that arise from running older operating systems on outdated computer hardware.
7. Advance Planning: Users should begin planning for the next phase several years before the control system is decommissioned to ensure production downtime is minimized. Most vendors offer migration paths. Using thin clients is also a good approach to help businesses minimize the impact of hardware replacement, as these operating systems are independent.
